ML20210Q095
| ML20210Q095 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 08/28/1997 |
| From: | Dick G NRC (Affiliation Not Assigned) |
| To: | Johnson I COMMONWEALTH EDISON CO. |
| References | |
| GL-87-12, TAC-M97877, TAC-M97878, NUDOCS 9708280098 | |
| Download: ML20210Q095 (4) | |
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August 28, 1997 Ms. Irene Johnson, Acting Manager s
Nuclear Regulatory Services-Commonwealth Edison Company Executive Towers West 111 1400 Opus. Place,- Suite 500 Downers Grove, IL 60515
SUBJECT:
BRAIDWOOD NUCLEAR POWER STATION, UNITS 1 AND 2 - GENERIC l.ETTt'R 87-12 (TAC N05. M97877 AND M97878)
Dear Ms. Johnson:
By letter dated October 19, 1996, Commonwealth Edison Company (Comed) submitted a supplemental response to Generic Letter (GL) 87-12. " Loss of Residual Heat Removal While The Reactor Coolant System is Partially Filled."
In the supplemental response, Comed informed the NRC of a revision to its commitments-for Braidwood Nuclear Power Station, Units 1 and 2.
The revision changes the allowable residual heat removal loop flow rate from "approximately 1000 gpm" to 'between 1000-3300 gpm" during draining and mid-loop operation.
The staff has reviewed the change to Comed's commitments and has determined that the change is acceptable. The staff's evaluation is enclosed.
Sincerely, 1"1 George F. Dick, Jr., Senior Project Manager Project Directorate 111-2 Division of Reactor Projects - lil/IV Office of Nuclear Reactor Regulation Docket Nos. SIN-50-456, STN 50-457
Enclosure:
Evaluation cc w/ encl:
see next page Distribution:
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s I. Johnson Braidwood Station Commonwealth Edison Company Unit Nos. I and,2 cc:
Michael Miller, Esquire Mr. Ron Stephens Sidley and Austin Illinois Emergency Services One First National Plaza and Disaster Agency Chicago, Illinois -60603 110 East Adams Street Regional Administrator U.S. NRC, Region III Chairman 801 Warrenville Road Will County Board of Su>ervisors Lisle, Illinois 60532-4351 Will County Board Court 1ouse.
Joliet, Illinois 60434 Illinois Department of Nuclear Safety Ms. Lorraine Creek Office of Nuclear Facility Safety Rt. 1, Box 132 1035 Outer Park Drive Manteno, Iliinois 60950 Springfield, Illinois 62704 Attorney General Document Control Desk-Licensing 500 South Second Street Commonwealth Edison Company Springfield, Illinois 62701 1400 Opus Place, Suite 400 Downers Grove, Illinois 60515 George L. Edgar Morgan, Lewis and Bochius Mr. William P. Poirier 1800 M Street, N.W.
Westinghouse Electric Corporation Washington, DC 20036 Energy Systems Business Unit Post Office Box 355. Bay 236 West Commonwealth Edison Company Pittsburgh, Pennsylvania 15230 Braidwood Station Manager Rt. 1, Box 84 Joseph Gallo Braceville, Illinois 60407 Gallo & Ross 1250 Eye St., N.W., Suite 302 EIS Review Coordinator Washington, DC 20005 U.S. Environmental Protection Agency 77 W. Jackson Blvd.
Ms. Bridget Little Rorem Chicago, Illinois 60604-3590 Appleseed Coordinator 117 North Linden Street Mr. H. G. Stanley Essex, Illinois 60935 Site Vice President Braidwood Station Howard A, Learner Commonwealth Edison Company Environmental Law and Policy RR #1, Box 84 Center of the Midwest Braceville, IL 60407 203 North LaSalle Street Suite 1390 Chicago, Illinois 60601 U.S. Nuclear Regulatory Commission Braidwood Resident Inspectors Office Rural Route #1, Box 79 Braceville, Illinois 60407
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EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CONCERNING CHANGE TO RESIOVAL HEAT REMOVAL FLOW RATES QVRING DRAINING AND HID-LOOP OPERATION
{0MMONWEALTH EDISON COMPANY BRAi] WOOD STATION. UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND STN 50-457
1.0 INTRODUCTION
In response to Generic Letter (GL) 87-12, Item 8, regarding the potential vortexing and air ingestion in the residual heat removal (RHR) pumps during draining and mid-loop operation, the Commonwealth Edison Company (Comed, the licensee) responded that the RHR loop flow rate will be reduced to approximately 1000 gpm prior to draining and mid-loop operation.
This proposed RHR flow limitation was supported by a Westinghouse analysis documented in its letter dated July 12, 1989 (Reference 1). The NRC staff reviewed and approved this commitment.
In order to facilitate reactor coolant system cooldown with increased decay heat removal capability, by letter dated October 19, 1996 (Reference 2), Comed informed the NRC of a change to the above commitment. Comed's revised commitment is to maintain the RHR loop flow rate between 1000-3300 gpm during reduced inventory operating conditions when the reactor vessel water level is maintained at 2.25 inches above mid-loop of the hot legs.
2.0 EVALUAIION The current RHR loop flow limit of 1000 gpm was supported by a Westinghouse evaluation performed for Braidwood Station documented in a Westinghouse letter dated July 12, 1989.
In this evaluation, all relevant concerns regarding the minimum RHR flow rate including decay heat removal, reactor vessel internals delta T limits, boron mixing and stratification, control valve cavitation inadvertent boron dilution, and RHR pump bearing evaluations were considered.
Based on this evaluation, Westinghouse has concluded that the minimum RHR flow rate of 1000 gpm will satisfy the RHR design function and this flow rate is low enough to preclude potential vortexing and air ingestion in the RHR pumps durir.g reduced inventory operating conditions.
To support the licensee's increase of the RHR loop flow rate during reduced inventory conditions, Westinghouse performed a bounding reanalyses which ENCLOSURE J
h
2-1 confirmed _ that the operation of an RHR train from 1000 gpm to 3300 gpm with-
- the reactor vessel water level at 2.25 inches above mid-loop of the hot legs would preclude the potential vortexing and air ingestion in the-RHR pumps.
The results of the Westinghouse evaluation'also confirm that all design functions affected by the minimum RHR loop flow rate are either improved or remain satisfactory. The results of the reanalysis are documented in a 4
Westinghouse letter dated October. 18, 1996 (Reference 3) which is attached to the licensee's letter dated October 19, 1997.
3.0 CONCLUSION
Based on the-consideration discussed in Section 2.0 above, the staff has i
concluded that the change to the RHR loop flow rate during reduced inventory operating conditions is acceptable.
4.0 REFERENCES
1 4.1 Letter from G. P. Toth (Westinghouse Electric Corporation) to Commonwealth Edison Company, " Byron and Braidwood Stations, Mid-Loop (GL 88-17) Task B Report," dated July 12, 1989.
4.2 Letter from Harold Gene Stanley (Commonwealth Edison Company) to NRC,
" Supplemental Responses to Generic Letter 87-12," dated October 19, 1997.
4.3 Letter from B. S. Humphries (Westinghouse Electric Corporation) to Commonwealth Edison Company, "Braidwood Units 1 & 2, RHR Operation During Reduced Inventory Conditions," dated October 18, 1996.
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