ML19220C127

Forwards Result of Investigation Re Failure of GE Type SBM Switches.Failures Due to Cracks & Breaks in Cam Followers.Replacements Order

ML19220C127
Person / Time
Site:	Crane
Issue date:	10/21/1977
From:	Herbein J Metropolitan Edison Co
To:	Grier B NRC Office of Inspection & Enforcement (IE Region I)
Shared Package
ML19220C124	List: ML19220C123 ML19220C127
References
GQL 1406, GQL-1406, NUDOCS 7904280276
Download: ML19220C127 (4)

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s a w. n zss METROPOLITAN EDISON COMPhNY :vssiciAny ce cesenat pustic uritir:ss cas?cnaricu OST OFFICE BCX 542 BE AOtNG, PENNSYLVANIA 19603 TELEPHCNE 215 - 929-2601 October 21, 1977 GQL lh06 Mr. 3. H. Grier, Director U. S. Nuclear ReSulatory Cc==issien Office of Inspecticn and Inforce=ent neg<cn a 631 park Avenue King of Prussia, pennsylvania 19hC6 Dea - Sir-2ree Mile Island ?iuclear Ctation Unit 2 (CC-2)

Lic ense No. CPPR 66 Decket No. 50-320 G7 *ypa.

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t On Septe=ber 21, 1977, Mr. Leu Narrev of ycur office was netified of a situatien which Metrepel_ tan Idisca Cc=pany censidered to be reportable in accordance with the requirenents of 10 CFR 50.55(e).

H is letter constitutes the required thirty day fellev-up letter.

Descrintion As a restit of several failures of GI tyce S3M svitches, an investigation en site revealed that the failures were due to cracks and breaks in the ca: rellevers within the svitch.

"he ca= followers cperate the =cving centacts vithin the switch.

GI was i==ediately notified of the proble: at which ti=e they advised the site of an cutstanding Serve.ce Advice letter which had been sent te Metrcpolitan Idison Cc=ps.ny in March of 1975 Attached is a copy of that Service Advice letter.

Analysis of Safety I nlicatiens Approxi=ately b00 CI type 53M svitches are located within 2C Unit 2.

Mr.ny of these svitches are fer safety related ce=penents.

Had this ccnditien gene undetecte it is possible thtt ene of these svitches vculd have failed du-ing an IS event which =ight have prevented a safety related cc=penent frc= functiening as designed.

Howeve:, since all safety related cc=penents required fer the safe shutdevn of the unit are redundant, it is extre=ely i= probable that the tvc independent switches for the redundant ec=penents veuld fail si=ultaneously.

Additicnally, periedic surveillance testing vculd have identified a large =ajority of the defective svitches and these vould have been replaced.

Eased en the above censiderations, this incident would net have had a= adverse effect en the health or safety cf the public cr the unit staff.

/

7904'2802 76, 8/

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Mr. 3. H. Grier October 21, 1977 G Z LLC 6 Cerrective Action Tne attached GE Service Advice shevs the cracking ca: follever proble: ithin the type S3M switches to be directly attributable to the Lexan plastic ca=

fc11cver having been exposed to hydro carbens dring the svitch asse=bly.

A date code affixed to the switch identifies the period of =anufactre when exposure to the hydro carbens tock place.

By use of this date ecde, S3M switches that vere asse= bled during this period have teen identified and located.

A review of the switches at TMI Unit 2 has indicated that abcut ene quarter cf the total nu=ber of switches en site vere =arnfactred during the questionable

• 'e have crdered replace =ent svitches for this total and expect to have pericd.

a all questionable switches replaced by ccre Ica:1. '

" ry tru.1 yces, f

/

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O h

/ J. G. Herbein Vice President JGE:a3S:dkf ec:

Dr. Z.v.st Volgenau, Director Office of Inspection and Enfcrce=ent U. S. Nuclear Begulatory Cc==issien

• • shington, D. C.

20555 aa Attach =ent: Service A:ivice Letter PSM 202.1 S3M Switches addressed to Met-Ed frc= General Electric Co. dated March 10, 1975 87 273

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G E N E R A l. 4@ E L E C T R I C

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GENERAL E L E C T A 1.C CCMPANY 3 PENN CENTER P L *. 7 A DIVIS IC N PHILAC ELP HI A.

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