ML062560277
| ML062560277 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 09/11/2006 |
| From: | Thadani M NRC/NRR/ADRO/DORL/LPLIV |
| To: | Hicks J TXU Power |
| Thadani, M C, NRR/DORL/LP4, 415-1476 | |
| References | |
| TAC MC9503 | |
| Download: ML062560277 (4) | |
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- 1 oa.
lohan Thaciani - MG9503 APLB Proposed HAIs -.wpd Page 4 REQUEST FOR ADDITIONAL INFORMATION RISK-INFORMED INSERVICE INSPECTION RELIEF REQUEST SECOND TEN-YEAR INSERVICE INSPECTION PROGRAM RELIEF REQUEST A-1 TXU ELECTRIC COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2 DOCKET NO. 50-446
- 1. Regulatory Guide (RG) 1.178, An Approach for Plant-Specific Risk-Informed Decisionmaking for Inservice Inspection of Piping, Revision 1, dated September.2003, replaced the original "For Trial Use" RG dated September 1998. Revision 1 of the RG 1.178 includes guidance on what should be included in risk-informed inservice inspection (RI-ISI) submittals, particularly in dealing with probabilistic risk assessment (PRA) issues.
Specifically, on Page 28 of RG 1.178, the following is stated regarding the information that should be included in' a submittal:
"A description of the staff and industry reviews performed on the PRA. Limitations, weakness, or improvements identified by the reviewers that could change the results of the PRA should be discussed. The resolution of the reviewer comments, or an explanation of the insensitivity of the analysis used to support the submittal to the comment, should be provided."
In your original risk-informed inseivice inspection (RI-ISI) submittal, dated February 15, 2001, you discussed PRA quality, noting that "the current PSA is scheduled to undergo the Westinghouse certification process in 2001". Hence, at that time your PRA had not yet been industry peer-reviewed, but it apparently has been since.
In your current relief request you note that "An update to the PRA was performed at the end of 2004. Although the revision to the PRA model occurred after the end of the Interval, it was decided to include the revision in this evaluation and update." The staff concurs with the decision to re-perform the analysis, given the update to the PRA model.
However, between the original RI-ISI submittal and the current relief request, there is no summary of results.of the above industry peer review, or status of the PRA model used to re-perform the analysis relative to it. Hence, to establish confidence that the quality of the PRA is sufficient to support your recent RI-ISI analysis:
- a.
Please provide a listing of the Level A and B Facts and Observations (F&Os) from the above peer review, along with their resolutions. If there are outstanding F&Os that were not resolved at the time of your re-performed analysis, please explain why resolving them would not have a potentially significant impact on the RI-ISI program (either from the risk-significance of pipe segments or from an overall delta-risk perspective).
- b.
In addition, please identify any other "open items" with the PRA model that was used to re-perform the RI-ISI analyses that would meet the threshold of a Level A or B F&O, and
lohan I hadani - MU9503 APL8 Proposed HAIS -.wpd h
a.oo sPage 5
5 ENCLOSURE explain why resolving them would not have a potentially significant impact on the RI-ISI program (again, either from the risk-significance of pipe segments or from an overall delta-risk perspective).
- 2. Partially as a result of the re-performance of the RI-ISI analysis, and partially due to your inclusion of 4 NPS Class 2 Auxiliary Feedwater piping into the RI-ISI scope, Table 1 indicates 12 additional inspection locations in the CPSES 2 FWS system and 9 additional inspection locations in the CPSES 2 AFW system proposed for the second interval, relative to the proposed inspection locations in those systems from the original RI-ISI submittal. All 21 of these locations are in High Consequence segments, susceptible only to the flow-accelerated corrosion (FAC) damage mechanism (DM). Due to your Generic Letter 89-08 augmented inspection program for FAC you were able to place the segments of these welds into Risk Category 4 (medium) (as opposed to Risk Category 1 (high)),
requiring inspection of 10% (rather than 25%) of these welds in each of the two systems.
- a.
Please describe the type of non-destructive examination(s) you intend to perform on these 21 welds, and whether or not you intend to credit the Generic Letter 89-08-related augmented inspection program examinations toward the completion of RI-ISI-required inspections for these 21 locations.
- b.
If you intend to credit the Generic Letter 89-08-related augmented inspection.
program examinations toward the completion of RI-ISI-required inspections for these 21 locations, please explain your rationale for doing this, given the nature of the examinations performed for FAC-susceptible locations.
- 3. In your original RI-ISI submittal, dated February 15, 2001, you stated that a deviation to the EPRI RI-ISI methodology has been implemented in the failure potential assessment for the potential for thermal stratification, cycling and striping (TASCS). In your response to NRC Request for Additional Information, dated October 25, 2001, you clarified that the methodology for assessing TASCS in the CPSES RI-ISI program is identical to the methodology described in the Electric Power Research Institute (EPRI) letter to NRC dated March 28, 2001, and indicated that you will update the RI-ISI program based on the final EPRI Materials Reliability Program (MRP) guidance as warranted.
- a.
Please confirm that, upon issuance, TXU will update the CPSES RI-ISI program to incorporate NRC-approved final MRP guidance on thermal fatigue management for assessing TASCS.
"In Table 1 of your current relief request, you indicate that for Category B-J elements in the RCS system with a damage mechanism of Thermal Transients (TT) only (one group of these elements was designated Risk Category 2 and a second group was designated Risk Category 5), there were typographical errors in Table 5-2-2 of your original submittal, such that instead of 6 elements in Risk Category 2 there are really 11 such elements, and instead of 45 elements in Risk Category 5 there are really only 40 such elements.
You indicated that this error had no impact on results (i.e. - number of required inspections for each of these groups). It appears that Table 5-1-2 of your original submittal, the counterpart table for Unit 1, may also contain these same errors.
- a.
Please confirm that you have addressed these potential errors in your RI-ISI program documents, making the appropriate corrections and assessing impact on results. Please report any changes made to the affected program documents as a result."
Mark Melnicoff