Materials and Metallurgy Subcommittee - September 21, 2000
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS *** MEETING: MATERIALS AND METALLURGY SUBCOMMITTEE USNRC 11545 Rockville Pike, Room T2-B3 Rockville, MD Thursday, September 21, 2000 The committee met, pursuant to notice, at 8:30 a.m. MEMBERS PRESENT: GEORGE APOSTOLAKIS, Chairman, ACRS THOMAS KRESS, Member, ACRS WILLIAM SHACK, Member, ACRS ROBERT SEALE, Member, ACRS NOEL DUDLEY, Member, ACRS Staff. PARTICIPANTS: E. HACKETT, RES S. MALIK, RES D. JACKSON, RES L. ABRAMSON, RES M. KIRK, RES N. SIU, RES H. WOODS, RES D. BESSETTE, RES D. KALINOUSKY, RES T. DICKSON, ORNL MODARRES, UNIV. OF MD.. BEGIN TAPE 1, SIDE 1: [8:30 a.m.] -- activities associated with PTS thermal hydraulic experiments, flaw distribution, fracture toughness distribution and model uncertainties, embrittlement correlations, and the favored probabilistic fracture mechanics code. The subcommittee will gather information, analyze relevant issues and facts, and formulate proposed positions and actions, as appropriate, for deliberation by the full committee. Mr. Noel Dudley is the cognizant ACRS staff engineer for this meeting. The rules for participation in today's meeting have been announced as part of the notice of this meeting previously published in the Federal Register on September 5, 2000. A transcript of this meeting is being kept and will be made available as stated in the Federal Register notice. It is requested that speakers first identify themselves and speak with sufficient clarity and volume so they can be readily heard. We have received no comments or requests for time to make oral statements from members of the public. The staff briefed this subcommittee on March 16 and April 27, 2000 concerning the status of the PTS technical basis reevaluation project. At the May 2000 ACRS meeting, the staff presented a draft Commission paper that described potential options and approaches for revising the PTS acceptance criteria. Today we will hear presentations about the results from some of the ongoing activities associated with the reevaluation project. We will now proceed and I call upon Mr. Edwin Hackett, Assistant Chief of the Materials Engineering Branch, to begin. MR. HACKETT: Thank you, Mr. Chairman. Nothing controversial in there. That's who I am. I guess this is starting to get kind of comfortable for us. We took this on as a major item. We took this on as a major commitment to be briefing the committee on a regular basis and we have been doing that. This is the background. I think Bill mentioned this. There's been a lot of encouraging developments on 99. We show potential for significant burden reduction, in a paper by Shaw Mallick and Terry Dixon, both of whom are here. Additional developments. Thermal hydraulics and PRA have occurred over the timeframe which we've been looking at this. And you'll hear about all of these pieces, improvements in thermal hydraulic codes, testing at the APEX facility for flow stagnation, which is ongoing, the context for PRA, and explicit considerations of uncertainties. I guess we're about a year and a half into it now. The project has also been fully participatory. The original plan completion, and I'll mention a little bit about this, is December 2001. We're currently assessing some schedule impacts. I think bottom line is we're behind that schedule, but we're right now working on exactly how much. Like I said, the project was fully participatory, which is a pretty major departure for us from things that we've done in the past, with input from key stakeholders, and, obviously, within the NRC, that's principally the Office of Research and the Office of Nuclear Reactor Regulation, and our contractors. The industry has been very active in this effort, as we've talked about before, with the primary lead coming from the materials reliability project for the PWRs, in cooperation with EPRI, also, and the vendors. They have provided probably close to half of the support for this project in terms of some of what we'll come to here. The plants that are participating, the participation has really been all coordinated by the industry and the MRP. EPRI and the MRP have also been very key players in the area of flaw density and distribution, in volunteering materials and time and expertise in that area. Debbie Jackson will probably talk about some of that in her presentation. The public is -- SPEAKER: Do they have their own codes, for example, for the probabilistic fracture mechanics? Do they use FAVOR, do they use VISA? MR. HACKETT: They generally -- the agreement previously was -- I guess I'd have to go back a ways. When Mike Mayfield was branch chief, quite a while back, or even section chief in Materials Engineering Branch, he had an effort with Tim Griesbock, through ASME and EPRI, to benchmark VISA at the time. So I think the bottom line is that folks were using VISA as kind of an industry NRC-wide view of looking at this particular problem. VISA basically evolved, of course, into what is now FAVOR, and that's not quite fair to Terry. Favor is much, much more than VISA was, but VISA and OKA-P, I think, formed the bases for what became FAVOR, and Terry can talk about some of that when he speaks later. But I think there is pretty much consensus between us and the industry that FAVOR is the code that will be used. That's not to say there haven't been other codes that people have applied. And, again, Terry could probably address that better than I could. But from Oak Ridge, there was OKA and OKA-P, I believe, vintage mid-'80s, something like that. VISA, of course, originated here with Ron Gambel and Jack Strosnider, and then later versions through PNNL. But the bottom line is that it's mostly been standardized and I think there is agreement, the NRC-industry working group, that FAVOR will be the code that will be used for the probabilistic assessment, which is a good thing. It's like we don't need -- SPEAKER: You probably ought to check to see if everything is still -- I say you probably ought to try to check to see if there has been any divergence in that expected uniformity and agreement. MR. HACKETT: Right now, one of the things you will here today is right now we've been focusing down on getting some of these key inputs ready for delivery for Terry to incorporate in the code. So right now, everybody, including the industry participants, is looking at getting a revised FAVOR that basically we can start turning the crank on. So that one has been there. I think the chairman mentioned the reviews that have happened, starting with over a year and a half ago and I think most recently with full committee in May. I think Mark Cunningham and I were here in both March and May to talk about the risk acceptance criteria and other pieces. You may remember that are four full-scale plants being analyzed, again, with an awful lot of help from the industry participants, and they are listed here. The major deviation, which occurred basically earlier this year, was H.B. Robinson dropped out of participating in the project formally and Beaver Valley 1 agreed to replace them, basically, and that's gone pretty well, but there were some delays associated with that. Palisades has been a participant in this from the beginning. The three IPTS plants, the integrated PTS assessments that were done in the 1980s were Oconee, Calvert Cliffs and Robinson. So we wanted to basically try to redo those, and we did lose Robinson along the way, but we think we've made up for that and we've made up some ground there. And this is kind of where we are overall. This is just big picture, and, again, you're going to hear an awful lot more detail the rest of the day. But the work is progressing in the major technical areas pretty well. Sometimes we're an awful lot in the mode of one step forward, two steps back, and trying to recalibrate, and there are schedule issues, at least one of which was related to Robinson dropping out and picking up Beaver Valley, but there are other areas that are taking us longer. It is a fairly ambitious undertaking overall. I did mention this piece here, though. The finalization of the materials inputs, we were hoping to have completed that earlier this year. It looks like right now we're hopefully on track for October-November, finalizing things like the statistical distribution of the fracture toughness, the embrittlement correlations, the flow density and distribution, so we can get those to Terry Dixon and others for incorporation into FAVOR. It's a very interesting piece here that Farouk Eltawila and Dave Bissette and others are working on with validation of some of the thermal hydraulics work at the APEX facility has been basically reconfigured to simulate the Palisades plant. Experiments are underway there. As a matter of fact, one has been completed, and I believe there are seven more that are anticipated between now and approximately the end of the calendar year. So that's a major step. Obviously, we're looking at conditions for flow stagnation and mixing. Progress in the PRA aspects, I think, was covered also by the chairman. A big part of this project, of course, that we stress every time is a process for explicit consideration of uncertainties. We've never really done that before. This has always been done as more of a bounding thing. There was a Commission paper completed which Mark Cunningham had the lead for on the acceptance criteria in July 2000. I think based on some comments from the committee, that was recast to the Commission as an information paper as opposed to asking for their specific input at this point. DR. KRESS: Can I ask you a question about the uncertainties? MR. HACKETT: Sure. DR. KRESS: What do you plan on doing with those when you get them? MR. HACKETT: Well, overall, we, for the first time, are looking at doing explicit uncertainty analyses of each of the inputs and hoping to cascade that through. Now, one of the things that's caused us some hesitation or some angst over this is where we're going to end up with that, and I think it's fairly -- DR. KRESS: That's actually my question. When you get there, what are you going to do with it? MR. HACKETT: When you get there, what we're not going to do, I think I can say, is we're not going to line up all the worst case scenarios, like we have before, and it looks like maybe Nathan wants to make a comment on that. But the intent was to do this -- I'll just say, and then let Nathan get into some details, the intent was to keep this as a, quote-unquote, best estimate analysis. It's not supposed to be a bounding analysis by just the way it's written in 10 CFR 5061. So the intent was to try to keep this as a best estimate and not go to a bounding case. MR. SU: This is Nathan Su, Office of Research. That's a great question. Part of the answer is we don't know until we start seeing what the results start looking like. If the results look like, for example, we've been very conservative in the past, then we may not have to do a whole lot with the calculation, just say, okay, we know how to calculate the mean very well, here it is and work with that. Of course, we'll have a sense of the uncertainty about that mean. If we're closer to -- if the risk is higher than we think it is at this point, then we'll have to do something about that. So you're asking the general question what do you do with the distribution once you've generated it and -- DR. KRESS: I liked one of your answers, and that is that's one way, in fact, probably the only way to know you've got a real mean. MR. SU: Yes. And we're certainly going to do our best to calculate that. But in terms of using the full distribution, I guess we haven't really worked that out. DR. KRESS: I was hoping it might have something to do with questions of defense-in-depth and risk acceptance criteria, but that's sort of another subject. MR. HACKETT: That obviously needs to be factored in, in a big way, and that kind of brings us to the next point anyway, because we did get a fair bit of good dialogue here with the committee on the risk acceptance criteria through the ACRS meetings in March and May. Basically, what was discussed a lot at those meetings and also in the paper that Nathan and Mark and others put together is a risk approach that's, quote-unquote, similar to what's contained in 1.174, which would obviously include explicit consideration of defense-in-depth and other factors. But it also has the effect, of course, in this case of resetting a risk criterion that was set in, I guess it's fair to say, kind of an ad hoc way originally at 5E-minus-six, has the effect probably of starting that baseline at 1E-minus-six, and arguing from there one way or the other as to which way this is going to go. DR. APOSTOLAKIS: What is defense-in-depth in this case? DR. KRESS: That's a very good question, George. I think it has to do with inspection and looking at coupons and monitoring and that sort of thing. MR. HACKETT: Inspection is an element. I think one thing I would say, too, and I don't know how much -- it's a very good question. I don't know how much this is actually defense-in-depth, but basically one of the things I would say for this project is that you're looking at a reactor vessel where you're assuming initiation of flaws leading to through-wall failure, which is leading to a big hole in the vessel, which is then likely going to be a pretty major event for the containment to deal with. So you're making those assumptions and maybe you could say there is some aspect of that that involves some defense-in-depth, whether all of that actually happens. We know, for instance, that you can initiate a crack and then arrest it. So you might arrest the crack. Or you could have a crack that goes through-wall, and Mike Mayfield would probably want to shoot me, but it may not go to this foot-wide, 13-foot long thing, maybe it doesn't. But the problem with saying that is I don't think there are any of us who could quantify that. It's beyond the state-of-the-art in fracture mechanics. SPEAKER: Dan Marzinski told me he sees is as you just get leak before break. SPEAKER: It strikes me that sometimes it's worthwhile to go back and recognize that there was enlightenment before RG-1.174. You know, we've kind of gotten jaded, I think, in our appraisal of what ten-to-the-minus-six means, because generally in the context of the application of 1.174, where you're comparing between two alternatives, which is one of the cases that 1.174 was set up for, you're still talking about relatively controllable consequences. By that, I mean, sure, you had a core that went to hell and breakfast with TMI, but it didn't do the Chernobyl thing, if you will. But if you go back far enough, you recognize, I think, that there were two categories of concern. One was the higher risk event; that is, the risk numbers were in the ten-to-the-minus-four and higher numbers. But the other was where the consequences were in the extraordinarily severe range. I wonder if we're being very smart if we allow ourselves to think in terms of ten-to-the-minus-six with those extraordinarily severe consequence events. It sounds to me that we're almost setting ourselves up for that. We're selling ourselves a bill of goods if we're not careful. So I guess I'm going to be the small mind that's going to provide the refuge for this idea, to paraphrase our chairman, but I worry. DR. KRESS: Let me ask you another question about that, along the same lines. Is it considered by you guys that if you have a PTS event that fails the vessel, you also fail containment? Is this a LERF, as well as a CDF at the same time? MR. HACKETT: That's why I put up -- and I have that on the last slide -- that's why I put up that last line there, because when we briefed the committee earlier, and I remember Dr. Kress and also Tom King was here, there was a pretty good discussion that ensued over that. I think the materials perspective, myself, Mike Mayfield, others like that, the answer would be yes, we think there would be some violation of containment somewhere. I think if Mike were here, he's almost of the mind that he thinks it's almost for sure that -- and he's not coming from the standpoint of even pressurization of the containment. He's saying that you now have this big jet force that you put a big hole in one side of the vessel and you're really pushing water and steam out and the vessel is designed to radially expand anyway on the supports. So you would slam the vessel into one side of the shield wall. You'd be into some plant specifics about gaps and so on, and that, of course, is going to drag along with it the other pieces of the primary and it would almost be naive to think that at some point, some containment penetration isn't going to be pulled loose or something. DR. KRESS: Do you have estimates for those forces and things or has that been part of the problem? MR. HACKETT: Dave Bissette was discussing this with us yesterday. The short answer is no, I don't believe, but there are estimates for things like hot leg and cold leg breaks, and I suppose jet force is associated with those. I'm obviously out of my depth here. Dave might be able to address some of that. But I think the bottom line is the expectation would be that it would be enough to move the primary in a significant way. But to the present the other point of view, I think if Mark Cunningham were here, I think Mark was looking at it as a -- trying to bound the problem. If you were to be able to take a subset, well, I only have X number of plants that I think I have a PTS problem with anyway and let's say it just happens to be they're all large dry containments and maybe I've got sliding supports on the generators and things aren't as bad as I've just described, for whatever reason, that maybe you could make that argument. And that's, I believe, where the committee was coming from, that, well, at least you could consider some arguments about containment integrity to set this criterion 5E-minus-six or even lower, if you could argue convincingly that your container was so robust. The problem, I guess, that we see is that making that argument, I think, would be a very difficult thing for a licensee to do. They would probably -- if I were a licensee, I think I'd say to Mr. NRC, I'd like to see a reg guide on how to come argue with you about my containment integrity, and then we're off into another multi-year effort of trying to define that. DR. KRESS: One of my interests is in risk acceptance criteria and I'm very interested in this one-times-ten-to-the-minus-six. My interpretation is that the Reg Guide 1.174, LERF is one-times-ten-to-the-minus-five, and this is one set of sequences and you don't want them to add the whole thing in, so a factor of ten is a good idea, maybe. So that's where the one-times-ten-to-the-minus-six comes in. But the question I have about that, and I think the committee will recognize where this is coming from, it seems to me that when you have a PTS event, that what it suddenly turns into is an ire ingression accident. The steam is not there. It's ire coming through the openings and naturally convecting. Ire ingression accidents are quite different than steam ingression accidents and that causes me to pause when I look at the ten-to-the-minus-six as the criterion, because that's based on steam oxidation driven core melt accidents. MR. HACKETT: Right. DR. KRESS: So I just wanted to point out I think that's where that's coming from and I have a little bit of a concern about that. MR. HACKETT: That's a good point and it's not really one we've considered. Good point. This, I'll go ahead and not take up too much of the time myself here, because we did cover it. Dr. Kress mentioned LERF and I have that on here just in terms of summary and conclusions, but this, for us, obviously, I think, is the first application of sort of the new NRC risk-informed methodology to revise, and we've been talking around this, but what basically is an adequate protection rule, which kind of puts us in an interesting space philosophically, I think as Dr. Kress has been pointing out. I think the progress has been good. We've tried this before. This is the project that's kind of defied my boss since I've known him. It's frustrated Mike for years and years, Mike Mayfield, and I think he was the driving force behind getting this going. So it's been going about as good as it ever has here and it's a lot of credit to Mike for that. The consideration of LERF and containment integrity is a major departure from what we've done before in this area, but I think it's incumbent on us to, in this environment we find ourselves in, it's incumbent on us to consider these aspects. I don't think it was something anyone went into thinking that we're going to have a lot of fun doing this maybe, but it's a valid thing to consider in the current framework. And the old rule does not, obviously, get into those kinds of considerations at all. Another interesting piece is that this project was basically marketed or sold as a licensee burden reduction type of project, but I would say right now it's very much complex enough that the final outcome is not entirely clear. Dr. Kress pointed out the insertion of the uncertainties and any kind of cascading effects, where what we're building up to right now, and maybe Terry will talk about some of this, is by the project schedule, we have an initial scoping study run for Oconee that's scheduled to complete somewhere in the December timeframe, which will hopefully give us an idea of which way this vector is going. We are hoping, obviously, that we are looking at a relaxation of the current PTS criteria, but I think right now it's fair to say it's probably too early to tell. So that's basically what we're hoping to get an indication of in the bottom piece. I think as far as the future goes, I don't remember the exact schedule, but we would probably be on the hook for coming back and having further discussions with the committee by about the turn of the calendar year, and we are down for a Commission paper, I think, Shaw, in February of next year, that's going to be addressing progress. Hopefully, this type of piece would have been considered by then, but we're a good ways away from that right now, so that we have some schedule impacts to address. But we're hoping that the next time we come forward, we'll actually have some results from incorporating all this good science and so on into what's actually a probabilistic run for the first time. So we're getting there. We're not exactly -- we were hoping to be there kind of about now, but we are behind in that schedule. So I guess I could take any overall questions, or otherwise we'll go into kind of a rundown of the three major technical areas. I guess, not hearing any, it looks like what we -- if we go in order here, I guess Roy Woods was going to come on up and talk about some details of the PRA aspects. SPEAKER: We'll just note that -- is ten-to-the-minus-six an adequate protection rule or an improved safety rule and will we have to backfit to get to that level? DR. APOSTOLAKIS: Right now, it's five-ten-to-the-minus-six, is it not? DR. KRESS: Now you're going down to one and my contention -- DR. APOSTOLAKIS: And that would lead to further reduction. DR. KRESS: No, that's going the other way. DR. APOSTOLAKIS: I'm confused, because I thought I heard that -- MR. HACKETT: The intent was -- the thought was there was enough conservatism in the way that you calculated the screening criteria that was used to assure you got to the five-times-ten-to-the-minus-six. If you removed that conservatism, you would get burden reduction. If you lower the criteria, even though you still have conservatism, you're going both ways now and it's not clear. If you kept it at five-times-ten-to-the-minus-six, I don't think there would be much question it would probably reduce some burden. DR. KRESS: Yes, but there was no real technical basis for the five-times-ten-to-the-minus-six and I think they were searching for -- DR. APOSTOLAKIS: That would depend a lot on the containment. DR. KRESS: It certainly would, in my mind, yes. DR. APOSTOLAKIS: And I think the definition that the Commission was giving to defense-in-depth and they talk about multiple barriers, there is an implication of redundancy. Otherwise, it wouldn't be multiple. DR. KRESS: Absolutely. DR. APOSTOLAKIS: So say that if the uncertainties are very large, we're going to inspect such things, so why defense-in-depth. DR. KRESS: No, but a lot of people consider that as one element of defense-in-depth. It's not your classic defense-in-depth. DR. APOSTOLAKIS: It's something you have to do. Is the containment defense-in-depth? I don't know. DR. KRESS: In this case, it may not be defense-in-depth, because what we heard is that when you have a PTS event, you're likely to fail containment. So in an event that it fails both at the same time, then the containment is not defense-in-depth for that event. DR. APOSTOLAKIS: Or if you need it to contain the accident consequence, that is not defense-in-depth. DR. KRESS: That's right. DR. APOSTOLAKIS: It's not redundant. DR. KRESS: No, I don't think you can -- DR. APOSTOLAKIS: You came up with some ideas like that. Remember that? You were very happy that day. Now it comes back to you. DR. KRESS: You got to be careful what you say around here. MR. WOODS: Good morning. I'm Roy Woods. With me is Nathan Su. We're with the Office of Nuclear Regulatory Research, PRA Branch. Also with us Eric Thornsbury, at the table. It's got a lot of the background information that you will be able to tell, if you've asked that kind of question, by the mad shuffling through the paper over in the corner there. I also want to point out that we did go through and kind of practiced for this and I'm aware that there's a lot of material to cover in my talk and the next two, and so I'm going to try to hurry through the stuff you've already heard before. If I go too fast, you will, of course, stop me, please. What we're trying to do, we're trying to basically support the development of the technical basis for the revised PTS rule and in order to do that, we're trying to ensure that it's a coherent risk-informed process, with appropriate integration of thermal hydraulics, PRA and fracture mechanics. There is a slide to follow that you've seen before that shows that as a picture. We're also trying to make sure we have a consistent treatment of uncertainties. DR. APOSTOLAKIS: Roy, speaking of uncertainties, is the paper from Maryland part of today's discussion? SPEAKER: We didn't include that in the schedule. DR. APOSTOLAKIS: When will it be discussed? Because I have a lot of questions. MR. WOODS: I thought Mohammed was going to be here, but -- SPEAKER: He was going to listen in, but we didn't have that scheduled. I know Ed Shaw -- MR. HACKETT: This is Ed Hackett. I guess what we'll do is we'll take an action, Professor, to make that. We might need to make that the subject of another meeting, but we -- DR. APOSTOLAKIS: I think we should, because I'm not sure I understand everything that is being said there, and, in some instances, I'm not sure I agree, and this seems to be a very important part of FAVOR because it -- I mean, it characterizes the uncertainties and then propagates them and so on and I thought we were going to discuss it today. SPEAKER: Although, just to clarify, the status at the moment is that the FAVOR works strictly on the statistical correlations at the moment, right? SPEAKER: I guess I need to probably here more about that, Bill. Just statistical as opposed to mechanistic? SPEAKER: Whether the treatment of uncertainties that are given in the Maryland paper, they're using the statistical correlations that were developed at Oak Ridge. SPEAKER: That's my understanding. DR. APOSTOLAKIS: No. They go beyond that. They provide -- SPEAKER: But, I mean, the calculation is actually not using that at the moment, I don't think. DR. APOSTOLAKIS: Oh, I see. So maybe there will be time here for us to discuss it before the -- SPEAKER: Well, FAVOR, and Terry, I'm sure, will talk to this, is going to incorporate the uncertainties in the different ways that we said in the white paper back in, I don't remember when that was issued, June or September, something like that, which is -- so in particular, we're deal with the aliatory uncertainties in the K1C and K1A terms and the epistemic uncertainties and all the other terms. So FAVOR is being set up to address that. Now, what specific distributions are going to be input to FAVOR is the point of what Maryland is doing and you're right, we haven't spoken about that to the committee. DR. APOSTOLAKIS: But before you guys invest significant amounts of effort in here, I think we ought to have a meeting, because I'm not sure -- you shouldn't take my comments as an ominous sign that there is major disagreement, but I just don't know right now. And by reading the paper, I get more confused than I was before I started and I don't like that. SPEAKER: Actually, I'm confused about that, too. DR. APOSTOLAKIS: It's tough going, I'll tell you, and I'm no sure I agree with the calculation scheme that is proposed and given the emphasis that you guys have placed on uncertainties and consistent treatment and so on, I don't see it there. SPEAKER: That's just self-defense. We keep beating them over the head with uncertainties. They've got to do some treatment of it. DR. APOSTOLAKIS: Yes. SPEAKER: But I went back to read Nathan's white paper and it seemed to me that the way FAVOR now treats the K1 distribution is purely aliatory. DR. APOSTOLAKIS: And it shouldn't be. SPEAKER: And it shouldn't be. Maryland is an attempt to go the other way, but I got confused as to -- just to get off the subject a little bit. Somehow I would pick those K1 curves. I see a family of curves in between there. SPEAKER: Yes, and -- you're right and -- SPEAKER: You would pick one of those curves and that's really an epistemic, because I don't know which of those curves to pick. But once I pick a curve, I'm following along that curve. I'm not walking up and down that whole distribution. SPEAKER: Right, right, right. SPEAKER: And FAVOR now doesn't do that, as I understand it. SPEAKER: I guess maybe -- I don't know, Terry, if you were planning -- I didn't think we were going to get into that depth in this particular presentation, even though -- SPEAKER: Actually, it used to take a curve and -- SPEAKER: That's because you picked a lower bound curve. MR. DIXON: I'm Terry Dixon, from Oak Ridge National Laboratory. The way that -- before the University of Maryland got into being our advisor on this, we did, in fact, pick one curve and we sampled from a Galsion distribution to determine which one of those curves and then we followed that curve down through the cool-down. Now, as you said, Dr. Shack, we don't do that. We actually, at a given moment in time or, in other words, a particular T-minus-RTNDT, we are dealing with the distribution at that vertical slice through T-minus-RTIT. DR. APOSTOLAKIS: So you've selected already a curve, but it would be epistemic, because you are selecting -- SPEAKER: No. It seems to me purely aliatory. DR. APOSTOLAKIS: Aliatory, yes. SPEAKER: The idea or at least -- and Professor Maderas can speak to this better than I can -- doing this method introduces the aliatory uncertainty. SPEAKER: I would have thought that you would have had a curve with a small scatter band around it to take care of the aliatory part, but to treat the whole scatter as aliatory seems to me to be incorrect. DR. APOSTOLAKIS: I think we're going to get into this, but I really think -- in fact, let me ask you. Is it possible to have a discussion here where you will walk us through a detailed calculation based on figure six of the Maryland paper? SPEAKER: I intend to this afternoon in my presentation. DR. APOSTOLAKIS: Today. Well, I won't be here this afternoon, but this is for -- I mean, I want a detailed, how do you pick things, then what do you keep track of. Do you really start by selecting a vessel? What does that mean? DR. KRESS: That's just a figure of speech. DR. APOSTOLAKIS: Yes, but there is a distribution and so on. No, but I really would like, because there are two uncertainties here that we have to keep track of. SPEAKER: Well, I like Nathan's paper, where you have an epistemic loop and an aliatory loop, and I'd like to know what's in the epistemic loop and what's the aliatory loop. SPEAKER: Yes. DR. APOSTOLAKIS: So how does figure six in the Maryland paper -- SPEAKER: I think we need to walk you through that and, again, as Tom pointed out, this is a nomenclature, picking a vessel, to fix the epistemic parameters. But, again, we -- DR. APOSTOLAKIS: That's not my problem. SPEAKER: I know. DR. APOSTOLAKIS: But following the loops, I think that's -- SPEAKER: Right, right. And this has been a point of discussion among us for a while, trying to make sure we got it right, and we do need to talk with you about that. SPEAKER: Some have actually floated back and forth in FAVOR. SPEAKER: Yes. And I intend to talk at some level of detail this afternoon about this. SPEAKER: And conceptually, again, we had every intention of addressing the epistemic uncertainties in the aliatory distribution. Now, whether we're doing it right, that's worth discussing. MR. HACKETT: I think what we can commit to do -- this is Ed Hackett, of Research, again. We'll take an action to make that happen, because I think that would be a very useful thing to do. I guess I would also just mention that later today, Mark Kirk will be giving a presentation, wherein he was going to at least attempt to cover conceptually the breakout, aliatory and epistemic, in the statistical evaluation of fracture toughness, because that -- I think the committee is absolutely right. That has not -- model uncertainty has not been addressed in that area before and we're attempting to do that now for the first time. I think what's been in there has been pretty much all aliatory so far. So we'll take an action to address that separately, but maybe some of what Mark will talk about this afternoon will at least try and conceptualize. DR. APOSTOLAKIS: So it's possible to go through one loop, the calculational loop, that would be extremely useful. MR. WOODS: Okay. I'm going to continue on with the second bullet here then and I'm going to skip over most of it. I thought we'd get hung up on the second one, but that already happened with Ed. Obviously, we're trying to develop a new screening criteria and it will be based on something like RTP or TS, embrittlement parameter, and also on the figures of merit, which would be CDF, and maybe LERF, and also what the acceptance criteria for the CDF or the LERF value would be, which is kind of a separate thing that we weren't prepared to talk about today. DR. APOSTOLAKIS: Incidentally, on the previous subject, Bill mentioned Nathan's paper and I also -- I read it some time ago, but I also read the Maryland paper and the paper by Dixon and Mallick. Is it possible, in the future, that you guys make sure you refer to each other, cite each other, and make sure that the stuff is consistent, instead of throwing in a reference, Nathan Su, and then we don't see any connection to Nathan Su. It would be very useful, in other words, if these things are coming from the same project, to have some consistency. That's not a major thing, but it's knowing. SPEAKER: I think what you're saying, it's partly a function of -- you know, we're hot in the development process. DR. APOSTOLAKIS: Right. SPEAKER: We are certainly intending to document how we deal with uncertainty in PTS in a specific report that will address that, and it will basically, as I see it right now, be