ML20033F130
| ML20033F130 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/05/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20033F129 | List: |
| References | |
| NUDOCS 9003160086 | |
| Download: ML20033F130 (5) | |
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WASHINGTON, D. C. 20555 k.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 85TO FACILITY OPERATING LICENSE NO. NPF-10 SOUTHERN CALIFORNIA EDISON COMPANY SAN DIEGO GAS AND ELECTRIC COMPANY THECITYOFRIVF,PjlDE, CALIFORNIA THE CITY OF ANA4EIM, CALIFORNIA SAN ONOFRE NUCLEAR GENERATING STATION, UNIT NO. 2 DOCKET NO. 50-361 l'. 0 INTRODUCTION By letter dated January 3,1990, Southern California Edison, et al. (SCE or the licensee) requested a change to the Technical Specifications for Facility Operating License No. NPF-10 that authorize operation of San Onofre Nuclear Generating Station, Unit No. 2 in San Diego County, California. The licensee proposed to revise Technical Specification (TS) 3/4.7.6," Snubbers." The proposed change would, on a one time basis, t
l defer reduced snubbers visual inspection interval (124 days-25%),and l
extend the maximum inspection period for inaccessible snubbers from 18 months 25% to 20 months i 25%. Additionally, the TS bases would be modified to reflect this TS modification.
SCE is seeking this one time extension since San Onofre 2 cannot complete the current extended fuel cycle (Cycle 5) of operation (nominal 24 months) without exceeding the Technical Specification allowable visual surveillance period.. In accordance with the surveillance requirements, the reduced inspection' interval would require multiple plant shutdowns prior to the next refueling outage to visually inspect inaccessible snubbers.
Perform-ance of these snubber inspections with the unit at power would be impractical because the equipment is operating, is located in high radia-tion zones, and ladders and scaffolding would need to be erected for inspection. As a result, radiation "as low as reasonably achievable" (ALARA)goalswouldbedifficultorimpossibletomaintain.
2.0 EVALUATION Mechanical snubbers are designed to prevent shock forces from danaging l
piping and components, and to accommodate for thermal expansion and contraction in piping systems.
The snubbers are attached to piping and support structures at both ends by load pins, which are secured by means of either snap rings, cotter pins, or with the load pin threaded and secured by nuts.
9003160086 900303 PDR-- ADOCK 05000361 P
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l SCE found a total of four inoperable snubbers during the visual inspection surveillance period. Of these four inoperable snubbers, three snubbers were found to be unpinned. These snubbers were functionally stroke tested, determined to be operable and repinned. The remaining snubber was found to be frozen due to side loading, perhaps caused by personnel steppine on or bumping the snubber. This snubber was replaced with an operable snubber. As a result of these failures, the visual inspection surveillance interval was decreased.
SCE has identified a problem with snubber load pin retaining snap rings on snubbers. As a result, SCE has a snap ring replacement program for all types of snubbers. This program replaces the snap ring with cotter pin load pins which are less susceptible to vibration which could loosen and unpin a snubber. Also, SCE has a snubber reduction program to remove unnecessary snubbers from the plant.
Finally, worker awareness of the importance and sensitivity of snubbers was increased by the placement of signs that specifically prohibit the use of snubbers as steps or as a hardhold. This appears to have been effective as there have been no further instances of side loading.
The licensee states that SCE's snubber maintenance program for both San Onofre Units ? and 3 has been very effective. Since 1983, Unit 2 had 7 failures out of 6,936 visual inspections.
Similarly, Unit 3 had 6 fail-ures out of 5,574 visual inspections. This indicates a failure rate of 1/10th of 1 percent. This data, in conjunction with the snap rinq replacement program for accessible and inaccessible snubbers on Units 2 and 3, should indicate a decreasing number of failed snubbers in the future.. Also, it should be noted that if an unscheduled outage of suffi-c l
cient duration occurs, as many inaccessible snubbers as practical will be visually inspected, and the results factored into the snubber service life p
program and future inspection intervals.
A significant change in the operating status increases the probability of l
unusual plant occurrences that are more likely to occur during transient plant operation rather than full power steady state operation. Approval of this emendment would preclude a significant change in operating status.
Also, performing the visual inspections during the requiarly scheduled refueling outage is most advantageous from an ALARA standpoint, because inaccessible area radiation dose will be substantially lower, and the L
outage duration is such that detailed radiation protection plannina can be applied to the inspection program. The staff is currently developing generic quidelines which would allow utilities to visually inspect snubbers at their scheduled outages. This proposal satisfies the requirements of those guidelines.
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SCE concludes that the probability of an inaccessible snubber failing before the Cycle 6 refueling outage has not increased due to the visual inspection failures found because the failures were due to a known cause which has been corrected on all appropriate snubbers. SCE's visual inspection program results have demonstrated a low failure rate, and the program should continue to maintain or reduce the failure rate. Therefore, waiving the reduced snubber visual inspection period and extending the period to encompass the refueling cycle on a one time basis would not be significantly detrimental to safety, and would avoid an unnecessary plant shutdown.
The proposed change by the licensee has been reviewed by the staff and was found to be acceptable. This modification to the TS will eliminate unnecessary testing of snubbers resulting in reduced man-ren exposure without undermining the effectiveness of the overall surveillance program.
Additionally, it will preclude an unnecessary plant shutdown. Moreover, this amendment to the TS will allow a one time extension of the inspection period during Cycle 5 operation while the NRC staff develops generic quidance on snubber visual inspection surveillance intervals applicable to 24 month operating cycles. Therefore, based upon the above information, the staff approves the amendment for the one time extension to the snubber visual inspection period for San Onofre Nuclear Generating Station, Unit No. 2.
3.0 CONTACT WITH STATE OFFICIAL The staff has advised the State Departnent of Health Services, State of California, of the proposed determination of no significant hazaros consideration.
Po comments were received.
A.0 ENVIRONMEttTAL CONSIDERATION The amendments involve changes to requirements with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or changes an inspection or surveillance requirement. The staff has determined that the amendments involve no sionificant 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. Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuantto10CFR51.22(b)noenvironmentalimpactstate-ment or environmental assessment need be prepared in connection with the issuance of these amendments.
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5.0 CONCLUSION
We have concluded based on the considerations discussed above that: (1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner; (2) public such activities will be conducted in compliance with the Commission's reguia-tions; 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: Lawrence E. Kokajko Dated: March 5, 1990 s
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[t-g AMENDMENT NO, 85 TO FACILITY OPERATING LICENSE NO.
March 5,'1990 f""f66 dei,[NICI
~NRC & Local PDRs PD5 Plant File J.Zwolinski(13H24)
P. Shea L. Kokajko OGC D. Hagan (MHBB 3302)
E. Jordan (MNBB3302)
G.= Hill ()(P1-37)
W.-Jones P-130A)
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