ML18024B338
| ML18024B338 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/14/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18024B337 | List: |
| References | |
| NUDOCS 8002140308 | |
| Download: ML18024B338 (6) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.
56 TO FACILITY OPERATING LICENSE NO.
DPR-33 AMENDMENT NO.
51 TO FACILITY OPERATING LICENSE NO.
DPR-52 AMENDMENT NO.
29 TO FACILITY OPERATING LICENSE NO.
DPR-68 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT UNITS NOS.
1 2 AND 3 DOCKET NOS. 50-259, 50-260 AND 50-296 1.0 2.0 Introduction By letter dated January 14, 1980, the Tennessee Valley Authority (the licensee or TVA) requested changes to the Technical Specifications (Appendix A) appended to Facility Operating Licenses Nos.
DPR-33, DPR-52 and DPR-68 for the Browns Ferry Nuclear Plant, Units.Nos.
1, 2 and 3.
The proposed amendments and revised Technical Specifications would permit operation of Unit No: 3 while Unit No.
1 is down for refueling by provid-ing a temporary second off-site power source to the Unit No.
3 4-KV shut-down boards through the 4
KV bus tie board.
These revised Technical Specifications will only be in effect while Unit No.
1 is in cold shutdown for refueling and until the principal source of off-site power for Unit No.
3 through the cooling tower transformers is repaired and back in service.
Discussion By Amendments Nos.
39, 37 and 13 to DPR-33, DPR-52 and DPR-68, respectively, dated June 23,
- 1978, we approved modifications to the Browns Ferry inplant electrical systems to maintain adequate inplant electrical system voltage for three unit operation.
One of the modifications was to rearrange the 4160 volt loads that had previously been connected to the common station transformers and reconnection of some of these loads to the cooling tower transformers.
The purpose of this modification was to reduce the voltage drop due to high impedance in the comon station service transformers.
The related safety evaluation to these amendments describes the modifica-tions and our evaluation thereof; the safety evaluation to Amendments Nos.
39, 37 and 13 is incorporated in this safety evaluation by reference.
On December 30, 1979 Unit 3 (BF-3) was shutdown when grounds were detected in the underground cable feeding off-site power through the cooling tower transformers to the Unit 3 4 KV bus tie board.
On January 3, 1980, Unit No.
1 was shutdown for refueling; Unit 1 is scheduled to be down until February 21, 1980.
To avoid a possible repetition of the grounding problem,
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3.0 TVA has redesigned the incoming line to run overhead above ground rather than in the, existing underground concrete conduit.
However, the replace-ment cable will not be available until about January 21, 1980.
Since Unit 1 is down for refueling - and will be down for another 4 to 5 weeks-this reduces the load on the off-site power sources to Unit 1.
The purpose of the proposed modification and.revised Technical Specifications is to supply a temporary second source of off-site power to Unit 3.to permit this facility to startup and operate based on the reduced load on Unit l.
Once the cable is replaced - estimated to be no later than Febraury 2, 1980-the Technical Specifications will be revised to revert to be the same as existed prior to the issuance of the amendments that are the subject of this safety evaluation.
Evaluation The modification proposed by the licensee is to remove the interlocks between the Unit 1
and 2 shutdown boards and the Unit 3 bus tie board.
The modification will allow either shutdown bus 1 or shutdown bus 2 to provide power to the 4
KV bus tie board.
During the current Unit 1 refueling shutdown, power to shutdown bus 1
and 2 wi.ll be provided through:
l.
Backfeed from Unit 1
500-KV main transformer through Unit 1 station-service transformer.
2.
Unit 2 generator through Unit 2 station-service transformer.
3.
Common station-service transformer 1
and 2.
This modification will provide a temporary second off-site power source to the Unit 3 4 KV shutdown boards through the 4
KV bus tie board.
The inter-locks on these breakers prevent the cross tie of the cooling tower trans-former with transformers supplying shutdown bus 1
and shutdown bus 2.
The cooling tower connection to the bus tie board has been physically removed until repairs are completed.
Alternate power from the Unit 3 4-KV bus tie. can only be provided to either of the units 4
KV shutdown board pairs 3EA and 3EB or 3EC and 3ED.
This limitation is due to the shutdown bus 1 and shutdown bus 2 feeder breaker 1200 amp current ratings.
However, loss of normal offsite power to all four.Unit 3 shutdown boards would require two independent single failures.
TVA has verified that the loading and voltage levels will remain wi thin equipment ratings under the worse case loading conditions.
TVA has also verified that existing protective relaying is fully adequate and no changes are required.
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4.0 In a telephone conversation with TVA personnel on January 14, 1980, they stated that the operating and emergency procedures have been changed as required to reflect the temporary modifications and that the operators have been instructed and trained to the new. procedures.
TVA also stated that the system will be preoperationally tested and will verify that the circuitry in which the modifications were made will function as designed by testing the power system operation.
Upon completion of the overhead line installation from the cooling tower transformers to the Unit 3 4 KV system, the licensee (1) shall verify, by test, the operability of the restored
- system, (2) shall restore the interlocks circuitry removed by this change request and (3) will return to the Technical Specification limiting conditions for operation and surveillance requirements that existed immediately prior to the changes effected by the amendments discussed herein.
The operating procedures and operator instructions shall also be revised at the same time to reflect the restored system.
We. have evaluated TVA's submittal of January 14, 1980 and the subsequent commitments by TVA discussed above.
We conclude that the proposed temporary changes to the electrical systems are acceptable and that it is safe to operate Unit No.
3 in the proposed manner - as long ~ Unit No.
1 is,in cold shutdown for refueling.
Environmental Considerations 5.0 We have determined that these amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that these amendments involve an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 551.5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be pre-pared in connection with the issuance of these amendments.
Conclusion We have concluded based on the considerations discussed above:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, and (3) such activi ties will be conducted in com-pliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Dated:
January 14, 1980
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