an expansion of the white paper. So we'll talk about how we're dealing with it in thermal hydraulics, how we're dealing with it in PFM, how we're dealing with it in HRA and so forth, and put it all under this consistent framework. But I guess we didn't think about doing that early on, but, yes, you're right. We're holding meetings and talking, but we're not necessarily documenting that in what you see. DR. KRESS: The risk acceptance criteria have been worked on by the Risk Analysis Group rather than the group you guys are in. Is that a different, sort of a separate project? SPEAKER: They are us, yes. DR. KRESS: They are us. Okay. MR. WOODS: Okay. Well, the last bullet I think everybody is probably aware of. We started with the IPTS, the plants that Ed mentioned. We're trying to reflect changes to those plants. In fact, one of the plants itself changed, Beaver Valley instead of H.B. Robinson. Also, the very last thing on that slide, we obviously have to get our arms around the risk from all the plants, based on the analysis of four plants. I'm going to just show this next one, but I think everybody has seen it. This is the basic framework. You start with identifying the PTS event scenarios that you're worried about with a fairly standard PRA. I'm going to show you an event tree in a minute, and that defines which thermal hydraulic analysis you need. You'll group certain events into a group and use one thermal hydraulic analysis for all those events. And the ultimate objective is to do the probabilistic fracture mechanics and what you're showing here is you're not certain of what the stress would be from a given event and there's also some uncertainty in the strength of the material, but you're interested in this little area right here, which would be the area where indeed the strength of the material is less than the stress that you put on it, and that area would be an indication of the failure. DR. APOSTOLAKIS: You are using the K's there along this line, right? SPEAKER: Correct. DR. APOSTOLAKIS: K is less. SPEAKER: That's right. SPEAKER: Not directly, yes. DR. APOSTOLAKIS: So all this now is the aliatory. SPEAKER: That's correct. DR. APOSTOLAKIS: And probably you will put the epistemic. SPEAKER: That's correct. DR. APOSTOLAKIS: I like this figure much better than figure six in the Maryland paper, although Maryland tries to go through more detail, but if -- that's what I mean by coordination. If they could refer to this and then start developing the algorithm referring to this, that would be a much better -- by the way, why do you use lambda? Do you imply a rate? SPEAKER: These are frequencies of the particular thermal hydraulic scenario classes. DR. APOSTOLAKIS: They are rates. SPEAKER: They are definitely frequencies, yes. You're ending up with a through-wall crack frequency at the end. DR. APOSTOLAKIS: Okay. But the aliatory part here would be the occurrence of the sequence, something in the thermal hydraulic, although I don't see how much aliatory you can have there. SPEAKER: That's a function of the -- that's intended -- the primes indicate that you're taking the PRA event frequencies and then you bend them, so you have a different frequency, but it's still aliatory. DR. APOSTOLAKIS: Then on the other side, the way I understood it is it's primarily the material variability that contributes to the aliatory part. SPEAKER: That's where -- again, the variability is largely the epistemic part, because we're looking at a specific spot in a specific vessel and looking at the characteristics of that point there. The aliatory part comes in the K1C, K1A, and that's, again, why we need to have this discussion about how -- DR. APOSTOLAKIS: The variability in K is due to material, isn't it? That's what it says here. SPEAKER: That's sort of my gut feeling. SPEAKER: No. The point is that if you fix -- how far do we want to go into this, because -- DR. APOSTOLAKIS: We don't have to go into it. DR. KRESS: It's materials and how you do the measurement. SPEAKER: Since George is leaving, maybe you could spend a few minutes on it. He's not going to be around for this afternoon's discussion, which is a better place for it. SPEAKER: The argument in the original white paper was that even if you knew your material properties precisely, and it's knowable because you're at a specific spot in the vessel, you're at the location of the crack tip. So you could know those properties, but you're uncertain about that. And, yes, there are all sorts of uncertainties that go into your distribution for quantifying that uncertainty. So it's actually a transformation from the aliatory uncertainties when you measure to an epistemic when you're applying it in the calculation. It's all in the context of the calculation. But even if you know those properties, some fraction of the times, your model will predict something and it will be right, some fraction times will predict something that will be wrong, basically failure or success of the vessel. And it's that fraction that's accounted for by this P here. DR. KRESS: K is not a perfect predictor of when the vessel will fail. SPEAKER: Exactly. That's the concept we're trying to bring forward here. DR. KRESS: In that same context, I know it's illustrative, but the temperature on the thermal hydraulic analysis, that's the temperature at the crack location as it grows, at the tip? SPEAKER: This is the downcomer temperature. DR. KRESS: Oh, it's the downcomer. SPEAKER: It's the environment temperature. DR. KRESS: I see. You would put that in your calculation of temperature. SPEAKER: Exactly. The heat transfer is done. DR. KRESS: You'd do another calculation. SPEAKER: That's right, yes. Again, this is just what the RELAP code will produce, for example. DR. KRESS: That's the downcomer temperature at the location you suddenly -- SPEAKER: That's right. DR. KRESS: -- selected that we're looking at. SPEAKER: That's right. MR. WOODS: You'll probably see that one again. It serves its purpose very nicely. Okay. The status of where we are. We are well into the Oconee and Beaver Valley PRA. We've developed event trees, starting from the IPTS studies. You remember we did Oconee before and we didn't do Beaver Valley before, but H.B. Robinson is similar enough, so you can start with those event trees. We're using generic initiating event frequencies and top event split fractions from industry data to focus and develop and decide where to work on the model. We are developing the fault trees for Oconee, where you have data for the top events. In other words, instead of just putting in a feedwater system fails, if you have enough data to support what part of it failed, then you would want to develop a fault tree to use that data. We are putting in potential human failure events developed from the Athena team and the quantification of these things is currently ongoing. We could give you more details, but I'll try to leave it with that. The other two things we intend to do are to review the analyses that are done by the licensee for Palisades and Calvert Cliffs and at the moment, what we're doing, we've collected a great deal of information from Palisades and some information from Calvert Cliffs, reason being we're going to do Palisades next after Beaver Valley, and we are assessing basically the adequacy of the information, but we really haven't reviewed, started the detailed review of those plants. Now, before I get to the next slide, I want to tell you, please, you're not supposed to try to read this. I do have a magnifying glass in my pocket that we might have to use to read it. But the objective of showing this slide is to show you that -- I think I can stand up here. This is part of an event tree. It's not even the whole event tree. This is the event tree for the initiating event and reactor trip, and this is reactor trip and it trips. Then across the top we have all the different things that can happen or not happen and you probably can't even read that, but the point is -- one point I want to make here is we are developing, in further detail, a different part of the tree from what you're used to probably, because we're worried about pressurized thermal shock, which is an over-cooling event. Usually, when you do one of these event trees, you're worried about core damage directly from failing to provide cooling. So you tend to develop the top side of the event tree, where you have what normally would be successors, like the HPI comes on, but it stays on and normally that would be fine, but you need to develop that further to analyze the over-cooling. And what I'm going to do with the next three slides, I think it is, is show you the details of this slightly darkened path, if I can follow it. It goes on over here and ends up on 14 or 15, whichever one we decided, but to kind of walk you through that. SPEAKER: Now, just from your comment there on success in the normal PRA, are you arguing that many conventional PRAs then don't pay enough attention to the PTS event? MR. WOODS: Conventional PRAs may not even include risk from PTS at all. SPEAKER: Okay. Because you're assuming it's screened out. SPEAKER: Because embrittlement is not an issue. SPEAKER: Yes. As long as you're not embrittled, who cares. MR. WOODS: It's a good point, but they're not there at all. They're not there at all. SPEAKER: So you really have to develop these event trees yourself. MR. WOODS: Yes. SPEAKER: You can't get them from the plant PRA. MR. WOODS: That's the point. DR. APOSTOLAKIS: They start with the plant. SPEAKER: They start with it. MR. WOODS: That one was developed from -- I just took it down, but -- SPEAKER: If I could comment. We certainly use the plant PRAs to the extent we can, but a lot of the information comes from the earlier IPTS studies, which did develop event trees, and we've expanded on those and customized them for the studies we're doing. MR. WOODS: I wanted to mention this, 163 end states, you can't read that number, but that's what it says. And this is only part of this one tree, because this particular thing is turbine bypass valves sticking open. This is none, one, two, and four. So these two lines would lead to equal size -- each of them would lead to an equal size of what's shown there and then this has to do with the PORV or the primary side safety valves sticking open, one or the other. So here's two more lines that would lead to something that looks like that. So that's a fourth or less of that one event tree. DR. APOSTOLAKIS: So this is not a binary tree anymore. SPEAKER: Correct. That's correct. MR. WOODS: And that's one of like six to eight event trees, depending on which plant you're talking about. There's one for steam line break and LOCA and whatever, in addition to this tree. DR. APOSTOLAKIS: So where in the tree do you have human actions that ATHENA will come in to help? MR. WOODS: That's coming up. That's why we wanted -- one of the reasons we wanted to work through one of these. Now, this is the part that I showed you that was highlighted and the next two slides have the words, some of the words that I intend to use describing this. So I'm really using three slides at once here. But walking through this, I think I can point better if I stand up. Okay. You start with a trip and the first question is does a PORV or a safety valve on the primary side stick open, and the one that we've chosen to use as an example, we say that it doesn't. It's okay. So having decided that it doesn't -- I mean, it doesn't open; so, therefore, it can't stick open, so it just goes straight through here. But we do say that one turbine bypass valve sticks open. You know, the turbine bypass valve would stock open on a trip, in a turbine trip, because you've got to dump the heat somewhere. So it's supposed to open, but it's not supposed to stay open. So we say that one sticks open and the operator doesn't isolate it. Now, there's the first human event that you have to look at. And in this particular case, the ATHENA team returns a table to the PRA analyst that says, okay, here's the probability that he won't isolate given that there's no other complicating factors in the plant or given that something else is going on that might distract him or mislead him or whatever, or several things maybe. You might have two or three different numbers, depending on the -- you choose which one you use depending on the circumstances. So this would be the one where it's most probable to isolate it, because nothing else is going on in the plant yet. And then the main feedwater in Oconee, this is the Oconee scenario, the main feedwater is supposed to run back. That's the normal situation for this event. But in this particular example fault tree, we say that instead it trips and then the emergency feedwater comes on and the normal situation that would control to a certain level, but instead it over-feeds both steam generators. The others are also in this event tree. I'm just showing you the example of the one where it over-feeds both steam generators. And I guess there's a failure to recover. I missed one. SPEAKER: No, it doesn't matter. It doesn't matter, because that's a fail to start. MR. WOODS: All right. So that's the secondary side. On the primary side, because of the over-cooling, the pressure goes down and the HPI comes on at 15 to 1,600 pounds. Anyway, it goes low enough so it comes on. And so we follow that part of the tree and the last part would be whether or not you lose subcooling and the main reactor coolant pumps trip or they don't. In this case, we don't think we would lose subcooling, but we're not absolutely sure of it. So there's another split here that says it trips or it doesn't. Then, finally, there's another split here, which is another human factor, where HPI flow is throttled or it's not, and then in this case, you don't take the simplest no load type human factor. You take the one where other things have already gone on, because you've already had a stuck-open turbine bypass valve and you've already failed to control the emergency feedwater. So other things are going on in the plant and it's, therefore, less likely that he will remember to throttle the HPI, and they use a different number. DR. APOSTOLAKIS: So ATHENA now has a way of telling us how likely it is. MR. WOODS: Yes. It's not exact, of course, but based on their experience and the data that they've seen and the simulator runs that they've seen for that sort of thing, they do have an organized process by which they come up with a table. But it probably has a name. SPEAKER: No. This is just -- basically what they're doing is a self-elicitation of the group. The group discusses the event. The probabilities are chosen on a very coarse scale. It's one of four values, it's either .5, .1, .01 or .001. So basically you're corresponding to notions of likelihood given the scenario. There is no attempt to make it any finer than that. And the group discusses it, brings up the reasons why the failure might occur, what sorts of things might prompt a failure, and then says, well, given the circumstances, given our observation of the operating crew, that performance scenario is for us, given our understanding of the procedures, talking with the training supervisors, here is what it is. MR. WOODS: Okay. The explanation, like I say, is on the next two slides. I hope that what I said is what's on the next two slides. I'm not going to go through it now and make sure I didn't miss anything. You can look at it later. I think it's self-explanatory, or largely so. I'll go on to slide nine. Information used in the analysis. The point of this slide really is just to show you that we don't just take a cursory look at these plants. We collect quite a bit of information and it's all listed there, and I don't think there's any need, again, we're running very late, to read that to you. But we basically start with the IPE and sections of the FSAR and the P&IDs that are available. We collect all the emergency operating procedures, some of the abnormal operating procedures, because they give you an idea of human actions that lead to the PTS initiators. Then down about a little over halfway, training provided to the operators is something that we really concentrate on. The ATHENA team has actually witnessed a simulator practice in both of the plants, in Oconee and in Beaver Valley. They asked for operating experience from the two plants on very related and relevant like PRVs, SRVs, whether they stick and that sort of thing. Now I've lost my next slide. I got my files mixed up, sorry. We've probably discussed a lot of that. Obviously, we're using the better operating experience. We got three or four times more operating experience than in 1980 when we did this before, and, also, that will contribute to the initiating event frequencies and also to the failure probabilities. We are using current plant design and operating procedures. Some of the procedures are even new specifically to avoid this kind of event since 1980, and that makes a big difference. We think we've got better coupling between the event sequences and the TH, because we've got capability to run more TH scenarios. Things are on a PC now instead of a $100,000 per run for a RELAP run on a big machine. I'll go on to the next one. It's a continuation of this one. I think some of the main things are on this slide, actually. We do think, and it's already come up, that we are taking contextual factors affecting the operator into account much better. In fact, I'm not sure it was even done at all back in 1980. I mentioned that there's two or three different numbers that you choose from based on whatever is going on in the plant other than that particular event. We're doing that. The last two bullets really are meant to show that we are using this to take into account the pluses and the minuses. With the new human methods that we have, we are better able to take into account errors of commission. In fact, we're able to try to take them into account. We didn't even attempt before. Such things as operator trips, RCPs when he's not required to do so, or the operator isolates the wrong steam generator or whatever. When that comes up in a tree like this that we have a number to put in, which is not an exact number, but it's better than no number, we think. Also, on the other side of the coin, then, like when we went to one plant, we could see that they were trained on not having safety injection on when you didn't need it on. It's one of the first steps that they go to and one of the procedures they always go to and they drill on it and we just -- the ATHENA team just thinks that it's very unlikely that they'll forget to take that action. So previously, where we might have had a fairly high probability of that, it isn't anymore. So it's a balance and it's a representation of the plant more as it really is rather than as you might think it would be from an analyst bench. Concluding remarks. There's not much new to say here either. We think we are able to screen out some event sequences that won't be a problem and like normal trips and the vents that don't cool down past a certain point, and we don't spend a lot of time, waste a lot of times on events that won't be a PTS problem. We think we're doing a better characterization of the event sequences, better binning of them, especially for Oconee. That's not to say we aren't doing a good job on Oconee and Beaver, it's just to say that they didn't do a very good job on binning things in Oconee back in 1980. They dumped most of the things into the "other" category and then ended up giving it a much higher consequence than they should have. So we are certainly correcting that. We mentioned we think we're doing an improved treatment of uncertainties, which Dr. Apostolakis wants to hear more about and we will do that. The issues are we haven't yet handled external events like we want to. An example of that would be a fire. A fire could certainly burn up some cables and cause all sorts of problems at once that maybe we haven't taken into account by the analyses that we've already shown you. We do know that when we get through with the four plants, we will have two analyses that we've done, being Oconee and Beaver Valley, and we will have two analyses that we have reviewed, that will be Palisades and Calvert Cliffs, and there are bound to be inconsistencies and we're going to have to come to grips with how we handle -- END TAPE 1, SIDE 1. TAPE 1, SIDE 2 FOLLOWS:. BEGIN TAPE 1, SIDE 2: -- four analyses that really are on a different basis. You're kind of trying to put apples and oranges in the same bin and we have to deal with that. Then the generalization is that obviously we've got four analyses and we're going to have to try to use that to represent the risk at all the plants, and we have some idea how we're going to proceed to do that. Then the acceptance criteria, which we mentioned, is sort of a separate presentation. That's all I had. And I'm sure we're way over, but we'll answer any questions that we can. SPEAKER: Thank you. SPEAKER: A non-controversial one. SPEAKER: Sure it is. MR. BISSETTE: My intention was just to give a brief summary of where we stand on the thermal hydraulics part of this three-part program, just so you have all the pieces. I'm David Bissette, from the Thermal Hydraulics Branch in Research. The objective of the thermal hydraulics work is to ensure that for the risk-significant classes of events, the thermal hydraulic input developed at the time of the IPTS study back in the early '80s are still operative or updated as needed, provided the uncertainty, estimating uncertainty of these calculated values, and, as you heard before, the IPTS study, there were three PWRs selected for analysis, one from each vendor, Oconee, Calvert Cliffs and H.B. Robinson. And as you've heard, in the current study, we've switched to a fairly similar, also a three-loop plant, that's Beaver Valley. These are the principal thermal hydraulic issues that we encounter in single and two-phase loop natural circulation, criteria for interruption of loop flow which causes flow stagnation in the cold leg and downcomer, number of cold legs which are supposed to be flowing to assure mixing in the downcomer, local fluid, fluid mixing, and non-thermal stratification in the cold leg, plume, this is the plume entering the downcomer, plume mixing in the downcomer, and all these are being studied in the experimental program underway in the APEX facility. DR. APOSTOLAKIS: Are you going to do a detailed uncertainty analysis, just as the other guys are proposing, the fracture mechanics? I mean, you're going to identify model uncertainty and parameter uncertainty and everything, or thermal hydraulics is immune to that. DR. KRESS: There is no aliatory. DR. APOSTOLAKIS: I know. MR. BISSETTE: It follows along similar lines. DR. APOSTOLAKIS: Flaws of nature. MR. BISSETTE: It's being done also at the University of Maryland. Do you want me to say more about it? Do you want to say anything? It's kind of a combination. Well, in the thermal hydraulics area, the way we treated uncertainty to this point in time is sort of the CSAU methodology, which you probably all have some familiarity with. What that is is you identify the most important phenomena and you -- for each phenomena, you find the models in the code that models phenomena and you vary them according them according to the uncertainty, which you physically understand the phenomena. So you run the code repeatedly and you see the sensitivity on the final answer that you're interested in; in this case, it's pressure and temperature in the downcomer. SPEAKER: Dave, maybe I can -- the short answer is yes, we're trying. We're taking our best shot. Some issues we think we can handle reasonably well, like what happens in the scenarios where it's basically single phase. For two-phase scenarios, it's more complicated. That's certainly where the model uncertainty issues arise. For the single phase kinds of situations, it looks more like it's an input parameter based on what's happening in the event sequence, which has only been defined to a certain level of detail. So when exactly is a particular action taken, for example, that's an aliatory issue which we need to reflect in the results. We're in the process of still developing the methodology and we're test applying it to Oconee. There's been ongoing discussions among the PRA thermal hydraulics and thermal hydraulic uncertainty analysis groups, but I don't know that we have a great answer for you at this point. Again, it sounds like something that would be worth talking about in the meeting when we talk about how we deal with uncertainty. DR. APOSTOLAKIS: But the amount of effort will be the same. SPEAKER: It's a significant effort on our part, I think. MR. BISSETTE: The plant, the first plant we started with parallels the other efforts, it's Oconee. We've been performing analyses using RELAP. Thus far, we've calculated 25 transients with RELAP-5, Mod 3. I don't know if you recall, but the picture Roy Woods showed, basically, these are 25 transients out of the hundreds of thousands of the sequences that he showed on his event tree. We've run these - the objective was to run these transients to at least 10,000 seconds. We have achieved that. This is a significant improvement over the former study, where most of the transients were only run out to about one or two thousand seconds and extrapolated out to two hours. Just some fairly simple straight line extrapolation. Also, contrary to the earlier study, we modeled the downcomer as a two-dimensional configuration as opposed to the former 1-D that was used before. SPEAKER: In the past, with RELAP, there have been some problems with running out for extended periods of time. Was this stable? MR. BISSETTE: It was surprisingly stable. We had a few code failures, but we were able to run through them by reducing the time step. So for all the 25 cases, we went out to 10,000 seconds. So I found it remarkably stable compared to what sometimes we've experienced in the past. DR. KRESS: You don't use REMIX at all anymore. MR. BISSETTE: We are going to use REMIX. We are using REMIX and I'll mention that a little bit further on. I don't have too much to say about it. So this is going to show you the conclusions from the 25 cases that we've generated so far. Rather a useful interchange between the PRA and the thermal hydraulics work, and I think that's also an improvement over the old IPTS study in the early 1980s. We've covered a great spectrum as part of the work we did for Oconee and it covers a range of interests, but the primary system pressure phase, let's say, high near the secondary side pressure, to where the primary system pressure drops below the accumulator pressure and further down to about 200 psi, which is the low pressure injection. Finally, results are sensitive to the trip criteria for the reactor coolant pumps. Procedures call for tripping the reactor coolant pumps on loss of subcooling. And once subcooling is lost in a small break LOCA, it will generally not be reestablished unless the break can be isolated. So that means that when the pumps trip, they stay off. We find that we've done combinations of primary side and secondary side failures. We find that when we combine secondary side failures, like stuck-open valves with, say, a small break on the primary side, it helps maintain subcooling and, therefore, reactor coolant pumps are not tripped. Like I say, it's a big difference if you trip the pumps or not, because if the pumps are running, basically you have a tightly coupled system between all the loops in the primary side and all the generators on the secondary side. So your heat sink is very large compared to a situation where you trip the pumps and now your focus is just on the volumes of water associated with the downcomer. So when you trip the pumps, at least for Oconee, stagnation begins very quickly. The downcomer cools in response to the high pressure injection. And, finally, comparing the primary side between breaks in the hot side and the cold side for a given break size, hot leg breaks are a little bit worse than the cold leg breaks. That just confirms something we saw in the old IPTS study. We have a small activity right no to coupling REMIX with the TRAC code. We're also going to run -- so we've got a couple the REMIX and TRAC code and run a two-inch break with the coupled code. We're also running the same break with REMIX using the boundary conditions that come out of the RELAP calculation. So this is right now what we're doing with REMIX in terms of the calculations. SPEAKER: So it's not a thermal hydraulic type. What is this giving you? MR. BISSETTE: It gives you -- REMIX gives you another indication of downcomer temperatures. SPEAKER: REMIX is a two-dimensional code. MR. BISSETTE: REMIX is, let's say, basically a -- it treats the mixing volument of interest. REMIX applies to stagnant flow conditions. It treats a part of the system that's of interest, which is the cold leg, the HPI injection, the downcomer and the lower plenum. It treats that as, let's say, a single volume that has five mixing regions in it. And the mixing regions are treated on the physical basis of -- based on like through number treatment of mixing and stratification and plume dissipation. So it's basically a physically based engineering tool to give you mixed temperatures. DR. KRESS: That's stuff you can't get out of RELAP. SPEAKER: Yes, right. DR. KRESS: And you really need that. SPEAKER: So it basically comes in when you get the stagnation. MR. BISSETTE: That's right. You use some boundary conditions that you get from RELAP, depicts the inlet and outlet boundary conditions. Our plan is to repeat selected cases that we've done already with RELAP and we're just about to get these calculations underway and we'll have the results in about one month. Now, this is the only further slide I had on uncertainty evaluation. This is the study that's being performed by the University of Maryland for Oconee. I had mentioned CSCU before. What they are also doing is we came up with a simplified model of the Oconee system. It was based on simply conservation of mass of energy, and performed calculations. DR. APOSTOLAKIS: Model uncertainty there. MR. BISSETTE: So my advice is we -- DR. KRESS: We don't have a write-up on that, at least I haven't seen it. DR. APOSTOLAKIS: I haven't seen it either. Is there anything we can read about it? MR. BISSETTE: We have a partial draft report that's in preparation. There should be, let's say, a first draft in a few months. There's nothing really -- right now, it's not much more beyond viewgraphs you can look at. DR. APOSTOLAKIS: That should be part of whatever subcommittee meeting. DR. KRESS: Yes. This should be part of the same one, when we talk about the other one. MR. BISSETTE: Yes, it should be. I had mentioned the testing program we have underway at APEX. APEX is located at Oregon State University. The objective is to provide experimental data on the thermal hydraulic PTS issues, as well as for code assessment. We did a scaling evaluation to compare the APEX facility to Palisades and, as far as that goes, to other CE plants, like Calvert Cliffs and Fort Calhoun. APEX was originally configured to model AP-600. CE plants are similar in size to AP-600. The facility is modified to add loop seals, HPI connections to the cold legs, and additional thermocouples in the cold legs and downcomer. We performed pre-test calculations using RELAP and REMIX. There's REMIX again. We conducted our first test in August and the remainder of the test program is scheduled to be done by the end of the calendar year. I'm just going to show you -- put this up just to briefly show you what the facility looks like. It's a two-by-four arrangement, similar to the CE plants, with two hot legs, two generators, four reactor coolant pumps feeding into four cold legs. Then this is just a top view, comparing the APEX loop layout with Palisades. DR. KRESS: The injections in the hot leg are all the same. High pressure injection is in the hot leg? MR. BISSETTE: No, the cold leg. Because all plants have connections to the hot leg, as well as the cold legs for the injection systems, but normal injection path is the cold legs. So I won't go through the test matrix, in the interest of time, but here it is. You can look at it. Basically, the tests are PTS sequences, in addition to more basic and separate effects kind of testing to cover the range of issues that I had mentioned earlier. Now, in addition to Oconee, we will be doing Beaver Valley, Calvert Cliffs and Palisades. We haven't done any calculations thus far beyond exercise the input models for these plants. We started converting H.B. Robinson decks to Beaver Valley. We're scheduled to have a set of calculations completed by January of the coming year and we'll follow that with Calvert Cliffs and Palisades, hoping to have the calculations by March of next year. The final slide is we have our Oconee calculations, RELAP, ready for transmittal to Oak Ridge. They use them as boundary conditions for FAVOR. We expect to provide the calculations for a Westinghouse three-loop plant based on Beaver Valley by, say, early the coming year, and Calvert Cliffs and Palisades by the middle of next year. SPEAKER: Are the thermal hydraulic boundary conditions for Oconee different than they were in the '81? I mean, have they changed substantially? MR. BISSETTE: I haven't done a -- we haven't looked at that in detail yet. That's something that we will be doing in the next month or two. DR. KRESS: Well, you had a single curve for the pressure and temperature. MR. BISSETTE: Yes. DR. KRESS: But now you're going to have a distribution. MR. BISSETTE: Well, we may have a curve with that uncertainty band on it. DR. KRESS: There may not be much uncertainty about the pressure, but there can be about the temperature, I guess. MR. BISSETTE: Yes. What we've found, in terms of looking at the phenomena, is that a lot of the phenomena are pretty well -- we believe the dominant phenomena are pretty well modeled by RELAP. There are some uncertainties because you can't model two fluids, two liquids in a one-dimensional code. DR. KRESS: That's your cold liquid and your hot liquid. SPEAKER: Which is one of the reasons we use REMIX, too. What we're going to do, we're going to hold off on the discussion of the probabilistic fracture mechanics until this afternoon and we'll have all the probabilistic fracture mechanics discussion together. We're going to take a break now and then come back and go into the flaw distribution discussion. SPEAKER: Great. SPEAKER: So be back at 10:15. [Recess.] END TAPE 1, SIDE 2. TAPE 2, SIDE 1 FOLLOWS:. BEGIN TAPE 2, SIDE 1: SPEAKER: The next discussion is the generalized flaw distributions, and I guess that's Debbie Jackson and Lee Abramson will be making the presentation. The first test is in. Okay. Passed. SPEAKER: They found it. MS. JACKSON: I'm Debbie Jackson, and Lee Abramson. We're going to present the results from the expert judgment process for the development of the flaw distribution. The first two slides just go over a little bit of background information and reasons why we are doing this flaw distribution. The last major work on flaw distribution was done in the mid '70s and early '80s. It was a Marshall distribution, and that was done not only with nuclear vessels, but also with non-nuclear vessels. So this work that we're doing now is a lot more expensive than the previous work on the Marshall distribution. This slide just discusses a few of the reasons why we decided to do an expert judgment process for development of the generalized flaw distribution. This is a list of the fabricators for domestic reactor