ML20040A677
| ML20040A677 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/28/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20040A675 | List: |
| References | |
| NUDOCS 8201210402 | |
| Download: ML20040A677 (3) | |
Text
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8(pp.usuq(o UNITED STATES-
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NUCLEAR REGULATORY COMMISSION
,I WASHINGTON, D. C. 20656 c
%,***** p' SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING MENDMENT N0. 81 TO PROVISIONAL OPERATING LICENSE NO. DPR-21 NORTHEAST NUCLEAR ENERGY COMPANY, ET AL MILLSTONE NUCLEAR POWER STATION UNIT NO. 1 DOCKET N0. 50-245
1.0 INTRODUCTION
To reflect accumulated experience obtained from operating plants in the past several years, NRC issued Revision 1 of the Standard Technical Specifications on the surveillance requirements for safety;related snubbers. On November 26, 1980, this document was transmitted to operating plants excluding those under SEP along with a request for
. submittal of appropriate license amendments to incorporate the requirements of this revision within 120 days. The same request was extended to SEP plants on March 23,_1981. By letter dated October 6, 1981, the licensee proposed changes to the Millstone Unit No. 1 Technicali Specifications (Appendix A to License No. DPR-21) in response to this request.
2.0 BACKGR0UtlD AflD DISCUSSION llumerous discoveries of inoperative snubbers in the period of 1973 to 1975 resulted in their surveillance requirements in the Tschnical Specifications for operating reactor plants. However, several deficiencies were identified after the original requirements werein force for several years. These deficiencies are:
1.
Mechanical snubbers were not included in these requirements.
2.
The rated capa' city of snubbers was used as a limit to the inservice test requirement.
3.
NRC approval was necessary for the acceptance of seal materials.
4.
Inservice test requirements were not clearly defined.
5.
In-place inservice testing was not permitted.
Since mechanical snubbers were not subject to any surveillance requirements.
some licensee and permit holders believed that mechanical snubbers were preferred by NRC. Many plants used mechanical snubbers as original equipment and many others requested to replace their hydraulic snubbers with mechanical ones to simplify or avoid an inservice surveillance program.
This is contradictory to NRC's intention ~where, for an unsurveyed mechanical snubber, the most likely failure is permanent lock-up. This failure mode can be harmful to the system during normal plant operations.
8201210402 811228 PDR ADOCK 05000245 P
During the period cf 1973-1975, when the first hydraulic snubber surveillance requirements in the Technical Specifications were drafted, a compromise was made to limit the testing of snubbers to those with rated capacity of not more than 50,000 lbs. This was because of the available capacity of the test equipment and the requirement to test some parameters at the snubber rated load. There is now greater test equipment capacity and better understanding of parametric correlation. To maintain this arbitrary 50,000 lb. test limit for hydraulic snubbers could mean an unnecen ary compromise on plant safety.
The original hydraulic subber problem started with leaking seals. Most seai materials of the 1973 vintage could not withstand the tenperature and radiation environment. Ethylene propylene was the first material to offer a reasonable service life for those seals. To discourage the use of unproven material for those seals, the words "NRC approved material" were used in the Technical Specifications. Staff members were asked to approve different seal materials on many occasions. Because the NRC approval crit _ria was not defined, the development of better seal materials by the. industry was in effect discouraged.
The lack of acceptance criteria in the earlier version of the testing requirements resulted in non-uniform interpretations and 'aplementation.
Acceptance criteria were set individually at widely different ranges.
Since the rationale of adopting a specific acceptance criteria was not clear, it was impossible to make improvements. Snubbers were often tested without reference to any acceptance criteria.
Testing of snubbers was usually accomplished by removal from installed positions, mounting on a testing cig, conducting the test, removing from rig, and reinstalling in the working position. Many snubbers were damaged during removal and reinstallation. This defeated the purpose for conducting tests.
Since methods and equipment have been developed to conduct in-place tests on snubbers, taking advantage of these developments could result in reducing damage to snubbers caused by removal and reinstallation.
On this basis it Was concluded that the snubber surveillance requirements for the Technical Specifications should be revised, 3.0 EVAL 0ATION Revised surveillance requirements correct these deficiencies in the following manner:
1 Mechanical snubbers are now included in the surveillance program.
2.
No arbitrary snubber capacity is used as a limit to the inservice test requirements.
3.
Seal material no longer requires NRC approval. ' A monitoring program t
shall be implemented to assure that snubbers are functioning within their service life.
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4.
Clearly defined inservice test requirements for snubbers shall be implemented.
5.
In-place inservice testing shall be permitted.
The proposed license changes submitted by Northeast Nuclear Energy -
Company (NNECo letter. dated 10/6/81) for operating license DPR-21 for Millstone Nuclear Power Station Unit No.1 with NRC modifications, i.e. TS 4.6.I.4.b, acceptable to NNECo have incorporated tJue necessary requirements of' Revision 1 of the Standard Technical Specifications for_
the surveillance of safety-related snubbers and are, th,e,refore, acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
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We have determined that the amendment does not authorize a change in effluent
- l types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact, and pursuant to 10 CFR Section Sl.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
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. e We have concluded based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (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 Comnission's regulations and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date: December 28, 1981
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