ML20154J802
| ML20154J802 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 09/15/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20154J773 | List: |
| References | |
| NUDOCS 8809230141 | |
| Download: ML20154J802 (3) | |
Text
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,o SAFETY EVALUATION _BY THE OFFICE _0F NUCLEAR REACTOR _ REGULATION RELATED TO AMENDMENT NO.64 TO FACILITY OPERATING LICENSE NO. DPR-34 PUBLIC SERVICE C0MPANY OF COLORADO 0
FORT ST. VRAIN NUCLEAR GENERATING STATION DOCKET NO. 50-267 1.0 _ INTRODUCTION By letter dated April 20, 1988, the licensee requested certain changes to the Fort St. Vrain (FSV) Technical Specifications (TS). These technical specifications concern the operation of the plant's DC power system. The changes are motivated by the fact that the licensee intends to replace the plant's batteries with a new type. The manufacturer of the new batteries has specified that up to 5 days may be required to perform an equalizing charge on these batteries. At FSV, the DC loads associated with a particular battery bus must be disconnected during an equalizing charge in order to avoid damaging the equipment with an overvoltage condition.
Additionally, the licensee and the staff have discussed potential irprovenents to the FSV TS. These improvements include maintaining independence between the DC buses by maintaining the tie breaker in an open condition. The licensee's requested changes reflect these previous discussions.
2.0 EVALUATION 2.1 Operability of the DC Bus l
The licensee has proposed to declare a station battery and associated battery charger inoperable when disconnected from its DC bus to perform l
an equalizing charge. This action is consistent with the Standard TechnicalSpecification(STS)definitionofoperable. When an equalizing charge is being performed, and the battery is disconnected from its DC bus, it cannot perform in its design function of providing uninterrupted limiting condition for operation (LCO) y inoperable and entering a power to the bus. Declaring the battercorrectly alerts the operators of the degraded system condition. This minimizes the potential for the operators to further reduce the margin of safety, by taking equipment on the redundant train out of service.
Therefore, the staff concludes that this proposed change is acceptable, i
?.2 Disconnection of the_S_tation Batte_ry_for_an_E ualizing Charge la_
1 The licensee has proposed that a station battery and its associated battery charger be declared inoperable when disconnected frcm their load bus for providing an equalizing charge. The battery and the charger may l
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2 be disconnected from their DC bus for up to five consecutive days. The current FSV Technical Specifications considers the battery and the charger operable if disconnected to provide the equalizing charge for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The staff's principle concern in this matter is the overall time that the plant is in this degraded condition. The use of the five day limit by itself would be acceptable, if it was not used excessively. A second factor that would be a mitigating condition for FSV is the relatively long time scale available to recover from most accident sequences. Therefore, in the event of an accident such as the loss of all ac power during an equalizing charge, the battery can be readily reconnected to its load bus as a few minimally weak cells will not prevent the battery from performing P
its design function.
This assures that DC power is availcble to perform a safe plant shutdown. Therefore, the staff finds the licensee's proposal is acceptable.
However, the staff requests that the licensee maintain a record of how long and how often equalizing charges are performed on the new battery over its first year of operation. This record should be submitted to the staff within 45 days after the first year of operation is complete.
The staff will revisit this issue after the first cycle of operation with this TS change.
If the staff concludes based on historical data (see following paragraph) that excessive time is spent in a degraded condition curing equalizing charge periods, revocation of this TS change or other TS changes may be necessary.
?.3 DC Bus _ Independence The licensee has proposed certain changes to the TS to enhance independence of the DC electrical system. These changes would remove current requirerents i
to maintain an intertie between the DC buses.
In normal operation, the DC intertie breakers would be in the open position. This new mode of opera-tion would allow the DC intertie to be used primarily when the back-up battery charger (10) is being used while a norral charger was inoperable or an equalizing charge was being performed. DC independence would be further enhanced by maintaining the disconnect switch for the pPS battery (10) in the open position when a station battery and/or battery charger is inoperable.
The staff concludes that these changes are acceptable, because they ensure DC bus independence to minimize the possibility of comon mode failure.
3.0 E_HIRONMENTAL_ CONSIDERATION i
I The amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has deterrined that the amendrent involves no significant increase in the amounts, and no significant change in the types of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposures.
The Comission has previously issued a proposed finding that the amendrent I
involves no significant hazards consideration and there has been no public
coment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR Section 51.22(c)(9).
Pursuantto10CFR51.22(b),noenvironmentalimpactstatementorenviron-mental assessment need be prepared in connection with the issuance of the amendment.
4.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of the amendaent will not be inimical to the concon defense and security or to the health and safety of the public.
Date: September 1",1988 Principal Contributors:
K. Heitner, PD-IV I. Ahmed, SESB F. Burrows, SELB