ML20055C878
| ML20055C878 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/18/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20055C875 | List: |
| References | |
| NUDOCS 9006250313 | |
| Download: ML20055C878 (3) | |
Text
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I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 51 TO FACILITY OPERATING LICENSE NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY, ET AL.
MILLSTONE NUCLEAR POWER STATION CNIT NO. 3 u
DOCKET NO. 50-423 INTRODUCTION By application for license amendment dated December 11, 1989, as supplemented by letter dated March 2,1989, Northeast Nuclear Energy Company, et. al (the licensee), requested changes to Millstone Unit 3 Technical Specifications (TS).
The proposed amendment would modify Technical Specification (TS) 3/4.5.1,
" Accumulators " to increase the allowable out-of-service time (for reasons other than a closed discharge isolation valve) from I hour to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
DISCUSSION AND EVALUATION The Millstone Unit 3 coolant system is equipped with four large tanks pressurized with nitrogen and containing borated water.
In the event of a loss-of-coolant accident (LOCA) that causes a significant decrease in reactor coolant system pressure, these " accumulator" tanks discharge their borated water into the reactor coolant system. The accumulator's function is to temporarily reflood the reactor coolant system and thus supply coolant until the Emergency Core Cooling System can begin operation.
At the present time, TS 3.5.1 requires that, during Modes 1, 2 and 3, each accumulator be operable with the following conditions being met:
a.
The isolation valve open and power removed, b.
A contained borated water volume of between 6618 and 6847 gallons, c.
A boron concentration of between 2200 and 2600 ppm, and d.
A nitrogen cover-pressure of between 636 and 694 psia.
If one accumulator is inoperable for reasons other than a closed isolation valve, TS 3.5.1 would require restoration of the inoperable accumulator to operable status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or place the plant in Hot Standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
The licensee has requested that the I hour restoration time be extended to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
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.. The NRC staff has reviewed a requested change to the TS for Seabrook Unit 1 Docket NO 50-443 that is identical to the request considered herein.
Seabrook
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Unit 1 utilizes a Westinghouse 4 loop PWR that is similar to Millstone Unit 3-in many respects.
In the case of Seabrook Unit 1, the change to TS to increase allowable out of service time for the accumulators (except as a result of a closed isolation valve) from one hour to eight hours was found to be safe and acceptable as the contribution to risk from this change was determined to be small ar.d the necessity that all four accumulators be operable is conservative.
The NRC staff considerations associated with the Seabrook Unit 1 TS change are documented in a Pay 20, 1986 letter from Thomas M. Novak, NRC, to Robert J.
Harrison,.Public Service Company of New Hampshire.
In addition, using an NRC staff-approved probabilistic risk assessment (PRA) model, the Millstone Unit 3 licensee found that the probability of a medium-to-large break LOCA concurrent with an inoperable accumulator increased from 3.75E-8/yr to 3.00E-7/yr.
The increase in core melt frequency, however, only increases by 2.63E-7/yr. This increase is negligible (e.g. less than.5%) when compared to the overall core melt frequency due to internally initiated events of 6.34 E-5/yr.
We have reviewed the licensee's calculations concerning inoperability of an accumulator and we concur that the associated increase in core melt frequency is negligible and acceptable. Accordingly, the proposed change to the TS is acceptable.
ENVIRONMENTAL CONSIDERATI_0_N The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. We have 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 staff has previously published a proposed finding that the
' amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
CONCLUSION We have 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 Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: June 18, 1990 i
Principal Contributor: David H. Jaffe 1
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t DATED: ' June 18 19'90 AMENDMENT.NO.'51 -TO FACILITY OPERATING LICENSE NO. NPF-49
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