vessels and the list is in order of the percentage of vessels that were manufactured by each organization. The last Rotterdam and Society Crusoe, they finished the fabrication. One of the fabricators, Babcock and Wilcox, ran behind schedule during their fabrication processes. So some of their vessels were finished by the Rotterdam and Society Crusoe. This is a slide that lists the reactor vessel material that's been inspected by PNNL that's going to -- that was used for the flaw distribution. The Midland vessel was inspected in the early '80s and it was with a different type of SAF-UT system, and since the Midland inspection, the UT exams have advanced a lot. So the inspection techniques were different, so we're actually not going to include the Midland data. We're only going to do the PVRUF-C, Shoreham, the River Bend and Hope Creek vessels. SPEAKER: PVRUF, what is that? MS. JACKSON: Pressure vessel research users facility. It's a cancelled vessel that was at Oak Ridge, and we've used that. SPEAKER: Debbie, I couldn't find it anywhere in the report. The three boilers, Shoreham, River Bend and Hope Creek, what are the weld processes that are used there? MS. JACKSON: The weld processes for those were submerged arc and then they are back-gouged with -- the inner sods were done with submerged arc. SPEAKER: How about the axial welds? MS. JACKSON: The axial welds were -- I believe they were submerged arc, but some of them may have been electroslag. I need to look that up. SPEAKER: Okay. I just wondered if we were mixing electroslag data in with the other data. MS. JACKSON: Not with the -- not for the PTS, no. We don't have a lot of data on the electroslag weld processes, because a lot of that was done with the boilers. SPEAKER: Okay. But I just wanted to make sure it wasn't being included for the PTS study. MS. JACKSON: During the examinations that PNNL was doing, we came up with categories to categorize the different flaws and what we came up with were different regions of the vessel. The inner region is the NR-25 millimeter, the inner one inch. The outer region was the outer one inch, outer 25 millimeter, and the mid region was the remaining part of the vessel wall. Volumetric and planar, we have the weld, the clad and the base metal and repair weld versus non-repair welds. We found out from some of the data that there are quite a few flaws in the repaired areas of the vessel. These next two slides are going to go over just the steps that we used in the expert judgment process. We first defined some of the issues, determined the level of complexity. We identified an expert panel. We sent some issues to the panel. The panel had a meeting and we had elicitation training, which was performed in Atlanta by Lee Abramson. DR. APOSTOLAKIS: I have a question here. MS. JACKSON: Yes. DR. APOSTOLAKIS: I think I read the report and, in my opinion, it's not clear how the expert judgment was used, what the objective of the elicitation was, and I formed an opinion after I read the whole report, and please correct me. This is my impression. That you actually started with a distribution for the size, the crack depth, and also for the density that is based on data and what you did with the experts is you modified that, depending on the various things that you have here, on whether it's unrepaired weld metal or unrepaired cladding or the various other things that you have here, plate versus welds. Is that correct? In other words, you did not elicit from the experts information that would give you the actual density. You didn't ask them that. SPEAKER: That's correct. MS. JACKSON: No, we did not. SPEAKER: That's correct. MS. JACKSON: You're right. SPEAKER: We just asked relative values. DR. APOSTOLAKIS: Relative values. SPEAKER: That's correct. DR. APOSTOLAKIS: So I suggest, since this is still draft, that you add a section someplace explaining this, because I was really trying very hard to understand what was going on and then you hit me on page 25 with all the information that comes from statistics and then I had to figure it out myself. MS. JACKSON: Okay. That's a point well taken and we'll make those -- DR. APOSTOLAKIS: And also it would be useful if you showed how these various factors were used, what was the arithmetic, in other words. SPEAKER: Okay. There is a considerable -- there is some detail in the report as to how -- SPEAKER: It's sort of lost in those notes. SPEAKER: Well, it's in the notes. DR. APOSTOLAKIS: The report says that this is the mid value of the median and so on. SPEAKER: Correct. DR. APOSTOLAKIS: And using that, we get. And I guess the "using" is the thing, how exactly -- I mean, maybe it's a simple multiplication. SPEAKER: It is, yes. MS. JACKSON: The report has been revised since then and the first revision, because it's going to be revised quite a bit before the final NUREG comes out at the end of next year, but the notes have been revised extensively. SPEAKER: I'm not sure which version you saw, George. The second version hopefully will be more explicit and the intention of the notes was to give you a road map to let you reproduce the calculations yourself without a great deal of trouble. SPEAKER: But George is right. You really ought to separate the ones where you're working from data from the ones where you've essentially modified the distributions based on the -- SPEAKER: This is -- we tried to make this extremely explicit in the notes. DR. APOSTOLAKIS: Yes, I understand that. SPEAKER: And some of the numbers that we got -- SPEAKER: Well, I ended up highlighting my table so I could tell which was which. SPEAKER: That's right. MS. JACKSON: That's been revised. DR. APOSTOLAKIS: I've read already 26 pages. On the 27th, there is note number three, these values are multiplied by -- this is such a big thing, it should be up front some place that this is what the objective was. We will rely on statistical data to get density and -- SPEAKER: We'll try to make it more explicit. DR. APOSTOLAKIS: -- distribution. And the reason why we have to go to experts is because the data is a mixture and you can't tell where it comes from, because if you could, then you wouldn't need the experts. Then you had to modify it or to adapt it to the particular circumstances of interest. SPEAKER: That's right. DR. APOSTOLAKIS: And that's what we're doing, that's what we're eliciting. Okay. And then here, and, for example, for this factor and this factor and this factor, to get this, we multiply this by that. That would go a long way towards helping the reader really place it in context. SPEAKER: Okay. MS. JACKSON: Okay. DR. APOSTOLAKIS: Good. MS. JACKSON: Thank you for that. SPEAKER: Just on that, too, I mean, you give the tables up front for the distribution and the PVRUF and I can't make the numbers add up to get the numbers in table 5-1 for the small flaws and large flaws and greater than five millimeter flaws, and you're referring me back to the original PNNL report. You ought to just bring those tables from the PNNL report and put them in here so that -- DR. APOSTOLAKIS: And I would like, by the way, to get your reference ten, Shuster, Dr. Hessler, characterization of flaws in U.S. reactor pressure vessels. It's a NUREG published in 1999. It seems to be an important document in this context. MS. JACKSON: It is. There's three -- DR. APOSTOLAKIS: So if you can send me a copy, I will appreciate that. MS. JACKSON: We have copies. DR. APOSTOLAKIS: NUREG-CR-6471. MS. JACKSON: There's three volumes of that now. The third volume just came out. DR. APOSTOLAKIS: That will do it. Three volumes. I would like to get that. SPEAKER: Beginning to get indigestion, George. DR. APOSTOLAKIS: That will teach me. SPEAKER: There's 10,000 flaws, George. When you discuss each one -- DR. APOSTOLAKIS: Each one, what happened. MS. JACKSON: Okay. Well, that will be good. This next -- DR. APOSTOLAKIS: Now, just to -- you know, we have to be nitpicky here. How the hell do you know it was successful? You just got some numbers and you used them. Why was it successful? MS. JACKSON: Because we completed 17 -- MR. HACKETT: This is Ed Hackett. I think I could speak for Debbie and Lee, because they're going to be humble and modest. But I think it's just the fact they made it through and people didn't die in the process. So it was kind of -- maybe this is a low bar for success, but at least that was part of it. MS. JACKSON: Our first elicitation session was with Vic Chapman. He's one of the authors of the Marshall report. DR. APOSTOLAKIS: I know him. MS. JACKSON: And the session lasted -- DR. APOSTOLAKIS: You don't call him Lord Marshall? MS. JACKSON: Retiree Marshall, now, Retiree Chapman. DR. APOSTOLAKIS: He's bored. MS. JACKSON: But this session was borderline nine hours. So after that, we decided we had to make some changes. And I say it's evolving because the first few elicitation sessions that we did were different than the final few. Each session, we learned some additional information from the experts. One thing in particular, we had cladding as a group in itself and then one of the experts suggested that we break cladding down into the different specific methods of cladding, strip cladding, multi-wire and single-wire. With that, we had to re-elicit the experts after we finished the final elicitation session, because there were so many changes throughout the process. DR. APOSTOLAKIS: Are you eliciting the experts or their opinion? MS. JACKSON: We elicited the experts to get their expert judgment and opinions on some things. This is a list of the areas of expertise we had for the different experts. DR. APOSTOLAKIS: Now, I have another question that's not on the viewgraphs. You say here in the report that in addition to the empirical data, PNNL has used the flaw simulation model of R.R. Prodigal to estimate the numbers and sizes of flaws in the welds of the PVRUF and Shoreham vessels. To estimate the number and sizes. What kind of a code is that? What input do you put in there? DR. KRESS: That's an expert. DR. APOSTOLAKIS: It's another expert. MS. JACKSON: It's an expert. DR. KRESS: It's expert-based code. MS. JACKSON: Prodigal was done some years ago and it was another expert judgment, as you said. SPEAKER: It puts a flaw in and then has a probability distribution for whether that flaw then goes to the next bead in the weld, depending on what you're doing. MS. JACKSON: It simulates a weld, the given welding process. DR. APOSTOLAKIS: This is a different use of expert judgment. Now you're referring to density. I would like to have that, too. MS. JACKSON: Okay. And that was one of the comments we got. We need to provide some additional explanation on the Prodigal code in that report. DR. APOSTOLAKIS: The commitment by the NRC's Office of Research to develop a generic flaw distribution has been received positively by the NRC's Advisory Committee on Reactor Safeguards. We said that? DR. KRESS: Yes, we said it was a good idea. SPEAKER: With the Marshall flaw distribution. DR. KRESS: Yes. SPEAKER: Too long. SPEAKER: Yes. DR. KRESS: Yes. SPEAKER: Even if he's a Lord. DR. KRESS: In fact, I think we said if you could do that better, you could go a long way to solving the whole problem of PTS. DR. APOSTOLAKIS: A lot of questions have a depth for information. DR. KRESS: I see. You've got too many answers. MS. JACKSON: The next two slides have three definitions that were developed for the flaw distribution for this process, and for consistency, we developed a definition for the flaw. This was done through a consensus process with the experts and the definition is an unintentional discontinuity that has the potential to compromise the reactor vessel integrity and is in the vessel after pre-service inspection. [Tape stopped and restarted.] MS. JACKSON: We began to use the definition that was in ASME and some of the experts felt that was inappropriate. So this is what we came up. DR. KRESS: So if it's an intentional one, it doesn't count. MS. JACKSON: Right. If it's an intentional -- if the base metal dinged during travel or something like that. And two additional definitions were for a small flaw and a large flaw and that's additionally broken down into a small flaw in the weld metal and cladding and flaws in the base metal. We developed a list of -- SPEAKER: When you do that, it would be helpful if you gave us bead sizes then for each of the welds we're looking at. MS. JACKSON: Yes, because the bead size does vary so much with the different processes. SPEAKER: I couldn't back that out of the reports. SPEAKER: The bead size range, I think, is in the tables, in one of the tables, 5.1. MS. JACKSON: Or some of them. SPEAKER: Or some of them. We gave the range of bead sizes in there. It varied. SPEAKER: Everything is in 5.1, if you can find it. DR. APOSTOLAKIS: How come you don't name the experts? MS. JACKSON: We do have them now in the backup slides. We've listed -- DR. APOSTOLAKIS: It's here? MS. JACKSON: Yes. That was one of the difficult processes, because many of the people who were actually in reactor vessel fabrication are retired and some of them are no longer here. So that was kind of a torturous process. I almost called someone and then someone informed me that the person had just passed away. So I didn't make that phone call. SPEAKER: That's a hard call. MS. JACKSON: This is the list of issues. We tried to come up with a comprehensive list so that we would include every aspect of reactor vessel fabrication and all of the different areas where a potential flaw could be introduced during the fabrication process. DR. APOSTOLAKIS: This is now another interesting point here. Since you're planning to adopt distribution that's based on data using information from these elements, is there a possibility that you are considering too many issues and that may lead to too many factors multiplying things? In other words, you are going to such detail that you may start getting optimistic results. And were the experts asked? MS. JACKSON: Yes. I'm going to go -- DR. APOSTOLAKIS: And, also, I'm not sure you can treat these things as independent. MS. JACKSON: That was one of the things throughout as we learned through the process. We broke the characteristics down. Some of the characteristics, the experts were able to give us quantitative numbers. I'm going to explain how we got information from them regarding the introduction of a flaw, but in the end, we found out that most of these in this column and some in this column -- oh, I'm sorry. DR. APOSTOLAKIS: See, my point is it's the same like in a fault tree. You can go way down into detail and -- DR. KRESS: But in this case, it's like entropy, though. It just broadens the distribution, the more you put in it. DR. APOSTOLAKIS: No. DR. KRESS: I think it does. DR. APOSTOLAKIS: Because they multiply by fractions the various -- the statistical density. DR. KRESS: That broadens it, though. DR. APOSTOLAKIS: They haven't done any uncertainty yet. SPEAKER: They blur the resolution, but it should keep -- DR. APOSTOLAKIS: Keep it down, because now you have -- and because of filled versus short and then welder skill are multiplied independently. SPEAKER: As Debbie said, some of these are qualitative and some are quantitative. It's only the quantitative and actually in the left-hand column -- actually, more than half are qualitative, and I'll explain more in detail when I give my presentation. And when you look at the report, we used data wherever possible and there was quite a bit of data. We only used the expert judgment to fill in when there wasn't any data. DR. APOSTOLAKIS: Yes, but that was not really my question, because if you have a bunch of experts and you give them the issues, then they tend to focus on, okay, what does product four mean, is it important and so on. But if you look at the whole list, are these really independent characteristics, so that I really have to worry about welder skill independently of the field, independently of the repairs and so on? Am I introducing additional factors that will start pushing the density down in an artificial way? SPEAKER: When we did the real elicitations, we tried to condition every question so that you got an answer -- for example, we said if you're interested, say, in weld material, we talked about unrepaired weld material done with a manual weld and so on and so forth, and they say compare repair to non-repair. So things were conditioned and presumably, hopefully, the experts took account of this conditioning in their judgments and we never, in the table 5.1 and the results, we never multiplied -- we only multiplied by one thing. We didn't multiply two of the expert judgments, because we didn't have to do that. DR. APOSTOLAKIS: Did any one of the experts raise the issue of overlapping? Did they overlap much, some of them? MS. JACKSON: Some of them do, but in the backup slides, on slide 35, that is the beginning of the breakdown of the quantitative and the qualitative characteristics. So in the end, we're only using the numbers from the characteristics that we were able to get exact numbers from the experts for. Specifically, that was for the product form, the weld processes, the flaw mechanisms, the repairs, the flaw location and the flaw size. So the majority of the characteristics, we don't have any -- we're not going to use numbers. In the first few elicitation sessions, we did ask the experts to compare welder skill for the different weld processes and finally some of them said, you know, that is such a human factors related issue, you can't pinpoint a number, same for inspector skill. So some of the things, we're not going to use the numbers. It will be used when we do the uncertainty studies, but -- DR. APOSTOLAKIS: I thought this kind of discussion will be beneficial if you were to insert it into section four, where you discuss the issue. MS. JACKSON: Section four, okay. DR. APOSTOLAKIS: So the qualitative issues were not used. MS. JACKSON: Well, they -- I have a slide here. Let me -- SPEAKER: The qualitative issues were not used to generate any of the numbers. MS. JACKSON: If we can go to this, this is a distinction that we came up with between the two different types of characteristics. The quantitative are the ones where the experts were actually able to provide numerical comparisons and we will be able to get some records. We're still receiving some construction records for some of the vessels that PNNL has. And these qualitative characteristics, the experts were unable to meaningfully quantify or the records are unavailable. So in essence, we're not going to be able to get any numbers for those qualitative characteristics. DR. APOSTOLAKIS: What do you mean necessary records are unavailable? MS. JACKSON: Like for some of the things on welder skill, there's really no records for welder skill. There is no way for you to quantify that on the welder skill, because that varies so much from welder to welder, what day; if, five days before a Super Bowl, welder skill goes down. There's just so many factors, it's hard to pinpoint exact numbers to compare welder skill for a submerged arc versus an electroslag, the automatic processes. So that's what we meant when we said the necessary records are unavailable. DR. KRESS: Measure of welder skill is how many flaws there are. It's kind of strange trying to use the same measure to determine the outcome. MS. JACKSON: Let me put these two slides up. I think in your handouts, they are in a different format, but this shows them a little larger. This is the sheets that we used when we were going for the elicitation sessions with the experts. So I'm going to do this as an example. We asked them about the product form and the product form was broken down into four different parts; forgings, plate, the cladding and the weld metal. So we asked the experts, we said which one of these is most likely to have a flaw, using that definition of a flaw that I showed you earlier. So we asked them to write them and for this one, for example, say this was one, weld metal had more -- more likely to have a flaw, one, two, three and four. I'll just use that arbitrarily. And then after that, we asked them to compare, okay, so weld metal has the most number of flaws. Compare the weld metal to the cladding. Which would have more flaws, the weld metal to the plate, and the weld metal to the forgings. Then after that, we asked them -- we added this late, because initially flaw size was not in here, but we wanted to know would you have a variation of flaw size and what effect the fabricator would have. We had three major fabricators and Combustion Engineering, Babcock & Wilcox, and Chicago Bridgeni. Chicago Bridgeni, most of their vessels were partially field fabricated. So a lot of information that we had received before eliciting the experts for the field fabricated vessels were not fabricated as well as shop fabricated vessels, and we found that not to be true, and we actually finished the elicitation process because even though the vessels were finished in the field, a lot of them were partially shop fabricated and we actually had two experts who actually worked with Chicago Bridgeni and one person was the actual welding inspector and we found out that they compensated for a lot of the problems that you would have in the field with the environmental conditions and things like that. So that's how we got the numbers. We went through this for each one. We went through the weld processes. We had five different processes. This is one of the areas that was since revised and went through the elicitation process because a few experts told us that you need to break this down, because there were manual and automatic types of cladding, and we needed to break that down. So that was actually broken down further. You had many, many different types of flaw mechanisms for base metal and for weld metal. So we went through this and this is where we began to find problems with the experts. They said the weld procedures were -- a lot of them -- most of them were qualified, so the weld procedure should not have that much effect. So that's where we decided we had to break down the characteristics into the quantitative and qualitative, because we couldn't actually get numbers from the experts. The next two slides just state some of the conclusions from the expert judgment process. They feel that it can be done, but it's going to have a wide range of uncertainty. The flaw density of base metal is substantially less than for weld metal. The number that's been used for many years is that the base metal had ten percent of the flaws of weld metal and the basis for that was a phone call between Mike Mayfield, Spence Bush. Now we have some additional data, so we have a basis for that. Discontinuities in the cladding, that was another issue that we discussed with the experts. DR. KRESS: When you say weld metal, are you counting the region around the weld part or just the weld? MS. JACKSON: The heat affected zone? DR. KRESS: The heat affected zone. MS. JACKSON: No, the heat affected zone, that was a big problem because it still is actually base metal, but it's been affected by the heat from the weld. So we include it as base metal, but take into account that it has been altered. DR. KRESS: Okay. DR. APOSTOLAKIS: I guess you're not getting into the actual processing of the numbers. MS. JACKSON: Lee is going to go into that a little bit. DR. APOSTOLAKIS: So we should hold off. Are you going to use the methodology, slides on methodology? MR. ABRAMSON: Yes. MS. JACKSON: This is another slide, the last slide, with some of the conclusions from the experts. The issue with the large flaws, most of those should be detected NDE. This discusses two of the qualitative characteristics, the welder skill and the inspector skill, and the weld processes are an important factor in the introduction of flaws. SPEAKER: When you say NDE, do you mean -- MS. JACKSON: The UT. SPEAKER: The UT rather than the radiography. But not all the vessels were UT, right? MS. JACKSON: They were all -- final to being put into service, they were all given a 100 percent UT, we understand, from the experts, prior to being put into service, either before the actual shell courses were welded, but we do understand that there was 100 percent UT of the vessels prior to being put in service. It may not have been that -- SPEAKER: Even though it only went into the code at a somewhat later time then. MS. JACKSON: Right. And it wasn't the extent of the UT exams that are done now, because these were done so long ago, but there were UT exams done on the vessels. MR. HACKETT: I think, Debbie, if I could. This is Ed Hackett again. I think maybe the more correct statement would be to say that they all received 100 percent volumetric exams and maybe the volumetric was a combination of radiographic testing and ultrasound. But, of course, given the vintage of when some of these vessels were fabricated, I think UT was, as Debbie pointed out, nowhere near in the kind of state it's in today in terms of the level of advancement. Plates were typically UT'd. I know if it's a plate fabricated vessel, as part of the certification for basically nuclear QA coming out of Lukens, they would have probably UT examined the plates. The final composite structure of the reactor vessel, probably, you could say for sure it received 100 percent volumetric exam and that's probably, at that point, restricted to the welds and the adjacent areas. And that was more than likely, with the early ones, majority RT and then maybe supplemented by UT, because we are aware of some of the vessels and it was an issue with the BWRs that some of them did not receive those level of exams that we would have liked to have seen and that was -- the committee maybe remembers the issue, Debbie was involved in this and so was Lee, over the inspection effectiveness of the circumferential welds in the BWRs. And part of the issue there was that some of them had never actually received one that people would have agreed upon was a reasonable inspection. And then you got into the question probabilistically of how important is that anyway and the industry demonstrated fairly convincingly, for circ welds in BWRs, that it really didn't matter a whole lot, is what it boiled down to, because these things were pretty well made from the beginning, a lot of the things that Debbie and Lee have been discussing. So I think I would probably say that is -- MS. JACKSON: That was one of the issues the experts brought up. The NDE that was done during the period of the Marshall distribution, it basically picked up larger flaws. So just the quality of the NDE is a question when you talk about the final vessel inspections. SPEAKER: Prodigal gives you a fair amount of credit for the x-ray, the radiography. MS. JACKSON: Yes, it does. It does. I just have some concluding remarks regarding the whole process. We still have a lot of work left to do. The report that you have that was dated in July, that's under revision, and one is coming out at the end of the month and then it will be revised again periodically before the final one comes out at the end of next year. DR. APOSTOLAKIS: But you don't have access to the experts anymore. MS. JACKSON: No, I do. I still -- DR. APOSTOLAKIS: The ones that are alive. MS. JACKSON: -- discuss with them. That's an issue. DR. APOSTOLAKIS: So you do. So you maybe can get some more information. MS. JACKSON: Some of them -- yes, because I've had some -- we weren't able to get an expert who was from Lukens, but I do have a gentleman who retired from Lukens who does answer questions that I have occasionally. But some of the people just didn't want to participate or were retired, and they were retired and they didn't want to have to go through the process. Lee? DR. APOSTOLAKIS: So you did conclude that the expert judgment process is complex. MS. JACKSON: Successful and complex, yes. MR. ABRAMSON: I'm going to talk about the flaw distribution methodology, and that's in contrast to the -- this is what was intended. It was an upgrade to the Marshall distribution. The Marshall distribution essentially combined all the various factors and came out with a distribution. What we've done is to separate out these things and I'll talk about, of course, how it was done and there are certain advantages to this. There are essentially three elements to the distribution. One is the flaw densities and two is the volumes or areas, and each of these is plant-specific. Then we have the distribution of crack depth, given that there is a flaw. So it's combined into these three elements and this is -- we're treating this so far as generic. DR. KRESS: Are all flaws treated as cracks when they get around to doing the fracture mechanics? SPEAKER: I can give that one a go. I don't think that's fair to Lee. MR. ABRAMSON: Yes. SPEAKER: The report that Dr. Apostolakis was referring to, at least on PVRUF, there were distinctions made between volumetric and planar. So from the detailed NDE, where the defect was considered to have volumetric characteristics, those were screened out. So in other words, if you had, in the idealized sense, a spherical defect of some sort, that was not considered to participate. The others were just assumed to be crack-like. MR. ABRAMSON: This is an outline of the methodology. The ultimate goal of the distribution, at least as far as the computation is concerned, this is what will be input to the FAVOR code, is to get two numbers, the number of small flaws and the number of large flaws. We do everything for small and large, because the experts have told us and, actually, we know from our own experience and knowledge, but mostly the experts have told us that there is a difference between small and large flaws. There could be a difference. And it's defined in terms of the bead thickness. A small flaw is one such the crack depth is less than the bead thickness, the large is larger than the bead thickness. Now, everything is -- distribution is dependent on three characteristics of a weld. The first is the product form, the second is the weld process, and the third is the repair state. The weld process we considered was estimated manual welds, automatic welds, electroslag, when it's appropriate, and then for the cladding, single and multi-wire, and repair state is repaired and unrepaired. So the distribution we're going to get is going to be dependent upon the various combinations of these. Then what we have is we have a density of small and large flaws as a function of the product repair state and it's per unit volume or area. Areas we use for cladding. For unit area, everything else is -- the weld metal is per unit volume. And you do the obvious thing. We first have, we have N-sub-S, which is just the number of small flaws. This, of course, is going to be a sum of products. We have particularly density as a function of the various characteristics multiplied by the appropriate volume or area for that point. So that takes care of the first two parts, aspects, and the last one, of course, is the density of flaws and they're defined as G-sub-S, these are the CCDFs, the complimentary distribution functions. For small flows, the probability of the crack depth is larger than whatever the quantity of X is, define those. And then putting all this together, each GFC, this generalized flaw distribution, is the product of the number -- actually, that should be the sum of -- oh, each one is the product of the number of flaws in the corresponding crack depth distribution. So we have -- this is what I started out with in the first slide. This is a number larger, flaw larger than X, it's the number of small flaws multiplied by the probability of it being larger than X, given there's a flaw, and just pull all this together. Now, what we have in this -- and this has been revised based on additional input and commentary from PNNL. So this is not example -- this is not what you got here, but this is the latest that we have now. This is the PVRUF distribution, because it's based on the PVRUF examination which PNNL did, and specifically for the volumes and areas. So this is, as I said, the distribution, of course, is going to be plant-specific and the plant -- the vessel we're using is a PVRUF vessel here. Let me just go over this. First of all, here we have the combination of product form, weld process and repair state. So we have this for relevant ones here, first, for the weld metal and plate and, secondly, for the cladding. We divided this up here. Then here are the measured PVRUF volumes in terms of cubic meters for these quantities. There were no -- this is the plate manual repair. There were no repairs that we're aware of in the plate. That's why this is zero rather than a dash. And similarly, for the cladding. Again, here, there was no multi-wire in the cladding. So that's why the zero here. And this is unknown, they're still working on this, I believe. There's a possibility that they haven't finished that yet. So that this column here is the plant-specific, in this case, PVRUF-specific numbers. Now, the densities, that is based on the PVRUF data and also on Shoreham data. Now, this may very well probably -- I'm sure it will change, because the PVRUF data has been validated. The Shoreham data has not been validated. So as we go through with this, it will be revised, but this is our best estimate on it so far. I should also say, too, talking about best estimates, the numbers here are best estimate values. They are based on data, where it's available, because data trumps expert judgment all the time, as far as I'm concerned, and we only use the expert judgment when it's necessary and we don't have the available data. So we're just using the actual data, the point estimates, if you will. And then the expert judgment, and I can discuss this later, if you like, we're using essentially the median values. We're using a best estimate for the -- DR. APOSTOLAKIS: But eventually there's going to be number two. MR. ABRAMSON: That's right. No. Absolutely. We're very definitely going to use the uncertainties and for the data, we'll be able to have it statistically based. The expert judgment, I'm not quite sure how we're going to do it, because the experts differed a lot among themselves. So we have variability, even when we use their best estimates, but we also elicited low values and high values for everything that we elicited. So we do have a lot of information that we can use to construct an uncertainty distribution, and we certainly are going to do that. DR. APOSTOLAKIS: Was the Marshall distribution based on expert judgment? I don't know. MR. ABRAMSON: Yes. My understanding of it is yes. Very much -- I think it was expert judgment and, of course, the available data at the time. That's right, definitely. DR. APOSTOLAKIS: You make the observation here that the density of flaws in the PVRUF and Shoreham vessels is significantly greater than predicted by a Marshall distribution. So I guess that's an indication that the experts were optimistic. Is that observation going to affect anything you're doing? MR. ABRAMSON: Depends on ultimate -- I mean, affect it, all of this is going to be input into the FAVOR code, which will ultimately calculate a probability of vessel failure. DR. APOSTOLAKIS: I understand that. But regarding the density, is it possible that your own experts will be optimistic just as those who helped the Lord? MR. ABRAMSON: Well, it's certainly possible. We did not ask any of them for density numbers. All of these are based on data. DR. APOSTOLAKIS: You're modifying them. MR. ABRAMSON: We're modifying it, that's right. DR. APOSTOLAKIS: So those factors -- MR. ABRAMSON: It's possible. Well, it certainly is possible, but -- DR. APOSTOLAKIS: I mean, there is no way you can