ML20058L665
| ML20058L665 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/02/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20058L601 | List: |
| References | |
| NUDOCS 9008070376 | |
| Download: ML20058L665 (3) | |
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NUCLEAR REGULATORY COMMISSION
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1 SAFETY EVALUATION BY THE OFFICE OF HUCLEAR PEACTOR RECULATION-l SUPPORTING AMENDMENT NO. 134 TO FACILITY OPERAT1HG LICENSE NO. DPR-3 l
YANKEE ATOMIC ELECTRIC COMPANY
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YANKEE NUCLEAR POWER STATION l
i DOCKET H0.50-029
-j INTRODUCTION i
By letters dated April 20, 1990, and June 27, 1990, Yankee Atomic Flectric Cocoany submitted a proposal which incorporated the USNRC guidance contained in Generi. Letter 88-17 into the Yankee Nuclear Power Station administrative controls and Technical Specifications. Three new Technical Specifications (TS) i which specify the plant conditions and equipment operability requirements to preverit core uncovery if. shutdown cooling is lost during reduced level operation i
have been proposed by the lisensee. The proposed TS changes also address Low Temperature Overpressurization (LTOP), allowing operable safety injection pumps during reduced level operation only after the Main Coolant System (MCS) has been adequately vented.
Static momentum and energy balances for the MCS were applied to determine the time to core boiling and make-up water required in the event of a loss of the shutdown cooling system.
The calculations assumed conservative values for decay heat, initial coolant inventory, and the initial MCS temperature. Time to core uncovery for each case was determined from both inventory loss due to core boiling and estimates of expelled fluid. These times were conservatively i
used to provide estimates of the time available for operator action. Make-up requirements were established from the static energy balances.
The three new Technical Specifications in conjunction w'th administrative controls provide assurance that the appropriate pumps and flow paths will be available to prevent core uncovery if shutdown cooling is lost during reduced level operation.
EVALUATION 1.
Reduced Level Operation Without Cold Leg Opening l.
The amount of coolant lost to a hot leg opening decreases to the boil-off rate before core uncovery occurs. At 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> after shutdown, the boil-off rate is l
less than 20 gpm. The hot leg opening core uncovery starts as early as 20 minutes after loss of shutdown cooling. To ensure that the injected water reaches'the core, the pump is to be lined up for discharge into the cold legs.
The licensee estimated that 20 gpm to the cold legs within 20 minutes after l'
' loss of shutdown cooling will prevent core uncovery.
Uncovery time is estimated based upor the most conservative coolant loss rate which would occur at the beginning of core boiling. Make-up to replace boil off can be accomplished p
using one (1) charging pump. The licensee has proposed to have two (2) ave.ilable.
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2 II.
Reduced Level Operations with Cold Leg Opening and P, educed Level Operation for Cold Leg Opening at Low Decay Heat Levels The core uncovery time for the worst case cold leg opening was analy(HPS zed. At decay heat levels above 500 kW, two High Pressure Safety Injection pumps and one Low Pressure Safety Injection (LPSI) pump are required to pro.ide the flow needed to prevent core uncovery by taking suction from the Safety Injection Tank (SIT) and discharging to the MCS loop 4 hot leg within 13 minutes after loss-of shutdown cooling. The licensee will also administrative 1y require, in the appropriate plant operating procedure, that one additional LPSI pump be capable of being placed in an anarable status whenever YNPS is utilizing specification 3.10.6.
P fied in a teleconference between the NRC and the licensee (July 5,1990,
, means that the additional LPSI pump will not be in a repair mode, will not ce disassembled, and will have been tested to demonstrate operability by performing a test similar to that specified in Technical Specification 4.10.6.1: the pump will be run for 15 minutes within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior " ceduced level operation.
A decay heat level of 4.500 kW is obtainable at the end of the refueling outage at a shutdown time of approximately four weeks with half the core replaced with fresh fuel. 'Less make-up flow is required to prevent core uncovery for a decay heat level of < 500 kW. Two charging pumps discharging to the loop 4 hot leg would provide the necessary flow for-a cold leg opening if core decay heat is less than or equal to 500 kW.
III.
Impact of LTOP The safety injection (SI) pumps would be needed to prevent core uncovery following a loss of shutdown cooling during reduced level operation with a cold leg opening and higher decay heat levels. Since the SI pumps could potentially overpressurize the MCS beyond Appendix G limits, the licensee evaluated the impact on LT0P.
A vent path created by removing either a single pressurizer safety valve or the pressurizer manway provide adequate LTOP protection for the SI pump combination required by the proposed change. With'the required vent the peak pressure due to the operation of the required charging or SI pumps is maintained below Appendix G limits, even if no opening exists on the loop piping.
ENVIR0tmENTAL CONSIDERATION This amendment involves a change in a requiremnt with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment 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 exposure. The Commission has previously published a proposed finding that the amendment 1
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4g involves no significant hazards consideration and there has been no public-comment on such finding. Accordirgly, this amendment meets the eli criteria for categorical exclusions set forth in 10 CFR 51.22(c)(9)gibility Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
CONCLUS10tl The Commission made a proposed determination that the amendment involves no significant hazards consideration which was published in the Federal Reaister (55 FR 20365) on May 16, 1990. No public coments were received and the State of Massachusetts did not have any comments.
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
A. Massey Dated: May 19, 1990 l
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TO DPR-3 ANKEE NUCLEAR POWER STATIOi1} (ROWE) DATED August 2,- 1990 q
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