ML20011B092
| ML20011B092 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 10/28/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20011B091 | List: |
| References | |
| NUDOCS 8111090142 | |
| Download: ML20011B092 (4) | |
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NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 50 TO FACILITY OPERATING LICENSE NO. DPR-42~
AND AMENDMENT NO. 44 TO FACILITY OPERATING LICENSE NO. DPR-60 NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT N05. 1 AND 2 DOCKET NOS. 50-282 AND 50-306
- Introduction By letter dated August 14, 1981, Northern States Power Company (NSP) requested to amend Appendix A to Facility Operating Licenses No. DPR-42 and DPR-60 for Prairie Island Nuclear Generating Plant, Units No.1 and 2.
The amendment would revise the snubber surveillance requirements in the Technical Specifications of Appendix A as requested by our letter dated November 20, 1980.
Discussion and Evaluation As a result of discoveries of numerous inoperative snubbers during the period from 1973 to 1975 we requested that all licensees include a snubber surveillance program in the Technical Specifications for operating reactor plants. However, several deficiencies in the requirenents were identified after the original surveillance programs were in place for several years.
These deficiencies are:
1.
Mechanical snubbers were not included in these requirements.
2.
The rated capacity of snubbers was used as a limit to the inservice test recuirement.
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 licensees and permit holders believed that mechanical snubbers were preferred by NRC. Many plants used mechanical snubbers as original equip-rnent and many others requested to replace their hydraulic snubbers with mechanical ones to simplify or avoid an inservice surveillance program.
This is directly contradictory to NRC's intention, where for an unsurveyed 8111090142 811opg DR ADOCK 05000282 p
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mechanical snubber, the most likely. failure is permanent lock-up.
This failure mode can be harmful to the system during normal plant operations.
In the propqfed amendmen* the licensee has not included surveillance requirements for m'echan'iial'silu't6eIs 'since~1ihese ' nubbers are n'ot'
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s installed nor planned for use at the facility. On that basis we agree with the licensee that surveillance requirements for mechanical snubbers need not be included in the Technical Specifications.of Appendix A.
During the period of 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 is because of the available capacity of the test equipment and the requirement to test some parameters at the snubber rated load.
Since then, greater equip-ment capacity and better understanding of parametric correlation have been developed. To maintain this arbit'rary 50,000 lb. limit could mean an unnecessary compromise on plant safety.
- The original hydraulic snubber problem started 'from leaking seals.
Most seal meterials of the 1973 vintage could not withstand the temperature and irradiation environments.
Ethylene propylene was the first material that could offer a reasonable service life for those seal..
In order to discourage the use of unproven material for those s
seals, the words "f1RC approved material" were used in Technical Specifi.
cations. Staff members were asked to approve different seal materials on many occasions.
Consequently, since the basis for the approval was not defined, the development of better seal materials by the industry was actually discouraged.
The not-well-defined acceptance criteria in the earlier version of the testing requirements resulted in non-uniform interpretations and implementation. Acceptance Criter's were set individually at widely different ranges.
Since the rationule of adopting a specific acceptance criterion was not clear, I&E inspectors found it impossible to make any necessary corrections.
In some cases, snubbers were tested without reference to acceptance criteria.
Testing of snubbers was usually accomplished by removing snubbers from their installed positions, mounting them on a testing rig, conducting the test, removing them from the rig, and reinstal?ing them to the working position. Many snubbers were damaged in the removal and reinstallation process. 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 results in minimizing the damage to snubbers caused by removal and reinstallation plus time and cost savings to the pla'.t.
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~ me Considering this accumulated experience described above we concluded that the existing Technical Specification be revised to reflect this experience gained in the pest several years. ' Therefore, 'the' revised
- surveillance requirements for snubters include the following:..
1.
If mechanical snubbers are used on safety related systems, then they must be included in the surveillance-program.
2.
No arbitrary snubber capacity is to be used as a limit to the inservice test requirements.
3.
Seal material no longer requires NRC approval. A monitoring program shall be implemented to assure that snubbers are functioning within their service life.
4.
Clearly defined inservice test requirements for snubbers shall be implemented.
5.
In-place inservice testing shall-tue permitted.
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By our letter dated November 20, 1980 the above revised requirements were transmitted to all licensees of operating plants, including NSP, except for those licensees whose plants are being reviewed under the Systematic Evaluation Program-(SEP). That letter requested that the:: licensees propose a Technical Specification change to amend Appendix "A" of the license, incorporating these requirements. By letter dated August 14, 1981, NSP responded to our request for Prairie Island Nuclear Generating Plant Units Nos. 1 and 2.
We have reviewed the licensee's submitt.al and find that the proposed amendment does include all of our require-ments for the surveillance of safety-related snubbers.
On this basis we find that the precosec amendrent which revises the surveillance for safety-related snubbers is acceptable.
Environmental Consideration We 'have' determined that the amendments do not authorize a change in effluent 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 amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environme ^ f. n.. pact statement or negative declaration and environ-mental impact app.aisal need not be prepared in connection with the issuance of t.hese amendments.
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4-Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probabitity ot consequenceT7f* acciderits previously'c6nsidered and do not involve a significant decrease in a safety margin, the amendments do 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 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.
Date:- October 28, 1981 e.
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