Issue Date: 10/11/01
| Inspectable Area: | Inservice Inspection Activities | |
| Cornerstone: | Initiating Events (50%) Barrier Integrity(50%) | |
| Inspection Bases: | Inservice inspection (ISI) activities can detect precursors to pressure
boundary failures in reactor coolant systems (RCS), emergency core
cooling systems (ECCS), risk-significant piping and components,
and containment systems. Degradation of pressure boundaries of
reactor coolant systems, steam generator tubes, emergency feedwater
systems, essential service water systems, and containments would
result in a significant increase in risk. This inspection is intended to
assess the effectiveness of the licensee's program for monitoring
degradation of vital system boundaries.
The scope of this inspectable area is limited to the following structures, systems, and components (SSCs): | |
| a. | Reactor coolant system pressure boundaries, including steam generator tubes in pressurized water reactors (PWRs). | |
| b. | Piping connected to the RCS, failure of which could result in an interfacing system loss of coolant accident. | |
| c. | Reactor vessel internals. | |
| d. | Risk-significant piping system boundaries. | |
| e. | Containment system boundaries (including coatings and post-tensioning systems, where applicable). | |
| Level of Effort: | Inspections are generally to be performed during each refueling outage at each reactor unit at a site. The level of ISI activities including steam generator inspections at each plant can vary significantly from outage to outage but typically should be as identified in this procedure. | |
| To assess the effectiveness of the licensee's program for monitoring degradation of the reactor coolant system boundary, risk-significant piping system boundaries, and the containment boundary. |
| 02.01 | Inspection Activities Other Than Steam Generator Tube Inspections. | ||
| a. | Review a sample of nondestructive examination (NDE) activities. The review sample should consist of: | ||
| 1. | Two or three types of NDE activities | ||
| 2. | Order of preference for reviewed NDE activities: | ||
| (a) Volumetric examinations | |||
| (b) Surface examinations | |||
| (c) Visual examinations | |||
| b. | For each NDE activity reviewed, perform the following through either direct observation (preferred method) or record review: | ||
| 1. | Verify that the activities are performed in accordance with ASME Boiler and Pressure Vessel Code requirements. | ||
| 2. | Verify that indications and defects, if present, are appropriately dispositioned in accordance with the ASME Code. | ||
| c. | Review one or two examinations from the previous outage with recordable indications that have been accepted by the licensee for continued service. Verify that the licensee's acceptance for continued service was appropriate, and in accordance with the ASME Code. | ||
| d. | If welding on the pressure boundary for Class 1 or 2 systems has been completed since the beginning of the previous refueling outage, verify for 1-3 welds that the welding acceptance (e.g. radiography) and preservice examinations were performed in accordance with ASME Code requirements. | ||
| e. | Review one or two ASME Section XI Code repairs or replacements. Verify repairs and replacements meet ASME Code requirements. | ||
| 02.02 | Steam Generator (SG) Tube Inspection Activities. | ||
| a. | In-situ Pressure Testing | ||
| 1. | Assess whether the in-situ screening criteria are in accordance with the EPRI Guidelines. In particular, assess whether assumed NDE flaw sizing accuracy is consistent with data from the EPRI examination technique specification sheet (ETSS) or other applicable performance demonstrations. | ||
| 2. | Assess whether the appropriate tubes are to be in-situ pressure tested (in terms of specific tubes and number of tubes). | ||
| 3. | Observe in-situ pressure testing activities and assess whether tubes are in-situ pressure tested in accordance with EPRI In-Situ Pressure Test Guidelines. | ||
| 4. | Review in-situ pressure test results for conformance with the performance criteria. | ||
| b. | Compare the estimated size and number of tube flaws detected during the current outage against the previous outage operational assessment predictions to assess the licensee's prediction capability. | ||
| c. | Confirm that the SG tube eddy current examination (ECT) scope and expansion criteria meet technical specification (TS) requirements, EPRI Guidelines, and commitments made to the NRC . | ||
| d. | If the licensee has identified new degradation mechanisms, the inspector should verify that the licensee has fully enveloped the problem in its analysis of extended conditions including operating concerns, and has taken appropriate corrective actions before plant startup (e.g., additional inspections, in-situ pressure testing, preventive tube plugging, etc.). | ||
