United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 83-02: Stress Corrosion Cracking in Large-Diameter Stainless Steel Recirculation System Piping at BWR Plants

                                                  SSINS No.   820 
                                                  OMB No.: 3150-0096  
                                                  Expiration Date:  12/31/84 
                                                  IEB 83-02 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                           WASHINGTON, D.C. 20555 

                               March 4, 1983 

IE BULLETIN NO. 83-02:   STRESS CORROSION CRACKING IN LARGE-DIAMETER 
                         STAINLESS STEEL RECIRCULATION SYSTEM PIPING AT BWR 
                         PLANTS 

Addressees: 

Those licensees of operating boiling water reactors (BWRs) identified in 
Table 1 for action. All other licensees and holders of construction permits 
(CPs) for information only. 

Purpose: 

IE Bulletin 83-02 is issued to further inform all licensees and CP holders 
about the recent generic pipe cracking problems involving BWR plants and to 
require actions of those licensees listed in Table 1. 

Description of Circumstances: 

As a result of the extensive intergranular stress corrosion cracking (IGSCC)
found at Nine Mile Point Unit 1, the NRC issued IE Bulletin 82-03, Revision 
1 for action to nine BWR plants scheduled for refueling outages in late 1982
and early 1983. Inspections pursuant to IEB 82-03, Revision 1, and 
NUREG-0313, Revision 1, have shown cracking of the main recirculation system
piping in five of seven plants examined to date. Table 2 presents a summary 
of affected plants based on information available to date. IEB 82-03 Rev.1 
discusses the IGSCC problems experienced at Nine Mile Point Unit 1. A brief 
description of the cracking problems at Browns Ferry Unit 2, Monticello and 
Hatch Unit 1 is presented below. 

At Browns Ferry Unit 2, the inservice inspection (ISI) was extended to 
include the welds joining the jet pump piping sweepolets to the manifold of 
both A and B loops. Unacceptable indications were found in the heat-affected
zone of the manifold in the loops A and B sweepolet-to-manifold joint 
nearest the end caps. All of the indications were interpreted to be cracks 
near the inside surface and were determined by UT to be about 1 1/4 inches 
long (roughly parallel to the weld), and of about 20 percent depth 
through-wall. As a result of further design analysis, review of shop 
fabrication records, and supporting in-situ metallography and ferrite 
determinations, the licensee established that the affected weld was solution 
heat treated and, therefore, not subject to the IGSCC. The licensee believes 
the cracking may be due to fatigue from flow-induced vibration. At this time 
the licensee is trying to resolve the problem. 


8212060368  
.

                                                            IEB 83-02  
                                                            March 4, 1983  
                                                            Page 2 of 6 

At Monticello, IGSCC was confirmed in one end-cap-to-pipe weld of the 
22-inch-diameter distribution header (manifold) and at five welds in the jet
pump inlet piping safe-ends which are 12 inches in diameter and are made of 
schedule 80 stainless steel. The cracks initiated on the inside surface in 
heat affected zones (HAZs) of the welds. Some cracks were oriented axially 
and some circumferentially. They varied from 1/4 inch to 1 inch in length. 
Some axial cracks in the recirculation inlet risers were found to be 
through-wall during subsequent repair activities and hydrotesting, although 
ultrasonic examination previously performed on these welds did not reflect 
this condition. 

At Hatch Unit 1, multiple linear indications characteristic of the IGSCC 
found at Monticello were identified at seven welds in the large-diameter 
recirculation and associated residual heat removal (RHR) piping. The 
affected welds were located as follows: All four 22-inch-diameter manifold 
end-caps, one 22-inch-diameter branch connection (sweepolet-to-manifold) of 
the recirculation piping, one elbow-to-pipe weld in the 20-inch RHR piping, 
and one pipe-to-pipe weld in the 24-inch diameter RHR piping. The location 
and orientation of the indications were very similar to those found at 
Monticello. The length of the indications ranged up to 1/2 inch in the axial
direction and 1 1/2-inch in the circumferential direction. Based on UT 
measurements, the depth of axial component of the crack indications were 
found to have essentially penetrated through the wall in three of the four 
end-cap welds repaired to date. 

