ML20039F973
| ML20039F973 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 12/31/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20039F971 | List: |
| References | |
| NUDOCS 8201150044 | |
| Download: ML20039F973 (4) | |
Text
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UNITED STATES 3.,
NUCLEAR FIEGULATORY COMMISSION N
WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 72 TO FACILITY OPERATING LICENSE N0. DPR-39 AND AMENDMENT NO. 66 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDISON COMPANY ZION STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 Introduction Commonwealth Edison Company (CECO) has determined that each of the six circulation water pumps at the Zion Station, Unit Nos.1 and 2 should be overhauled during the next two years. This is an extension of a previous estimate of the repair time for the circulating water pumps and is the result of findings during the minor repair and maintenance program addressed by license Amendments 57 and 54 for Units 1 and 2, respectively, as issued on September 9, 1980 (Reference 1). The overhaul of each pump will require draining the associated forebay which is shared with a service water pump.
Thus, the overhaul will disable a service water pump.
The original Zion Station Technical Specifications (Reference 6) required all six service water pumps (three for Unit 1 and three for Unit 2) to be operable.
if one pump was declared inoperable in one unit, the licensee had seven days to restore the pump to its operable condition.
If these conditions cannot be met, the reactor was to be brought to hot shutdown within four hours and cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after that.
The Technical Specifications were last amended on September 9,1980 to permit temporary operation until December 31, 1981 with one service water pump out for maintenance. Thus, a change to the Zion Technical Specifications is needed to allow continued plant operation while this extended maintenance is being performed on the circulating water pumps and on the service water pumps.
In a letter dated December 9, 1981 (Reference 2), CECO requested an expeditious review and approval of 2 temporary change to the Zion Technical Specifications.
The proposed change would allow one of the six service water pumps to be out of service indefinitely and two of the six service water pumps to be out of service for a maximum of seven days. A minimum of two pumps would be available to each unit. The preposed change was to be temporary and would expire on about December 31, 1983. Following discussions with the staff, CECO modified their request and on December 18,1981 (Reference 3),
CECO requested a permanent change of their Technical Specifications to be consistent with the intent of the Standard Technical Specifications. The permanent change would acknowledge the approved operation of the service water system at Zion and would assure the required redundancy and consideration of common mode failures.
8201150044 811231 PDR ADOCK 05000295 P
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Discussion The six service water pumps feed two separate main supply headers, one header for each unit with three pumps on each header.
The headers are cross-tied so that any combination of pumps can serve both units under normal operating conditions. Normal operation requires two pumps on each unit with the third pump serving as a standby or while in the cross tied mode of operation on the discharge header, three pumps are sufficient with two standby pumps. The system pressure is maintained between 55 and 75 psig in the main supply header as the standby pumps will automatically start when the header pressure drops to preset setpoints (not below 50 psig).
The Zion FSAR (Reference 4) and the NRC's SER (Reference 5) state that only two service water pumps are required for each unit for normal operation and that only one service water pump is required for each unit for emergency shutdown or accident conditions.
Emergency requirements are less because various non-safety related systems are isolated during accident conditions.
The Zion FSAR and the NRC's SER also address and approve the cross-tied operation of the 48-inch service water discharge header.
Evaluation Based on our review of CECO's proposal, as well as a review of the above noted references, we agree that two operable service water pumps and an operable standby pump are sufficient for reactor operation and one pump is sufficient for any accident if the units are operated with the 48-inch discharge header split between the units. This split is accomplished by two motor operator valves in the common header.
We also agree that five operating service water pumps will provide sufficient cooling for any postulated loss of coolant accident coincident with a loss of offsite power, any other single failure of an active components and for operation of both units when the 48-inch discharge header is cross-tied between the units.
In the cross-tied mode the service water requirements for one unit may be satisfied by pumps from either unit, however, only one pump from a unit may be allowed to satisfy operability requirements on the other unit to prevent shutdown of needed pumps should one unit shutdown.
CECO is currently reviewing and possibly will propose adopting the NRC's current Standard Technical Specifications (STS) for Zion Station. The original Zion Station Technical Specifications are more conservative than our current STSs and required the operability of all six service water pumps. The Zion request in their December 9,1981 letter would extend the temporary License Amendments Nos. 57 and 54 approved on September 9,1980 from the original completion date of December 31, 1981 to December 31, 1983. Subsequent to
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i discussions with CECO, the licensee in a December 18th letter has proposed to substitute the temporary license amendment for a permanent license amend-ment whereby the cross-tied header operation would require only five service water pumps operable at any given time. This technical specification change would allow the one pump to be out of service for a sufficient time for repairs and modifications to be made. This mode of operation of sharing pumps between units also carries the possibility of failure of the "0" diesel to start on loss of offsite power.
This diesel powers the service water pumps lA and 2A. To protect against this possibility, the technical specifications preclude the use of these pumps when defining the required pumps operable for either or both units.
Therefore, based upon our review, we conclude that sufficient justification exists to modify the licensee's Technical Specifications and these changes are acceptable. We have also modified the surveillance requirements for the service water pump systems to be consistent with the intent of the Standard Technical Specifications.
For service water pumps out for extended repair times, the licensee has assured that adequate procedures exist for testing the pump when it is returned to service.
Environmental Consideration We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that tne amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of these amendments.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the proba-bility or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Date:
DEC 31 y
. References 1.
Letter from Commonwealth Edison Company (W. F. Naughton) to USNRC (H. R. Denton) dated August 15, 1980.
2.
Letter from Commonwealth Edison Company (F. G. Lentine) to USNRC (H. R. Denton) dated December 9,1981.
3.
Letter from Commonwealth Edison Company (F. G. Lentine) to USNRC (H. Denton) dated December 18, 1981.
4.
Zion Final Safety Analysis Report, Section 9.6 5.
NRC's Safety Evaluation Report for Zion Station, Unit Nos. 1 and 2, Dated October 6, 1972, pages 9-5 and 9-6.
6.
Zion Station Technical Specifications, Section 3.8.7.