ML050450584

E-mail Dated 05/03/04 RAI Questions Regarding RBS Drywell Test Interval Intervention

ML050450584
Person / Time
Site:	River Bend
Issue date:	05/03/2004
From:	Michael Webb NRC/NRR/DLPM/LPD4
To:	Brice W Entergy Operations
Webb M, NRR/DLPM, 415-1347
Shared Package
ML050610499	List: ML050450581 ML050450584 ML050450585 ML050450588 ML050450592 ML050450593 ML050450595 ML050610487
References
LAR 2004-02, TAC MC2071
Download: ML050450584 (3)

Text

Michael Webb - RAI Questions regarding RBS Drywell Bypass Test Interval Extension - With attachment Page 1 From: Michael Webb To: WBrice~entergy.com Date: 513/04 9:19AM

Subject:

RAI Questions regarding RBS Drywell Bypass Test Interval Extension - With attachment Bill, I have attached RAI questions that were formally forwarded to me by the staff of the Safety Programs Section of the Probabilistic Safety Assessment Branch regarding the River Bend Station License Amendment Request (LAR 2004-02) dated February 16, 2004, (NRC TAC MC2071) which seeks a one-time extension of the Drywell Bypass Test Interval.

These questions are unchanged from the draft ones I sent to you April 13, 2004.

In your response to NRC, please reference today's e-mail date.

Thanks, Mike Webb NRC Project Manager for Rver Bend Station I eerg d4 to T't 301-415-1347 CC: Robert Palla M ci4 'ed

I C:\W INDOWS\TEMP\GW}00001 .TMP -Page 1 is Mail Envelope Properties (409646E0.95D: 5: 21368)

Subject:

RAI Questions regarding RBS Drywell Bypass Test Interval Extension -

With attachment Creation Date: 5/3/04 9:19AM From: Michael Webb Created By: MKW~nrc.gov Recipients Action Date & Time entergy.com Transferred 05/03/04 09: 19AM WBrice (WBrice @entergy.com) nrc.gov owf2_po.OWFNDO Delivered 05/03/04 09:19AM RLP3 CC (Robert Palla) nrc.gov owf4_po.OWFNDO Delivered 05/03/04 09: 19AM MKW BC (Michael Webb) Opened 05/03/04 09:34AM Post Office Delivered Route entergy.com owf2_po.OWFNDO 05/03/04 09:19AM nrc.gov owf4_po.OWFNDO 05/03/04 09: l9AM nrc.gov Files Size Date & Time MC207 lRAI.wpd 6502 05/03/04 09:18AM MESSAGE 1367 05/03/04 09: 19AM Options Auto Delete: No Expiration Date: None Notify Recipients: Yes Priority: Standard Reply Requested: No Return Notification: None Concealed

Subject:

No Security: Standard To Be Delivered: Immediate Status Tracking: Delivered & Opened

NRC Staff Request for Additional Information Regarding Drywell bypass leakage test (DWBT) Interval Extension for River Bend Station (RBS)

Request dated February 16, 2004 (TAC MC2071)

1. Over the past three years, NRC has issued at least four separate amendments to the River Bend Station (RBS) operating license based in part on risk considerations. These include amendments dated July 3, 2001 and August 16, 2001, allowing removal of the inclined fuel transfer system (IFTS) primary containment isolation blind flange and operation of the IFTS bottom valve when primary containment operability is required, an amendment dated September 25, 2002, extending the allowed outage time (AOT) for a Division I or Division II emergency diesel generator from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 14 days, and an amendment dated March 5, 2003, allowing a one-time extension of the containment integrated leak rate test (ILRT) interval to 15 years. Please discuss whether and how each of these changes have been included in the baseline RBS PRA model used to support the present request for a one-time extension of the drywell bypass leakage test (DWBT) interval.

2. Please describe the major differences in models and assumptions between: Revision 3 of the PRA on which the IFTS change and ILRT extension were based, Revision 3A of the PRA on which the RBS diesel generator AOT extension was based, and Revision 3B of the PRA on which the current DWBT extension request is based. Provide a table summarizing the contribution to total CDF and total LERF by accident class for each of these PRA versions.

3. NRC recently issued amendments to the Grand Gulf and Clinton operating licenses extending the test interval for both the ILRT and the DWBT to 15 years. These amendments were based in part on a determination that the combined effect of both test interval extensions on risk was small. In contrast, Entergy previously requested and received a one-time extension of the containment ILRT interval to 15 years, and is now separately requesting a similar extension for the DWBT interval. To provide insights into cumulative risk impacts, please provide an assessment of the combined effect of the ILRT and DWBT interval extensions on risk (i.e., population dose, LERF, and conditional containment failure probability) similar to that provided in the baseline analyses for the other two Mark IlIl plants.