ML091970004

Draft RAI on Containment Overpressure Issue for the Proposed EPU Amendment

ML091970004
Person / Time
Site:	Monticello
Issue date:	07/14/2009
From:	Lobel R, Ahsan Sallman NRC/NRR/DSS/SCVB
To:
Tam P
Shared Package
ML091970003	List: ML091970002 ML091970004
References
TAC MD9990
Download: ML091970004 (2)

Text

Document Accession NO. ML091970004 Package Accession No. ML091970003 ADDITIONAL QUESTIONS REGARDING MONTICELO EXTENDED POWER UPRATE CONTAINMENT OVERPRESSURE ISSUE The following questions refer to Section 2.6.5 of the PUSAR (NEDC-33322P), i.e., Enclosure 5 to the November 5, 2008, submittal.

1. Figure 2.6-7: Why do RHR C 1% and 3% lines merge for the needed containment accident pressure?

2. Describe or reference a description of the App R scenarios for the Appendix R events on which the App R NPSH analyses are based. Please include the timing of significant events and operator actions and their timing.

3. For the station blackout event, please explain the scenario in the first paragraph of the station blackout section (Page 2-184) which states that the HPCI pump takes suction from the CST, then switches to the suppression pool, then switches suction back to the CST.

4. Figure 2.6-3: Please explain why the 1% and 3% RHR 'B' NPSHr curves coincide.

5. Please provide numerical values in the following table in the blank cells and verify the information in the filled-in cells:

Event Pump Flow rate Peak Max Containment Duration of Min NPSHR NPSHR (ft)

(gpm) Suppression Containment Pressure Use of NPSHA Criterion Pool Pressure available @ Containment (ft)

Temperature Needed (psia) time of Max Accident

(°F) Containment pressure Pressure Needed (psia)

LOCA-ST CS 1 8489 (2 pumps) 3%

CS 2 RHR 1 17282 (4 pumps)

RHR 2 RHR 3 RHR 4 LOCA-LT CS 1 3035 3%

CS 2 3029 RHR 1 4000

RHR 2 RHR 3 RHR 4 ATWS- CS 1 3035 3% 22 PRFO CS 2 0 -

Case 1 RHR 1 4000 -

RHR 2 4000 23 RHR 3 4000 -

RHR 4 4000 -

ATWS- CS 1 3035 3%

PRFO CS 2 0 Case 2 RHR 1 4000 RHR 2 4000 RHR 3 4000 RHR 4 4000 ATWS CS 1 3035 3%

LOOP CS 2 0 RHR 1 4000 RHR 2 4000 RHR 3 4000 RHR 4 4000 APP R- CS 1 0 3%

SORV CS 2 3029 RHR 1 0 RHR 2 4000 RHR 3 0 RHR 4 0 APP R No CS 1 0 3%

SORV CS 2 3029 RHR 1 0 RHR 2 4000 RHR 3 0 RHR 4 0 Small CS 1 3020 3%

Steam Line CS 2 0 Break RHR 1 4320 to 600 sec 4000 (> 600 sec)

RHR 2 0 RHR 3 0 RHR 4 0 Station CS 1 0 Blackout CS 2 0 RHR 1 4000 RHR 2 4000 175.5@4 hrs RHR 3 4000 RHR 4 4000 HPCI 3000

6.a Please provide the basis for each of the flows in the above table and why the flows are conservative for analyses using containment accident pressure.

6.b How do these flows compare with the flow rates from the same pumps assumed in other Monticello EPU safety analyses for the same events. For example, how do the flow rates for the CS and RHR pumps used for the LOCA NPSH analyses compare with the flow rates used to show compliance with 10 CFR 50.46?

7. Explain the choice of PRFO Ccase 1, PRFO Case 2 and LOOP as the ATWS cases to consider in evaluating the need for ident pressure.