ML20214W205
| ML20214W205 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/09/1987 |
| From: | Thomas C Office of Nuclear Reactor Regulation |
| To: | Mroczka E NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 8706150155 | |
| Download: ML20214W205 (4) | |
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6t1 UNITED STATES F.
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NUCLEAR REGULATORY COMMISSION -
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June 9, 1987 i.
Docket No.: 50-245 1
L Mr. Edward J. Mroczka, Senior Vice President Nuclear Engineering and Operations Northeast Nuclear Energy Company.
Post Office Box 270 Hartford,. Connecticut 06141-0270 I
Dear Mr. Mroczka:
SUBJECT:
IMPLEMENTATION OF DEGRADED GRID PROTECTION FOR CLASS IE POWER SYSTEMS.
Re: Millstone ' Nuclear Power Station, Unit No.~ 1 In a letter dated November 14, 1985, NNEC0 requested a delay in the implemen-l' tation of plant modifications related to Degraded Grid Protection for Class:1E-Power Systems until the outage for Reload 11. The request ~for delay was based-on a NNECO analysis whose results indicated that the new degraded voltage-detection system would increase the frequency of-station blackout' over the.
existing system by 240%. This delay was approved by the NRC in a letter dated December 12, 1985.
In a related action, NNECO submitted-Degraded Grid Voltage Procedures to be used under non-accident conditions at Millstone-Unit No.1.
4 In a letter dated May 20, 1986, the NRC found these procedures acceptable until the final degraded grid protection modifications were completed.
It was anticipated that these modifications vould be completed during-the outage i
for Reload 11, which is currently in progress.
By letter dated May 22, 1987, NNECO stated that the Millstone Unit No'. 1 electrical bus arrangement, due to its lack of symmetry, is not readily com-patible 'to a modification which requires an auto-reinstatement of load shed -
feature. NNEC0 decided to model the new scheme on the Millstone Unit No.'l t
plant-specific simulator because of the complexity of the proposed modification 4
and because of the need to assess the_ operators' ability to respond to'a de -
graded grid voltage scenario. NNEC0 stated that they have determined that i
insufficient time remains to address these issues and to incorporate -the required modifications during the Reload 11 outage. -NNEC0'has proposed to defer the implementation schedule until the outage for Reload 12 in late 1989 -
l to allow appropriate design changes to be made.
The staff recognizes that the use of probabilistic safety techniques and the plant-specific simulator by NNEC0 in the design of the degraded grid protection-system has identified significant concerns which must-be resolved before the system can be installed.
In the December 12, 1985, and May 20, 1986, letters, 8706150155 870609 PDR ADOCK 05000245 i
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Edward J. Mroczka -
June 9, 1987 the NRC found that the existing undervoltage protection system and the interim procedures provide an adequate level of safety until the final degraded grid modifications are complete.
In light of the design problems identified by NNECO and the interim acceptability of the existing degraded grid protection system and procedures, the staff finds it acceptable to delay final plant undervoltage modifications until the outage for Reload 12.
However, because of the safety significance of this system, it is our position that further delays are not justified.
Sincerely, 0ed 0 FWAf Cecil 0. Thomas, Director Integrated Safety Assessment i
Project Directorate Division of Reactor Projects - III, IV, V and Special Projects cc: See next page.
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l Mr. Edward J. Mroczka Millstone Nuclear Power Station Northeast Nuclear Energy Company Unit No. I cc:
Gerald Garfield, Esquire Kevin McCarthy, Director Day, Berry & Howard Radiation Control Unit Counselors at Law Department of Environmental City Place Protection Hartford, Connecticut 06103-3499 State Office Building Hartford, Connecticut 06106-Wayne D. Romberg Vice President, Nuclear Operations Richard M. Kacich, Manager Northeast Utilities Service Company Generation Facilities Licensing Post Office Box 270 Northeast Utilities Service Company Hartford, Connecticut 06141-0270 Post Office Box 270 Hartford, Connecticut 06141-0270 Bradford S. Chase, Under Secretary Energy Division Office of Policy and Management J. Stetz, Plant Superintendent 80 Washington Street Millstone, Unit 1 Hartford, Connecticut 06160 Northeast Nuclear Energy Company P.O. Box 128 Waterford, Connecticut 06385 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 Northeast Nuclear Energy Company ATTN: Superintendent Millstone Nuclear Power Station P. O. Box 128 Waterford, Connecticut 06385 Resident Inspector c/o U.S. NRC Millstone Nuclear Power Station P. O. Box 811 Niantic, Connecticut 06357 First Selectman of the Town of Waterford Hall of Records 200 Boston Post Road Waterford, Connecticut 06385
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Edward J. Mroczka June 9, 1987 the NRC found that the existing undervoltage protection system and the interim procedures provide an adequate level of safety until the final degraded grid modifications are complete.
In light of the design problems identified by NNEC0 and the interim acceptability of the existing degraded grid protection system and procedures, the staff finds it acceptable to delay final plant undervoltage modifications until the outage for Reload 12. However, because of the safety significance of this system, it is our position that further delays are not justified.
Sincerely, Original signed by Cecil 0. Thomas, Director Integrated Safety Assessment Project Directorate Division of Reactor Projects - III, IV, V and Special Projects cc: See next page.
DISTRIBUTION Docket File ISAPD File NRC & Local PDR DCrutchfield FSchroeder MShuttleworth MBoyle OGC-Bethesda EJordan JPartlow ACRS (10) 0FC:ISAPD e
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C DATE:06/{/87
- 06/f /87 0FFICIAL RECORD COPY