ML20206P084
| ML20206P084 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/20/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20206P038 | List: |
| References | |
| TAC-60067, TAC-60068, TAC-60657, NUDOCS 8607010569 | |
| Download: ML20206P084 (4) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION j
wAsHWGTON, D. C. 20666
%.....j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 9 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT NO. 7 TO FACILITY OPERATING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2_
DOCKET NOS. 50-275 AND 50-323 INTRODUCTION The Pacific Gas and Electric Company (PG&E, the licensee), by letter dated December 26, 1986, (DCL-85-375, LAR-85-15) requested a change to the i
combined Technical Specifications (TS) for the Diablo Canyon Nuclear Power l
Plant, Units 1 and 2.
The proposed change requests a one-time Technical Specification relief to perfonn during the Unit I refueling outage preventive maintenance on the swing diesel generator "1-3", shared by both units, without requiring both units to be in cold shutdown, and without requiring the operable diesel generators to be tested every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
Under the present TS's operation of a unit is allowed for only 3 days if one of the DG's for that unit is found inoperable. The remaining DG's for the unit are required to be tested every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> during this action statement.
This proposal requests a period of 10 days to take the swing DG out of service for preventive maintenance without requiring the other operable DG's l
to be tested every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. IJnit I will be in Mode 5 (cold shutdown) or 6 l
(Refueling) before diesel generator "1-3" can be removed from service and Unit 2 will be operating.
SYSTEM DESCRIPTION l
l The Diablo Canyon Plant onsite power system consists of three 4.16 KV i
engineered safety feature (ESF) buses for each unit. The ESF loads are assigned to these buses such that operability of any two 4.16 KV ESF buses and their attendant distribution systems will supply the minimum safety requirements for that unit.
The onsite power for both units is supplied by five 4.16 KV diesel generators. The two diesel generators "1-1" and "1-2" are dedicated to two ESF buses for Unit 1; the two diesel generators "2-1" and "2-2" are dedicated to two ESF buses for Unit 2.
The fifth diesel generator, i.e., diesel generator "1-3", is assigned to the third ESF bus of each unit. This shared diesel generator "1-3" will swing to that unit having a safety injection signal.
70 0569 860620 p
DOCK 05000275 PDR
The offsite power system for the Diablo Canyon Plant is comprised of a 230 KV' transmission system and a 500 KV transmission system. The 230 KV system consists of two incoming 230 KV transmission lines', one from nearby Morrow Bay Power Plant, the other from the Mest Substation.
Both lines feed the 230 KV switchyard having three 230 KV circuit breakers, one for each line and one for the standby startup transformers. The 230 KV power system provides an immediate source of offsite power.
The 500 KV system is the backup offsite power supply to the plant. Three incoming 500 KV transmission lines are located on two rights-of-way and provide power to the 500 KV switchyard which is a breaker-and-a-half configuration with the capability of backfeeding through the main transfonner to the unit auxiliary transfomers of either of the two units.
This source of offsite power is made available by manually initiating a motor operated disconnecting link which is an integral part of the main generator's isolated phase bus. This disconnect link is operated from the control room and can be made available by manual initiation in a few minutes providing a delayed tource of offsite power.
Additionally, both units of the Diablo Canyon Plant are designed to handle a 100%
net load rejection and remain connected to the plant equipment loads without tripping the reactor.
EVALUATION Extending the allowed outage period for the swing diesel generator from the current 3 days to the proposed 10 days in order to perform preventive maintenance does not represent a significant danger to the health and safety of the public as discussed below.
The two dedicated diesel generators for Unit 2, which will remain operable during the period when preventive maintenance is being performed on the swing diesel generator "1-3", have proven highly reliable.
Each has 100%
reliability based on 17 and 23 tests for generators "2-1" and "2-2",
respectively.
The 230 KV and 500 KV switchyards provide reliable offsite power sources for both units of the Diablo Canyon Plant. Also, each unit is designed to handle a 100% net load rejection and remain connected to its plant equipment without tripping the reactor. Thus, a loss of offsite power event does not necessarily result in a demand on the emergency AC system.
In the event of a loss of offsite power, while the swing diesel generator "I-3" is on maintenance, Unit 2 can still be shutdown safely with the two
- dedicated diesel generators for Unit 2.
The licensee has stated that Unit 2 can be safely shutdown with only one diesel generator, using appropriate procedures.
Before the diesel generator "1-3" can be removed from service, Unit I will be in Mode 5 (Cold Shutdown) or Mode 6 (Refueling), and the other two diesel generators required for Unit 2 will be demonstrated to be operable within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
In addition, during the 10 day period, these diesel generators must be verified to be in operable condition at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> by examining logs or other information.
In accordance with TS 3.8.1.1 Action a.,
the offsite circuits must be verified to be operable by checking the correct breaker alignments and indicated power availability every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> during the 10 day maintenance period for Unit 1.
The staff has determined that an event requiring plant shutdown concurrent with a loss of offsite power and the loss of a diesel generator is a very unlikely event during the 10 day maintenance period for the swing diesel generator >'l-3".
Therefore, the proposed amendments to the Diablo Canyon TS is acceptable.
Further, the proposed amendments of not requiring the other two
, operable diesel generators for Unit 2 to be tested every 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> while the swing diesel generator "1-3" is out of service is also acceptable since this is consistent with the intent of Generic Letter 84-15 to improve and maintain diesel generator reliability by reducing excessive DG testing.
Based on the above, the staff concludes that the one-time relief from the requirement of the combined Technical Specifications for Diablo Canyon Units 1 and 2 is acceptable. The licensee's request is hereby granted.
ENVIRONMENTAL CONSIDERATION These amendments involve a change in the installation or use of the facilities components located within the restricted areas as defined in 10 CFR 20. The staff has determined that these amendments involve 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
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significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that I
these amendments involve no significant hazards consideration and there has been no public comment on such finding. Accordingly, these amendments meet 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 these amendments.
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.c CONCLUSION The staff has 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 the issuance of these amendments will not be inimical to the co;nmon defense and security or to the health and safety of the public.
Dated: June 20, 1986 PRINCIPAL CONTRIBUTOR:
- 0. Chopra l
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