ML20245F904

Safety Evaluation Supporting Amend 103 to License DPR-54

ML20245F904
Person / Time
Site:	Rancho Seco
Issue date:	04/18/1989
From:	Office of Nuclear Reactor Regulation
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ML20245F881	List: ML20245F877 ML20245F893 ML20245F904
References
NUDOCS 8905030033
Download: ML20245F904 (2)

Text

[

'of UNITED STATES NUCLEAR REGULATORY COMMISSION

[5:h "y/ q[gj WASHINGTON, D. C. 20555

%...N,J SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0.103T0 FACILITY OPERATING LICENSE DPR-54 RANCHO SEC0 NUCLEAR GENERATING STATION, UNIT 1 l

DOCKET N0. 50-312

1.0 INTRODUCTION

In response to the valve manufacturer's recommendations, the licensee  !

(Sacramento Municipal Utility District) for Rancho Seco Nuclear Generating i Station modified the reactor building purge system (RBPS) isolation valves to  !

limit the valve opening positions such that adequate closing torques would l be maintained while limitino stress below recommended operating levels. The j inboard purge valves were modified to limit their stroke angle to 6 80 of 1 their full open position, and the outboard purge valves were limited to 5 60 l of their full open position. As a result of these reduced valve stroke l angles, the original design purge air flow rate of 66,700 cfm 10% s ecified j in Section 4.11.1A of the existing plant Technical Specifications (TS. cannot i be achieved. Subsequently, by letter dated December 12, 1986, the licensee  !

proposed a change to Section 4.11. A of the TS. The proposed TS change wil)  !

lower the purge air flow rate from 66,700 cfm 10% to 60,000 cfm 10%. l 2.0 EVALUATION The RBPS was desi ned to provide approximately two air changes per hour of l filtered, heated as required), outside air to the reactor containment to i permit safe access during cold shutdown or refueling. The purge exhaust l 1s routed through a series of rough, HEPA and charcoal filters prior to j discharge to the atmosphere. A slight decrease in containment air changes l (approximately 10%) resulting from the lower RBPS air flow rate would have no j effect on pemitting safe access during cold shutdown or refueling. During nomal plant operation, the RBPS isolation valves are closed per TS. Therefore, j the decreased RBPS air flow rate would have no effect on the radiological dose j consequence following a LOCA.

In the event of a postulated fuel handling accident within the reactor building during refueling, the radiation monitoring system high radiation signal would initiate the closure of the RBPS valvcs. The proposed reduced air flow rate for the RBPS has no effect on the purge valve isolation closure j times. However, with the lower proposed purge air flow rate (60,000 cfm 10%)

prior to the velve closure, the amount of containment atmosphere released would be less, and the residence time within the HEPA and charcoal filters would be longer. Therefore, the containment radioactivity released to the atmosphere prior to complete isolation would be lower than for the initially j higher purge flow rate.

i Based on the staff's review, we find that the licensee's proposed TS change to reduce the containment purge air flow rate is acceptable, because the change will not affect the previously approved design basis accident dose values.

8905030033 89043g I hDR ADOCK 05000312  !

PDC 1

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, 3.0 CONTACT WITH STATE OFFICIAL The NRC staff has advised the Chief of the Radiological Health Branch, State Department of Health Services, State of California, of the proposed determination of no significant hazards consideration. No comments were received.

4.0 ENVIRONMENTAL CONSIDERATION

This amendment involves changes in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.

The staff has determined that the amendment involves 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 Comission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuantto10CFR51.22(b),noenvironmentalimpactstatementor environmental assessment need be prepared in connection with the issuance of this amendment.

5.0 CONCLUSION

Wehaveconcluded,basedontheconsiderationsdiscussedabove,that(1) there is reasonable assurance that the health and safe +" of the' will not be endangered by operation in the proposed ma,. ;. , (2) public such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendment will not be inimical to common defense and security or to the health and safety of the public.

Principal Contributor: D. Shum Dated: April 18, 1989

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