take this into the ratio, I suppose. I don't know. MR. ABRAMSON: You have to look at the whole process. When we elicited the experts, we not just elicited the opinion. Matter of fact, in a sense, that was the least time spent on that. We wanted to know their rationale for all of this and in the report itself there's going to be a much more fuller summary of the rationales for all of this. There was also a significant amount of disagreement among the experts and so on. So the only thing I can say is -- and there was certainly significant uncertainty and insofar as the uncertainty is going to affect the answer, that will certainly be reflected in it. In some cases, it won't matter. DR. APOSTOLAKIS: Speaking of uncertainty, I have a couple of comments on the report. You have used, in this calculation, as we just said, the mid value of the range of the medians. MR. ABRAMSON: Essentially. Or the median of the mid values. However you want to look at it. DR. APOSTOLAKIS: Median of the mid values. Now, I hope you're not going to define medians and high values and low values when you actually do your uncertainty analysis. I think the accepted way of doing it now is to actually have the distribution of each expert, put them all on the same plot, like NUREG-1150 did or the Shack report did -- not this Shack -- it's S. Shack -- and you select a point on the abscissa and you go up and you find all the experts take the mean, and that will give you a distribution of the fraction because of the expert assessments, or you can analyze it in a different way and there is a long discussion in the appendix of that seismic report. If you want to single out the variability -- the expert-to-expert variability, I don't know what you're going to do with it when you go to FAVOR, but maybe that would be an additional insight. But what I think -- and the whole idea behind all this -- this is the idea of equal weights. You are giving equal weights to the expert distributions because, as you make a point here on page 14, the ensuing discussion served to ensure a common understanding of the issues and the data. Since you had this feedback, then there is no reason really for you to give different weights from different experts, which is really -- MR. ABRAMSON: We have no intention of doing that. Absolutely not. DR. APOSTOLAKIS: But I think you should give equal weight to their distribution, not to the -- don't take the medians and add them up and divide by 17. See the difference? MR. ABRAMSON: I'm not sure that a distribution has any meaning here, because all we're asking is low, mid and high values. I don't see that -- it doesn't make any sense, to me, to -- DR. APOSTOLAKIS: You would have to make some assumption regarding the distribution. I mean, is it a lot -- normally, these things are -- MR. ABRAMSON: I don't think so. I don't think it has any meaning. All we did is we asked -- when we asked the experts for the low, mid and high values and we went through a training session, I think they all understood what we were asking. The mid values, of course, are the approximately median and a low value is one such that there's only a five percent chance, in their judgment, that you could be lower than that, and a high value is only a five percent chance you could be above that. DR. APOSTOLAKIS: Yes, but the fact that you don't have that piece of information probably doesn't justify adding the medians and dividing by 17. MR. ABRAMSON: I'm not adding the medians. I don't -- DR. APOSTOLAKIS: All I'm saying is in the future, if you do that, it will not be consistent with what the community thinks. Now, you don't have the information of the distribution between low, medium and high, but maybe you can put something there and speculate and then see how the summation comes up. I mean, you will have to do something anyway, because you don't have sufficient information. MR. ABRAMSON: I know. DR. APOSTOLAKIS: All I'm saying is there are two major studies, 1150 and the other one, the senior seismic hazard analysis committee report, which really spent a lot of time on these issues. They both recommend that when you are reasonably satisfied that the experts deserve equal weight, then you do what NUREG-1150 did. You have the variable, you put the distributions, and then you go up each point and you add up the probabilities of what the experts gave you and find the value, and that gives you the composite uncertainty. And there are other ways you can analyze it, too, but this is the accepted way. This is just a suggestion for the future that you may want to consider, because you're on the right track. I mean, you had this discussion of the issues and assuring a common understanding. Then you can say because of that, this is what we're going to do. Let's see. Now, for these purposes here, taking the mid value is just a representative example. MR. ABRAMSON: We're just trying to get a ballpark estimate at this point, that's right. DR. APOSTOLAKIS: Okay. I guess that's it for the time being. MR. HACKETT: This is Ed Hackett. I'd like to add a comment on what Professor Apostolakis mentioned on the density, so as not to cause undue alarm. Several factors come into play there. The issue with saying this distribution has produced a much higher density of flaws than Marshall, first off, shouldn't be surprising, because what you're seeing is advancement in the state-of-the-art of the NDE. Then you could direct your attention to the boxes over to the bottom right on Lee's chart there and that's kind of illustrative right there. You look at the number of small flaws and you see this 22,000 number and then you get down to large flaws, which are getting closer to the category of what would participate, as Terry would put it, if you were looking at FAVOR probabilistically in a PTS type transient. It's going to be a much, much reduced number. So the fact that you're seeing, which is mainly focused at the clad-base metal interface or in the weld metal, is not an alarming thing. It is one of the things I'd just like to leave everybody with. DR. APOSTOLAKIS: I think it would be helpful and useful to have these comments in the report, because this statement is hanging there. MR. HACKETT: That's one of the reasons I brought it up, because it has tended to alarm some people and it's really not the case. Most of those flaws are not going to -- the vast majority of that number there that's got 22,000 is not going to participate significantly in response to a PTS transient. MS. JACKSON: I think in one of the documents that we're going to send you, you'll see that a lot of the flaws are just very, very small and they have no interest, no interest at all. MR. ABRAMSON: The details are going to be given in the report and these densities are based where they were applicable, and, in many cases, they were based on data from the PVRUF, both from the Shoreham and the PVRUF flaws. And when they weren't, we augmented it with expert judgment. SPEAKER: Well, I mean, let's be specific. The welds are based on data, the others are based on expert judgment, right? MR. ABRAMSON: Let's take a look. Well, there's also a question of repair and non-repair. I think, yes, I would say the welds were the expert judgment, where the -- SPEAKER: The repair is probably an expert judgment. MR. ABRAMSON: Where the expert judgment was used was -- it was in the plate, that's right. DR. APOSTOLAKIS: And this is the expert judgment -- MR. ABRAMSON: Now, the plate -- DR. APOSTOLAKIS: The 17 experts? MR. ABRAMSON: Yes, that's what I mean. The expert judgment, modified. That's right. They do not have very much plate data, but they are getting some. So this will be replaced by the plate data once we get it, and the cladding, also, I think, was used to some extent in the expert judgment. And then, of course, to fill this out, we just took these estimated densities by the measured volumes and multiplied and that's where these came out. Now, there were a very large number of small flaws, but we fully expect that they really are going to contribute essentially nothing or very close to nothing when it comes down to the fracture mechanics in the FAVOR. The ones that, of course, will contribute will be the large flaws. Now, we divided this table into two parts. The bottom half is the cladding and there large flaws can be most of the thickness of the cladding, which is six to eight millimeters. So, again, we feel that that will probably not contribute at all once it goes through the fracture mechanics. So the ones that will contribute will be the large flaws here and, again, we emphasize, this is just a preliminary estimate base that we have now. A vast majority of these were from the weld metal manual, repaired, and repairs are manual. And this is what we've learned from the experts, that repairs are much more likely than non-repair for metal to have flaws in them. So that's what is driving this. And we do have data on this, as well. I think this was based on data because there were some repaired regions here, like we see here. DR. APOSTOLAKIS: So the density of large flaws is 96. MR. ABRAMSON: No. The number, this is the number of flaws. This is the estimated number of large flaws in the entire -- in the PVRUF vessel, the part of it's subject to PTS. That's the estimated number. A total of 96 large flaws in the valve line. DR. APOSTOLAKIS: So what will be the input? MR. ABRAMSON: Into FAVOR? DR. APOSTOLAKIS: Yes. Ninety-six? MR. ABRAMSON: The number will be 96. Of course, it will be distributed to location, and Terry will go into this in detail. But if we used this, if we ran FAVOR tomorrow, we would say, yes, you start with a total of 96 flaws in the valve line region. DR. APOSTOLAKIS: So you start with 96 flaws. MR. ABRAMSON: Right, exactly. Of all sizes, I should say. This is the total number of large flaws. And you would apply the distribution, which I'm coming to, to get the specific sizes of those. DR. APOSTOLAKIS: Now, if I go back to the Maryland paper on uncertainty, that figure six, it says flaws exhausted. What does that mean? They will do it for each of the 96? MR. ABRAMSON: Yes. DR. APOSTOLAKIS: Each of the 96. Why? I mean, they have a distribution, don't they? I don't understand that. Anyway, we'll discuss that when the time comes. Flaws exhausted, you do it for every single one? You're going to take the probability that there is a flaw there and the distribution of the size and just do it? I don't understand what it means to exhaust the flaws. You're given the total number, you have a certain volume, right? SPEAKER: You're talking about in the context of the University of Maryland paper, flaws exhausted. What that means is each vessel, let's say, has 96 flaws, if that's what the case is. You calculate the probability of fracture for each one of those flaws and then the probability of fracture for the entire vessel is kind of a summation process. DR. APOSTOLAKIS: How do they differ? SPEAKER: Well, flaw number one, you're going to first sample it to find the size of it, and it may be in a different location. DR. APOSTOLAKIS: Each flaw may have a different size. SPEAKER: Yes. As well as be located at a different part of the belt line region. DR. APOSTOLAKIS: All right. SPEAKER: As well as be located at a different location through the wall. DR. APOSTOLAKIS: Anyway, we'll discuss that in November. DR. KRESS: And if you get enough samples, we'll just sample 96, you sample thousands to cover that. SPEAKER: However many flaws are in the vessel, that's how many you sample. DR. APOSTOLAKIS: See, if you postulate that you have 96, then you have to do it, right? But I don't know. That's new to me. DR. KRESS: I would have thought -- DR. APOSTOLAKIS: You're postulating that there are 96, no matter what, and now you worry about where they are and what the distribution of the size is. DR. KRESS: Yes, but if you just take one flaw and then fix its location and size by sampling, it seems to me like 96 samples is not enough. You have to -- you don't cover the map that way. DR. APOSTOLAKIS: I guess that's why it's important to understand what sampling means. Is it from the aliatory -- is it epistemic, aliatory, how do they come together, but I guess we'll have another subcommittee meeting on this. All right. Back to you. SPEAKER: Maybe a point that's not clear for Professor Apostolakis' question. Of course, you're going to be doing many vessels, perhaps a million vessels, each with the 96 flaws. DR. KRESS: That's what I'm -- SPEAKER: Each one of the vessels has a certain number of flaws and you're doing many, many vessels. DR. KRESS: That covers many vessels, yes. DR. APOSTOLAKIS: You select the vessel. DR. KRESS: It's the way you phrase it. MR. ABRAMSON: As I said before, this is also a modification. To show that I meant what I said, I'm going to modify it right now. Actually, this was a slide taken from the presentation we made in August, but subsequent to that, we've modified it and as I said, the current thing is going to appear in the report, which is going to be out, I guess, in a couple of weeks or so. Where it's going to be modified is that this -- the large density, this is -- DR. APOSTOLAKIS: I don't think it matters. MR. ABRAMSON: -- 700, densities. The numbers -- this becomes 40, the number was 40 here, so the total becomes 66. So it's somewhat less than this. Don't rely on this as far as -- and it may be modified -- it's a new table and, also, since the FAVOR runs are not going to start for a number of months, the numbers that we put into it, as we get more information from PNNL, we certainly are going to modify the inputs for FAVOR. So that may change it further. But right now, it's somewhat less than 66, rather than 96. SPEAKER: Which is certainly different than 2,581. MS. JACKSON: Right. MR. ABRAMSON: That's right. It keeps going down apparently. Now, the final part of this is the -- this is CCDF for the large and small flaws and here is what we're using right now, what's available right now. This is based on the large and small flaws that were observed by PNNL. END TAPE 2, SIDE 1. TAPE 2, SIDE 2 FOLLOWS:. BEGIN TAPE 2, SIDE 2: Most of these came from Shoreham, which has not been validated, and some of them, maybe about a third or so, came from PVRUF, which has been validated. But I put them all together and we get this distribution, empirical distribution, which is based on something like 64 total flaws all together, which, to my way of looking at it, is remarkably smooth. This has not been smoothed, by the way. We just connected up the points. DR. APOSTOLAKIS: So this is large flaws anywhere. MR. ABRAMSON: That's right. Large flaws -- well, in the weld metal, that's right. Repaired, non-repaired material, we just threw them all together. That's right. And the assumption we're making, working assumption we're making right now is that this is a legitimate thing to do. We can combine flaws from all different kinds of weld metal and so on made under different welding conditions and, in other words, a large flaw is a large flaw, as far as this is concerned. It doesn't matter what material it was in as far as the crack size distribution is concerned. So this gives us the power of doing that. That's how we're planning to use it at this present time. And there's a -- DR. APOSTOLAKIS: So ten percent chance of having a flaw greater than ten millimeters. Wow. MR. ABRAMSON: That's what the data showed. I mean, this is based on the data, that's right. This is based on the data. Ten percent of the large flaws were -- that's right, exactly. Which isn't a very large -- remember, George, this is -- we're talking about maybe six flaws all together. DR. APOSTOLAKIS: How many? MR. ABRAMSON: We're talking about maybe six flaws all together, but that's how it's coming out. DR. APOSTOLAKIS: So if the process was faulty and there is a large flaw, then probability that it's really large is not negligible. What saves you is that you don't have too many of those. MR. ABRAMSON: And, of course, there is a significant amount of uncertainty in this. DR. APOSTOLAKIS: The process. MR. ABRAMSON: A significant amount of uncertainty in this distribution and when we do the final analysis, that will be reflected in that. DR. KRESS: Is that for the base metal? MR. ABRAMSON: It's for flaws found everywhere. Actually, I don't think we have any flaws in the base metal because they didn't inspect any of that yet. DR. KRESS: Okay. MR. ABRAMSON: This is just flaws in the weld material. MS. JACKSON: A small area. MR. ABRAMSON: Only a small area. DR. KRESS: That's why the distribution goes below five millimeters. MR. ABRAMSON: That's right, yes. DR. KRESS: Because it's bead size rather than -- MR. ABRAMSON: Bead size, right. We did that definition. Exactly, that's right. MR. HACKETT: I guess the other comment I would add -- this is Ed Hackett -- is this is not -- I think Lee stated this earlier. This is also not addressing location. So it could be that even out of the six, in all the greatest likelihood, they're not located on the surface, in which case you may not have any participation at all, depending on where these flaws are located. SPEAKER: How does this compare with what you find when you do UT inspections in the field? How many one-inch long cracks have you found? MR. HACKETT: This is Ed Hackett, again. I know there may be some others in here who could comment on this, too. My understanding is nothing in that range has been found, that I'm aware of. Bob Hardy is here. MR. ABRAMSON: We're predicting six per vessel. MR. HACKETT: I think what you're looking at is the statistics of the process and then, also, we have not gotten into -- and Lee and Debbie haven't included this -- how good are the inspections versus what was done for PVRUF and Shoreham. Obviously, these are laboratory conditions and they're able to destructively verify what's there and what isn't. Of course, you can't do that in the field. The NDE is better than it's ever been. But I don't believe -- maybe others in the room can comment. I'm not aware of hearing anything in that kind of size range that's come from a field inspection that would be in a surface location. I think there have been isolated cases where larger flaws, like on the order of multiple millimeters, have been located at different points in the depth or maybe towards the outer surface, but I'm not aware of any. I don't know if you are, Debbie. MS. JACKSON: No. MR. HACKETT: Not in field inspections. MS. JACKSON: On the large flaws that we've been finding in the PVRUF and Shoreham are in the repaired area. There was a large one that we found in Shoreham that's about 30 millimeters, but it hasn't been validated. So we don't know. According to proximity rules, if it's a cluster of many small flaws, but the largest one found so far in PVRUF was 17 millimeters. MR. HACKETT: I would also add, though, Bill, you're right in that if we do enough of these and we're right about what we're doing here in the lab, eventually we should find these things. I think it's just a question of the statistics of the process and how good is the field NDE. MS. JACKSON: Right. MR. HARDIES: This is Bob Hardies, from Baltimore Gas & Electric Company. The largest flaw so far that's been validated, the 17 millimeters, was a cluster of small volumetric things. So really everything so far that's been destructively examined that's been larger than ten millimeters are really little porosity clusters. MS. JACKSON: Right. MR. ABRAMSON: Three of those, and here are 14, 21, and 32, these are from Shoreham data, which has not yet been validated. Also, these large flaws bigger than ten, three of them -- some of them were repaired, but others were non-repaired. We had -- again, this is not validated. It's 21 and 32 came from non-repaired material. Again, this is all subject to possible revision once they validate the data. And this is the CCDF for small flaws and this, I believe, is based only on the PVRUF, I believe. This is a lot choppier, but, again, this is what the data show at the present time. Again, I repeat that we don't expect the small flaws are going to contribute in any significant way to vessel failure. So this is of interest, but it's not really going to affect the bottom line as far as PTS is concerned. Now, how is this going to be used in the FAVOR code? There's a little bit more detail here. First of all, we have large flaws and small flaws and we have weld material and plate material. We don't expect the cladding to contribute anything significantly, although certainly we will put it in, but we don't expect it to contribute anything very significantly. And what will the -- what the actual input will be, we'll take the total number of large flaws, in this case, it's the revised number of 66, and then we'll apply that distribution to it and come up with the specific X-sub-I, those are the crack depths. So we'll take these 66 flaws, 66 large flaws in the weld material, a certain number in the weld material, whatever the number is, and a certain number in the plate material, whatever that total number is, and then we'll just assign numbers from the large flaw distribution. These will then be a set of numbers, a set of crack depths, and this is the weld large flaw and so on. And similarly for small flaws. So the input to PVRUF will be the specific; that is, specific in terms of their crack depth. That will be the input to PVRUF and then FAVOR, and then FAVOR will take it from there, locate them and so on. DR. APOSTOLAKIS: This will be both the aliatory and epistemic component. MR. ABRAMSON: I don't know if that is here. DR. APOSTOLAKIS: You have a distribution. MR. ABRAMSON: We have a distribution. DR. APOSTOLAKIS: That would reflect the aliatory and if you have many distributions, then epistemic. MR. ABRAMSON: Okay. For any -- that's right. How we're going to do the uncertainty analysis, that's right. In effect, we could do -- we'll make draws from those distributions, correct. That's right. DR. APOSTOLAKIS: So this would have both. MR. ABRAMSON: Yes. We'll certainly reflect all of the uncertainty, absolutely. SPEAKER: Again, I think that this is something that we'll need to talk to you guys about at the subcommittee meeting, because I think depending on how you view the problem, even though you can talk about aliatory components leading to observed variability, let's say, in samples or in vessels, when you lock down on a vessel now, say, you're hypothesizing a vessel with certain characteristics and I think it's arguable whether the number of cracks, for example, is aliatory or you could, in principal, find them and characterize them, which is a function of how this is being used in the model. So that's, again, worth, I think, talking about when we get together. DR. APOSTOLAKIS: Okay. See, the problem is that if you were talking about certain conditions which are from all different plants, then, of course, it's aliatory because you pick one plant. SPEAKER: That's right. DR. APOSTOLAKIS: Now, if you have one, though, that distribution becomes subjective. SPEAKER: That's right. That's how we're viewing it right now. DR. APOSTOLAKIS: But the problem is even if you pick one and you find, say, ten flaws, they will probably have different lengths, and if you don't have the aliatory element, then you will probably assume that all of them are of the same length. SPEAKER: Again, this process, as I understand it, is going to say you pick a location -- you effectively, although it doesn't literally do this, you're going to be picking a particular flaw with certain characteristics and those characteristics will include not only the characteristics of the flaw itself, but the properties in the neighborhood of the flaw, and that's knowable, in principal. DR. APOSTOLAKIS: Okay. We'll discuss that. SPEAKER: And, George, we would never assign the same length to every one of those. DR. APOSTOLAKIS: See, that's the fundamental distinction between the two, that if you have an aliatory component, you allow for this randomness. But as Nathan says, if I understand, will you know enough about this particular vessel so that you eliminate the random element. You know the conditions and so on and this and that, will you have only epistemic. SPEAKER: The CCDF, this thing, this distribution is strictly aliatory. DR. APOSTOLAKIS: That's what I thought. For a particular vessel, it may not -- SPEAKER: We're going to be sampling using that distribution. It's how we use that sample in the calculation that is the point that we're talking about. There is certainly variability in the flaw sizes if you look across the population of flaws. How you use that uncertainty -- this is the plant to plant variability versus a single plant issue that we look at in the PRA side, and I see it as the same thing. Once we start fixing on a particular location of a particular vessel, and, again, this is all hypothesized, once you've done that hypothesis, that's what FAVOR is doing, given that now, is there really going to be that kind of variability that you're talking about. And that is where I think -- we have made certain assumptions in the white paper which try to bring these things out explicitly. This is why we're saying that this particular issue is aliatory, this is epistemic, and I think that would be a good basis to go through the paper. DR. APOSTOLAKIS: But that would not apply to K. SPEAKER: Right. That argument does not apply to K. That's why we said in the paper now we think there is an aliatory component that needs to be addressed separately from the things that you're talking about, because there is the model issue. DR. APOSTOLAKIS: If you can walk us through a particular calculation with all these observations, I think that will be very helpful. SPEAKER: One thing, again, I need to point out. I think we've been working through this as part of the overall PTS analysis and I don't know that we are fixed right now on the approach that's going to be everlasting that way. It's evolving, we're discussing these things. We will talk to you about where we are, of course, at the time that we meet. But things certainly can change. I think we've had a lot of discussions on these specific issues and how to address them and we do need to walk you through how we're looking at it now. MR. GUNTER: Paul Gunter, Nuclear Information Service. Noting the number of small flaws that you've noted, I'm wondering if it's too quick of a judgment to eliminate them as participating in a PTS event. So could you just give me a quick idea of how you can make that blanket statement that that many flaws and -- SPEAKER: I'm making that statement based on what I heard about the likely effects when you put this through the fracture mechanics code and everything like that, that small flaws will just contribute very, very little, if at all, to the probability of vessel failure. And, actually, I'm not the person -- you need somebody who can maybe speak more eloquently about that. MR. DIXON: Terry Dixon, again, from Oak Ridge. All of the flaws will be input into the FAVOR code. The small flaws, as well as the large flaws. Small flaws will be in the analysis and as much as they contribute, they contribute. But, I mean, we know certain things just about fracture mechanics. We know that probably a flaw below four millimeters would never contribute, but it will be in there. Essentially, it will be part of the bookkeeping, but we anticipate that it will contribute very, very little. So it will be in the fracture mechanics analysis. It won't be culled out. MR. ABRAMSON: And just some concluding remarks about the generalized flow distribution. What it does here is it combines three areas, three elements, the densities, which is generic, that would be the flaw distributions. That's right. The densities are generic in the sense that they are not plant-specific. They are certainly product form specific. They are certainly weld process specific and they are repair state specific, but they don't depend on the particular plant that we're talking about. So in that sense, it's generic. Crack depth distributions, as I indicated, are generic, and the plant specific will, of course, have to be the specific volumes and areas of the weld metal and the base material in the plant and how much of that was repaired, how much of that was not repaired, and the weld process and so on. All of them are very specific about that plant. And the generic inputs are based on all available data and where we don't have the available data, we have to fill in, then we use the expert judgment from this panel of 17. So that's the general structure of the generalized flow distribution, as we have it now. That's the end of my presentation, if you have any questions. SPEAKER: You make the comment in the report that this thing agrees reasonably well with the Prodigal predictions. I just wonder what -- MR. ABRAMSON: I didn't make that comment. I'm not familiar with the Prodigal. MS. JACKSON: That was some work that PNNL has done before the PVRUF data was validated. So we've made some changes to that. But it was the data from PVRUF and Shoreham was put into the Prodigal and the predictions came out pretty close to what came off of Prodigal. That's one of the things we're going to put in the repot, comparisons of the PVRUF and the Shoreham. SPEAKER: I think it's safe to say, Debbie, that we're also planning to use -- or we don't have data to use Prodigal runs, as well as expert judgment. DR. APOSTOLAKIS: See, Prodigal is expert judgment. That's what confuses me all the time when I see that. SPEAKER: It's a different kind of expert judgment. SPEAKER: George, it's different expert judgment. The questions are very different and Prodigal -- I mean, you need certain inputs into the Prodigal. The Prodigal does model very explicitly the physical process of welding and creating flaws and how they would propagate. MS. JACKSON: And the same with Prodigal. The Prodigal doesn't deal with base metals. So when we get into the base metal issue, we can't use Prodigal. It only deals with weld. SPEAKER: I just wondered. These numbers seem to be floating around so much and I assume that depends on whether you're multiplying by the right weld volumes times the densities or -- MS. JACKSON: That was another thing, because initially we had had a different -- I was just concentrating on the weld volume in the belt line area, that's all. Not every other thing, the belt line. SPEAKER: Every other weld. MS. JACKSON: Right. And then we just recently got some construction records from PVRUF. So we found some of the numbers were a little different from what PNNL had. So hopefully we'll be able to get more information on the construction records from the fabricators themselves, that's what we're hoping to do. SPEAKER: It's comforting to find numbers that converge. When I see numbers that go from 2,581 to 90 to 66. MS. JACKSON: Right. Some of those were due to operator error, also, with the calculators at some point. SPEAKER: I guess we can start with Shaw's presentation. MR. MALLICK: I am Shaw Mallick, the Materials Handling Branch, and I will be providing a bit on probabilistic fracture mechanics within the PTS project. A brief outline is we're going to go provide one of the major technical areas, the progress made in all those technical areas, and some concluding remarks. Here are the six technical areas we are currently working on. You already have heard about the fabrication flaw distribution and there will be presentations on distribution, fracture toughness, improved irradiation involvement, and the computer code. So this will be a more explicit presentation. I will briefly discuss these ones. I'm not sure if I should go and tell you a little more on that, that you already have for over an hour. So I will skip that part of the presentation. DR. APOSTOLAKIS: I wish you didn't say statistical representation. Presentation of the uncertainties. MR. MALLICK: Okay. SPEAKER: Well, but this report is statistical. DR. APOSTOLAKIS: It shouldn't be. SPEAKER: Well, there is the Oak Ridge report, which is statistical. Whether it should be or shouldn't be. I would like to go over the fabrication, number six, which is the fracture toughness distribution. The objective here is to provide initiation of fracture toughness based on expanded ASTME-399, the standard type of data, and using statistical methods. And just as background, our latest revision was developed based on '70s and '80s toughness data and they were -- not only that, those data were put through an ad hoc distribution based on lower bound curve. The Research staff is Mark Kirk, myself and Nathan Su, in PRA area, and our contractors at Oak Ridge, as well as University of Maryland, and we are also getting some help from EPRI and a contractor PEI, Phoenix Engineering Associate, Professor Marge Natisha, who used to be at University of Maryland earlier. Briefly describing the progress made, we will hear that in about 45 minutes worth of presentation on that in the later afternoon. Searched and collected additional data and almost doubled the rate and based on those data, set the distribution for both different parameters and those distributions for initiation of fracture toughness K1C, as well as the K1A. And one thing in that report that's missing was uncertainty in the normalizing parameter RTNDT. That is being looked at separately. And University of Maryland is assisting in separating those into epistemic, as well as aliatory uncertainty, as well as effect of material variability and model uncertainties. And we expect to have completion by November. DR. APOSTOLAKIS: So the variable distribution is aliatory. MR. MALLICK: Yes. DR. APOSTOLAKIS: And then you have three parameters, A, B, C, each one being a complex function of delta RTNDT. MR. MALLICK: RTNDT. DR. APOSTOLAKIS: RTNDT now will have epistemic and aliatory itself? MR. MALLICK: Yes. SPEAKER: If someone will explain to me again. I still have problems with whether I'm following a curve or I'm walking up and down this whole distribution, and I assume we'll talk about that. MR. MALLICK: There will be discussion on that this afternoon. DR. APOSTOLAKIS: Are you going to have any expert elicitation exercises in addition to what Lee did? MR. MALLICK: In the flaw distribution area -- DR. APOSTOLAKIS: You are saying here that Maryland and EPRI are assisting in model uncertainty. How are you going to assess the model uncertainty? MR. MALLICK: They are going through the root cause diagram, going through what are the basic parameters building up to the model uncertainty and deciding what are the uncertainties in those areas. DR. APOSTOLAKIS: Yes, but there is a model someplace that is not in a good shape. Somehow you have to evaluate the uncertainties associated with the predictions of this model. MR. MALLICK: Yes. DR. APOSTOLAKIS: How are you going to do that? SPEAKER: Let me try that a different way. Short answer is between us on the staff and University of Maryland and Oak Ridge, but the question that you're getting to is the how good of a model is RTNDT at predicting what the -- if we're assuming truth of the situations, we want to get to the fracture toughness and we get there by using RTNDT as an index, how good is that as a model. We have never addressed that explicitly before and as you mentioned, there are both aliatory and epistemic components to that. That is going to be addressed -- I guess I can back up and say this is another area that could have easily lended itself to expert elicitation. I think what we're looking at is running up against resource limitations on being able to do that. So what we're doing is trying to do that as a group between the staff and, in this case, University of Maryland and Oak Ridge. DR. APOSTOLAKIS: Internal experts. SPEAKER: