ML16138A805
| ML16138A805 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/27/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16138A803 | List: |
| References | |
| NUDOCS 9601030106 | |
| Download: ML16138A805 (3) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 213 TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO. 213 TO FACILITY OPERATING LICENSE DPR-47 AND AMENDMENT NO. 210 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 July 26, 1995, as supplemented by letter dated November 20, 1995, Duke Power Company (the licensee) submitted a request for changes to the Oconee Nuclear Station, Units 1, 2, and 3, Technical Specifications (TS). The requested changes would add a footnote to TS 3.7.8 to provide for a one-time extension of the allowable outage time from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days for the Oconee overhead emergency power path to be inoperable, so that proposed modifications to the degraded grid protection system (DGPS) and the external grid trouble protection system (EGTPS) may be performed. The licensee estimated that 5 days would be required to complete the proposed modifications.
Currently, the degraded voltage is sensed from the Capacitor Coupled Voltage Transformers (CCVTs) connected to the 230 kV transformer busses on the Z phase only. The proposed modifications would provide a separate set (one per phase) of CCVTs for the degraded grid circuit which provides indication to the plant operators of a low voltage condition in the 230 kV switchyard. The three new CCVTs, with each on a different phase, would minimize a potential imbalance problem which could result from sensing the voltage from only the Z phase.
Also, the new CCVTs will be accurate within 0.3% compared to the existing CCVTs which are accurate within 1.0%. The licensee states that this increase in accuracy will allow a decrease in the degraded voltage setpoint of approximately 2 kV, which would potentially decrease the probability that the protective actions provided by this system would be needed.
The November 20, 1995, letter provided additional information that did not change the scope of the July 26, 1995, application and the initial proposed no significant hazards consideration determination.
9601030106 951227 PDR ADOCK 05000269 P
2.0 EVALUATION
-2 With the Oconee overhead emergency power path inoperable, TS 3.7.2 allows an outage time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to restore operability before reactor shutdown must be initiated. The overhead path must be out of.service to perform the proposed modifications. The proposed change in the form of a footnote to TS 3.7.8, requests a one-time extension of the allowed outage time to 7 days to perform the proposed modifications, provided that the restrictions of TS 3.7.8 are observed. When the inoperability of the overhead power path is due to the unavailability of the Keowee Main Step-up transformer, TS 3.7.8 permits the allowable outage time to be extended to periods not to exceed 28 days, provided that certain restrictions are observed. These restrictions include (a) energizing the 4160 volt standby busses by a Lee gas turbine through the 100kV circuit, (b) connecting an operable Keowee hydro unit to the underground feeder circuit, and (c) making the remaining Keowee unit available to the underground feeder circuit. The unavailability of the Keowee Main Step-up transformer specified in TS 3.7.8 would result in the inoperability of the overhead emergency power path required to be operable in TS 3.7.2. Therefore, so far as the availability of emergency power is concerned, the condition of Keowee Main Step-up transformer unavailability is equivalent to the condition of overhead power path inoperability.
The proposed footnote to TS 3.7.8 provides for a one-time extension of the allowable outage time for the overhead power path to be inoperable from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days, well under the 28-day limit specified in TS 3.7.8(d).
The reason for the outage of the overhead power path is different in this case (planned system modifications) from the reason in TS 3.7.8 (Main Step-up transformer unavailability), but in both cases, the availability of emergency power via the overhead path is lost. However, a number of emergency power sources that do not require the overhead path remain available during the planned modifications. Offsite power would still be available through the startup transformer. Additional power sources would be made available by applying the restrictions in TS 3.7.8.
In the November 20, 1995, letter the licensee made the following statements related to the proposed amendments:
- 1. The Standby Shutdown Facility would not be removed from service for planned reasons for the duration of the planned modifications while the overhead path is out of service.
- 2. The unavailability of the overhead path for emergency power is a relatively small contributor to the overall probability of core melt due to loss of power. A one-time extension of this unavailability to 7 days from the currently authorized 3 days would not significantly increase the core melt frequency.
- 3. The proposed modifications to the yellow bus would not be undertaken (1) with the red bus out of service at the same time, (2) during other unrelated switchyard activities, or (3) when adverse weather conditions are anticipated.
-3 4:
During the one-time 7-day outage, no work beyond the installation of the CCVTs that might affect the availability of the underground power path will be performed.
The staff concludes that the availability of offsite power and assuring the availability of additional power sources by implementing the restrictions of TS 3.7.8 provides adequate assurance of the availability of emergency power during the planned system modifications. In addition, the 4-day extension of the allowed outage time would result in an insignificant change in core melt frequency. Therefore, the change 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
The amendments change requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. 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 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 consideration, and there has been no public comment on such finding (60 FR 42601 dated August 16, 1995).
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 environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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 Contributor: S. S. Kirslis Date:
December 27, 1995