ML16138A746
| ML16138A746 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 08/26/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A745 | List: |
| References | |
| NUDOCS 9209080186 | |
| Download: ML16138A746 (4) | |
Text
REG UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 196 TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO. 196 TO FACILITY OPERATING LICENSE DPR-47 AND AMENDMENT NO.193 TO FACILITY OPERATING LICENSE DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
By letter dated May 20, 1992, the Duke Power Company (the licensee or DPC) submitted a request for changes to the Oconee Nuclear Station, Units 1, 2, and 3 Technical Specifications (TS).
The requested changes would allow a one-time extension of the allowable outage time from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days per battery for each 125 volt dc (VDC) battery and associated distribution center servicing the 230 kV switchyard. The extension would allow battery replacement without shutdown of the Oconee nuclear units.
The 230 kV switchyard (SY) 125 VDC batteries at Oconee are approaching their end of life and need to be replaced. Currently, TS 3.7.2(e) allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for inoperability of a complete single string (train) or single component of the 125 VDC 230 kV switching station power system; 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> are permitted if the inoperability is for an equalizer charge following a battery service test or performance test. The licensee plans to replace the existing 59 cell batteries with greater capacity 60 cell batteries. Replacement of the existing batteries, equalizing charge of the new batteries following installation, and associated modifications will require approximately 7 days per battery.
2.0 EVALUATION Oconee has a unique onsite ac electric power system. Instead of using emergency diesel generators as onsite ac power sources, Oconee uses two Keowee hydro units as the two onsite sources backed by a circuit from Lee Steam Station via the 100 kV transmission network as an additional onsite source.
At Oconee, Units 1 and 2 generate electric power at 19 kV and step up to transmission voltage of 230 kV. Unit 3 generates electric power at 19 kV and steps up to transmission voltage of 525 kV. A 230/525 kV autotransformer connects the 525 kV switching station to the 230 kV switching station. The Keowee hydro station contains two units rated at 87,500 kVA each, which generate at 13.8 kV. Upon loss of power from the Oconee generating unit and 9209080186 920826 PDR ADOCK 05000269 P
-2 the 230 kV switchyard, both of the Keowee hydro units can provide emergency power to any of the Oconee units through either the overhead 230 kV circuit switching station to the unit's respective startup transformer or the underground feeder and transformer CT4. Whenever the underground circuit from Keowee is unavailable, a circuit from Lee Steam Station can be connected to the Standby buses through transformer CT5 and serve as an emergency power source.
Two separate 230 kV switchyard 125 VDC batteries (SY-1; SY-2) are provided in the SY Relay House, each with an associated battery charger. A spare charger, which can be connected to either switchyard battery, is also provided. A bus tie with normally open breakers is provided between the distribution centers to backup a battery when it is removed for servicing. The capacity of a single SY battery is sufficient to carry the loads of both distribution centers. The two distribution centers are redundant, each providing power to all components necessary for performing the safety functions of the 230 kV SY dc system. The redundant panel boards supply power to separate channels of the degraded grid protection system (DGPS) circuits, separate channels of other protective relaying circuits, and separate feeds for each 230 kV power circuit breakers closing and tripping coils. The staff's review indicates that the dc systems are designed to have sufficient independence, redundancy, and testability to perform their safety functions.
In addition, for each nuclear unit, a 125 VDC system provides power for control and instrumentation for normal operation and orderly shutdown, and a separate 125/250 volt dc system is provided to supply large power loads for each unit. For each Keowee hydro unit, separate and independent dc power systems are provided to assure a source of reliable continuous power for normal and emergency operation. These dc systems will not be affected by this change.
The licensee states that the proposed modification to replace the SY batteries will include:
replacement of the existing 59 cell batteries SY-1 and SY-2 with 60 cell batteries, replacement of the railings on one row of each battery rack to accommodate the additional 60th cell, replacement of several circuit breakers, and an equalizer charge of the new batteries following installation.
Although TS 3.7.2(e) does not specify compensatory measures in the event of 230 kV switchyard dc degradation, the licensee will take the following actions in support of this modification:
- 1.
TS 4.6.9.a requires a weekly verification of pilot cell electrolyte level, specific gravity, and float voltage, as well as overall battery float voltage. Prior to removing a battery from service, the remaining battery will be tested in accordance with TS 4.6.9.a. In addition, while a battery is inoperable, the remaining battery will be tested daily in accordance with TS 4.6.9.a.
- 2.
In order to maintain both DGPS's actuation logic channels available (although vulnerable to single failure of the battery) and to provide redundant power feeds to other supported equipment, the distribution centers will be cross tied when practical during implementation of the
-3 modification. Further, when one channel of the DGPS is de-energized, switchyard voltage will be monitored by the system dispatcher. In the event of an actual degraded grid condition, the provisions of TS 3.7.5 (all 230 kV transmissions lines lost) would apply and actions would be taken to improve the grid situation.
- 3.
Both the overhead emergency power path and the underground emergency power path from Keowee will be maintained operable during implementation of the modification.
- 4.
The modification will be implemented in accordance with approved procedures.
We have reviewed the licensee's submittal and found that the emergency power is not significantly affected by a one-time extension of allowable outage time for one train of the 230 kV switchyard dc system. The remaining dc train is adequate to assure operability of the Keowee overhead emergency path, and the Keowee underground emergency path will be maintained operable during the battery outage. In addition, the additional source from Lee Steam Station via the 100 kV transmission network can still be connected to the standby buses and serve as an emergency power source. Also, adequate administrative measures will be in place to help prevent loss of the switchyard during implementation of this modification.
To replace each of the two SY batteries one at a time, the licensee has proposed a one-time extension of the LCO for the inoperability of a complete single string or single component of the 125 VDC 230 kV switchyard from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days.
The staff has reviewed the licensee's submittal and concluded that adequate basis for the extension of the LCO has been provided.
Based on the above evaluation, the staff has determined that Oconee can be operated safely without undue risk to the health and safety of the public and there is reasonable assurance that adequate ac and dc power sources will be available to mitigate credible events that might occur during the period of 7 days and, therefore, we conclude that this one-time extension is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the South Carolina State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an Environmental Assessment and Finding of No Significant Impact was published in the Federal Register on August 26, 1992(57 FR38700).
Accordingly, based on the Environmental Assessment, the Commission has determined that issuance of the amendments will not have a significant effect on the quality of the human environment.
-4
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 amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
L. A. Wiens, PDII-3/NRR N. Trehan, SELB Date: August 26, 1992