ML051260283
| ML051260283 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/21/2004 |
| From: | Michael Webb NRC/NRR/DLPM/LPD4 |
| To: | Schinzel G Office of Nuclear Reactor Regulation |
| Webb M, NRR/DLPM, 415-1347 | |
| Shared Package | |
| ML051600374 | List: |
| References | |
| Download: ML051260283 (4) | |
Text
Michael Webb - STP Characterization Process Page 14 From:
Michael Webb To:
Schinzel, Glen Date:
5/21/04 3:10PM
Subject:
STP Characterization Process
- Glen, I have attached comments that were forwarded to me by the staff of the Safety Programs Section of the Probabilistic Safety Assessment Branch regarding the South Texas Project characterization process as discussed in STP letters dated October 7, 2003, and March 4 and 16, 2004.
After you and your colleagues have had a chance to evaluate them, we can set up a call to discuss them further. We will target late morning on Tuesday, June 1st, as a possible time for the call.
- Thanks, Mike Webb NRC Project Manager for South Texas Project 301-415-1347 CC:
crgrantom@stpegs.com; Head, Scott DI JI-4 :
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STP Characterization Process 5/21/04 3:10PM Michael Webb MKW@nrc.gov Recipients nrc.gov owf2_po.OWFN_DO SCD1 BC (Stephen Dinsmore) nrc.gov owf4.po.OWFNDO MKW BC (Michael Webb)
Action Delivered Opened Delivered Opened Date & Time 05/21/04 03:1OPM 05/21/04 03:10PM 05/21/04 03:1OPM 05/21/04 03:1 I PM stpegs.com crgrantom CC (crgrantom@stpegs.com) geschinzel (Schinzel, Glen) smhead CC (Head, Scott)
Transferred 05/21/04 03:10PM Route nrc.gov nrc.gov stpegs.com Post Office owf2_po.OWFNDO owf4_po.OWFNDO Delivered 05/21/04 03:1OPM 05/21/04 03:10PM Files STPCategorization.wpd MESSAGE Options Auto Delete:
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Size 10229 1377 Date & Time 05/21/04 02:56PM 05/21/04 03: 1OPM No None Yes Standard No None No Standard Immediate Delivered & Opened
Change to South Texas Project's Categorization process Change 1, Letter October 7, 2003, Clarification of the up-date interval The procedural change clarifies the difference between updating the PRA, re-calculating the SSC risk-rankings with the PRA, and finalizing the risk-rankings in the Working group. All the PRA manipulations, including recalculations of the SSCs risk-rankings are done o the 36 month schedule. The working group must review and approve the SSC rankings and incorporate any changed rankings into the implementation documentation and processes. This is to be done in a "timely manner" after recalculating the SSCs risk ratikingsr/'
Evaluation:
d;a the The original documentation could be interpreted to req thatthe n eded to complete the review, approve, and incorporation of the new SSC rankihgs intoAI implerintationjprocesses by the end of the 36 month interval. STP correctly notes that this would requirea 'less than 36 month update schedule for the PRA because it takes some months for the WG to cothplete its work.
The 36 month interval is not a derived value but a selected value intended to assure that periodic updates are performed. Allowing some extra time to incorporate and change into the processes does not defeat the intent of periodicfpdateX;
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Conclusion:==
5, t::'-e This clarification is reasonable.
/
A
-8 Change 2?L6tter MarcI,4:,2004, Change inhwthe out-of-service for maintenance sensitivity study isl6onducted.
Initially, all the SSCs thate'might be out for maintenance were set in an unavailable state and the risk-rankingrall -otheS SSCs evaluat6d. This illustrates the safety significance of the population of SSCs during the maintenance activities. The licensee will now increases the unavailability of the SSGs that might be out for maintenance by a factor of ten instead of setting them to unavailable.
Evaluation:
s noted in the icen e's letter the SE states that "equipment planned to be out of service.. Is et to unavailable." The licensee process no longer complies with this statement. Further discussion'withithe license is warranted to clarify what the sensitivity study was intended to investigate and how the old and new method supports this investigation.
Change 3: Letter dated March 16,2004, Change in the use of quantitative sensitivity study results in the categorization process.
After approval of the GQA program, all SSCs were placed in the highest safety-significance category indicated by the base line results and all of the sensitivity studies. The expert panel was not authorized to reduce the ranking. STP now ranks the SCC according to its baseline ranking and provides the results of the sensitivity study for consideration by the expert panel in case they want to increase the significance.
Evaluation; Both the GQA RG and the staff's SE allow for the plai significance of the base-line result, and providing the sensitivity studies for their consideration.
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Conclusion:==
The change results in a process that fully comports w more conservative process that was used earlier.
of the