Right. DR. APOSTOLAKIS: But you will do it. SPEAKER: Yes, absolutely. DR. APOSTOLAKIS: That seismic -- is Lee here? SPEAKER: Yes. DR. APOSTOLAKIS: That seismic report gets you way out of this, because it defines two ways, two major ways for doing an analysis using the technical integrator or the technical facilitator integrator, and depending on the significance of the issue, you may go with the technical integrator, which is a less formal way of eliciting judgments and I think that's what they have just described. But as for the other stuff that you just presented, you really did the tier five, because it was bigger, broader and so on. So I think there is a lot if information there that will help you. There are two volumes and -- I don't know. Do you know which volume I'm referring to? SPEAKER: Yes. DR. APOSTOLAKIS: Okay. Because the technical integrator approach was used without this for Diablo Canyon, we were told at the time, and it worked very well. Everybody liked it very much. You didn't have to go out of your way to bring experts and fly them over to Albuquerque, usually, and do these things. SPEAKER: We did a lot with video conferencing. DR. APOSTOLAKIS: So there is some merit to that. You know, if you give something a name, it's automatically more respectable. MR. MALLICK: The next area we are looking at is embrittlement correlation development and the objective here is to revise the predicted shift in RTNDT using up-to-date data, as well as the statistical data, and not only that, we are also trying to -- in the process to revise the Reg Guide 1.99, which two of the three -- there will be a three document draft developed and we want to have consistency with that guide, as well. Then they become part of the rule, as well as a guide, going in parallel and they are addressing the same issues. Currently, we're looking at the correlation for Reg Guide 1.99, and it's based on earlier data. Again, we have at least three times more data now on embrittlement correlation than we had at that time of the data set. And this is Mark Kirk and Carolyn Fairbanks, and the contractor for the NRC side is Modeling and Computing Associates, which is Ernie Leeson. Oak Ridge National Lab is Randy Nanstadt and his group, as well as University of Maryland is, again, helping us. SPEAKER: What is PEAI? MR. MALLICK: It's the Phoenix Engineering Associates Incorporated. Progress made in this case. We have a mean correlation. End of August -- end of July, sorry, we have a mean correlation. DR. APOSTOLAKIS: What is a mean correlation? MR. MALLICK: Mean is best estimate correlation and we are trying to -- the next step is to characterize. DR. APOSTOLAKIS: So much educating to do. So the uncertainties characterize using the approach that Debbie described. MR. MALLICK: Yes. SPEAKER: That's correct. DR. APOSTOLAKIS: So among us. MR. MALLICK: After lunch, we'll have some more discussion on that. SPEAKER: This is one that I think it's fair to say an expert elicitation might have been a benefit here. DR. APOSTOLAKIS: Again, you don't have to limit yourself to the -- SPEAKER: The formal process. DR. APOSTOLAKIS: -- inside people. I mean, you don't have to have a very formal process and still consult with outside experts. Sometimes even a phone call. It's better to have information than not to have it. SPEAKER: This has actually been the case with this one, because this actually, in terms of -- the mean correlation that was developed by the work of Ernie Leeson and Bob Odette principally was sort of vetted out even in the 1998 timeframe. SPEAKER: But when you get an ASTM, you're essentially getting a certain advantage of opinions. SPEAKER: And then ASTME-10 committee has had a lot of discussion, influence, et cetera, on some of the direction where that's going. So that's been vetted at least among industry groups and consensus codes and standards folks, too. DR. APOSTOLAKIS: Please don't call it mean. MR. MALLICK: Best estimate. DR. APOSTOLAKIS: Just nothing. There is no such thing as best estimate either. That's okay. Best estimate is better than mean. SPEAKER: Best guess. MR. MALLICK: Both in Maryland, the correlation analyzes the fracture toughness and the specific material, so we can see the solution to the input, and these activities are using industry data to come up with the distribution in terms of distribution for copper, nickel and phosphorous. Also, it is to get the local variability. For the weld case, we have four PTS plants. In this, we have something like 15 weld heats, with two nickel addition, as well as 16 plate heats, and the work is virtually internal. Doug Kornoski, Tammy Samples, and Lea Berser, as well as the industry to get their data, a lot of data from the industry. For the weld case, we have some heat distribution already. They are essentially normal. And we also have local variability. Welds are presented using distribution of copper and nickel, as well as normal distribution for phosphorous. In the case of plates, the data set is somewhat limited. So data is limited for the heats in the PTS plants. So chemistry was taken as heat estimate and we didn't have as good a distribution as we had for the weld material, but the plates are much more uniformly fabricated and things like that. So they were much less as it would be in this case, the effect of variability, that is. So, again, plates, we have limited data we obtained and we need to develop a solution on that as well. SPEAKER: By looking at this variation, are you going to change the margin type terms that you would usually use in a Reg Guide 1.99? MR. MALLICK: They will go as a -- the distribution will go in the analysis. We probably do not have a margin. SPEAKER: You'll replace the margin with this distribution. MR. MALLICK: Yes. The next major area we are working on is the neutron fluence calculations and our objective for this activity is to determine an up-to-date end of life fuels map for the plants, all the four plants we are looking at, using currently available cycle by cycle data of the fuel loading, as well as the plant data and also to have some kind of estimate for uncertainty in the fluence calculation, as well. And we are using draft dosimetry guide 10.53, I think this will be coming soon, as well as corresponding NUREG report. That staff is Billy Jones and we're getting help from Brookhaven National Lab on that. Plants on-line so far, all the three plants, Oconee-1, Palisades and Calvert Cliffs have been analyzed. We also had analyzed Robinson, but it's not in the running. So we are replacing it with Beaver Valley and we are just receiving the plant data from Beaver Valley, we have to look at to what extent we have to perform analysis on that. And Brookhaven has performed very defined grids for actual circumferential, as well as the radial direction. For example, here is the example given for Oconee, Palisades and Calvert, actually is 218, and the corresponding circumferential is 60 nodes. Similarly, we have a very refined grid going in. Now, Brookhaven also has calculated some kind of uncertainty in the fluence calculation and for each of these three plants, one sigma in fluence is about three percent of the mean value. And we are internally looking at do we need to perform some kind of modeling interaction among these various fluence parameters, such as vessel damage or nuclear cross-section, they are the major contributor for the uncertainty. So we're going to go look at the interaction between them and that may have some effect on this number of 13 percent answer. SPEAKER: Your comment on the non-linear interaction of parameters, you mention the core inlet temperature. Is that a strong parameter? MR. MALLICK: Those parameters are -- it's five percent of the mean or something like that is contributing toward that. But I can find out more on that. SPEAKER: That's the inlet. MR. MALLICK: Yes. SPEAKER: Okay. I will ask. In looking at these parameters, have you asked yourself are there any parameters -- core inlet, I guess, doesn't do it, but core outlet might -- any parameters that might be significantly changed as a result of things like power upgrades and so on? Is there anything in here, for example, that might be dependent on flow rates? MR. HACKETT: I'll try and take that one. This is Ed Hackett. We haven't' gotten to that level of refinement, Bob, but that's a good point. Among other things that haven't really been considered here that may come into play in the future, that would be one, power upgrades. Another thing would be the change in the neutron spectra relative to higher burn-up fuels or MOX fuel possibly. SPEAKER: It's really a shame. You play the game with your hands tied behind your back and then somebody comes along with an innovative idea and suddenly all of your data is kind of -- it's not all that great anymore, and it's your fault. MR. HACKETT: It seems like that's what happens at times. SPEAKER: Just from the analysis that you've done, how well do these sort of refined calculations match the calculations that the plants used to estimate their fluences? MR. MALLICK: They are very much similar, I would think so, but their details are not that - they have not done calculations or it's not as refined. But there is not that much difference, I would think so. SPEAKER: Okay. So that even though you're doing a more refined calculation, there's nothing to indicate that the plant calculations are unreasonable or unconservative. SPEAKER: But if they use a less dense grid, then they get less peaking, don't they? I mean, their integrals are the same or roughly the same. So you will show higher peaks in general than they will. MR. MALLICK: Probably so, yes. SPEAKER: I guess -- I'm trying to think of the right way to come back at that one. Bill posed the question of which way would this go. I think this is a level of refinement that's beyond what most folks would have submitted, well beyond what most folks would have submitted on the PTS rule. And what they would have assumed there is look at the maximum asmuthal fluence and assume that that applied all around the belt line. That's what was historically done before. Palisades was the first time, when we did the Palisades PTS evaluation, this would have been vintage '96-'97, that people -- that they first got into a plant-specific fluence map. And then what you're looking at is the integration of that around the core and that always acts in their favor, related to what they had done previously. SPEAKER: Because you have a huge -- SPEAKER: Right. SPEAKER: And everybody else just took that peak all the way around. SPEAKER: Exactly. Now, Bob is getting to the point of how well that was modeled at the peak, and I guess I don't have the wherewithal to come at that one without Lambrose or somebody like that being here. I think what was done is they would capture, however the capture it, the peak asmuthal fluence and then apply that fluence around the belt line. SPEAKER: Okay. SPEAKER: So they could tolerate a fair amount of change and still be conservative, in all likelihood. SPEAKER: I'm thinking about axial now, and that's where all the structure is, or a lot of it. SPEAKER: Good point. MR. MALLICK: The next major activity that integrates all the work together is the PFM code, which is being revised and implemented. This objective is to implement the refined PFM methodology as well as up-to-date materials data into the code and make it consistent with current PRA, as well as thermal hydraulics output data, as well as methodology. And myself, Nathan and Lea Berser, and Oak Ridge, contractor, Oak Ridge National Lab, Terry Dixon, who is integrating everything together, and University of Maryland in terms of uncertainties and all those things will be brought into this program. Brief conclusion here, concluding remarks. The analysis models are being finalized, such as embrittlement correlation, fracture toughness distributions, and flaw distributions. Then we are also going to -- based on these finalized models, we're going to do some scoping studies with reality doing some, but we are going to do a formal scoping study on the particular plant, such as Oconee. The application for the first plant at Oconee has started and PRA, as well as thermal hydraulic area, but PFM analysis to start soon on the scoping analysis. But once we have finalized the whole model, actual work on the complete analysis will start in the March timeframe, we have modified other FAVOR code. And just to comment, additional primary sources are being used to build rigorous uncertainty model for the key variables. SPEAKER: Well, I congratulate the staff. Despite the best efforts of the subcommittee, they've been right on schedule. We'll take a break now for lunch, and be ready to start at 1:00. [Recess.] END TAPE 2, SIDE 2. TAPE 3, SIDE A SPEAKER: [In progress] -- the embrittlement trend curves, and Mr. Kirk is going to give us the discussion. DR. KRESS: Captain Kirk? SPEAKER: Captain Kirk. DR. SEALE: Shall we beam him up or beam him down? MR. KIRK: That's why going into the Navy was never an option, because I figured I might have some luck with the career up to the level of captain. DR. SEALE: Oh, there you go. DR. KRESS: Then that would be it. MR. KIRK: Then nobody would return your calls. SPEAKER: With great foresight, he has put his uncertainty analysis on the last view-graph. DR. KRESS: That's a good idea. He knows what he's doing. MR. KIRK: Okay. I've got to reverse the order of my slides, because I have the second presentation first. SPEAKER: Well, the question is will we notice the difference? MR. KIRK: Well, I don't know. How much did you eat for lunch? Oh, here we go. Okay. That works. Okay. The topic of the current presentation is revision of the delta-T-30. That's the shift in the 30-foot-pound sharpie transition temperature embrittlement trend curves. My name is Mark Kirk. I work at Hackett's branch. This information sees two applications. One, of course, is the project that we're here to talk about today and revision of the PTS screening criteria, but the project that actually has generated the information you're going to see here is another project that we're working on on revision to Reg. Guide 1.99. It will be Revision No. 3 when it finally comes out, and of course, the application of that document is in both a PTS assessment methodology where plant operators calculate what their reference temperature for PTS is, it then compares to the screening criteria, but it also gets applied in the calculation of heat-up and cool-down curves. So, in the development of this information, we had those sort of dual applications in mind. Now, the reg. guide itself will include information and guidance on things that are not needed for the PTS re-evaluation. I've listed here sort of the -- this is the high-level discretization of the reg. guide. There is the transition shift embrittlement trend curve. There is the uncertainty analysis of that trend curve. There is the through-wall attenuation function, because all of these -- all these transition shifts that we'll be focusing mostly on here are calculated from surveillance capsule data, and of course, that's bolted right to the ID of the vessel. So, they're essentially at ID fluence, ID spectrum. That then needs to be attenuated through the wall, so that's another thing going into the reg. guide. We have treatment procedures for plant-specific data and how we adjust for surveillance or not, and then we also have upper-shelf energy trend curves and uncertainty analysis. Of those, these last two just don't come into the PTS re-evaluation at all. All the other parts do. The work to date and what the rest of the presentation reflects is that the major focus has been up here in getting the embrittlement trend curve, and that's sort of where we are today. The work is basically completed. We're in the process of writing the technical basis document, and that's an activity that's going to be going on among the NRC staff for probably the next three to six months. The embrittlement trend curve just became available, or I should say the current manifestation of the embrittlement trend curve. The uncertainty analysis has just begun to be performed, and the current view on that is that will be done sometime in the November to December timeframe, although I can share with you some early results from that. We're just starting to have some discussions regarding what the proper through-wall attenuation function is, and similarly on treatment of plant-specific data, although again, you know, just to give you a perspective on this, the thought is -- and I'll discuss this in more detail as we go through the presentation -- that probably as we move to Rev. 3, we're going to be moving away from giving as much credit to the plant-specific information and instead going with more of the generic chemistry-based trends. SPEAKER: When you say upper-shelf energy, is that the JR curve? MR. KIRK: No. Upper-shelf energy -- SPEAKER: -- means upper-shelf energy. MR. KIRK: Yes. SPEAKER: What about the JR curve work? Is that going to be updated, the JR curve correlation? MR. KIRK: Ed, help me out here. I wasn't aware JR curves were in the reg. guide. SPEAKER: They're not in the reg. guide, but there's a JR correlation that has a through-wall attenuation. SPEAKER: It's a JR-curve-based attenuation, and the answer is no plans for that right now, based on the fact that it was the equivalent margins analyses that were done with the industry to show that basically there wasn't a need for it. There are -- my understanding, although I haven't paid attention to this a whole lot -- I think it was addressed in Ernie and Bob's NUREG in 1998 in terms of a refinement, but that refinement didn't indicate that there was a need to re-do any of that work. So, the short answer is no, we aren't going to be pursuing that. SPEAKER: Just to make sure I've got this right, Ed, what goes in the reg. guide is an equation that predicts the drop in upper-shelf energy. SPEAKER: Right. SPEAKER: Wouldn't have affect the heat-up/cool-down analyses? SPEAKER: It does, or it could. I guess I'd put it that way. The difference is, I guess, based on the equivalent margins analyses, that it wasn't -- didn't look like it was going to be any effect on plant safety for even below -- significantly below 50-foot-pounds, which is where the cut-off was in the 10 CFR 50, Appendix G. SPEAKER: Okay. DR. KRESS: You are going to share with us what your perception of a plant PRA-consistent uncertainty framework is. MR. KIRK: Yes, sir. DR. KRESS: Is that right? SPEAKER: That's the last view-graph. MR. KIRK: And I'll defer all the tricky questions to Nathan on that one. DR. KRESS: Okay. MR. KIRK: Since I see he's sitting there smiling at me. Okay. Just as a point of reference, the trend curve in the current reg. guide that we currently regulation to is shown here. You've got your sharpie shift is a product of two different factors, a chemistry factor and a fluence factor, and absorbed into the chemistry factor are all the dependencies of copper and nickel and product form. Those are the ones that are explicitly called out in the table that gives you the chemistry factor numbers. When you see it in a few slides, the form of the equation has increased considerably in complexity over the years. Where we started with this, to develop a new shift curve, is that we've got considerably more data than we had that Reg. Guide 1.99, Rev. 2 was based on. Rev. 2 was based on something a little bit shy of 200 surveillance data points. We're now up almost to 800. That's the database that Ernie and Joyce used to calibrate the model. The other thing that's changed considerably in the past, I guess now, decade-and-a-half is our understanding of the underlying physical causes of the embrittlement mechanisms, and that has also played a role in the correlation development. So, the -- just a few notes on the modeling considerations that were used in developing this correlation: It's -- for anybody that's looked at embrittlement correlations, it's pretty obvious it's going to be a non-linear fit, and as a consequence, some of the fit coefficients are based on the entire data set, like, say, the copper coefficients and the coefficients on nickel, whereas some are based only on subsets, like there's a term in there that expresses the influence of flux at low times, and obviously, you can't -- or at long times, I'm sorry. Obviously, you can't calibrate that with short-time data. So, data subsets have been used in the fit. Some of our metrics for what a good fit has is, of course, minimum standard error, and Ernie and Joyce did a lot of looking at the residuals. Of course, they were looking for an average residual, zero balance plus and minus residuals, but perhaps the main focus in model development was looking at trends of residuals where, of course, residual is just the difference between what the model is predicting and what the original data said, that there's no trend in the residuals with either a modeled variable or an un-modeled variable. If there's a trend with a modeled variable, then that suggests you don't have the functional form right. If there's a trend with an un-modeled variable, well, that's a suggestion that perhaps you should include it in your model. In terms of statistical significance tests that we apply, our understanding coming from the physics and working with folks like Bob Odette gives us some guidance in how we run our statistical significance tests. For example, if we have a variable like phosphorous where we might not understand all the in's and out's of phosphorous damage in a radiation environment, but we do understand enough to say, well, if there is a phosphorous effect, it's going to go in the positive direction, that then suggests that you do a one-tailed test, whereas if you have an element or an indicator variable or whatever that you don't really know, then you'll be doing a two-tailed test on statistical significance. Also, the stability of the model was checked extensively. Since it's a non-linear model, there's not just one right answer, there's an infinity of potential answers. So, we check the stability of the fit coefficients relative to the initial estimates by just making a bunch of initial guesses and making sure that we always came out with the same coefficients at the end, and also, we checked the stability of the model relative to the data set used to do the calibration. The coefficients that actually came out were based on a calibration of -- came from a calibration that used all of the available data, but we wanted to make sure that the trend curve wasn't over-fit and wasn't just somehow specific to that data set. So, we ran a number of calibrations on data subsets to make sure that those coefficients came out statistically similar to the coefficients in the equation, where we used all the data, and indeed, they did. Just to give you some examples of the type of information that Ernie and Joyce were looking at as they developed this correlation -- and I think these are graphs you can probably better see on your hand-outs than in my overheads, because the print's kind of small, but the upper curves show the trend of both copper -- of shift with copper and shift with phosphorous, whereas the lower curves show the residual, the difference between what was predicted by the model and these measure data relative to the final model. And of course, you see what we just said was the criteria for having a successful model, that the residuals do, indeed, show no significant trend with the modeled variables, and indeed, if you look at the next slide, there are, of course, other variables that don't appear, that you won't find in the equation, like flux, specifically, and manganese, but there were reasons to suspect that these might be important factors. Of course, the justification for leaving them out is that you've got a model that has zero residual, a balance residual anyway, so there's no burning need to put these in at this time. As we got -- I should note, this is an effort in terms of -- when we go back in history, this is an effort that probably dates back to about 1992, where we let a contract with Modeling Computing Services to start looking at developing this correlation. They gave us a report in 1998, and we've been doing some refinements on that model ever since, some of the things, as we sort of came down to the 11th hour, some of the variables that we were considering. So, I should say -- I guess what I want to say is there were other variables, of course, like copper and nickel that were already in the correlation at this point, but recently we've been looking at a copper saturation effect, which you saw the empirical evidence of a couple slides ago, that once you get to a certain amount of copper, it no longer is damaging and the amount of shift saturates, phosphorous, which you saw, and interaction between flux time and fluence, which is to say that fluence isn't the only descriptor of irradiation damage. So, we needed to include other -- or potentially needed to include other terms. In looking at the data and in getting some new data, there was also revealed what came to be called a long-time effect, where the data points sort of at the end of our statistical database, above 97,000 hours, show a systematically higher shift than would be predicted by any of the models that we had, systematically higher shift on the order of 10 degrees Fahrenheit. And then there was also an effect that was discovered in the process of trying to find out what was going here of vessel fabricator, where it was discovered that, if you looked at the shifts in the plate data, those plates that were in CE-manufactured vessels had shifts that were systematically under-predicted by the model, whereas plates in non-CE-manufactured vessels had shifts that were systematically over-predicted by the model. I'm not going to delude you that we have any physical understanding, at least at this stage, of why the heck that is, because -- I'll say it before anybody else does -- 99 percent of those plates came from Lukens. Now, of course, that's not to say -- there are things that happen after the steel leaves the manufacturer's shop and at the fabricator. So, it's not completely implausible that something like that could be true, but our physical understanding of it right now is non-existence. There is, however, a very compelling body of statistical evidence that the effect is really there. As we got down to these more -- what I will call more nuancy effects than those of copper, nickel, and fluence, we felt it was important to impose a bit of rigor on ourselves in terms of thinking about, well, what of these should we let into the model and what of these should we leave on the table perhaps for next time. So, we developed at least a gating criteria with a lot of fuzzy words in here to help calibrate ourselves. We said, well, we're trying to think about this both in terms of what the statistical argument is for inclusion or exclusion of a term, as well as what the physical -- how well understood the underlying physics are of the damage mechanism. So, in terms of statistical basis, we looked at the situation where we could have a strong statistical basis, greater than 95-percent confidence that we have a trend in the model that couldn't be attributed to a mis-interpretation of random error. You could have a weak amount of evidence or you could have something in between, and then for physical rationale, you could have a damage mechanism that's well accepted, like copper, for example, all the way down to something where you're sort of left scratching your head, and like I said, this is -- you know, I drew lines in there, but of course, in our minds, there weren't any hard lines drawn, but certainly if you had something that was a well-accepted rationale for the degradation mechanism and strong statistical basis, well, of course, you'd include it. If you had something that you couldn't see in the database and you didn't know why, you'd never see it anyway, but you would exclude it, and in between, you'd have to exercise engineering judgement, but we tried to draw this up to sort of guide our thinking. Now as it turned out, when we actually ran the statistics on the model, all the variables, or the effects, I should say, that are being considered lately -- and by lately, I mean within the last year -- came up very high in the statistical significance category. So, the physical rationale didn't enter much into it. I would like to focus, at least anecdotally on the next few slides -- there's been some concerns expressed both within the NRC and outside, within the industry. I should warp ahead to say that our current proposal, so that we can move forward and do the work that needs to come next, is that we suggest to Terry for inclusion in FAVOR a model that includes all of these terms. The rationale for making that suggestion right now is as follows: There are certain things that you -- in order to proceed, we need to have a model to proceed with. We can't do an uncertainty analysis until we have a model. We can't do a regulatory impact analysis until we have a model. We can't do any sensitivity studies until we have a model So, we felt it was important to suggest something with the recognition that, in doing all of these analyses and in further working on the technical basis document, we may find things that make us say, well, no, maybe not, maybe we don't want that in there. But certainly, in recommending this model to Terry in the PTS re-evaluation project, and as you can see by the fuzzy words in our matrix, we did give definite deference to statistical evidence over an existing physical rationale, and like I said, there has been some exception taken to that by both parties in the industry, as well as parties within the NRC, and I just wanted to suggest that that's not a bad engineering practice and, in fact, is fairly well-founded. Sort of the essence of engineering discovery is that we find out things by having field failures or by doing experiments, and we might not understand the physical rationale for why they're happening at all, but that never stopped anybody from coming up with a design curve and continuing to operate structures. This just happens to one of my personal favorites: In the 1860s, German railway axles were failing by the truckload, and a gentleman named Wohler did a very famous set of fatigue experiments where he developed what was, in fact, the first SN curve, showed endurance limits, and then those endurance limits were passed off to designers, who then designed their axles to be below them. Nevertheless, the physical understanding of the phenomenon of fatigue at the time was wrong. There were publications in esteemed scientific journals that said the metal crystallized, and so, it broke. That was obviously wrong, but it didn't stop the design process. Similarly, just another fun example, is that, in 1972, ASME developed an LEFM-based K1C curve that we have used in vessel integrity calculations since that time and, in fact, continue to use. Nevertheless, the circa 1972 physically-motivated prediction of the transition fracture phenomenon in foritic steels did pretty well close to the lower shelf, but as you got up off lower shelf, nobody understood the mechanism at the time enough to predict this very sharp upswing that was well-demonstrated by the data, but that didn't stop anybody from believing the statistical evidence over the physical model and moving on. So, having now spoken heavily in favor of empirical evidence, I should say that it is certainly not the staff's intention to go only with empirical evidence. Understanding the physics of what's going on is especially important in this field, because we find ourselves in the unfortunate but necessary position of always having to extrapolate our data. We never have data at the fluence or material conditions that we actually are trying to predict. So, we need to extrapolate all these trends, and that's why, in what you'll see coming out of the technical basis document, there is very definitely going to be a treatment of both the physics of irradiation damage as well as the statistical evidence of it. In terms of the correlation, I thought I'd just show the basic functional form. It's got three terms in it, one related to stable matrix damage, one to copper-rich precipitates, and then the long-time bias, and you can see on the screen the various input variables that go into each one. The stable matrix damage is a function of phosphorous, fluence, the product form, and the coolant temperature, whereas the copper-rich precipitate term is a function of copper, nickel, fluence, time, product form, and manufacturer, obviously a more complex relationship than we had previously. We've done a few calculations, just sort of a start of our regulatory impact assessment to see what changes we might experience in going from Reg. Guide 1.99, Rev. 2 to this new proposal, and like I said, this is very early information, but I just show it for your information. The graphs on the lefthand side of your screen show the change in shift with the -- if we go to the proposed model. So, here, positive values mean that the new model is predicting more shift than Reg. Guide 1.99, Rev. 2, negative is less, divided it up into PWRs and BWRs, obviously a lot of scatter between the two correlations, but on average, for the PWRs, those that didn't have -- and this all -- I'm sorry -- plotted versus the old Reg. Guide 1.99, Rev. 2 shift. For the PWRs, if there was -- if you had a material that was low-shift already, on average, it might get a little bit higher. If you had a lot of shift before, on average, it's going to get a little bit lower. The BWRs are higher by about 13 degrees Fahrenheit across the board. So, the mean shifts are somewhat higher, especially for the BWRs. I've also summarized in this table a comparison of the fit uncertainties, the new values coming out of the new correlation work by Ernie and Joyce, and then the values that are currently in the regulation, and you see that, for the welds, the uncertainty seems to be going down a little bit, but not a whole lot. Now, in terms of your previous question on a PRA-consistent uncertainty framework, this is where I'm wishing I was able to do the second presentation first and the first second, because I talk more about this in the second, but we're developing the uncertainty framework here using the same methodology as we've employed to characterize the RTNDT K1C uncertainty, which is the topic of my next presentation, regrettably. The steps in the process are basically that we've assembled the data and fit the curve, and that's what I've been talking about, and that was done by Modeling Computing Services and University of California, Santa Barbara, under contract to the NRC. We're now working at understanding the nature of the uncertainties and developing a framework for a mathematical model using a root cause diagram approach that has been developed by Dr. Nitishan at Phoenix Engineering, who is an EPRI contractor, and then that information is passed on to Professors Maderas and Moseley at University of Maryland, who term that sort of diagrammatic understanding and physical understanding into a mathematical model that then gets fed into favor. That process will probably be a little bit more well explained in my next presentation, but here is sort of the -- again, the diagrammatic representation of what will become a mathematical model in FAVOR, and I really don't want to get into the details here, unless anybody wants to drag me in, and then I guess I'll have to go, but what I want to do is to point out a couple