| e. | Confirm that all areas of potential degradation (based on site-specific experience and industry experience) are being inspected, especially areas which are known to represent potential ECT challenges (e.g. top-of-tubesheet, tube support plates, U-bends). | ||
| f. | Confirm that all repair processes being used have been approved in the technical specifications for use at the site. | ||
| g. | Repair Criteria. | ||
| 1. | Confirm that the TS plugging limit is being adhered to, unless alternate tube repair techniques (e.g., sleeving or alternate repair criteria) have been approved by the NRC. Typically, the TS plugging limit is 40 percent through wall, although most licensees "plug on detection" due to the unavailability of qualified depth sizing techniques. | ||
| 2. | Determine whether the depth sizing repair criterion (typically 40 percent through wall) is being applied for indications other than wear or axial primary water stress corrosion cracking (PWSCC) in dented tube support plate intersections. | ||
| h. | If steam generator leakage greater than 3 gallons per day was identified during operations or during post-shutdown visual inspections of the tubesheet face, assess whether the licensee has identified a reasonable cause for this leakage based on inspection results. In addition, determine whether appropriate corrective actions are planned or were taken to address the cause. (Additional guidance on this issue is available in Part 9900: Technical Guidance, "Steam Generator Tube Primary-to-Secondary Leakage.") | ||
| i. | Confirm that the ECT probes and equipment are qualified for the expected types of tube degradation. Assess the site specific qualification of one or more techniques (e.g., equipment, data quality/noise issues, degradation mode). | ||
| j. | If the licensee has identified loose parts or foreign material on the secondary side of the steam generator, focus on licensee corrective actions in conjunction with step 02.03 below. Specifically, confirm that the licensee has taken/planned appropriate repairs of affected SG tubes, inspected the secondary side of the SG to remove foreign objects (if possible). If the foreign objects are inaccessible, determine whether the licensee has performed an evaluation of the potential effects of object migration and/or tube fretting damage. | ||
| k. | If serious questions arise regarding eddy current data analyses from steps 02.02a., d., or i., review one to five samples of eddy current data. If adequate expertise for this activity does not reside in the regional office, NRR/DE should be contacted via telephone call or e-mail and it will provide this resource. | ||
| 02.03 | Identification and Resolution of Problems. | ||
| Verify that the licensee is identifying ISI/SG problems at an appropriate threshold and entering them in the corrective action program. Determine whether the licensee's procedures direct the licensee to perform a root cause evaluation and take corrective actions when appropriate. For a selected sample of problems associated with inservice inspection and steam generator inspection documented by the licensee, verify the appropriateness of the corrective actions. See Inspection Procedure 71152, "Identification and Resolution of Problems," for additional guidance. In addition, a licensee's evaluation of industry operating experience can be critical. Determine whether licensees are correctly assessing the applicability of operating experience to their respective plants. | |||
General Guidance
| Cornerstone | Inspection Objective |
Risk Priority | Examples |
Initiating Events
or Barrier Integrity |
Verify the effectiveness of programs for monitoring the conditions of: 1) the RCS pressure boundary and containment barriers, 2) the boundaries of risk-significant components in auxiliary and ECCS piping systems | Reactor vessel
Steam generator tubes Recirculation piping ECCS connections to the RCS Auxiliary feedwater system piping Essential service water system piping Other risk-significant piping components Steel containment vessel Post-tensioning systems and steel liner for Concrete containment Shutdown and spent fuel cooling system pressure boundaries |
Reactor vessel
ultrasonic examination
Steam generator tube eddy current testing Volumetric or surface examinations of risk-significant piping components Inspection and testing of containment post-tensioning systems |
For PWRs, the effort expended and the level of detail considered in performing these activities will be determined on the basis of review of the previous inspection results summary report required by Technical Specifications, findings from the previous NRC inspection, and interaction with NRR/DE/EMCB staff with some possible edification for observations made during the upcoming inspection. Each region shall during its annual inspection planning determine for the total inspection effort where to place the emphasis in regard to non-SG ISI activities and SG inspection activities within the estimated resources.
