ML19343B181
| ML19343B181 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/19/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19343B180 | List: |
| References | |
| NUDOCS 8012150120 | |
| Download: ML19343B181 (2) | |
Text
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UNITED STATES y,
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g NUCLEAR REGULATORY COMMISSION 5-
'. C WASHINGTON, D. C. 20555
'.... +,o SAFETY EVALUATION 8J _THE OFFICE OF UUCLEAR REACTOR REGULATION SUPPORTING RELIEF FROM REQUIREMENTS OF SECTION XI ASME CODE NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR P6"ER STATION UNIT NO. 1 DOCKET NO. 50-245
1.0 INTRODUCTION
i By letters dated April 9, 1980, and June 10, 1980, Northeast Nuclear Energy Company (the licensee) identified the scheduling requirement of Examination Category B-L-2, Table IWB-2500, pump casings of Section XI ASME Code, 1974 Edition including Summer 1975 Addenda, as an impractical exc.nination require-ment for the reactor recirculation pump casings at Millstone Unit No. 1, in accordance with Paragraph (g)(5)(iii) of 10 CFR 50.55a. The licensee, therefore, requested relief pursuant to 10 CFR 50.55a(g)(6)(i) to allow pcstponement of the Category B-L-2 examination beyond the inspection interval ending December 28, 1980, until major maintenance is performed on one of the pumps.
I 2.0 EVALUATION l
2..
CODE REQUIREMENT A visual examination of the internal pressure boundary surfaces of one pump in each of the group of pumps performing similar functions in the system shall be examined during each 10-year inspection interval. The examination may be performed at or near the end of the inspection inte: val.
l 2.2 BASIS FOR RELIEF The Millstone Unit No. I recirculation pumps have operated satisfactorily for 10 years. The last refueling outage in the current inspection interval is scheduled for October,15'80. Visual examination of the pump casing exteriors during operational leak tests at refueling outages has shown no sign of degrada-tion during the first 10 years of plant operation. Northeast Nuclear Energy l
Company will, instead of the examination procedures required by Section XI ASME Code, at this time, perform visual inspections of the casing exterior of both recirculation pumps during periodic leak tests and/or hydrostatic pressure tests at each refueling outage.
8032150/20
! In the absence of required recirculation pump maintenance, the Section XI ASME Code requirement to disassemble and perform a visual examination of the internal surface of the pump casing is an impractical requirement. Disassembly and inspection of a recirculation pump would result in personnel exposures of about 100 man-rems and require approximately $200,000 in spare parts and other costs. The benefits derived from the Section XI Code examination requirement warrants neither the personnel exposure nor the spare parts and other costs.
The integrity of the recirculation pumps will be assured by performing monthly vibration signature analyses. The analysis is sufficiently sensitive to detect cnanges occurring as a result of either wear, internal surface erosion, or cavitation dar. age. Accelerometers mounted at right angles on each recirculation pump y? in areas most sensitive to detect change in internal configuration and cooldhi flow Although monthly vibration signature analysis will be made, the accelerometeis will continuously monitor the pumps operational and structural 4
characteristics.
In addition, the integrity of the recirculation pumps will be assured by a sensitive leak detection system. The Millstone Unit No. 1 Technical Specifica-tions limit unidentified leakage inside containment to 2.5 gpm.
In the event a through-wall crack develops in either pump casing, the leak detection system is adequate to provide warning of pump degradation at an early stage of leak occurrence.
3.0 CONCLUSION
Wehahereviewedandevaluatedthebasisoftherequestforrelieffromthe requirement of Examination Category B-L-2, pump casings, of Section XI ASME Code, transmitted by letter dated April 9, 1980, from Northeast Nuclear Energy Company. We conclude that the Section XI ASME Code requirement is impractical to complete during the next refueling outage in the Fall of 1980, and that relief is justified. We have reviewed the alternate methods of inspection proposed in lieu of the impractical inspection requirement, and conclude that they will ensure on adequate margin of component integrity. Pursuant to 10 CFR Section 50.55a(g)(6)(i) we hereby grant relief from the specific Millstone Unit No. 1 requirement that the licensee visually examine internal pressure boundary surfaces for one of the two recirculation pumps during the 10-year inspection interval ending December, 1980. We have also determined that granting such relief is authorized by law and will not endanger life or prope-ty or the common defense and security and is otherwise in the public interest i
considering the burdens imposed on the licensee if the relief is not granted.
We have concluded, based on the considerations discussed above, that:
(1) because the relief does not involve a significant increase in the probability
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l consequences of accidents previously considered and does not involve a ve significant decrease in a safet)y margin, the relief does not involve a signif-icanthazardsconsideration,(2 there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Comission's regulations and the issuance of this relief will not be inimical to the common defense and security or to the health and safety of the public.
Date: November 19, 1980
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