things. This just shows the information flows from right to left on the diagram. The input variables are circled in yellow, and this is how the math would actually be represented into FAVOR. So, you'd have to know who the manufacturer was, is it a weld or a forging, what's the phosphorous, the coolant temperature, the nickel, the end-of-license fluence. You do all that and then you can use the new embrittlement trend curve to calculate a shift. You compare that shift with information that you might have from surveillance, decide if you're going to use the shift or the surveillance data, and come out with a predicted shift value. So, the points to make on this is that, one, the root cause diagram is, in fact, just an illustration of a mathematical model, and that mathematical model allows uncertainties to propagate through it from input variables to output, and then the third -- and I also noted here that this is the new embrittlement trend curve at node 14 here, which, of course, has model uncertainty in it, and perhaps the most important thing, from at least my understanding -- and I'm getting an education on this -- from a PRA perspective is to distinguish between types of uncertainties, namely aleatory and epistemic. This is the diagram that helps us to understand that. This shows the model uncertainty in the data that Eason, Wright, and Odette used to develop the embrittlement correlation. So, for any given -- we can sort of work it backwards, just so you can see. For any given sharpie shift is, of course, just a simple subtraction of a 30-foot-pound transition temperature, un-irradiated, and a 30-foot-pound transition temperature at some fluence, and that was determined from a TANH fit to a plot of sharpie V-notch energy versus test temperature, and then you can start to work it all backwards and it then gets down -- the sharpie V-notch energy, of course, gets down to very fundamental things like, well, what was the chemistry, what was the heat treatment, etcetera. I should very quickly point out, this isn't a model that ever gets mathematically run, but it helps us to understand the natures of the uncertainties involved, and Dr. Nitshan has color-coded it such that the epistemic contributors to uncertainty are showed with the brown slash marks, whereas the aleatory are shown with the solid brown coloring. And this is my interpretation, and this is, of course, subject to more of the expert judgements of those who know, but it sort of looks like the epistemic uncertainty -- the epistemic contribution has to do with things that are fairly well-controlled -- the test temperature, the notch acuity, the machine calibration, the test method, and so on. So, while there is clearly, in any delta-T-30 value, components of both aleatory and epistemic uncertainty, it would seem to me that the epistemic contributors to uncertainty -- as an old lab rat, I'd say these are fairly well controlled relative to some of the things in the solid brown boxes. So, one might come away from this understanding with the conclusion that, while delta-T-30 does include, in fact, both aleatory and epistemic components, perhaps it's mainly aleatory, although that's -- you know, that's just a poor man's interpretation of the diagram, but that's the purpose of putting this together, and that's sort of a use of this type of information, is to provide the materials understanding to the PRA people and provide them with a commentary that that they can understand to help make these sort of decisions. Just got a few slides left here. Treatment of surveillance data: Currently, we give credit for surveillance data in the form of a factor of two reduction on the uncertainty and the shift provided the surveillance data is deemed to be credible, and I don't think I want to go into discussion of that, but let's just say it's not always clear what credibility -- credibility, in general terms, means that the data are well-behaved, that you don't have something at 1E19th that's a shift of 200 and 2E19th that's a shift of only 50. That would not be a credible data set. But if you have at least two credible surveillance points, by our current regulations one would be permitted to reduce the uncertainty in the state of knowledge about the shift by a factor of two. There has never been any rigorous justification or documentation of why that factor reduction is appropriate. That's not to say -- I mean it's certainly completely appropriate to update your date of knowledge based on material or case-specific data. So, I don't ever want to say anything that says, well, we're not going to do that, because that's, in fact, the appropriate thing to do, but our current plan is just not well-based, and at this time, since that plan was developed, there's not been really any work to give us a better plan. The work that has been done has gone mostly on what you just saw, into development of the mean curve. So, the current proposal that's on the table is that the -- sort of the default condition for the shift for a particular plant or particular material condition will be calculated based on the chemistry and all the variables in the equation, you'll get a shift, you'll then compare the predicted shift to a measured shift, if you have it, from surveillance, and as long as it's -- you know, again, I'll say reasonably close, as long as it's, say, within plus or minus 2 sigma, one would use the shift predicted from the model that's based on 800-some data points, rather than adjusting that model-based shift to correspond to two measured data points. You know, again, that's the current proposal that's on the table. That proposal is, I suspect, going to be the subject of some fairly intense discussions among the staff in the coming three to six months, but you've got to start somewhere or you don't know what you're talking about. An even perhaps more interesting one is the through-wall attenuation question. Right now, in Reg. Guide 1.99, Rev. 2., we figure out what the fluence is at a particular thickness location from the ID-X, where X is measured in inches from the ID by taking the ID fluence and decaying it by this negative exponential with the .24 coefficient. Really, the only -- and I should say that there hasn't been a whole lot of work since this equation was developed that would give us a basis to do anything else. There have been a very few test reactor studies where basically a whole bunch of steel samples were machined, blocked together, and then irradiated, so it simulated like they were at different positions in the wall. There was one study done like that which we'll be looking at, and to my knowledge, that's -- I can't ever pronounce it -- the Gundrumagin vessel. Those are really the only data available that say anything to attenuation. There's also the question of what the appropriate damage -- radiation damage function is to use, should one be using DPA or fluence to attenuate through the vessel wall. So, there is some new information available that the staff will be looking at. There's not a whole lot, because quite frankly, it hasn't been an area of focus, but there is a very practical impact that we need to look at in that, with the old embrittlement trend curve, everything was a function of fluence. So, when you attenuated the fluence, you attenuated the shift in direct proportion, according to this relationship, whereas with the new equation, it's got terms -- with the new equation, there are two terms. There's a time term and there's a bias that don't depend on fluence at all. So, if you believe -- and now, this is a good question, and as I said, again, I'm sure it will be the focus of some interesting discussion over the next few months. If you believe that this is really attenuating fluence -- although when you look at Randall's basis document, you decide that it might not really be attenuating fluence. It's an engineering approximation. Anyway, if you attenuate the fluence in the new function according to that form and apply it only to the fluence, then you certainly don't attenuate that and you don't attenuate time, because time just marches boldly forward. Well, for some vessels, that's not going to matter at all, because they're at such a high fluence anyway, the contribution of that is nil, and so, you're giving up a fractional degree, but for things like BWRs that tend to be at lower fluence, it can be quite a significant impact. It's going to be very important to -- like I said, we don't have a lot of new information, but it's going to be very important to consider the regulatory impact of this on BWRs, especially for heat-up and cool-down, where we attenuate the quarter-T and three-quarter-T to do our calculations. For PWRs and PTS calculations, the recommendation that we've made to Terry right now is that, for right now, pending further thought and information, use the Reg. Guide, Rev. 2 function to attenuate the fluence in the new embrittlement trend curve, it's not so much a problem in the calculations that Terry is doing, because if a flaw is deeper into the vessel than an eighth of a T, it's not going to matter anyway. So, this plot shows the impact of that recommendation on the horizontal axis, is the old attenuation at an eighth of a T. So, this is how much less shift you had at an eighth of a T than at the ID using Reg. Guide 1.99, Rev. 2. This is how much less shift you have using the new correlation but the old attenuation function, and what you see is your have some situations, the heavy triangles or PTS plants -- the worst it gets is you might have had one material in one plant where it was previously attenuated by 15 degrees, now it's only attenuated by seven. Again, the focus here -- I don't know if this has come out earlier -- has been to get off the dime with the calculations and get Terry something to use, with the recognition that we might need to come back and change it later. It doesn't seem to be as significant an influence here as it could be, certainly in this case. For the reg. guide, it's going to be something that we have to very carefully consider, because the impacts can be quite incredible, up to 100 degrees Fahrenheit. And I think that's basically it, just a discussion of ongoing steps now. SPEAKER: Doing that -- is that basically equivalent to saying there's an aging effect that's independent of irradiation? MR. KIRK: Yes. SPEAKER: And have we seen that -- you know, except for when you dump a lot of philosophers into here, I mean is there any -- MR. KIRK: That's a good question. Professor Odette, in fact, just provided us with a report, which I understand includes some of that information, but that, I think, is one of the open questions that needs to be looked at. Of course, the difficulty being the availability of material that's been cooked for that amount of time is pretty low. My understanding of what Bob's told me on the phone -- and unfortunately, we just got the report last week and I haven't had a chance to go through the details -- is there is some information from hydro-cracker service of similar materials at somewhat higher temperatures, but you get into some pretty dicey cases of knowing when you're extrapolating beyond the bounds of where you should be extrapolating. So, that's an open question, and in fact, of all the terms in the equation -- and again, just a personal view -- for my money -- well, this is probably the one that's got people scratching their heads the most. It's like how the hell did that happen? Bad luck. I'm thinking that the procurement agent at CE was, well, perhaps not as nice to the steel mill folks as they were at the vendors, but that's just my theory. But this is the one -- this term in here seems to be the one that's the most theoretically contentious, because some of the physical theories seem pretty good, but getting the evidence to back them up in terms of what you just pointed out, long-time data, is just very hard to do. But as I pointed out by that graph, it has some very significant practical implications in the heat-up and cool-down mode. SPEAKER: Now, I assume that Ernie has scrubbed this looking for a phosphorous dependence, which would be the -- you know, everybody's first -- MR. KIRK: I'm sorry. Scrubbed the long-time? SPEAKER: Yeah. MR. KIRK: That's a good question. I honestly don't know for sure. That work sort of predated my involvement. But that would certainly be a good question to ask. I know he's scrubbed it every which way from Sunday, but I can't swear to you that he's specifically looked at that. You mean just looking for heavier incidents of tramp elements in those. SPEAKER: Right. Is there a reason an element like that would be the prime candidate for just an aging effect without irradiation? MR. KIRK: Yeah. Of course, the feeling is that's also showing up here. SPEAKER: Right. MR. KIRK: See, the thing is this got very evolutionary. This term came along first, in the historical development of the model. There was the so-called flux time term, and there was significant contention about that, and we looked and looked and found more data, and then this one popped up in trying to understand that. This one actually exists independently of this, because this is driven by data at low fluence, long-time, BWRs, is what's driving the existence of this term. But in collecting more data, we got -- of course, as time goes on, you get more long-time data, and we found that, beyond 100,000 hours, the data points beyond 100,000 hours were systematically under-predicted by the model on the order of 10 degrees Fahrenheit. SPEAKER: These are very low fluences for kind of an irradiation-assisted segregation, but -- MR. KIRK: True. Yeah, if you're looking for a synergistic effect, you might want more atoms going through it. So, we found this looking for that, and then, in saying, well, now, this really isn't making a lot of sense, what's going on, this one popped up. SPEAKER: That one's really tough. MR. KIRK: But like I said, I can say to you with confidence that -- I've worked enough with Ernie to know that, if he says they're statistically significant, they are, and the other thing that I perhaps should note is that the industry group, EPRI and Sam Rizinski, contracted with Dan Naman, who's a professor of statistics at Johns Hopkins University, to take an independent look at this, and Professor Naman came up with this quite independently of Ernie, because we weren't letting Ernie talk at that time, and Dan found it all by himself. So, it's really there. I mean it frustrates people, but it is, indeed, really there. But in terms of where we're going on from here, we're going the uncertainty analysis. Like I said, that just got started, and we were able to turn over the information to Dr. Natashan and Professor Medarez in August, so they've sort of just started on that, probably looking for seeing something out of that sometime in the November timeframe. We're working here on doing the regulatory impact analysis and also having discussions about how surveillance data should be treated, and of course, we're going to have to get Ernie involved in those discussions, discussions about through-wall attenuation, and we're in the process of drafting the tech basis document for review. And of course, the PTS project is going to be continually updated, you know, on where we're going, and we'll have to work with Shaw to see how that best slots in, but what we did, I guess it was basically last month, is gave Shaw and Terry our current best guess of, you know, okay, if you hold a gun to our heads and say give me something today, well, here you go, and what we've tried to do is not just say here you go but tried to identify the warts in it, so that nobody is misled that, well, you know, this is true for all time. Well, it might not be. But we also need to make very sure that we sync the information that's in the reg. guide with the information that's included in the PTS re-analysis, because of course, we want both of those to be self-consistent and supportive. Any questions on that? [No response.] MR. KIRK: Okay. Then my next -- should I go ahead? SPEAKER: Yeah. MR. KIRK: Okay. The next set of slides is on fracture toughness distributions and uncertainty analysis. What I'd like to work through with you is talk about our goal in doing this work and the folks that have participated in what's become a fairly extensive cooperative effort, talk about our approach, what new data we collected, the uncertainty framework, show you some of the current results, and then talk about where we're going next. As I just suggested, there have been quite a few people involved in this particular piece of work, and I think to very good effect, because we've got a diversity of experience and perspectives here that most projects have -- indeed, this is a fairly small-scale effort -- don't normally enjoy. I should say the goal here is to characterize toughness for input into FAVOR in a way that's consistent with current PRA methodologies, which is to say a proper treatment of uncertainties. At the NRC, I've sort of been coordinating this, and Shaw and Nathan have both been involved. At the University of Maryland, we've been working with Professor Medarez to do the uncertainty work. His graduate student is Faye Lee, and his associate is Allie Moseley. And at Oak Ridge, they've been involved in various aspects of this work, both in collecting the K1C data and developing a statistical curve, as well as more recently, in looking at RTNDT model uncertainty. That includes Paul Williams, Kenny Bowman, Terry Dixon, John Murkle, Richard Bass, and Randy Nanstead. And then we've also had significant support from EPRI. Stan Rizinski is the project sponsor there, and he's been kind enough to allow us to involve Marjorie Natashan of Phoenix Engineering, and she's been doing the root cause diagram work and interfacing directly with Professor Medarez. And what I'm presenting here is really the amalgamated work of all those folks. So, the goal I've already stated. The three boxes below the goal show you the process that we've gone through. We started off at Oak Ridge, and this probably goes over a year ago now, assembling all the available valid K1C and K1A data and developing a purely statistical fit to that. We then moved on and involved University of Maryland and PAI to establish sources of uncertainty using the root cause diagram analysis to allow us to distinguish epistemic from aleatory uncertainties and give us a procedure to treat both parameter and model uncertainties, and then, coming out of this, of course, our goal is a description of K1C and K1A with uncertainties that we can plug into FAVOR. This slide summarizes the work that was done by Oak Ridge, now something over a year ago. On the lefthand side, you have the K1C data; righthand side, K1A. The numbers in reverse video show you how the data set size increased relative to that which was used to establish the original K1C and K1A curve. So, originally, we had 171. We wound up with 254. The K1A database had a more substantial percentage increase. The black specks on each of the diagrams is, of course, the data itself. The red curves on your screen are the way we used to model the scatter in the data based on the ASME K1C curve and moving that up and down by a sigma, whereas the black curves are the new Oak Ridge model which is based on a Wible formulation, and the same thing are shown over here. One thing, just sort of looking at this and saying, well, so what, that you come away with is you come away with the immediate impression that the old scatter bounds that we used in FAVOR were too narrow, especially for K1A. The consequence of that, the effect on the calculated probability of vessel failure, of course, depends upon the transients considered. Terry did a nice little study of that probably a little bit less than a year ago now, found in some cases it mattered a whole lot, in some cases it doesn't matter quite so much, depending on if you have late re-pressurizations, whether arrest is important, and things like that. Of course, this all needs to be considered in the context of everything else that's going on. The uncertainty analysis -- we started off with the root cause analysis to identify the sources of uncertainties, appealed to a physical model, so that we could try to understand where the uncertainties came from and distinguish -- Dr. Natashan and Professor Medarez worked a lot together in terms of her trying to express the physical understanding and the test lab understanding of where these uncertainties come from to Professor Medarez, who was working on the mathematical model. So, they worked that out, developed a mathematical model, which then Professor Medarez and Terry Dixon have been working on to get it implemented into an actual FAVOR programming structure. The root cause diagrams -- and this is sort of like talking about the horse after it got out of the barn, because I've already done a couple of these. It's just a way to diagram mathematical relationship, show how uncertainties move from one place to the next, but I do want to point out that the big change in this way of doing things relative to the way we've coded uncertainties in FAVOR before is that here we input uncertainties and parameters back here and then propagate those into uncertainties and output variables in a way that's very systematic and critiqueable because you can see it and say, no, that box doesn't belong here, it belongs over there, rather than the margins being prescribed to the analysis a priori, which is exactly what we used to do. So, this is a very integrated and systematic approach, and it actually works very nicely when you need to get input from a whole lot of people in that you can lay it out and explain it to them and they can see where -- how the various pieces interact very easily. So, it's worked out, actually, quite well. Just to look at the diagram at its highest level, for K1C RTNDT, of course, at the end, we want to get out the uncertainty in K1C. Going into that is the uncertainty bounds on the fracture toughness data that I showed you previously coming out of the statistical analysis of the data, but of course, that's an index to an irradiated RTNDT value to position the data in temperature space. The RTNDT irradiated value itself is a function of both an un-irradiated value and a shift, and of course, there's a whole lot more that are in the detailed reports but aren't shown here. But again, similar to the last time, I do want to make a couple of points here about some of the new or significant features coming out of this analysis. This diagram is just an expansion upon the one I just showed you, and it even flows off on to other diagrams, but one point is that we've got a process that matches or models, I should say, the current regulatory framework for how we determine RTNDT irradiated, and we're putting this into the code, I should say, right for the first time. So, that's a good thing. We've got a statistical representation of toughness that I already told you about, and that plugs in here, and then, I guess the newest of the new things is a recognition that there is a -- I shouldn't use the word "systematic," because it's not always the same -- there's always a bias in RTNDT. It's just simply not the right value to use. I can illustrate that to you -- and I should say that's going to be taken account of in the calculations. I can illustrate that to you just by putting up data from two different heats of steel. This is an A533B plate, HSST plate, are two tested by Marsden back in '87 -- I'm sorry -- reported by Marsden, tested long before that. This was the basis of the original K1C curve. So, you've got the K1C data and a K1C curve indexed to RTNDT having absolutely no relationship to the data other than the RTNDT value, was determined from specimens cut from the same plate, and you see that, in this case, RTNDT does a pretty good job of putting the curve where you wanted it to go. You can look at other data sets, like the Midland-Beltline weld in the un-irradiated condition test by McCabe in '94 and find out that RTNDT, in this case, is not doing as good a job as you want it. This is not at all unexpected. In fact, it is expected, since RTNDT was designed to be a bounding, an upper bounding estimate of fracture toughness transition temperature. So, we expect this to be the case, but it's highly inconsistent with a PRA approach that's based on best estimates. We've got a parameter here that we use to figure out where we go into our K1C distribution that we know is always off, and it could be off anywhere from, say, zero degrees to 150 degrees, and some accounting needs to be taken of that. Now, how that's going to be done, I can't tell you, because we haven't quite figured that out yet, but will it be accounted for, I think I can state unequivocally, yes. We're still having some discussions between all of the parties that I mentioned before regarding what the correction function should be -- well, the correction function being the probability distribution that relates RTNDT to truth, however truth might be defined, and we're arguing about what truth is, so I'm hesitant to put a timeframe on that, and then -- that's perhaps a more sticky question, and then we're also having some discussions, mainly between Professor Medarez and the folks at Oak Ridge, regarding what the proper mathematical procedure is to create the correction once we know what truth is, and I'd be the wrong one to talk about that. But having said that, I think we're making progress. We seem to be -- I think we're converging. But we don't have an answer quite yet. And Bill looks like he wants to ask a question. SPEAKER: Well, I'm trying to figure out how I know truth when I see it. What do I need to know to know truth? MR. KIRK: I could make a suggestion. I think -- this is going to really reveal my biases. I think the data is truth. I mean you've got -- do you believe that linear elastic fracture toughness characterizes the fracture resistance of the material in an appropriate way for this calculation? If you can answer yes to that question, then you say, okay, well, then truth is my K1C data for a particular heat of steel, because that's what we need to characterize to FAVOR, is the fracture toughness of the material on a heat-by-heat basis. So, then, if you can agree with those things, then I think truth is some -- well, if truth is the data, then the data is there, and the measure of how untrue RTNDT is is just the distribution of -- for heat one of the steel, it was off by 5 degrees; for heat two of the steel, it was off by 100 degrees; for heat three of the steel, it was off by 50 degrees. SPEAKER: Now, was this RTNDT determined from a sharpie specimen of the same material as the K1C? MR. KIRK: Yes. SPEAKER: I'm not depending on a correlation to get RTNDT. MR. KIRK: No. All these RTNDTs are, for what it's worth, credible MB2331 RTNDTs determined on the same material, yes. SPEAKER: Okay. MR. KIRK: So, no, that's not in there making the situation worse. SPEAKER: Now, is it the same material seen under the same flux, the fluence? MR. KIRK: With very few exceptions, all of the RTNDTs are on un-irradiated materials. There is only -- END OF TAPE 3, SIDE A; BEGIN TAPE 3, SIDE B MR. KIRK: [In progress] -- four materials I think we have a real RTNDT value on in an irradiated condition, because quite frankly, most people don't irradiated NDT specimens. What I could tell you -- I don't have this graph with me, but the -- really, what we're arguing over, the distribution of the shifts, you know, what's the smallest shift to what's the lowest shift, or how wrong can wrong be, is always on the order of 125 to 150 degrees Fahrenheit. What we're arguing over -- and this is where the physics of it comes in -- what we're arguing over is where this is positioned, but what I can share with you is that we've made plots before of the various data points for all the un-irradiated materials, and of course, we've got a much larger number then that we do the irradiated. The irradiated seemed to follow very closely to the same trend, and I wouldn't -- I think the reason there's a difference here is it's a test procedure problem, and it's a stress state problem within the -- the differences in stress state between the sharpies and the NDTs and the fracture toughness. The irradiation really isn't changing that dynamic. I don't expect there to be a different distribution. I can't demonstrate that to you very convincingly with data, because I've only got four data points, but I don't really expect there to be a difference. But in answer to your question, I mean I think here, you know, we've sort of -- well, in doing these calculations, we premise truth on -- you know, that K1C is an appropriate failure criteria, you know, for this material under this application. If we're going to question that, well, Pandora's Box. For me, I think the data is truth, and we need to find out how far the RTNDT prediction is from the data. If we don't believe the data, we've got bigger problems. MR. HACKETT: This is Ed Hackett. I think I'd just like to add sort of a tone commentary here. A lot of this discussion sort of feels like we're running down RTNDT, and of course, that was the basis of a lot of good work that went into sections 3 and 11 of the ASME code by a lot of folks who preceded us. I think what Mark says is correct, but don't want to leave anyone with the impression, because we've said we don't maybe think it's a good indicator of the exact or more accurate behavior of what we think we might see in a vessel. However, it's worked pretty well for the ASME code in terms of demonstrating in a convincing way safety assessments of boilers and nuclear vessels and so on. Just don't want to leave anyone with the impression that that's a problem, that the current framework is a sound framework from that perspective. This would hopefully be an iteration on improving the accuracy. MR. KIRK: Yeah, and it works because it's been -- it's doing what it was designed to do. It was designed to be conservative, and lo and behold, it is, you know, good job, but that -- you know, again, my understanding, in working with Mohammed and Nathan is that that doesn't really fit very well into this approach, so we've got to do something to try to take this -- you know, this being what we understand it to be and what, in fact, it is and turn it into a best estimate in our simulations, or at least correct for the fact that it's not. I'm not sure if I'm saying that quite the right way. DR. KRESS: Well, you expect to do it on a heat-by-heat basis? MR. KIRK: Yeah, that's what you would be doing. DR. KRESS: And then have a series of curves, depending on the heat? MR. KIRK: No. DR. KRESS: You'd have one mean curve for all the heats? MR. KIRK: No, the idea would be, if you pick any of these correction functions, just for purpose of illustration, it doesn't matter which one, but you go through the simulation and you decide, for a particular region, I've got a particular set of material properties. In a particular sub-region, that set of material properties has a fluence associated with it. DR. KRESS: Right. MR. KIRK: I go through all the calculations and I get a RTNDT irradiated, and then I go into a hat and I pick up a number, and that's a number between zero and one, and based on what that number is -- say it's .6, and let's say I'm using this red one. I would then take that number and reduce it by 80 degrees Fahrenheit, but I might go through the simulation the next time, come up with exactly the same number here -- I'm sorry -- exactly the same estimate of irradiated RTNDT, go into my hat, and this time pick up a .2 and decide that I'm only going to reduce that number by 20. What we're saying is this is our best state of knowledge about how far off RTNDT could be, and since you don't have any other information, you don't have the fracture toughness data in this case, all you know is that it's off by somewhere between this and that, and that, of course, adds uncertainty to the analysis. It also -- well, depending upon what -- it adds uncertainty to the analysis, but it also adds a pretty hefty mean shift. DR. KRESS: Isn't that the same thing as drawing the mean line through all the data and putting a distribution around that line? MR. KIRK: I'm afraid I don't understand what you're saying. DR. KRESS: That's all right. MR. KIRK: Okay. Just to summarize, what we've completed so far is the statistical model of transition fracture toughness. At Oak Ridge, they collected the data and made a fit to that data. In the development of PRA uncertainty framework, we understood the current process that we use to calculate an irradiated RTNDT using the root cause diagram approach and develop mathematical models of that. Details of implementing those models in FAVOR were discussed and clarified between Mohammed and Terry, and ongoing work -- we're working on finalizing that mathematical model and resolving the issue that we've just been talking about for the past few minutes, the RTNDT bias, and also as ongoing work, we're still working on assembling input data to run all these models, and that's all I had prepared. Are there questions? SPEAKER: Does the uncertainty in RTNDT mean -- should you also go back -- the way you're accounting for this uncertainty -- should that also have been included when you did the fit to the K data? MR. KIRK: Okay. That's one of the questions we're considering under what the correction procedure is. One proposal was the way I described it, which is to go through, simulate an RTNDT irradiated in FAVOR, pick a correction value, and get a corrected RTNDT. Proposal 2, or 2(a) -- I've lost track -- is to do exactly what you said, which is essentially to apply this to the data and re-fit the data, take the consideration and the uncertainty outside of FAVOR and allow it to be treated as input data. DR. KRESS: I think that's what I was saying. MR. KIRK: Okay. I'm sorry. I didn't understand it that way. SPEAKER: It really puts it where it belongs, because you don't know what RTNDT is when you're measuring K. MR. KIRK: True. And I think, Mohammed, would it be true to say that's sort of the way the wind's blowing now? MR. MEDAREZ: I'm Mohammed Medarez from the University of Maryland. I think it's right. What we are trying to do now is -- Oak Ridge is using a methodology, a bootstrap methodology to shift the data by this correction, actually the 256 or so data points that we have, and basically shift it according to this curve that you have on the left. There about about four or five ways of doing that, and each of them have different implications. We are in the process of doing that, and also, my belief actually is that the two methodologies would yield the same answer, although we are seeing some differences, but I think we know what the differences are, why we are getting those differences. I agree, also, that it's cleaner to go and correct the data, as opposed to, as you mentioned, actually go back and calculate an RTNDT which is biased and then try to correct it afterwards, but we have to understand exactly the process here. We are not still there. I think it will be about a month or two. Next time, we should be able to propose a definitive process for computing this error here. MR. KIRK: Okay. Thank you. DR. KRESS: You know, among everything else that's here, I must say these materials guys have come up with the sexiest slides produced in the last year-and-a-half. SPEAKER: Break for 15 minutes. [Recess.] END OF TAPE 3, SIDE B; BEGIN TAPE 4, SIDE A MR. DIXON: The title of this presentation is the status of the FAVOR code development. I'm Terry Dixon, and I'd like to acknowledge