The discovery of extensive IGSCC in the large-diameter recirculation piping 
at Nine Mile Point Unit 1 (NMP 1) after a decade of acceptable service has 
resulted in increased concern about the effectiveness of UT methodology used
in the inservice inspection of stainless steel BWR pipe welds, particularly 
in large-diameter piping. Therefore, the goal of Item 1 of IEB 82-03, 
Revision 1 was to obtain reassurance of the capability of UT inspection 
systems, techniques, and operators to detect significant IGSCC problems in 
the nine BWR plants that were performing ISI during fall/winter outages. The
performance test protocol as stated in Item 1 of IEB 82-03, Revision 1 
required the licensee and/or ISI agencies to demonstrate their capability to
detect IGSCC in large-diameter recirculation system piping before resuming 
power operation. Within this context, Electric Power Research Institute's 
NDE (EPRI-NDE) Center arranged to have five reasonably characterized, 
service-induced cracked pipe samples from the NMP 1 plant available at 
Battelle Columbus Laboratories (BCL) for industry performance capability 
demonstrations (PCDs). 

All nine plants have now satisfied the demonstration phase of IEB 82-03, 
Revision 1. By letter dated January 28, 1983, EPRI provided each licensee a 
summary of all teams performances, based on composite results from the five 
samples, plus a key to identify their ISI team's achievement. 

The PCD results at BCL have shown that excellent performance can be achieved
by well trained and experienced personnel with appropriate procedures and 
evaluation methods. However, personnel from a relatively few licensee/ISI 
organizations achieved this level of competence during the first 
qualification attempt. The overall results revealed a high failure rate 
which required retesting of the licensee/ISI organization teams. Several 
interrelated factors contributed to this rate of failure: 
.

                                                            IEB 83-02  
                                                            March 4, 1983  
                                                            Page 3 of 6 

1.   UT procedures essentially meeting only the minimum requirements of the 
     ASME Section XI code were ineffective. 

2.   UT procedures lacked specific detailed guidance on UT systems and 
     methods proven capable of detecting IGSCC in thick-walled piping. 

3.   Some UT operators were inexperienced in evaluating signal patterns of 
     reflectors in thick-walled, large-diameter piping. Thus, some cracks 
     were missed, or were called geometry effects; some geometry effects 
     were falsely called cracks. 

4.   Many UT operators, inexperienced about the nature of IGSCC in 
     large-diameter piping, did not establish finite metal path calculations
     during scanning; this resulted in falsely identified conditions. 

In view of the collective results at BCL, a continuation of the PCD program 
appears necessary. Accordingly, the EPRI-NDE Center has arranged to have a 
series of service-induced cracked specimens available for this purpose at 
their facility about March 14, 1983. 

The NRC recognizes that the prescribed actions of this bulletin exceed 
present plant ISI surveillance requirements under ASME Code Section XI 
rules. However, in view of the apparently generic pipe cracking experience 
and results of the UT demonstration trials, the NRC believes such an 
augmented ISI plan is necessary to reasonably assure the integrity of the 
recirculation system for continued operations. These actions are intended to 
apply only to the currently scheduled refueling outage for those plants 
listed in Table 1. Any licensee who finds these actions will significantly 
impact the duration of the refueling outage may request relief by written 
request to the appropriate NRC regional office. Such requests must address 
(1) the impact on the length of the outage, (2) proposed alternative 
actions, and (3) technical basis for continuing operation. 

Actions to Be Taken by Licensees of BWR Facilities Identified in Table 1: 

1.   Before resuming power operations following this scheduled or extended 
     outage, the licensee is requested to demonstrate the effectiveness of 
     the detection capability of the UT methodology planned to be used to 
     examine welds in recircirculation system piping. It is intended that 
     the demonstrations be performed at the EPRI-NDE Center on 
     service-induced cracked pipe samples made available for this purpose. 
     Each licensee should assure that the demonstration is valid for the 
     weldments of the recirculation system piping of their plant. 
     Arrangements should be made to facilitate NRC witnessing of these 
     tests. The demonstration tests will employ the following criteria. 

     a.   Ultrasonic Testing System: To ensure that the field UT system will
          respond in the same way as the demonstrated system, the same 
          procedures, standards, make and model of the UT instrument, and 
          transducers to be utilized in the plant ISI are to be used in the 
          IGSCC detection capability demonstration. 
.

                                                            IEB 83-02 
                                                            May 4, 1983 
                                                            Page 4 of 6 

b.   Personnel Performing Demonstration: UT personnel teams drawn from the 
     licensees ISI contractor who will be actually supervising, performing 
     examinations, recording data, and evaluating indications at the plant 
     site will participate in the performance demonstration tests. All 
     members of the teams must participate directly in the UT scanning, data
     recording, and evaluation of the test samples. To ensure completion of 
     testing within the time constraints below, the team should be limited 
     to six persons. For subsequent plant inspections, the 
     personnel/equipment requirements noted below will apply. 

c.   Pipe Samples: The total number of pipe samples selected should 
     constitute an equivalent of 120 inches of weld for the demonstration 
     tests. 

