ML19341B086
| ML19341B086 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/31/1980 |
| From: | Mays S EG&G IDAHO, INC., EG&G, INC. |
| To: | Shemanski P Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6256 EGG-EA-5327, TAC-42249, TAC-42250, NUDOCS 8101300175 | |
| Download: ML19341B086 (4) | |
Text
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FOHW EGSG 396 (Rav 1179)
INTERIM REPORT Accession No.
Report No.
EGG-EA-5327
, C:ntract Program or Project
Title:
Electrical, Instrument and Control System Support Subject of this Document:
Instrument Bus Modifications, Point Beach Nuclear Plant, Units 1 and 2 Type of Document:
Technical Evaluation Report Author (s):
S. E. Mays D2e of Document:
December 1980 R;sponsible ;JRC Individual and NRC Office or Division:
Paul C. Shemanski, NRC-NRR This document was prepared primarily for preliminary orinternal use. it has not received ful; review and approval. Since there may be substanC*re changes, this document should l
not be considered final.
EG&G Idaho, Inc.
Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. DE-AC07-761D01570 NRC FIN No. A6256 INTERIM REPORT HC lesecrd and Tec1nica Assisimco Ret! art M
9/0/30 0 M
INSTRUMENT BUS MODIFICATIONS POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 Wisconsin Electric Power Company Docket Nos. 50-266 and 50-301 December 1980 S. E. Mays Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.
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_ TAC Nos. 42249.and 42250 l-t f
1.
INSTRUMENT BUS MODIFICATIONS POINT BEACl! NUCLEAR PLANT, UNITS 1 AND 2
1.0 INTRODUCTION
Wisconsin Electric Power Company requested approval for modification to the design of vital instrument bus power supplies in its letter of May 29, 1980. The purpose of the modification is to correct an unaccept-able power supply arrangement discovered durirg the safety evaluation of plant changes resulting from IE Bulletin No.,v-06A, dated April 4, 1979.
The safety evaluation of April 21, 1979, indicated that the existing instrument bus design did not provide protection against single failares causing a spurious starting of all emergency loads in both units which would overload the shared emergency diesel generators. Wisconsin Electric provided additional information describing the proposed modifications in its letter dated November 3, 1980. The purpose of the review is to deter-mine if the proposed design rectifi.s the single failure inadequacy discov-ered in the earlier safety evaluation.
2.0 EVALUATION The modification to the instrument bus power supplies consists of the eddition of two batteries, three battery chargers, six static inverters, and associated distribution buses and wiring to supply power to the white (lY03 and 2YO3) and yellow (lYO4 and 2YO4) instrument buses of both units (see Figure 1).
These modifications essentially duplicate the existing 6
power supply arrangement for the red (1Y01 and 2YO2) and blue (1YO2 and 2YO2) instrument buses.
Under the proposed design, each instrument bus would be powered by one of two static inverters receiving power from a DC bus.
Redundant instru-ment buses (white and yellow) would be powered from independent and redun-dant DC buses. The DC buses would each be powered by a battery bank or a battery charger. A third, shared battery charger would be capabic of serving either DC bus but would be interlocked to prevent the redundant DC buses from being connected.
The proposed modification in combinacion with the existing power supply design for the red and blue instrument buses results in an instru-ment bus system whien can be operated without offsite power. The design is such that the worst case single failure in conjunction with a loss of off-site power and a LOCA in one unit, would result in the failure of only one instrument bus per unit. Such failure could not result in a spurious starting of all emergency loads in both units.
3.0
SUMMARY
The proposed modifications to the Point Beach Nuclear Plant, Units 1 and 2, instrument bus power supplies results in an instrument bus system which is capable of operation without offsite power. Additionally, the four instrument buses per unit are redundant and independent such that no single failure in conjunction with a loss of offsite power and a LOCA in one unit would result in a spurious starting-of all emergency loads in both 1
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Accordingly, we recommend that the NRC approve the proposed design modifications.
4.0 REFERENCES
1.
Wisconsin Electric Power Company letter (Fay) to NRC (Denton) dated May 29, 1979, " Instrument Bus Power Supplies Point Beach Nuclear Plant, Units 1 and 2."
2.
NRC letter (Schwencer) to Wisconsin Electric Power Company (Burstein) dated April 21, 1980, forwarding NRC Staff Safety Evaluation of pro-posed modifications to the instrument bus power supplies.
3.
Wisconsin Electric rower Company (Fay) to NRC (Denton) dated November 3, 1979, " Instrument Bus Modifications, Point Beach Nuclear Plant, Units 1 and 2."
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