ML041770176
| ML041770176 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/13/2004 |
| From: | Thadani M NRC/NRR/DLPM/LPD4 |
| To: | Buschbaum D South Texas |
| Thadani M, NRR/DLPM, 415-1476 | |
| Shared Package | |
| ML042110357 | List: |
| References | |
| Download: ML041770176 (2) | |
Text
..:%I L:1rt-1VVJUUUU 1.1I MV Page 1 7oq4-- 0 - Lrq -
Mail Envelope Properties (407BF5B7.B89:15: 21310)
Subject:
Creation Date:
From:
PREIDMNARY RAI FOR TS 3.6.3 CHANGE 4/13/04 iO:14AM Mohan Thadani I
Created By:
MCT~nrc.gov Recipients nrc.gov owf2_po.OWFNDO MAS7 CC (Martin Stutzke)
Action Delivered Opened Date & Time 04/13/04 10:14AM 04/13/04 10:15AM txu.com dbuschbl (1nternet:dbuschbl @txu.com)
Transferred 04/13/04 10:16AM Post Office owf2_po.OWFNDO Delivered 04/13/04 10:14AM Date & Time 04/13/04 10:14AM Route nrc.gov txu.com Files MESSAGE Options Auto Delete:
Expiration Date:
Notify Recipients:
Priority:
Reply Requested:
Return Notification:
Concealed
Subject:
Security:
To Be Delivered:
Status Tracking:
Size 4336 No None Yes Standard No None No Standard Immediate Delivered & Opened
1IU11alt I [IdtUdWH - r1nCL11wN1MhT rimi rum i,Z3.0. UjIPdA1tZPae Page 1 From:
Mohan Thadani To:
lntemet:dbuschbl @txu.com Date:
4/13/04 10:14AM
Subject:
PRELIMNARY RAI FOR TS 3.6.3 CHANGE Denny.
We have reviewed your request 03-004 for license amendment revision to Technical Specification (TS) 3.6.3, regarding extension of the containment isolation valves' surveillance frequency. We have identified a need for additional information, outlined below. to assist us In completion of our review.
Please review the questions below, and arrange for a telephone conference to discuss your response. A formal response to these questions, and action completion schedule will be discussed during the call.
Thanks.
Mohan Thadani (301) 415-1476 PRELIMINARY REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST 03-004 TO EXTEND SURVEILLANCE FREQUENCY FOR COMANCHE PEAK CONTAINMENT ISOLATION VALVES.
- 1.
Describe the two methods mentioned in Section 4.4 of the license amendment request that were used to evaluate the risk significance of the proposed change (ISLOCA methodology and RI-IST methodology). For each methodology, provide calculation details and results that support the conclusion that the proposed change is not risk significant.
- 2.
Identify the approach used by TXU to estimate LERF (e.g., a complete Level 2 PRA, the simplified approach in NUREG/CR-6595, etc.). Provide the LERF prior to implementing the proposed change (baseline LERF), the percentages of its major contributors, and the percentage attributed to containment isolation failure.
- 3.
In the Level 2 PRA, what is the definition of containment isolation failure? Relate the size of the isolation failure assumed to cause a large release in the PRA to the administrative limits for measured leakage through the valves with resilient seats (12,500 sccm for the containment purge and hydrogen purge valves, and 15,100 sccm for the containment pressure relief valves, as stated in Section 4.2 of the license amendment request).
- 4.
Describe the significant causes of containment isolation failure (e.g., isolation valves fail to close on demand, isolation valve leakage, etc.) and indicate the approximate percentage that each failure cause contributes to the overall containment isolation failure probability.
- 5.
Describe the time-dependent leakage rate through valves with resilient seats, citing relevant studies or research. How much increase in leakage rate can be expected after extending the current surveillance test interval (3 months or 6 months, depending on valve type) to 18 months? Since (a) the total containment leakage rate is the sum of individual component leakage rates, and (b) the proposed increase in test interval may cause increased leakage rates for valves with resilient seats, the licensee should demonstrate that the proposed 18-month test interval does not increase the total containment leakage rate to the extent that it approaches the size of the isolation failure assumed to cause a large release in the PRA.