ML16138A686
| ML16138A686 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/13/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A687 | List: |
| References | |
| NUDOCS 8912190403 | |
| Download: ML16138A686 (3) | |
Text
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0 00 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.179 TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT NO.179 TO FACILITY OPERATING LICENSE DPR-47 AMENDMENT NO.176 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
In a letter dated June 28, 1989, Duke Power Com pany requested relief from the requirements of Technical Specification (1S) 4.8.2, Main Steam Stop Valves, for the Oconee Nuclear Station, Unit 2. This TS specifies leakage rate testing of the main steam stop valves (MSSVs) during each refueling outage. Relief from the TS was requested on the basis of the testing Leing unnecessary to demonstrate operability of the MSSVs. Enforcement discretion was granted by the NRC as documented in a letter from Stewart Lbneter to H. B. Tucker dated July 10, 1989. The licensee subsequently requested a TS amendment to delete the MSSV leak rate testing for all three Oconee units in a letter dated July 14, 1989.
2.0 EVALUATION The Main Steam System (MSS) design for the three Oconee units does not include main steam isolation valves (MSIVs) for steam generator or steam line isolation. In this design, the MSSVs, also referred to as turbine stop valves, perform this isolation function.
For each steam generator, two MSSVs are installed in parallel and must shut to isolate the steam generator. The safety function served by the MSSVs is to prevent simultaneous blowdown of both steam generators following a steam line rupture in one steam line.
The current TS specifies that the MSSVs be leak rate tested at 59 psig during each refueling outage, with a leakage rate limit of 25 cubic feet per hour. The basis for this leak rate test provided in the TS basis is a simultaneous break of a reactor coolant line and a steam generator feedwater header, resulting in a containment atmosphere leakage path through the feedwater header, into the steam generator and out through the main steam line. The feedwater lines and feedrings at Oconee are seismically designed, and the reactor coolanit system piping design minimizes the possibility of a rupture of the feedring or feedwater line as a result of a reactor coolant piping break. As such, the NRC staff concurs with the licensee's determination that a concurrent break of the reactor coolant piping and the steam generator feedring or feedwater line is not a credible accident scenario.
8912190403 891213 PDR ADOCK 05000269 P
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-2 The main steam lines are also seismically qualified from the steam generator up to and including the MSSVs. As such, these lines are considered a closed system not exposed to containment atmosphere in a post-accident condition and, therefore, do not require local leak rate testing under 10 CFR 50, Appendix J. Also, Appendix 0,Section II.H.,
requires the testing of containment isolation valves in main steam and feedwater piping, but only in boiling water reactors, not in pressurized water reactors.
In order to perform their safety function, the MSSVs must shut when required and within the time required. This function is tested in accordance with TS 4.8.1 which requires a timed stroke test each refueling outage. Closure of the MSSVs prevents excessive cooling of the reactor following a steam line break and limits the release of activity to the atmosphere for a steam line break with 1% failed fuel and a 1 gallon per minute primary to secondary leak in the faulted steam generator. Closure of the MSSVs is also required to isolate the faulted steam generator during a steam generator tube rupture. In each of these scenarios, prompt closure of the MSSVs is necessary to remain within the bounds of the current design basis analysis. However, seat tightness of these valves is not required, in that any credible leakage through these valves, when shut, would be insignificant compared to the release through the ruptured steam line. As such, the NRC staff concurs with the licensee that leak testing of the MSSVs at Oconee is unnecessary.
3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change in surveillance requirements. We have 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 these amendments involve no significant hazards consideration, and there has been no public comment on such finding. 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 these amendments.
4.0 CONCLUSION
The Commission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal Register (54 FR 32709) on August 9, 1989, and consulted with the State of South Carolina. No public comments were received, and the State of South Carolina did not have any comments.
We have 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
-3 (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 common defense and security or to the health and safety of the public.
Principal Contributor:
L. Wiens, PDII-3/DRP-I/II Dated: December 13, 1989