ML091831359

Draft RAI on EPU Containment Overpressure Issue

ML091831359
Person / Time
Site:	Monticello
Issue date:	07/02/2009
From:	NRC/NRR/DSS/SCVB
To:
Tam P
Shared Package
ML091831358	List: ML091831355 ML091831359
References
TAC MD9990
Download: ML091831359 (1)

Text

Accession No. ML091831359 DRAFT MONTICELLO EPU Additional RAIs

1. Please refer to calculation CA-07-038 Rev 0, page 6, the head loss (Hloss) in pump inlet piping and strainer is given by:

Hloss = (Hpool - Hpump) - (Ps/( + Vs2/2g + Z)

Where:

Z=0 Hpump = centerline elevation of pump suction

= 897.833 ft (given in calc # 2008-11723 Rev 0, Table 2.6, page 6 of 23)

Hpool = 908 ft- 7.364 in = 908.614 ft (calc # CA=007-038 page 16 of 72 for case 2, and has the same value for all cases)

Therefore Hloss = 10.78 - (Ps/( + Vs2/2g) ft For Case 2, page 18, the limiting value of the term (Ps/( + Vs2/2g) is 5.9691 ft for RHR-B pump (time 472096) and flow of 4000 gpm.

Therefore the maximum piping and strainer head loss in RHR B suction piping and strainer loaded with debris is given by, Hloss = 10.78 - 5.9691 = 4.81 ft Please refer to calculation # 2008-11723 Rev 0, page 12 of 23, Table 5.3, for the SBA case the piping friction and strainer (with debris) loss is calculated to be 5.7 ft which is for RHR-C. for the same flow of 4000 gpm as above for RHR B pump.

Please explain why RHR B was chosen as a limiting pump for long term LOCA NPSHA calculation for case 2 for which the piping and strainer head loss is 4.81 ft as compared to RHR C which has a piping and strainer head loss of 5.81.

Please explain why CS B was chosen as a limiting pump for long term LOCA NPSHA (case 2 in calc # 07-038) for a flow of 3029 gpm, and CS A pump was chosen as limiting for SBA with a flow of 3020 gpm (calc # 2008-11723 Tables 2.3 and 5.3)

2. Safety Analysis Report for Monticello Constant Pressure Power Uprate (Enclosure 5 of the license amendment request), Section 2.5.1.4, page 2-118, for case 1 and case 2, states This case assumes one Core Spray (CS) pump and one Residual Heat Removal (RHR) pump with one heat exchanger operating. Suppression pool cooling is manually initiated at 40 minutes into the event. In document OPL-4a, under the heading LPCS/CS parameters, item m and n states, vessel water level below which LPCS/CS will automatically be actuated is 422.5 in, and vessel water level above which LPCS/CS will be shut off is 531.5 in.

For an Appendix R event, please describe how is the CS pump operation modeled in the SHEX code and confirm that it is consistent with operating procedures. If it is operator initiated, at what time during the event is the CS flow (3029 gpm given in calculation #

2008-11723 Rev 0, Section 2.3, Table 2.3) initiated. In case the operating procedures require automatic initiation of CS system, please confirm that OPL-4a, and the SHEX model is consistent with the procedures.