ML100630233

Response to Tennessee Valley Authority Request for Plant Water Flow Information

ML100630233
Person / Time
Site:	Watts Bar
Issue date:	01/26/2010
From:	Yang H - No Known Affiliation
To:	Office of Nuclear Reactor Regulation
References
TAC MD8203
Download: ML100630233 (3)

Text

Response to TVA Request for Plant Water Flow Information Page 1 of 3 Response to TVA Request for Plant Water Flow Information I. Questions

a. Provide flow rates and the number of operating pumps of the ERCW and RCW systems during dual unit operation. Supporting documents and design information are also requested.

b. Provide technical justifications in response to NRC RAI Number H-21:

The ER states: Operation of Unit 2 along with Unit 1 would result in an increase of raw water intake usage at the IPS by an estimated 33 percent compared to sole operation of Unit 1. Why does water withdrawn at the IPS only increase 33 percent for a doubling of the amount of cooling needed?

II. Response to Item a Essential Raw Cooling Water Calculation EPMJFL120285 (Reference 1) determines the Essential Raw Cooling Water System (ERCW) flow requirements during various operating modes and design accident conditions of WBNP Units 1 and 2. Based on Table 18 of Reference 1, the total ERCW flow supporting normal power operation for both units (or the normal/normal condition) is approximately 21,500 gallons per minute (gpm). The normal maximum condition (with Unit 1 Cold Shutdown and Unit 2 Hot Shutdown) is approximately 36,100 gpm. The accident maximum ERCW flow for a worst case scenario (with Unit 1 LOCA and Unit 2 Containment Cooling) is 47,600 gpm.

Reference 1 (Page 66) states that the operation of two pumps per train is sufficient to supply ERCW water during normal operation for the two unit plant. However, the operator would determine the number of pumps required in each train on the basis of operating mode combination, alignment of the equipment to the train and total train flows. As an example, Page 17 of Reference 2 indicates that a total of two pumps (i.e., one pump per train) is used for dual units during normal operation (Mode 16). However, depending on the system demand, the operator could run four ERCW pumps (i.e., two pumps per train) as long as the minimum flow requirements for the pumps are met.

Raw Cooling Water Based on the Raw Cooling Water (RCW) System Operating Instruction, SOI-21.01 (Ref. 3),

the RCW system is a non-safety related shared system. The RCW system includes seven pumps at the IPS. Six of these pumps operate during normal plant operation, while the seventh pump serves as an installed spare. The rated capacity for each RCW pump is 5,135 gpm at 240 ft head (Ref 3, Page 18). However, the pumps will not be running at rated

Response to TVA Request for Plant Water Flow Information Page 2 of 3 capacity during normal operation due to the system pressure drop. The MULTIFLOW model of the RCW system is based on a previous calculation of the pressure drops in the RCW system (Ref. 4). A total flow of 30,600 gpm at the IPS for dual unit flow is estimated based upon the data contained within Reference 4 and the MULTIFLOW model; however, Reference 4 itself does not explicitly state the total flow.

Summary The flow rates and number of pumps discussed above are summarized in the table below:

System No. of Pumps Flow Rate (gpm) Source Document ERCW (Normal Normal)(a) 2 21,500 Ref 1, Table 18; Ref 2, Pg.17 ERCW (Normal Maximum)(b) 4 36,100 Ref 1, Table 18; Ref 2, Pg.17 ERCW (Accident Maximum)(c) 4 47,600 Ref 1, Table 18; Ref 2, Pg.17 RCW (Normal) 6 30,600 Estimate based on Ref 4 (a) Both units are in normal power operation.

(b) Unit 1 Cold Shutdown and Unit 2 Hot Shutdown.

(c) Unit 1 LOCA and Unit 2 in Containment Cooling mode.

References

1. ERCW System Flow Requirements, EPMJFL120285, Rev. 015.

2. Essential Raw Cooling Water (ERCW) System Pressure Drop Calculation, MDQ00006720080341, Rev. 000.

3. RCW System Operating Instruction, SOI-24.01, Rev 0044.

4. Startup Pressure Loss Calculation For The Raw Cooling Water System, 0HCGMJG063082, Rev 002.

III. Response to Item b:

During Unit 1 only operation, the RCW serves as the cooling water source for both the Unit 1 specific components and common components of various non-safety related systems located in the Auxiliary and Turbine Buildings. Common non-safety related systems received RCW cooling water include: Raw Service Water System, Water Treatment Plant System, Ice Condenser System Heat Exchanger, and General Ventilation System Chillers located in the Auxiliary Building.

When Unit 2 operation begins, the existing RCW cooling loads will increase by the amount of water used to cool only those Unit 2 specific components. Therefore, the RCW cooling load requirements will not be double for dual unit operation. The percent increase in the raw water intake (mainly for ERCW and RCW) due to Unit 2 operation is estimated as follows:

Response to TVA Request for Plant Water Flow Information Page 3 of 3 Estimate of Water Need Increase due to Start of Unit 2 Operation Unit 1 Operation Dual Unit Operation (with Unit 2 under Construction) gpm gpm ERCW Water Need 18,860 Note 1 ERCW Water Need 21,500 Note 2 RCW Water Need 17,300 Note 4 RCW Water Need 30,600 Note 3 T otal 36,160 T otal 52,100 T otal Increase 52,100 - 36,160 = 15,940 Corresponding % of Water Need Increase after Adding Unit 2 Operation 44%

Note 1: Data from ERCW System Flow Requirements, EPMJFL120285, Rev. 015, Table 39.

Note 2: Data from ERCW System Flow Requirements, EPMJFL120285, Rev. 015, Table 17.

Note 3: The RCW's 30,600 gpm for dual-unit operation is estimated based upon the data contained within "Startup Pressure Loss Calculation For The Raw Cooling Water System", 0HCGMJG063082, Rev 002 and the MULTIFLOW model; however, this referenced calculation itself does not explicitly state the total flow.

Note 4: The RCW's 17,300 gpm for Unit 1 operation is based on estimated RCW flow distribution for the 30,600 gpm (Note 3).

(4,000 gpm for Common Systems, 17,300 gpm for Unit 1, and 17,300 gpm for Unit 2, totaling 30,600 gpm)

Prepared by: Hang Yang Date: 1//26/2010 Reviewed by: Lien Nguyen Date: 1//26/2010 Approved by: Kirk Peterman Date: 1//26/2010