d.   Acceptable Criteria: Eighty percent of the total number of preselected 
     cracks in the sample control group must be called correctly to 
     constitute an acceptable test. Excessive false call rates may result in
     an unacceptable performance rating. 

e.   Demonstration Time Limit: ALARA radiation dose considerations place 
     constraints upon the time spent in field inservice inspection of a 
     weld. Therefore, a time limit of six hours, not including equipment 
     calibration time, will be imposed for the examination and data 
     recording. Completion of data evaluation and preparation of final 
     results of individual licensee/ISI contractors should take no longer 
     than one additional working day. 

f.   Review of UT Procedures: The specific procedure(s) to be used by the 
     licensee/ISI contractor(s) for plant inservice inspection is to be made
     available for review as part of the demonstration activity. It is 
     expected that the UT procedure and equipment system will have been 
     validated to be capable of detecting IGSCC by the licensee/ISI 
     contractor before initiating the scheduled demonstration activities. 

     NOTE: Some of the licensees listed in Table 1 have completed efforts to
     validate the UT detection capability to be used to perform plant 
     inspections in accordance with the requirements of Action Item I of IEB
     82-03, Revision 1. These licensees need not repeat this effort in 
     accordance with Action Item 1 of this bulletin provided that the 
     previous validated inspection group performs the new plant examination 
     using identical UT procedures, standards, make and model of UT 
     instrument, and the same make and model transducers that were used to 
     complete the previous validation effort. In addition, the UT personnel 
     employed in the new examination must be the same; or those having 
     appropriate training (documented) in IGSCC inspection using cracked 
     thick-wall pipe specimens, and are under direct supervision of the 
     Level II/III UT operators who successfully complete the performance 
     demonstration tests. 
.

                                                            IEB 83-02 
                                                            March 4, 1983 
                                                            Page 5 of 6 

2.   Before resuming power operations licensees are to augment their ISI 
     programs to include an ultrasonic examination of the following minimum 
     number of recirculation system welds: 

     a.   Ten welds in recirculation piping or 20-inch diameter, or larger. 

     b.   Ten welds of the jet pumps inlet riser piping and associated 
          safe-ends. 

     c.   Two sweepolet-to-header (manifold) welds of jet pump risers 
          nearest the end caps, if applicable to the design. 

     If flaws indicative of cracking are found in the above examination, 
     additional inspection is to be conducted in accordance with IWB 2430 of
     ASME Code Section XI. 

3.   Before resuming power operations following the outage, the licensee is 
     to report the results of the Item 2 inspection and any corrective 
     actions (in the event cracking is identified). This report should also 
     include the susceptibility matrix used as a basis for welds selected 
     for examination (e.g. stress rule index, carbon content, high stress 
     location, repair history) and their values for each weld examined. 

4.   The NRC has an on-going program to evaluate possible additional 
     longerterm requirements relative to the IGSCC problem in the BWR 
     recirculation system piping. The NRC may need additional information as
     part of this program. Therefore, licensees are requested to retain the 
     records and data developed pursuant to the inspections performed in 
     accordance with Item 2. 

5.   The written report required by Item 3 shall be submitted to the 
     appropriate Regional Administrator under oath or affirmation under 
     provisions of Section 182a, Atomic Energy Act of 1954, as amended. The 
     original copy of the cover letter and a copy of the reports shall be 
     transmitted to the U.S. Nuclear Regulatory Commission, Document Control
     Desk, Washington, D.C. 20555 for reproduction and distribution. 

This request for information was approved by the Office of Management and 
Budget under clearance number 3150-0096 which expires 12/31/84. Comments on 
burden and duplication should be directed to the Office of Management and 
Budget, Reports Management, Room 3208, New Executive Office Building, 
Washington, D. C. 20503. 

Since Big Rock Point and LaCrosse do not have jet pumps, the licensees 
     of these plants should provide an equivalent sampling of the 
     recirculation  piping system based on the plant design. 
.

                                                            IEB 83-02  
                                                            March 4, 1983  
                                                            Page 6 of 6 

Although no specific request or requirement is intended, the following 
information would help the NRC evaluate the cost of implementing this 
bulletin: 

     o    Staff time to perform requested demonstration. 

     o    Staff time to prepare written responses. 

     o    The occupational radiation exposure experienced. 

If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office or one of the technical
contacts listed below. 


                              Richard C. DeYoung, Director 
                              Office of Inspection and Enforcement 

Technical Contact:  William J. Collins, IE 
                    492-7275 

                    Warren Hazelton, NRR 
                    492-8075 

Attachments: 
1.   Table 1 
2.   Table 2 
3.   List of Recently Issued IE Bulletins
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