Richard Bass and Paul Williams, two of my colleagues that work with me that helped me put this presentation together, and the intent here of this presentation is to describe the evolution of an advanced computational tool for reactor pressure vessel integrity evaluations, namely FAVOR, and basically, this presentation is sort of broken up into five different categories. The first one is going to talk about how FAVOR is applied in the PTS reevaluation. The second one is the integration of evolving technology into FAVOR, the FAVOR structure, PRA methodology, and the last one, which I'm sorry that Professor Apostolakis left -- the very thing he was talking about, kind of stepping through a calculation, was my intent here, assuming that we have time. Okay. Someone asked this morning or alluded to this morning, how would the results be used that comes out of FAVOR, and this is an attempt to sort of answer that question. So, application of FAVOR to this particular effort, PTS reevaluation, addresses the following two questions. Here's a graph that shows frequency of vessel failure as a function of effective full-power years. Now, the abscissa here could just as easily be RTNDT. It could be neutron fluence. In other words, you could have this, different variables, but most people can relate pretty well to effective full-power years. But anyway, the two things that will be addressed: at one time in the operating life does the frequency of vessel failure exceed an acceptable value, which currently, in the current regulations, is 5 times 10 to the minus 6. However, someone presented this morning that this number is probably going to change to 1 times 10 to the minus 6. DR. KRESS: Look what that does to you on the graph. MR. DIXON: Yes. It could be dramatic. Now, these curves, by the way, aren't -- these don't correspond to a particular plant. This is just an illustration. DR. KRESS: But it could be a plant. MR. DIXON: Obviously. And then the second question is how does the integration and application of the advanced technology affect the calculated result, and by that, what we're talking about here is -- say that, you know, you have a model and you do the analysis, and at some time in the operating life of the plant, say 32 years, shows that you -- that's how long you can operate your vessel and be in compliance with the screening criteria to come back -- if you improve your model, which is what we're trying to do -- this whole effort is to try to improve our computational models, and you re-do it and you get a reduced value, essentially what you've done is you have increased the time, the period of time that you can operate your vessel and still be in compliance with the screening criteria. DR. KRESS: I presume, with that improved model result, you make some guesses of what the changes would be in the various parts of your model to get a different result? I mean you kept everything the same, except you looked at the -- for example, the K1C, you probably made it less bounding and things like that? MR. DIXON: We haven't done too much of this yet, because as you've heard today, a lot of these models are still being developed, but there was a paper that was published. DR. KRESS: We have a copy of that. I remember it. MR. DIXON: That was an attempt, as of about two years, to do exactly what you're talking about. DR. KRESS: Just to see if it's worthwhile to continue. MR. DIXON: Yes. It was like taking several elements and saying, okay, if you change this to this, what's the effect, and then what's the cumulative effect, and that was sort of what kick-started this whole effort, that that study showed that there was a potential, at that time, for this type of -- in other words, to get additional time in compliance. DR. KRESS: If I were to look at the curve and it was the only information I had and if I were to really believe that the new acceptance criteria were going to be 1 times 10 to the minus 6, I might conclude that all this effort is not worthwhile, if that were the acceptance criteria, because you're not changing things much in a year or two. MR. DIXON: I couldn't say that until -- sometimes you got to go down that road to know. DR. KRESS: Yeah, you really do, I think. MR. DIXON: You know, I couldn't make that statement right now until we actually do this effort. DR. KRESS: But it seems like it's pretty important to pin down this acceptance criteria pretty early in the game. MR. DIXON: Right. But another thing that I would like to point out here -- and it's referring back to the question this morning. Notice, this is just one line here. So, you can think of this as being the mean value. Now, every time that you execute the FAVOR code, you get one point on this line. In other words, you execute the FAVOR code at a snapshot in the operating life of the vessel, in other words corresponding to a particular fluence map that -- you know, 15 years, 30 years, 60 years, whatever. So, you would run FAVOR at several times in the life of the plant, and actually, you would get a distribution. Now, this doesn't show that, this just shows a line, but actually, there is some uncertainty. We've propagated the uncertainty through the model. So, this line actually has a band around it. DR. KRESS: So, my question earlier on was, once you get that, what are you going to do with that? MR. DIXON: Well, that's a good question, and I don't know that we have that answer yet. I will just say that that kind of gets into interpretation and regulation. DR. KRESS: That's not your area. MR. DIXON: Right. I'm not real sure that anybody knows the answer to that just yet. The schedule has been sort of sliding, but the latest schedule decision is that, you know, the FAVOR code will be ready for reevaluation analysis by around March 1 of next year. Now, in the meantime, models are being finalized. You've heard discussion this morning about several of the models. Then these finalized models have to be implemented into the FAVOR code. Some of them are, some of them aren't, and in the meantime, there's going to be scoping studies performed specifically for Oconee, I believe it is, because as Dave Besette said this morning, the Oconee thermal hydraulics is essentially ready. I believe the PRA is close to ready. We need the flaw data that was discussed. So, all the input data, maybe not in a finalized form but at least enough for us to kind of start cranking some numbers. Also, there was some discussion this morning about kind of the history of FAVOR, how did it come about, and the development was initiated in the early 1990s by combining the best attributes of OCA and VISA with evolving technology. So, we show OCA-1, OCA-2, OCA-P -- all of these were developed at ORNL in the early 1980s, and VISA was -- in the same timeframe, was developed primarily -- first at the NRC and then later at PNL, and then there was lessons learned from IPTS and a lot of lessons learned from the Yankee Rowe experience, and Mike Mayfield was in Oak Ridge at one time for a meeting, and I remember him making the statement that the NRC was no longer going to support two codes, VISA and OCA-P. He said I want a completely new code, I want a new name, and I want it to combine the best attributes of -- basically to do this. So, that's what we've attempted to do. There was public releases of FAVOR in 1994 and 1995, and then there was a limited release in 1999, a limited release insofar as this group of NRC staff, industry representatives and contractors, anybody that came to those meetings got a copy of the code, and as I said, the current development version is -- the plan right now is to be fixed in March of next year for the PTS evaluation. Now, of course, as you've seen, this is somewhat dependent on other people feeding stuff into FAVOR. So, this date is as good as the schedule that people feed things in. DR. KRESS: What kind of language is the code in? MR. DIXON: FORTRAN. DR. KRESS: Does it work on a PC? MR. DIXON: Yeah. Okay. Kind of the second part of this presentation is kind of the integration of evolving technology into FAVOR. This is kind of schematic to show how elements of updated technology are currently being integrated into the FAVOR computer code to reexamine the current PTS regulations, and this just shows kind of several blocks of things that are done better now than they were done back in the days of the IPTS and SECY-8265. Detailed neutron fluence maps -- you've heard a little about that. You'll hear a little more. Flaw characterizations -- plates and welds -- you've heard a considerable amount about that. Embrittlement -- new and better embrittlement correlation that Mark Kirk talked about. Thermal hydraulics -- the APEX experiments -- hopefully, RELAP, this latest version, confirmation through experiments -- hopefully, we're getting better thermal hydraulics data than we were 15 years ago. PRA -- that's just kind of a generic term to talk about kind of the overall methodology that I will talk about in a moment. RVID is the reactor vessel integrity database that was created and is maintained by the Nuclear Regulatory Commission that sort of, I guess, holds the official data for every vessel. If you wanted to know what the accepted chemistry was for a particular weld or plate in a particular plant, this is where you would go. Extended K1C and K1A database -- the statistical representations are -- I believe it's Professor Apostalakis -- he said don't refer it to that way -- the uncertainty representations of the K1C and K1A database. Again, Mark talked about this. I'll talk a little bit more about it. Fracture mechanics -- the FAVOR code itself -- in other words, all of these are going to feed in what we would say updated technology and we're going to apply this to the four plants, which has been discussed, and then plot curves like I showed a moment ago, and where are we, you know, where are we when we do that? DR. KRESS: Does FAVOR have the thermal hydraulics built into it? Do you have to calculate the temperature distribution through the wall? MR. DIXON: Yeah. You're just one step ahead of me, but FAVOR doesn't do thermal hydraulics. FAVOR accepts thermal hydraulics as input. In other words, output from RELAP becomes input to FAVOR. DR. KRESS: Yeah, but don't you have to translate that into temperature distribution through the wall itself? MR. DIXON: Yes. DR. KRESS: But that doesn't come from RELAP. MR. DIXON: No. RELAP gives you the coolant temperature on the inside surface of the wall as a function of time. We'll talk about that, a little more detail about that in just a moment. DR. KRESS: Okay. MR. DIXON: Okay. This is getting a little bit redundant, I suppose, but advanced technology is integrated into FAVOR to support possible revision of PTS regulation, and again, this is just sort of saying in words what we just said -- new flaw characterizations, detailed fluence maps, improved correlations, embrittlement correlations, reactor vessel integrity database, better fracture toughness models. Now, here is one that is very significant. FAVOR will now be able to handle surface breaking as well as embedded flaws, whereas previous versions of FAVOR, as well as OCA, VISA did surface breaking flaws only, because all the current regulations were derived from analysis that assumed all flaws were on the inner surface. Now, we include through-wall weld residual stress, and then there's a lot to talk about in new methodology. Certainly -- I referred -- Ed Hackett referred this morning -- I referred already to the study we did in 1999 that showed a lot of potential existed for the relaxation of the current PTS regulations, and the one single thing -- Tom asked did we do sensitivities with respect to different elements, and the answer is yes, and the one that had the biggest impact was this significant improvement in the flaw characterizations, when they actually went and started cutting up -- non-destructive examination as well as destructive examination of the P.V. Roth, as well as Shoreham and other vessels, because the current regulations, the current PTS screening criteria, as well as Regulatory Guide 1.154, all your flaws are surface-breaking flaws. They took the Marshall distribution, even though the data that Marshall distribution was derived from, the flaws were, in fact, embedded, they said we'll still put them on the inner surface. It was conservative. But when they actually start cutting up the specimen material, what they find is that there's a higher number of flaws than what was postulated in the PFM analysis from which the current regulations were derived. However, all flaws detected so far are embedded. In fact, Lee had some numbers up there this morning. When you take the PV rough flaw densities and apply them to a commercial PWR, you get about 3,500 flaws in the first three-eighths thickness of the RPV vessel. So, you're talking about considerably more flaws, but none of them are on the surface, they're embedded, and the impact of that was that you get considerably reduced failure probabilities. So, this, more than any single other thing, element, showed the potential existed for impact in the current regulations. I pointed out lessons learned from IPTS and lessons learned from Yankee Rowe. One of them was that what we're dealing here with -- we're dealing with an entire beltline, you know, and typically we consider the beltline to be from one foot below the core to one foot above the core, and the older codes, OCA-P and VISA -- they would allow you to put, you know, one chemistry, one neutron fluence. So, you'd have to take kind of the worst case and apply it everywhere. But the current version of FAVOR now utilizes a methodology that allows the beltline to be discretized in the sub-regions, each with its own distinguishing embrittlement-related parameters such as copper and nickel, phosphorous, neutron fluence. So, this accommodates the chemistries from RVID and the detail neutron fluence map. This just shows how, you know, you can break the vessel up into different sub-regions, each with its own embrittlement characteristics, each with its own number of flaws, and so forth. So, this was a pretty big step forward from the older version codes to version codes that we have now, and Brookhaven National Laboratory is generating very detailed neutron fluence maps. Shaw Malletshow talked about the number of points, literally thousands. I mean they're talking about breaking that vessel up into thousands of points, if you desire, and this just shows some of the gradients. Here's asmuthal location, and this is at mid-core. So, this is 72 inches above the bottom of the core. So, this is kind of the highest, and this shows the asmuthal location at the mid-core, this shows it 13 inches above the bottom of the core, and this shows it, you know, at the extreme top and bottom. So, you see there's dramatic gradients here, asmuthal gradients, as well as axial gradients. This shows, as a function of your axial location, at core flats, and this shows at some various other angular locations. The point here is that there's dramatic gradients and fluence that need to be accounted for. DR. KRESS: That was a question I was going to ask. Why do they need to be accounted for? Why don't you just use the location that has your highest fluence and use that as your -- that's where it's going to fail, right? MR. DIXON: Well, I'll refer back to the figure where I showed the two curves, where one is an improved model. By discretizing -- it's guaranteed that when you discretize and put in the map that includes these values, as well as this, you're going to get smaller failure probabilities. What you're talking about doing is doing a bounding analysis, taking the highest value and applying it everywhere. DR. KRESS: That's because your flaws are density-per-unit volume. MR. DIXON: You will have just as many flaws here, probably, as you do at this level. DR. KRESS: Okay. How come the ones at that level up there aren't the ones that fail, then? MR. DIXON: They may be, but not necessarily. SPEAKER: [Inaudible.] DR. KRESS: That's the answer. SPEAKER: [Inaudible.] MR. DIXON: He said it better than probably anything else I say. You've got to distribute everything. DR. KRESS: That's the right answer, yeah. I understand that. MR. DIXON: Right. So, think in terms of overlaying those fluence maps, you know, those type fluence maps onto here, and you know -- and you'll have flaws distributed over these regions. DR. KRESS: The question is what's the probability of a flaw of given characteristics being at the same spot that the high fluence is. MR. DIXON: Right. By doing a Monte Carlo over all of these permutations of possibilities, we feel you're getting closer to reality. SPEAKER: Why does that circ weld sit on that axial plot? MR. DIXON: Well, that would vary, I think, from plant to plant, but I'm familiar with one -- I won't call its name, but I believe the center line of this weld might be about one foot above here, and a lot of plants, by the way, will have an upper circ weld that falls into this category. This actually corresponds to a plant, and I won't call its name, but the whole idea here is you have one, two, three intermediate axial welds, three lower axial welds, a circ weld, you've got six plates, that when you went to the RVID database, that's how much chemistry you would have. So, I would call those major regions, you know. This would have a different chemistry, and the RVID -- it won't tell you that you had a chemistry here and a chemistry here. It will just say this weld has a certain chemistry. The same with this plate and this plate, but it's when you start overlaying the neutron fluence map onto those chemistries that you get what I would call the embrittlement map. And again, why did we do this? Because when we were doing -- when we were in the Yankee Row analysis, evaluation and analysis, this was certainly a question. People said, well, why can't you account for fluence gradients? Well, the computational tools that we had at that time just didn't. Nobody had taken the time to put that in. This is redundant. Mark Kirk's already discussed this. I'm just going to say that I'm talking about things that are already into FAVOR code. These new statistical models, statistical representations, uncertainty models, whatever you want to call them, for enhanced plane strain, static initiation and arrest, fracture toughness, have been implemented into FAVOR, and this just shows our 254 valid LEFM points, and this shows the WIBLE distribution. This is like the .001 percent curve, the 99.9999 percent curve, this is the median curve, and this very lowest curve here is what, in the Wible distribution, is called the location parameter. There's three parameters -- A, B, and C. The parameter A is the location parameter, and this is a plot of that, and basically, that is the lowest possible predictive value of K1C that you could ever have, okay? Again, I guess if we were to get 10 more data points, everything would change, but right now, that's where we're at, and here it is for K1A. Now, this was -- the old EPRI database, I believe, was 171 points. We went to 254. I believe this was 50 or 54 data points. This one almost doubled. So, we've got extended databases, and we've got much better uncertainty representation of that data. So, this is -- we feel this is a significant step forward. Okay. Again, I've already alluded to this. This just shows an inner surface breaking flaw, as opposed to an embedded flaw, and as I mentioned earlier, the current PTS regulations and reg. guides all deal with this guy, but what is being found when they go out and do NDE and destructive examination of vessel material -- they don't find these, they find these. So, if we want a better model, better representation of what's out there, we have to be able to model both inner surface breaking and/or embedded flaws. So, the current version of FAVOR now -- it will handle both, I mean at the same time. You can have a combination of surface breaking and embedded. Even though they haven't found any surface-breaking flaws yet, it's my understanding that there will be probably some surface-breaking flaws in the characterization that goes into these analyses, because perhaps they've looked at one-tenth of 1 percent of the vessel material, and I don't think you would want to conclude that, because you haven't found on there, doesn't mean that there might not be one out there, and it becomes a problem of statistics, and Lee Abramson is working on that. Okay. Just one slide here about the structure of FAVOR. Maybe it helps. People that are code developers or code users can relate to this. When you talk about the FAVOR code, it's not like just one module. It's actually broken down into three modules, three completely separate modules. The first one is what I'll call the load generator, okay? And this top line of data is input data. This middle yellow line -- that's the actual codes, the executables. And this bottom line of data is output data from each of the modules. So, this module -- this first module is the load generator, and the input to it is like the thermal elastic material properties of the clad in base, the vessel geometry, and the thermal hydraulic boundary conditions, or in other words, the output from RELAP. Now, the output from RELAP is going to be time histories, coolant temperature, pressure, heat transfer coefficient that's imposed on the inner surface of the vessel, and FAVOR will allow you to give 1,000 pairs, time-history pairs for each of those three for each of the transients, and you can do 30 transients in one run of FAVOR. So, you can see this becomes a bookkeeping thing, too. You're literally talking hundreds of thousands of points. Dave Bessette said this morning, for Oconnee, he was going to give me 27 transients. Each one of those has the three traces. So, 27 times 3 is 81, each one with 1,000. We're talking 81,000 data points or time-history pairs. So, we're talking about a lot of data. DR. KRESS: Is that automated? You don't do that by hand. MR. DIXON: No. He gives me a disk. DR. KRESS: He gives you the input curves? MR. DIXON: He doesn't give me curves. I have to make sure it's in the correct format, but that's relatively simple. But anyway, you feed this in -- and I'll talk a little more about this in a minute -- you feed this in to -- basically, this is a finite element program, and out comes your -- this is what you were asking, Tom, a moment ago. You do get your space and time-dependent temperature through the wall, how that gradient through the wall at each location is changing as a function of time, the same with regard to axial stress and hoop stress, and the same for stress intensity factors for inner surface breaking flaws, for different flaw geometries at different times. Okay. So, you run that module by itself. You run that, and you get this output file, and it's just a lot of numbers, but they're formatted in such a way that this module, the PFM module, knows that format, and it can read them in accordingly. So, when you run the PFM module, you input the flaw data, the beltline embrittlement data, all those sub-regions and corresponding chemistries and fluence maps, with all the flaw data, and also all of this load data for each of the transients. All that is used as input into the PFM module, and out of that comes distributions for conditional probability of initiation, conditional probability of failure for each transient. Now, it should be said that conditional probability of initiation is dealing only with cleavage or fast fracture. There is no EFPM. Somebody mentioned a moment ago about JR curves. Okay. There is no ductile tearing considerations going on. This is a cleavage fracture, LEFM cleavage fracture analysis only at this point. Okay. Then the third module is the post processor. Actually, this only exists in my head right now, but I know what to do, and the input to that is the transient initiating frequency distributions, which comes from the PRA people. Okay. So, that's input, as well as these distributions that you got from the PFM module. All that goes in the post processor, and out of that comes the bottom line of an analysis, and the bottom line is the frequency of initiation. This is kind of a mismatch. It's the frequency of RPV fracture, which is CPI, and the frequency of RPV failure. So, the distribution -- that distribution would have a mean value associated with it. So, the mean value of this distribution would be what was plotted in that figure I showed earlier, because remember, I'm doing this at a moment in time, because there's one fluence map here. SPEAKER: Fracture in this case means initiation, and failure means failure. MR. DIXON: Good point. Initiation means fracture occurs. Now, whether that flaw propagates through the wall is another question, and frankly, that's something we're still working on, and I'll talk about that in a moment. In fact, now we're going to shift gears and talk a little bit kind of about, before we get too lost in the PFM, probabilistic fracture mechanics detail, let's step back and kind of talk about the overall PRA methodology. This is a pretty busy slide, but this is just showing that on the last -- on the slide a moment ago, I showed the load generator. This is just showing the load generator again. But first, let me read this caption, because I think this is important. The FAVOR analyses incorporate the uncertainty associated with the thermal hydraulics by including variants for each of the transients, okay? This shows RELAP generating a lot of output data, okay, and major transients. Transient one might be a small-break LOCA. Transient two might be a stuck turbine bypass valve. Transient three, something else, dot, dot, dot, transient N. Okay. Now, within each one of those major transients, there's variance. The way that a small-break LOCA comes down, it could be this, could be this, could be this, could be this. So, if you want to consider all those possibilities, each one of these is three -- represents the three time histories, each one of these errors. Maybe this is a small-break LOCA, one possibility. Here's the temperature, pressures, heat transfer coefficient for that. So, all of that goes in in one run of the load generator, which performs a one-dimensional, axi-semetric, finite element analysis to calculate the loads for each transient, and again, this is redundant, temperature, circumferential axial stresses, stress intensity factors, tremendous amount of data here, big bookkeeping exercise right here. Okay. The other module was the PFM module, and what it does, it generates these arrays for the conditional probability initiation -- I call that PFM-I -- and failure, PFM-F, for vessel J subjected to transient I. It's starting to get a little bit esoteric here, but think of this as being a two-dimensional array, where each row in this array corresponds to a particular transient -- in other words, one of those representations that was shown on a previous slide, and each column in this array corresponds to a vessel, and the entry that goes into a particular I-J entry into that array is the conditional probability of initiation that that vessel fractured when subjected to that transient. Same thing for failure, okay? And this module -- this is redundant. This is just another way of showing what I showed a moment ago, where the loads, all the stresses, temperatures, and everything that was done in the finite element analysis is input into here, as well as the flaw characterization files, which Lee and Debbie will provide, for weld material, plate material; the PFM input, the embrittlement maps for all those various sub-regions, along with probabilistic input such as what's the one standard deviation, you know, a lot of things like that. I think I've about talked that one out. A third module, if you recall, is a post-processor, and the objective of the post-processor is to integrate the uncertainties of the transient initiation frequencies with the PFM-I and PFM arrays to generate distributions for the frequencies of RPV fracture and RPV failure. This just shows the initiating frequency for transient one, the distribution of initiating frequency for transient one, two, dot, dot, N, okay? And these are shown in histogram form, because it actually comes into the program numerically. You don't say this is gaussian, this is beta, because then you've got to create a whole library of the possible distributions. So, we just said just do it numerically. So, that's the way that it's going to be done. Also, the arrays that I showed a moment ago, the PFM-I array, where the IJ entry, you remember, is the conditional probability that that vessel will fail when subjected to that transient, as well as the PFM-F comes into here, and the output is the distribution of whichever one you're doing, the initiation or the failure, okay? So, you get a distribution, and this shows that this distribution is, I guess, what statisticians like to call bi-modal. It will have -- typically, it will have a big value, kind of a skyscraper here at zero, because hopefully most of these were zero, and then you'll have some other kind of distribution. So, the mean of this distribution is not here. It's going to be way over here. So, it's going to be a very unsymmetrical distribution. Okay. Now, the process to get here, what goes on in this post-processor is that, for each vessel -- in other words, for each column in one of those arrays, you sample the initiating frequencies. So, you have -- I like to think of it -- you'd have a row vector of initiating frequencies, you know, one value for each of the transients. Then you combine that with like the PFM-I array, which I like to think of that as a column vector. So, if you multiply a row vector times a column vector, you get a number, get a scaler. So, that would be one value that would be the frequency of initiation or, if you were doing failure, the frequency of failure. So, that would give you one value. Well, if you do this, say, 100,000 times, you've got 100,000 values. So, you sort those, arrange them into a distribution, then you calculate the mean and standard deviation. So, that's the bottom line right there. In going back to that picture that I showed earlier, you could take the mean of that, plot it for that time, then you'd go do another analysis for another time in the life of the vessel, and of course, what I didn't show -- and I'm being redundant -- what I didn't show on that first slide was the amount of uncertainty, but we will know it. Okay. That could stop right there and that be the end of the presentation, but we'll now try to talk a little bit about some of the details of the PFM analysis. That was just -- in other words, I'll try to talk about some of the details of how you get a number into that PFM-I array, okay? All I'm going to talk about here is how do you get a number into the PFM-I array? Now, I'm going to digress here just a moment, because you asked a very good question this morning, Dr. Shack, about -- you said you weren't sure if we were riding one curve down or what, and I'm going to talk in more detail, but now's a good time to interject that what I showed a moment ago, in each IJ entry of that PFM-I array, it's a number between zero and one. Each entry has -- it's a probability, with the way that we do it now. The way we used to do it, which is what you said, grab a curve, sample, ride it down, and either it's a yes/no. It either breaks or it either doesn't. And that was the old way of doing it. In that case, it was a zero or a one. It's kind of digital. It was either broke or it either wasn't broke. But now, with our new methodology, you can have something between a zero and a one. Anyway, that will sort of lead in. This is a terrible slide, and I'm going to maybe try this a little differently. Instead of showing that -- that's even worse. I'll try this, and like I said a moment ago, I could have stopped, but we're going to jump off into some details now. The name of this section is PFM details. Actually, I was hoping that it would be time for people to go catch planes and stuff by the time I got to here, but looks like not. The idea here is -- remember, I said that I'm talking about how you get a number into those arrays, okay? I've showed you what you do with them after you get them. How do you get a number? Okay. I told you we're going to do many vessels. So, let's let our outer loop be vessels, vessel equal vessel plus one. Then we know that all the vessels are going to have multiple flaws. You saw Lee's presentation this morning, and I had a slide here that showed that they have around three or four thousand flaws, every vessel. So, you're going to increment your vessels. Okay. Now, that particular flaw -- where on that beltline region is it? Is it in a plate? Is it in a weld? You choose that. You sample and determine that. You place the flaw on the beltline region, and in that beltline region, there's a certain copper, nickel, phosphorous, neutron fluence, all the embrittlement properties in there. So, here, you've got a flaw located on the beltline, with its embrittlement properties. Now, we're going to sample the flaw characteristics. How big is the flaw? Where is the flaw in the wall? Is it a surface flaw? Where is it embedded? So, now, we know enough to calculate the RTNDT of the cracked tip. We know where the cracked tip is. We know all the things that goes into the correlation that Mark was showing, the chemistries, the neutron fluence. So, you get an RTNDT. So, at this point, we've got a flaw with a tip located somewhere that's got a certain RTNDT. Now, the next loop is going to be transients. We're going to subject that to the various transients. Okay. And the next loop is time, transient time. So, we're going to step through here this time loop, calculating the conditional probability of initiation and failure for each one of these flaws. SPEAKER: Let me ask my question here. MR. DIXON: Okay. SPEAKER: I've just calculated RTNDT. Why don't I calculate a toughness? MR. DIXON: Well, you do. You can see that this was already pretty busy. This is high-level. That's the next couple of slides of how we do that. SPEAKER: Yes, but doesn't it make a difference whether I compute the -- I pick that curve sort of outside the time loop or I sample -- MR. DIXON: No. SPEAKER: I guess this is my riding down versus -- MR. DIXON: No, either way. RTNDT is not a function of transient time. To calculate K1C, it's T -- it's a function of T minus RTNDT. T is transient time dependent. So, I can calculate my RTNDT outside of even my transient loop or my time loop, but you're right, once I get into this time-loop, I'm going to be saying T minus RTNDT, T minus RTNDT, and it doesn't matter if I'm moving down a curve or moving across a distribution, my RTNDT is not going to change. It's the same RTNDT at that crack tip throughout not only this transient but all the other transients, as well, okay? And you're right, there's a lot going on in here that I don't show, but there's some slides coming up in a moment that attempts to address that. But basically, you do this until all the time's over, all the transients are over, you've done it for all the flaws, okay, and then you have to go through this whole multiple flaw thing. I'll talk a little bit about that. At this point, you would have a value for one flaw, and then you have to do kind of some algebra to combine the effects of multiple flaws for that vessel, and we'll talk about that in a moment. And then the last -- you close your last loop, which is vessel. So, you set there, you got these four loops going on, but physically, I like to think of it -- you know, you take vessel one, you locate a flaw