ML20045C162
| ML20045C162 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/15/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045C150 | List: |
| References | |
| NUDOCS 9306220144 | |
| Download: ML20045C162 (4) | |
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UNITED STATES
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIOS RELATED TO AMENDMENT NO.107T0 FACILITY OPERATING LICENSE N0. NPF-10 AND AMENDMENT NO. 96 TO FACILITY OPERATING LICENSE NO. NPF-15 SOUTHERN CALIFORNIA EDIS0N COMPANY SAN DIEGO GAS AND ELECTRIC COMPANY THE CITY OF RIVERSIDE. CALIFORNIA THE CITY OF ANAHEIM. CALIFORNIA SAN ON0FRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 DOCKET NOS. 50-361 AND 50-362
1.0 INTRODUCTION
By letter dated April 13, 1993, Southern California Edison Company, et al.
(SCE or the licensee) submitted a request for changes to the Technical Specifications (TS) for San Onofre Nuclear Generating Station, Unit Nos. 2 and 3.
The proposed changes would revise TS 3/4.8.1, "A.C. Sources," to provide a one-time exception to TS 4.8.1.1.1.a to allow replacement of the 480V transformers B04X and B06X during the Units 2 and 3 Cycle 7 refueling outages.
2.0 EVALUATION TS 3.8.1.1 requires two physically independent circuits between the offsite transmission network and the onsite Class lE distribution system to be OPERABLE during Modes 1 through 4 for Units 2 and 3.
The primary independent A. C. circuit is through the reserve auxiliary transformer of each unit. The second independent circuit for A. C. power for Units 2 and 3 is through a cross-tie with the opposite unit.
For example, if Unit 2 loses its primary source of offsite A. C. power, the Unit 3 4kV cross-tie breakers would close and Unit 2 would receive offsite power through this cross-tie.
The cross-ties between the units are established at the 4kV level only. The 4kV/480V transformers B04X and B06X allow 480V loads to be connected to their own unit's respective 4kV buses (2B04 to 2A04, 2B06 to 2A06, etc.). The 125 VDC buses that provide motive power to the tie breakers to close the cross-ties (buses 2D1 and 202 for Unit 2 and buses 3D1 and 3D2 for Unit 3) receive power from either their associated safety-related battery banks or from their associated battery chargers. These battery chargers are fed from transformers B04X and 806X.
9306220144 930615 PDR ADDCK 05000361 P
- During the upcoming Units 2 and 3 Cycle 7 refueling outages, the licensee intends to replace the 480V load center transformers B04X and B06X.
In accordance with SR 4.8.1.1.1.a, the Unit 2 load centers, including these transformers, are required to be OPERABLE for the Unit 3 cross-tie and vice versa. Therefore, during the Unit 2 Cycle 7 refueling outage, the replacement of load center transformers 2B04X and 2B06X will cause the cross-tie to Unit 3 to become IN0PERABLE.
The replacement work is expected to require approximately 5 to 7 days per train to complete. TS 3.8.1.1 ACTION a.1 allows only 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with one of the two A. C. sources unavailable before the unit must be shut down.
Therefore, Unit 3 would also need to be shut down. This situation will be reversed during the Unit 3 Cycle 7 refueling outage.
This proposed change will add a footnote to SR 4.8.1.1.1.a for Units 2 and 3 to allow the tie breakers to remain OPERABLE with load centers B04 and B06 INOPERABLE because of the 480V transformer replacement during the opposite unit Cycle 7 refueling outage. This will allow the replacement of the transformers (2804X, 2B06X, 3B04X, and 3806X) without requiring both units to shut down.
This one-time exception to TS 4.8.1.1.1.a will effectively extend the normal 72-hour action statement associated with this TS approximately 5 days.
In addition, the Unit 3 SR 4.8.1.1.1.a, which ct.rrently lists the incorrect breakers, will be corrected to properly list tie breakers 2A0417 and 2A0619.
Although load centers B04X and B06X are inoperable during the replacement of the 480V transformers, the cross-tie capability (i.e., 125 VDC bus) will be physically maintained operable. This will be accomplished by:
(1) Making a temporary connection to a battery charger from a non-Class lE power source to the battery bank associated with the 480V transformer being replaced, and; (2)
Demonstrating the OPERABILITY of the associated battery bank by performing SR 4.8.2.1.a.1 within I hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter to determine if the battery meets the Category A criteria of TS Table 4.8-2.
The staff concludes that this temporary configuration provides an acceptable level of assurance that the cross-tie function will perform as designed. This conclusion is based on the following considerations.
(1)
Both the normal and temporary configurations begin with a non-Class IE source, either the unit or Reserve Auxiliary Transformer.
The difference between the two configurations is at the 4kV/480V level. The non-Class IE equipment is designed and maintained in accordance with the same ANSI and NEMA standards for switchgear and motor control centers as i
the Class IE normal equipment.
The licensee will modify the TS surveillance procedure for the 7-day surveillance on the normal power supply to include the temporary circuit breaker alignment.
This surveillance will be performed immediately after switching to temporary power.
Based on these factors, the temporary substitution of non-Class IE equipment for IE equipment in this situation does not significantly
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affect system performance.
(2) Because the associated safety-related battery bank remains OPERABLE by performance of TS 3/4.8.2.2 ACTION b, there is high assurance that the.
associated 125 VDC bus will be available to perform its intended function of closing the cross-tie breakers when required.
The licensee is planning to remove 4kV bus 2A06 from service for normal maintenance during the Unit 2 Cycle 7 refueling outage. Since this. bus is part of the onsite equipment used to connect the backup source of offsite power to Unit 3, removing this, bus from service will require entering TS 4.8.1.1.1.a.
The one-time exception from TS 4.8.1.1.1.a for replacement of the 480V transformers B04X and B06X does not apply to this situation, and this bus will be placed back in service within the 72-hour period allowed by this TS (or Unit 3 will begin shutdown procedures).
During the period when the 4kV-bus 2A06 is out of service, the licensee will also perform the TS required discharge test on battery bank 202, which is connected to the cross-tie breaker for this 4kV bus. The staff finds the timing of the discharge test to be acceptable, since this cross-tie has no function during the time the'4kV bus is out of service, and because the licensee has committed to return the battery to operable status before-the 72-hour LCO entered for the maintenance of the 4 kV bus has expired.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or'use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released i
offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards considera-tion, and there has'been no public comment'on such finding (58 FR 25865).
- Accordingly, the 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 l
environmental impact statement or environmental assessment need be prepared in
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connection with the issuance of the amendments.
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5.0 CONCLUSION
The Commission 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, (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.
Principal Contributor: Mel B. Fields Date:
June 15, 1993