ML041770171

Email from Mwebb to Wbrice RAI Questions Regarding RBS Bypass Test Interval Extension

ML041770171
Person / Time
Site:	River Bend
Issue date:	04/13/2004
From:	Michael Webb NRC/NRR/DLPM/LPD4
To:	Brice W Entergy Operations
Webb M, NRR/DLPM, 415-1347
Shared Package
ML042110357	List: ML041770157 ML041770164 ML041770166 ML041770168 ML041770170 ML041770171 ML041770176 ML041770178 ML042110302
References
LAR 2004-02, TAC MC2071
Download: ML041770171 (4)

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- . DylAdbi I It UU04di MALVI ISIU1 I t-age i From: Michael Webb To: WBrice@entergy.com Date: 4/13/04 8:27AM

Subject:

RAI Questions regarding RBS Drywell Bypass Test Interval Extension Bill, I have attached RAI questions that were 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.

After you and your colleagues have had a chance to evaluate them, we can set up a call to discuss them further if you desire to do so.

Thanks, Mike Webb NRC Project Manager for Rver Bend Station 301-415-1347 kIVE-k 8101JA 7-n-77,0^,/

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Subject:

RAI Questions regarding RBS Drywell Bypass Test Interval Extension Creation Date: 4/13/04 8:27AM From: Michael Webb Created By: MKW@nrc.gov Recipients Action Date & Time entergy.com Transferred 04/13/04 08:27AM WBrice (WBiice@entergv.com) nrc.gov owf4_po.OWFNDO Delivered 04/13/04 08:27AM MKW BC (Michael Webb) Opened 04/13/04 08:27AM Post Office Delivered Route entergy.com owf4_po.OWFNDO 04/13/04 08:27AM nrc.gov Files Size Date & Time MC2071RAI.wpd 6502 04/13/04 08:14AM MESSAGE 1312 04/13/04 08:27AM 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.