ML20214U001
| ML20214U001 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/11/1978 |
| From: | Switzer D NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-7524, NUDOCS 8706100536 | |
| Download: ML20214U001 (3) | |
Text
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- ,D April 11, 1978
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Docket No. 50-336 m
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Director of Nuclear Reactor Regulation 3
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Attn:
Mr. R. Reid, Chief g
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Operating Reactors Branch #4 U. S. Nuclear Regulatory Commission r)
Washington, D. C.
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&/ %, y Gentlemen:
This letter is being forwarded to request NRC approval of hydraulic snubber seal material in accordance with Millstone Unit No. 2, Appendix A, Technical Specifica-tion 4.7.8.1.a.
This approval is necessary to resolve a current open item from a recent Region I inspection, in addition to providing us with information con-I cerning currently approved seal materials.
As you are aware, the hydraulic snubber seal material concerns were raised as a result of seal f ailures attributable to incompatibilities between hydraulic snubber fluids and the operating environment and certain snubber seal materials, notably millable gum polyurethane.
The hydraulic snubbers installed at Millstone Unit No. 2 have never had millable gum polyurethane seal materials.
Of the 170 hydraulic snubbers installed at Millstone Unit No. 2, some 40% contain seal materials other than ethylene propylene. These other seal materials, except for one case, are valve seal 0-rings and include molythane and seal injected poly-urethanc components.
Since the hot functional startup test phase, Millstone Unit No. 2 has accumulated l
almost three years of operating cxperience with the installed hydraulic snubbers.
During this period, no snubber seal failures have ever been experienced, nor have there been any indications of excessive leakage or other anomalf es to sug-gest abnormal seal degradation, l
ITT Grinnell, the primary snubber vendor confirmed in writing prior to imple-j mentation of the snubber Technical Specifications that there had never been a l
reported generic problem with the seals in a Grinnell snubber, j
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Due to the reliable service provided by the snubber seals currently in use and
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the confidence expressed in the seal materials by the snubber vendor, it is concluded that the snubber seals in use at Millstone Unit No. 2 are fully com-l patible with the operating environment.
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The hydraulic snubber inspection interval of Specification 4.7.8.1 provides
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adequate assurance that any other form of snubber degradation will be detected.
It is requested that you provide us with written confirmation of your approval of the seal materials in use at Millstone Unit No. 2 such that this matter will be resolved concurrent with the issuance of the refueling license amendment.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY M
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D. C. Switzer President cc: Director, Region I, Of fice of Inspection and Enforcement i
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