Specific Guidance
| 03.01 | No specific guidance. | |
| 03.02 | Guidance for Steam Generator (SG) Tube Inspection Activities
The inspection should be scheduled towards the end of the SG inspection activities, if possible, because the licensee performs a significant number of evaluations (listed in 02.02) at that time. Attachment A lists specific situations which, if identified by the inspector, require notification of NRR/DE staff. In addition, the inspector is encouraged to contact NRR/DE staff to discuss any other situations or issues that are identified, that are unexpected based on the inspector's experience. As a part of the preparation for SG tube inspections, the inspector should consider reviewing the licensee's commitments in response to Generic Letters (GLs) 95-03, 95-05, 97-05, and 97-06 (see References Section 05). In addition, the inspector should review the licensee's most recent SG inspection summary report. The inspector should also consider reviewing NRC generic communications, such as relevant information notices and regulatory information summaries. Lastly, the inspector should become familiar with the industry steam generator program guidelines contained in Nuclear Energy Institute (NEI) 97-06 and several related Electric Power Research Institute (EPRI) reports (see References Section 05). The EPRI guidelines referenced do not constitute NRC requirements or commitments and technically acceptable alternative methods may be used by the licensee. Also, the staff has determined that while the guidelines represent an improvement over practices followed in the past, use of the guidelines alone does not ensure that the regulations will be satisfied. However, if the licensee has deviated from the guidelines, the basis for the deviation should be documented by the licensee. Periodically, for plants that have SGs with active degradation or other SG issues, NRR/DE staff conduct a conference call with the licensee to discuss SG tube examination activities. If scheduled by NRR, the inspector should participate in the conference calls set up between NRC and licensee staff (as the timing of the call permits), during which steam generator tube examination activities are discussed. In addition, the inspector should review summaries from previous similar conference calls and can obtain these from NRR/DE staff. The information obtained during these calls will be beneficial to the inspector for background information as well as potentially providing direction for inspection activities. | |
Use the factors discussed below to determine the allocation of the inspection effort for review of the licensee SG inspection activities as described in 02.02. If none of these factors apply, the minimum inspection requirement is to complete steps 02.02a., c., d., g.(1), h., i., and j. If any of the factors apply, this baseline inspection effort should include the inspection of all SG activities identified in 02.02. If the safety significance of the operating experience warrants, then consider increasing the depth of the baseline SG inspection effort beyond the maximum estimated resources if recommended by NRR/DE/EMCB and approved by NRR/DIPM/IIPB. | ||
| 1. | SGs with mill-annealed or stress relieved Inconel Alloy 600 tubes should receive a review as described in this section at least every other outage, or more frequently if other factors discussed below apply. For SGs with thermally-treated Inconel Alloy 600 and thermally-treated Alloy 690 tubes this review may not be required unless considerable inservice time (>9 yrs since beginning commercial operation and more than 2 operating cycles since the last NRC inspection of the licensee's SG inspection activities) or other factors discussed below apply. | |
| 2. | Deteriorating SG tube material condition as indicated by new degradation mechanism(s), or a large number or significant increase in the number of degraded or defective tubes reported by the licensee during the previous SG tube examinations. This information can be obtained from the licensee's most recent SG inspection summary report. | |
| 3. | SG tube performance criteria (i.e., operational leakage, structural integrity, or accident leakage) were not met during the previous operating cycle. | |
| 4. | PWRs with a history of primary-to-secondary leakage during the previous operating cycle (e.g. > 3 gallons per day). | |
| 5. | Reported potential degraded condition (e.g. NRC and industry information notices) due to SG design, water chemistry, material properties, or newly identified degradation mechanisms. | |
| 03.02 a-f | No specific guidance | |
| 03.02.g.2 | This criteria may be acceptable and in accordance with the licensee's TS, although experience has shown, for example, that many types of IGA/SCC cannot be sized with a sufficient degree of accuracy or reliability. In addition, this may indicate licensee practices that are inconsistent with their response to GL 97-05. If that is the case, contact NRR:DE. | |
| 03.02 h-k | No specific guidance | |
| 03.03 | No specific guidance | |
This inspection procedure is estimated to take, on the average, 16 to 32 hours for each BWR unit, and 32 to 64 hours per PWR unit, respectively, every refueling outage.
This inspection should be performed by inservice inspection specialist(s).
Inspection of the minimum sample size will constitute completion of this procedure in the Reactor Program System (RPS). That minimum sample size will consist of samples for four non-SG ISI activities representing the review of two NDE activities, one examination from the previous outage accepted by licensee, one weld on a pressure boundary, and one ASME repair; and in addition for PWRs for SG inspection activities, one sample consisting of the activities stated in 02.02.
ASME Boiler and Pressure Vessel Code Sections III, V, IX, and XI.
Plant-specific ISI program.
GL 95-03, "Circumferential Cracking of Steam generator Tube,"
GL 95-05, "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking."
GL 97-05, "Steam Generator Tube Inspection Techniques."
GL 97-06, "Degradation of steam Generator Internals."
NEI 97-06, "Steam Generator Program Guidelines."
"PWR Steam Generator Examination Guidelines," EPRI Report TR-107569.
"Steam Generator Integrity Assessment Guidelines," EPRI Report TR-107621.
"Steam Generator In Situ Pressure Test Guidelines," EPRI Report TR-107620.
Inspection Procedure 71152, "Identification and Resolution of Problems."
Part 9900: Technical Guidance, "Steam Generator Tube Primary-to-Secondary Leakage."
Tube Integrity Issues Requiring Further Evaluation by NRR Staff
If the following situations are identified by the inspector, NRR/Division of Engineering (DE) staff should be promptly contacted. NRR/DE staff will determine whether NRR involvement is necessary. In addition, the inspector is encouraged to contact NRR/DE staff to discuss any other situations or issues that are identified, that are unexpected based on the inspector's experience.
END