ML20090E231

AO 73-12-1:on 731201,Magnetrol Switch 352624 in Scram Dump Vol Level Sys Failed.Caused by Oxidized Mercury in Switch Bulb.Bulb Replaced

ML20090E231
Person / Time
Site:	Nine Mile Point
Issue date:	12/10/1973
From:	Schneider R NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20090E233	List: ML20090E231 ML20090E235
References
8914, AO-73-12-1, NUDOCS 8303140162
Download: ML20090E231 (2)

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O O NIAGARA MOHAWK power CORPORATION NIAGARA MOHAWK 300 CRIE BOULEV.4RO WEST SYRACUSE N.Y 13207 December 10, 1973  :

AOR 73-12-1 Mr. Donald J. Skovholt  !

Assistant Director for Reactor Operations y p":-a0 rN Division of Reactor Licensing M

- , Odl M United States Atomic Energy Commission Washington, D. C.

h 20545 a g,,n enn wxan Re: Provisional Ooerating License: DPR-17 h(4

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ml Docket No.: 50-220 9

Dear Mr. Skovholt:

On December 1,19'F3 at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> at Nine Mile Point Nuclear Station Unit #1, a Magnetrol switch #352624 in the Scram Dump Volume level system f, Ailed to operate during routine surveillance testing. Persuant to Technical Specification 1.13 d,:

d. Failure of one or more components of an engineered safety feature or Station system that causes or threatens to cause the feature or system to be incapable of perfoming its intended function, this is an abnormal occurrence and was reported by telephone ou December 1, 1973 and photocopy on December 3,1973 to Director of Regulatory Operations, '

Region I.

- Prior to the occurrence the unit was operating at 1272 MWt with all plant systems nomal. Routino surveillance testing was in progress.

The scram dump volume level switches (37 gal.) cause a reactor scram in-a 1 out of 2 twice logic. . RD08C failed to cause the required actuation of

1. 12 trip channel. 'Ihe remaining three . instruments in this system-perfomed

.as. required.

The apparent cause. of this occurrence was the resu!; of . oxidized mercury in the tulb of the switch. Although the switch carriage would rotate as-required the mercury would not move out of contact with. the switch wire inside the bulb. A pin hole leak was found in the. bulb.

Since the redundant component. was fully operable 'a scram would have been ~ )

produced if. required and no hazaid would have been presented to the . general public.

To correct this situation, the mercury bulb was replaced and in the future as much as possible all mercoids will be chec':ed Sr this condition during surveillance testing.1 This is the first failure of this type.

8303140162 731210

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- ss,f m Jir. lionald J. Sko Q elt - December 10, 1973 ti.S. Atomic Energy Commission, As the mercury starts to oxidize it loses its mirror shine and becomes increa<ingly dull . The lastrumentation and Cont rol Technicians will be alerted to Icok for this condition.

Very t ruly yours, Original signed by - R. R. :m.

• Rudolph R. Schneider Vice President - lilcetric Operations RRS:cm f

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