somewhere on that beltline, you get an embrittlement, and then you set there and hit that flaw with all the transients, okay, and then you go to the next flaw, and you do that until all the flaws are exhausted for that vessel, at which point you have an entry into your PFM-I and PFM-F array. I know that's a very busy slide, but it also contains a lot -- what Dr. Apostolakis was asking this morning. He would like to see you step through one iteration. There it is. There's one iteration. MR. HACKETT: Terry, let me add a comment while you have that up there. This is Ed Hackett. I think another thing that's come up in some previous discussions with the committee is that it's important to note that these are done -- as far as I understand it, they're done randomly and independently. So, there's no linkage, for instance, between an area that's high in copper with some kind of idea that that would be inherently more flawed than some other area. Those are going to be, you know, in separate loops, as much as something like that could exist. We're not modeling that kind of thing. DR. KRESS: But you did say you attempted to model multiple flaws some way. MR. DIXON: Yeah. DR. KRESS: These are, you know, one flaw there by itself. MR. DIXON: Yeah. DR. KRESS: And you're saying that there might be another one close by and they link up or something like that? MR. DIXON: No. Yes, but right now, let me just say -- maybe I'll just say this. Right now, there is no -- right now, there's an assumption that every flaw is independent from every other flaw as far as fracture. The presence of one flaw does not influence the fracture response of another flaw. However, at the PVP conference in Seattle this past July, a professor from the university of Ottawa presented a paper that I went to, and he had done some work. So, I think -- I've read his paper. I actually think -- I don't know if we want to, but I was going to discuss it with NRC staff at some point in the future. He's got curves that you could use to sample that, but I'm not sure that we want to go there. I don't know. His work was kind of the first, I think, in this area. Right now, the answer to your question is every flaw is independent of every other flaw. SPEAKER: How long does it take for a single run from vessel equal vessel, from the first vessel that's chosen to the end point? MR. DIXON: Okay. That's a good question. It depends on a lot of things. I've got a machine that's a 533-megahertz machine, and to run it for, say, 100,000 vessels, for a single transient, 100,000 vessels, where each vessel has around 3,500 flaws, it's about -- like I'll start it when I leave work, like at five o'clock, and I'll come back the next morning and I'll see where it finished at 2:30 in the morning or something. So, it's eight, nine hours on a 533-megahertz machine for one transient, and Bessette said this morning that he's going to give me 27 transients for Oconee. So, I can already see that we may have to -- I know, right now, you can buy 800-megahertz machines for the same thing that you could buy this one for last February. So, I think we may have to -- maybe by next March, when we get ready to do this, we may go buy us a couple giga-flop machines, which will probably be out there for what we bought the 533 for last year. So, I mean you can see that this is pretty computationally intensive. And remember, at the end of the day, when you do that, that's just one point on your curve. Okay. I told you that I would try to -- between that transient time loop -- I just stepped over it. Now I'm going to try to address that a little bit here. Here's a transient. In fact, this is taken from the IPTS studies. This is designated in the IPTS studies as Calvert Cliffs transient 8.3, and it has a distinguishing characteristic that was a distinguishing characteristic of most of what was called the dominant transients in the IPTS, those that contributed most significantly to the vessel failure, and that is this late re-pressurization. You know, your temperature is here. It's a pretty sudden cool-down down to about 150. No, it's not very sudden. It's pretty gradual. Over a period of two hours, it cools from 5.10, I believe, to around 150. Pressure drops suddenly, stays low. Get over here about 95 minutes, boom, you spike back up to full pressure. Bad news transient. But anyway, I'm going to use this transient to illustrate this new methodology of calculating the conditional probability of initiation, as opposed to the old way of going up and getting a curve, picking a curve and riding it down, and either the vessel breaks or it either doesn't. Okay. This is a lot of words. I'll read it. The conditional probability of initiation is calculated by solving the Wible K1C cumulative distribution function for the fractional part, percentile, of the distribution that corresponds to the applied K1 as a function of T, a lot of words, but what that means -- what this is an attempt to illustrate is here's your Wible location parameter. I showed earlier, that's the lowest value of K1C you could every have, okay? And I chosen an arbitrary flaw. I said let me take a half-inch-deep flaw that's embedded, that's located such that it's inner cracked tip is one-half-inch away from the RPV inner surface. So, I've got a flaw that's a half-inch, through-wall, located a half-inch from the inner surface of the vessel, and I subject that to this transient, and here is the K1. Now, this is T minus RTNDT. So, time is going this way, okay? This shows the applied K1, this K1 as a function of T, moving this way, and you notice that it never breaks into the -- it never penetrates the K1C space until the re-pressurization. At 95 minutes, about 95 minutes, boom, it spikes up here, and at that point, that is the 6.35-percent curve, okay, or the .0635, which you solve if you put the K1 into the Wible cumulative distribution function along with A, B, and C, which are functions of T minus RTNDT, you get the conditional probability of initiation for this transient at this time for this flaw, okay? So, this is pretty fundamental right here of what's happening down at the innermost kernel of this algorithm, okay? Now, here's another -- here's an attempt to show that same thing another way. In the illustrative example problem, the Calvert Cliffs, 8.3, at the time of re-pressurization, K1 is greater than .0635 of the Wible distribution at this particular vertical T minus RTNDT. So, at that moment in time, when you spike up below that lowest value, the question is how far did you get up into that K1C space, which I showed how you solve for that, but all you're doing is you're just solving for what part of that total distribution is applied K1 greater than, okay? Now, if you want to ask questions, this is a good time to do it, because this is new. This is new PFM methodology that -- basically working with the University of Maryland, and it's my understanding that this includes the aleatory uncertainty that we used to didn't include. When we used to get up and ride a curve all the way down and it was either a zero or a one, that did not include the aleatory uncertainty, whereas this method does. SPEAKER: But it says that that variation in K is all aleatory. MR. DIXON: There's no variation in K. K is only as a function of time. SPEAKER: K1C. MR. DIXON: Right. SPEAKER: Somehow, I would pick that as families of curves for a given material. MR. DIXON: It is families of curves. It is, in fact, families of curves. You can think of it that way. SPEAKER: But once I've picked the material, I have a curve, with perhaps some scatter around it. MR. DIXON: You're right. Once you pick RTNDT, you have -- I'll tell you what. Maybe this will help. Maybe it won't. We can go back to that slide. This is an attempt to show -- this is showing it as a function of time. Now, you know, we're moving this way. This is a different situation. This is not that transient 8.3. This is a different case, a different flaw. But this shows how the Wible location parameter changes as a function of RTNDT. As RTNDT increased, that Wible location parameter gets lower. Now, here comes this -- in time, here comes the applied K1 in time. So, the question is, how much does this applied K1, if at all, how much does it penetrate the K1C space, you know? That's the question that we're asking when we do this particular computation, and the little dots correspond to the discrete times that we're analyzing it at. Now, this is a plot of the instantaneous conditional probability of initiation; in other words, solving -- as I showed a moment ago, solving the Wible cumulative distribution function as a function of time, or in other words, as a function of applied K1. You can see that, at 325 degrees, RTNDT, which is pretty high -- I did it just for a good example -- how far is it above this line, and for 275, how far is it above this line, and this answers those questions. This shows the conditional probability of initiation as a function of time. I don't know if that helps or not. SPEAKER: Let me just take a more simple-minded approach. MR. DIXON: Okay. SPEAKER: If I went back and, you know, I plotted that data, all my 274 data points -- MR. DIXON: Yeah. SPEAKER: -- for the K1C, and I have all the data for a single material, you know, where I've made all the samples, will those sort of occur randomly within that band, or will the material for a given sit somewhere either at the top, bottom, or middle of that band? MR. DIXON: I don't know. Mark could probably answer that better, and he stepped out. SPEAKER: Could you give that one more time, Bill? I'm not sure I followed that. SPEAKER: If I take my 254 data points, and those are multiple heats of material, and I look at a single heat of material, will I find it uniformly scattered up and down that band, or if I look at single heat of material, will I find it sitting somewhere in the middle of that data as I move from RTNDT? SPEAKER: Looking at a single heat, I'd be inclined -- I guess I can't answer for the current situation. I think previously I know -- I can say the way we addressed Pallisades, it would have been uniform, is that way we've done it previously, and I don't know if that carries through to where Terry is now. SPEAKER: Yeah. He's saying you can go anywhere from the top to the bottom. SPEAKER: Then that's a random choice. SPEAKER: That's a random choice, whereas, you know, I'm sort of -- I would have argued that maybe that band really indicated that some materials are tougher than others, and therefore, you pick a material and you would have had some aleatory distribution, but it would have been a much narrower aleatory distribution. SPEAKER: I see what you're saying now. I think I understand now. That would be the intent of the new methodology, would be what you just said there. SPEAKER: No, I think the new methodology says I go up and down the whole damn curve. SPEAKER: Yeah. SPEAKER: See, I thought it was more the -- you know, this is going to depend on how these uncertainties, you know, cascade into this, but I would have thought it would be more what you just said. Maybe I've got the wrong impression. MR. DIXON: Going back to our K1C database -- END OF TAPE 4, SIDE A; BEGIN TAPE 4, SIDE B MR. DIXON: [In progress] -- a vertical slide through there at a given value of T minus RTNDT. Now, I don't know if what I'm fixing to say addresses your question. I may not get this exactly right, but you'll get the idea. That 254 data points -- I believe there was 16 groups, okay, 16 groupings of various T minus RTNDT, okay, you know, plate, HSST, one four plate, HSST, 02, dot, dot, dot, and so, they were grouped by heat, but the Wible distribution that is derived from that does not include those considerations. It's just data. SPEAKER: Right. That's okay if the data for all those plates sort of falls up and down that thing uniformly, but if they were all colored and I saw all green balls down at the bottom and I saw all red balls up at the top, then doing my Wible -- I can't answer my question until I know where the balls lie. DR. KRESS: Are you going to be able to know which heat a given vessel -- SPEAKER: No, but then I would sample -- I don't know where the curve is, and so, I would sample -- you know, what I would think of as families of curves and pick a curve. DR. KRESS: Yeah, but on what basis would you pick that curve? SPEAKER: Because it would be some material, and I would pick it at random, but once I picked that, I would say -- the material never changes through the whole transient. Every time he goes to a time step, he goes up and down that whole distribution, and I would say no, once I've picked my material, I've sort of got a tough material -- MR. DIXON: No, no, no. What you just said is not correct. SPEAKER: It's not? MR. DIXON: What you just said is misleading. Keep that picture in your mind. Now, let me see. Let's go here. We're not bouncing up and down. The question is, the way I like to think of it -- I don't know which picture is best. We're not bouncing up and down anywhere. The question at any time is what percentage of the Wible distribution is the K1 greater than? That's not bouncing up and down. In other words, if I was to -- in fact, one of my back-up slides may do this. No, it will just confuse it. In other words, if you were to go at this time, 10 minutes later in the transient, you don't come over here and completely re-sample. You're not sampling. There's no sampling going on here. The question is, you've got this K1C space defined, between here and here. Now, the question is, when I bring my K1 as a function of T into play, how does it penetrate that space, if at all? That's the question. There's no sampling involved. DR. KRESS: But you're saying if you define that curve a little finer, with the different colors, you could have sampled it. SPEAKER: If I can interject here, I want to point out a couple of things. One, the curves that Terry is showing here are certainly necessary for us getting on with the work and formulate things, but I don't think this is the final word. This was based on the statistical analysis of the data set. If you go back to Terry's slide showing the Wible equation, he mentioned the parameters A, B, and C. One can develop different distributions for those parameters. That's where the epistemic comes in, what's the value of A, B, and C, and if you segregate the data based on different characteristics -- and I'm way beyond my depth now, but conceptually, what you would do is, if you identified different classes for which you have different families of values for A, B, and C, that's how you would enter that process. So, that would be the same thing as what you're talking about, selecting the curve. In this case, you'd be selecting A, B, and C, and then, once you have that now -- SPEAKER: It depends on whether you're doing that inside the delta time group or outside the delta time group. SPEAKER: That's right, and the epistemic loop is outside, by definition. The inside is when you're dealing with the aleatory component, because now you're dealing with a transient and the response on a time step by time step basis. SPEAKER: When I say bouncing every time, Terry, at every delta-T, you're sampling a K1C. MR. DIXON: No. SPEAKER: Where do you determine the K1C? That's outside the delta time group? MR. DIXON: There is no sampling of K1C. Once you've got your -- you've got your K1C space defined by the Wible statistical representation. Now, the question is -- I'm going to put the K1 into that function, and what I get out of that is the percentile K1C curve or which one of those family of curves, if you wish to look at that way, does that K1 correspond to? Let me try it this way. This is the Wible cumulative distribution function that, if you had K1C in here, if you had K1C in here, it would tell you which one of those families -- in other words, which percentile K1C curve is that, as a function of K1C, A, B, and C, but when I plug K1 in instead of K1C, the question that I'm answering is what -- I mean, right there, that shows -- that's the 6.35-percent K1C curve. So, I'm not sampling K1C. I'm asking the question, how far does my K1 penetrate into K1C space? MR. KIRK: Mark Kirk, NRC. Can I say it maybe a different way, relative to Terry's ugly slide? Maybe we've found a use for that. Could you put it back up? MR. DIXON: Okay. MR. KIRK: Terry's certainly right in what he's saying, he's not sampling K1C, but the material properties for any given -- if you look at the loop that says calculate RTNDT at cracked tip, that's outside the time-loop. So, at that point, I guess the way I'd think of it, once he's calculated RTNDT at the cracked tip, at that point, he's determined where the K1C curve is for that material. That's then fixed on a toughness versus temperature plot. He then goes and runs the time loop, and that's what the illustration -- if you go to your slide 23 -- so, once he's determined RTNDT at the crack tip, he's determined where the K1C curve is for the whole time loop. He then runs the time loop, I think, as he said, from right to left, and that's the applied K1 changing with time, and how it winds up with in the K1C curve gives you your final probability of failure -- of initiation, I'm sorry. But once you get inside the time loop, the material characterization has been fixed. It's not re-evaluated each and every time. SPEAKER: I see what he's doing now. MR. KIRK: Is that a correct interpretation, Terry? MR. DIXON: Yeah. Notice, at these points down here, you can positively say the conditional probability of initiation is zero. It does not get equal to or above this lowest possible value of K1C, the location parameter. You can positively say, you know, with a confidence interval very high, that the probability here is zero, until you re-pressurize. SPEAKER: [Inaudible.] MR. DIXON: Yes. In other words, any time the K1 is above this location parameter, you've got a non-zero value of conditional probability of initiation. SPEAKER: Could you put that other slide back up, Terry, the schematic again? I just want to see if I'm clear on where Bill was coming from. MR. DIXON: This one? SPEAKER: No, the methodology. MR. DIXON: Oh. SPEAKER: Because I was wondering -- maybe I'll pose it as a question, Bill. I was wondering if you were on the third box down where we're looking at sampling sub-regions and where that relates to the generation of the K values in terms of maybe compartmentalizing the K1C or that type of generation, because obviously, we are looking at different values for the different sub-regions, but that also, by Terry's chart here, is fixed outside the loop, outside the transient loop. I don't know if that helps at all, but I was wondering if that might be where you were coming from. MR. DIXON: The only material property that's varying in here is K1C, and it's varying because temperature is varying. RTNDT is fixed. In this loop right here, your temperature is changing. Therefore, T minus RTNDT is changing. Mohammed? MR. MEDAREZ: Mohammed Medarez. Maybe if I can show you -- MR. DIXON: Sure. MR. MEDAREZ: This one view-graph -- maybe it explains this a little bit better. If you're looking at it, here's the K1C distribution, and as time goes by, the distribution will have different shapes. It slightly changes, because as time goes by, the temperature changes slightly. Typically, if you take a sample of this as a percentile here and if this is your K1, this shows the time that it exceeds, okay? If I take many of these samples, I can build a distribution here of the time that I initiate that flaw. Everything inside a flaw, flaw is fixed, and I'm just going over time now, okay? So, I take -- typically, I think this is what you do. You take a sample here, and this is a sample of the percentile. From the old time, he had only a bounding value. Now he has a distribution of these, because he has a variability, and therefore, he gets a distribution of the time to initiation of the flaw. So, for instance, the probability that he would have any initiation between this time and this time in this area which is hatched, which is also equal to that area. So, that's the difference from the last time of operation. Essentially, he used a bounding line, and now he is taking a percentile of this curve, but he stays constant. Once he takes that, he stays constant over that line, and finds what time the crack starts to initiate. So that's the process. SPEAKER: Why is your cumulative probability on the bottom -- why doesn't that go out to where your K1T crosses your bottom line again? MR. MEDAREZ: This one, why it goes down? SPEAKER: Your probability that you're accumulating the probability of failure. MR. MEDAREZ: Because physically, if you start in here, you started right here, if it goes down, it has already started. So, you don't start it again. That's why. If it goes up and down, it can only start one time, and that's it. So, that's why you have, actually -- once you reach the maximum, you trap it out completely. There is nothing else after that. MR. DIXON: I don't know if this will help, but Mohammed basically is saying, okay, given this applied K1 as a function of time, you could set here and do a Monte Carlo analysis on this flaw and sample this Wible K1C distribution and come down here and get a distribution. What I'm saying -- and we have verified this, he at the University of Maryland, as well as I at Oak Ridge -- you get exactly the same answer as if you go ahead and algebraically solve the cumulative distribution function. It's the same thing, because if you do this Monte Carlo, which becomes computationally prohibitive, because now you're doing a Monte Carlo within a Monte Carlo, and that gets a little bit crazy, but what you're really asking is, you know, what's the percentile of your K1 space that you penetrated? That's the way it comes easiest for me to understand. SPEAKER: I don't think we should get too hung up on the -- I mean there is a difference between the mechanism used to do the computation, and we can use sampling or we can use quadrature, we can do lots of things, and then the basic model as to where the variability is coming in, as a function of time, and where the epistemic uncertainty and how that's treated, and clearly, we need to do a better job of explaining that. So, I think, in the upcoming meeting, we will certainly put together a better story as to how your issue is being addressed, because we understand the question. SPEAKER: Okay. MR. MEDAREZ: And right now, of course, we're treating it as aleatory, but we recognize that that may not be correct. SPEAKER: There are components that are epistemic. You're not seeing that right now in this curve. MR. MEDAREZ: But right now, we basically carry the whole uncertainty through, and what we're calculating is the probability of vessel failure, which is all aleatory, in that case. SPEAKER: I guess what I missed was the fact that you're really looking at these cumulative curves. MR. DIXON: Shaw, did you tell me that you distributed to these guys a copy of that IAEA paper that we wrote? MR. MEDAREZ: Yes. MR. DIXON: It's called updated probabilistic something. It's a paper Shaw and I wrote for the IAEA conference. That says in words what I'm getting tongue-tied trying to say up here. In other words, that problem with that re-pressurization -- there's a narrative that describes that in that paper that probably says it better than I'm trying to say up here right now. I can write better than I can speak. SPEAKER: I'm not sure I completely understand everything, but now I understand what you're doing. MR. DIXON: Until now. And this is a very complicated looking slide, but -- and I probably made this more complicated than I had to. But this whole thing about accounting for multiple flaws -- remember, each vessel may have three, four, five thousand flaws, and you go through that loop and you get values of conditional probability of initiation for flaw number one, flaw number two. Actually, the way it seems to turn out, maybe out of that 3,500, maybe four or five of them will be non-zero, okay? So, the question is now, for that vessel, what's the probability of initiation, and I'm not going to go through all this equation-looking stuff, other than to say, if CPI is the conditional probability of initiation, one minus CPI is the probability of non-initiation, and then, if you -- for two flaws, if you take one minus CPI for the first flaw and multiply it times one minus CPI for the second flaw, what you have is the probability that neither one of those flaws initiated, you have a joint probability that neither one of those flaws initiated, right, and if you have 3,000 flaws, it's still just one minus the CPI times one minus the CPI all the way out to however many flaws you had. So, at the end of that, that's the probability that none of those flaws initiated. Then, if you subtract that from one, it's the probability that at least one of them did initiate it. That's the value -- that's what this is an attempt to show. That's the value that goes into your PFM-I array for that vessel transient, that IJ entry in your PFM-I array. So, you go through that business about how did K1 penetrate K1C space, you get a value of CPI for that flaw, you do it for many, many flaws. Then you do this and you get a value to go into your PFM-I matrix. One other little -- this max in here -- you do it for the maximum value as a function of time for each flaw. In other words, take the peak value. So, for this particular flaw, you know, let's say this was the case. We would come out here and we would take that value for flaw number one, and then if, you know, we had another non-zero, we would do the one minus that time one minus that to get the value that goes into the PFM-I array. DR. KRESS: Multiply that probability times the time? MR. DIXON: Not times the time. That's the conditional -- each one of these is instantaneous, but if you think about it -- that's a good question. This value here really is the cumulative value of everything that's gone before. DR. KRESS: I'm trying to get a probability density function integrated over time, but I don't see how to do it. MR. DIXON: That's not what's going on here. I know it's a lot to get your fingers around at one time. I'll just conclude with, you know, one that I showed earlier. You know, the goal is to have the code ready to go by March 1, 2000. This assumes, you know, that all the models are finalized according to schedule. In the interim period, we're going to finalize some models, implement models in the FAVOR, and perform scoping studies, and it looks like Oconee will be the unit that's the guinea pig for the scoping studies, because the thermal hydraulics and the PRA are going to be finished. That's it. That concludes everything that I have. SPEAKER: [Inaudible.] Pieces of this don't break off all that easily. DR. KRESS: No, it doesn't seem to. SPEAKER: What do you think is important for the rest of the committee to hear out of this, to let them know where the staff is, possibly raise questions about the recommendations on where they should go? SPEAKER: George seemed very concerned about the uncertainty analysis in the K1A. DR. KRESS: Terry walking through that thing would bring that out, I think, would be one of the things. SPEAKER: That might be my candidate. DR. KRESS: Yeah. I was about to say that would be my candidate. SPEAKER: And hold off on the flaw distribution until they're ready with a final report, although I would have thought it was going to go the other way around. DR. SEALE: I think something about how they plan to integrate the PRA data into FAVOR -- that is, the PRA process -- what they expect to have as a communication vehicle in order to get the risk-based output. DR. KRESS: Terry had one slide on that which would cover it, I think. SPEAKER: I really think these two pieces are the ones that maybe -- DR. KRESS: Which is that? SPEAKER: This fracture toughness uncertainty with the RTNDT. DR. KRESS: Yeah. SPEAKER: Because it sort of puts those pieces together. SPEAKER: That's with an understanding that there will be a more detailed, updated meeting on the uncertainties? SPEAKER: Certainly, the whole uncertainties, but at least to give us the chance to go through the mechanics of what we're doing. DR. KRESS: I'm quite interested in this risk acceptance criteria, 1 times 10 to the minus 6, but I can't see that there's anything they can present to us at the next meeting for that. I mean somebody is working on that and thinking about it. We didn't hear anything today about it. SPEAKER: I guess I'd agree with Dr. Kress. I don't think we're ready to talk about it. My understanding is there's some work going on there, but we won't be ready for that. I guess I'd agree with Bill on those two pieces, with one caveat, I guess. I know Nolan, Nathan, and I were talking separately that to do the meeting that I think Professor Apostolakis was asking for, we may not be quite ready for that till maybe December timeframe, to really spend a day on uncertainty and track through that, but I think we could do a reprise of those -- you know, Terry's and Mark's presentations, maybe trying to articulate some -- SPEAKER: I sort of realized you weren't going to be ready to do the full uncertainty. It was just a question of what we could do sort of leading up to that and, I think, highlighting some places where it seemed especially uncertain how to handle the uncertainty. SPEAKER: Yeah, and I guess our reluctance, a bit, is because this is work in progress. SPEAKER: That is the problem here, that everything is work in progress. SPEAKER: Right. DR. SEALE: Not that we don't like to be able to put our finger in the soup while it's still fresh. SPEAKER: No doubt. SPEAKER: You know, I am a little concerned, you know, with Tom's question that, you know, we're raising a fairly fundamental issue about the acceptance criteria, you know, can we work from the LERF goal in 1.174. Do we need to formally somehow get that raised for staff consideration, or do we consider it raised at this point? SPEAKER: It's certainly been raised. I mean I believe the SECY paper recognized that this was an issue that had to be dealt with. We said that we were going to do a scoping study that would -- SPEAKER: But the SECY paper really started with the 1.174 criteria as the ultimate acceptance criteria. SPEAKER: That may be. I was under the impression, speaking with Mark, that there were still questions about that. That was certainly a model of how we're going to proceed. It was not necessarily the only model that we were going to look at. I thought that that was part of the discussion on -- once we apply -- we tried to apply some of the latest thoughts on how we're doing the risk-informed applications, whether or not we'd come back to PTS and say, okay, now we need to look at things a little bit differently now. I thought that was open under the SECY. Anyway, if the SECY didn't say that, we're not saying that's necessarily the ultimate goal. DR. SEALE: Certainly, the one size fits all is not the right way to go because of this question of the containment and issues like the spent fuel fire and so on. DR. KRESS: It's the same issue. DR. SEALE: It's the same issue, but it shows up in very specific examples. SPEAKER: Understood. SPEAKER: That may be a judgement call, but that may be worth some more discussion. We had a meeting for the RES division directors, for Farouk and Tom King and Mike Mayfield, where we talked about, you know, fleshing out this issue of the containment integrity in LERF. Obviously, the committee has weighed in on that already once and, I think, weighed in on the side of we'd like to see the staff take that on, is what I recall. SPEAKER: I'm not sure Tom's issue came up in that discussion. DR. KRESS: I doubt if it came up then. SPEAKER: What we don't want to do is raise this six months from now. I just want to make sure that it gets -- you know, the notion that, you know, the source term that was used to generate that LERF may not be the right source term for the PTS. DR. SEALE: We may need to highlight it. SPEAKER: Widely different situations. SPEAKER: Does that address your concerns that we, you know, somehow have to get that into a letter or a formal presentation of the committee? SPEAKER: I think the committee needs to think about what message and what way they're going to transmit it. SPEAKER: And we haven't really raised this issue with the full committee either. DR. KRESS: We can't do it as a subcommittee. It has to be the full committee. That may be a subject we might want on the full committee agenda, even though they're not ready to talk about it. SPEAKER: You can just have a few minutes to raise that concern. DR. KRESS: Okay. Let's do it that way. I'll raise the concern. SPEAKER: The staff is not ready to address it, but you know, it's a concern that we've raised. DR. KRESS: That way we'll raise it to the level. SPEAKER: So, you're not looking for a staff presentation on that. SPEAKER: No. SPEAKER: Unless you're ready. SPEAKER: At least philosophically, just to go around sort of what the division directors were talking about the other day, I believe Farouk or Dave Bessette have talked about they've tasked Professor Diafanis with looking at containment pressurization and any failures that may result from containment pressurization due to PRS, and then Mike Mayfield chimed in with the thing we talked about at the beginning here, that I'm not overly worried about containment pressurization, I'm worried about this displacement of the vessel. SPEAKER: But see, that all relates to containment failure, and Tom's concern is, once the containment fails, you know, what's an acceptable probability that you have a different consequence. SPEAKER: And again, I think a number of folks have raised different issues, and different people on the staff have different opinions as to what's going to happen or how this will be addressed, and we're clearly not ready to talk about that in any consistent way. SPEAKER: If the committee has some recommendations on how to proceed, I think it would be worthwhile hearing. DR. KRESS: Well, I can maybe suggest something, but what I'll plan on doing is articulating the concern to the full committee, and that will raise it. SPEAKER: So, we'll have the presentations, then, on the -- the two presentations. SPEAKER: What do we have, two hours, Noel? SPEAKER: Two hours. We don't need to use the whole amount. SPEAKER: Okay. We'll try and come in with shortened versions of these. DR. SEALE: Dana will figure out what to do with anything you give the committee. SPEAKER: Somehow, I suspect, with Professor Apostalokis, I wouldn't count on shortening it too much. DR. KRESS: I'd shorten it, but I wouldn't count on shortening it two hours. I'd shorten the presentation. SPEAKER: I'd shorten the presentation, but I wouldn't take too much of the time back. DR. KRESS: That's right. SPEAKER: Okay. Sounds good. SPEAKER: Thank you. DR. KRESS: As usual, a very professional presentation. We appreciate it. SPEAKER: Could we get a copy of the most recent version of the generalized flaw distribution paper, since the one we have seems to be a somewhat out of date version? SPEAKER: Yeah, I guess I should have summarized, because I knew George had asked for the P.D. Ruff NUREGs, basically, volumes one and two are available publicly now, and also the reports on Prodigal. So, Debbie took an action to get those, and I guess we can get them. SPEAKER: I have those, but I don't know whether I get those as ACRS or UC-5. You never know how they're coming in. [Inaudible conversation.] END OF TAPE 4, SIDE B
Page Last Reviewed/Updated Tuesday, July 12, 2016
Page Last Reviewed/Updated Tuesday, July 12, 2016