ML20209C742

Annotated Memo Submitting Info Re Failure of Circuit Breakers & Snubber as Discussed During 840215 Telcon Between T Bishop & H Canter of Region V

ML20209C742
Person / Time
Site:	Diablo Canyon
Issue date:	02/16/1984
From:	Schierling H NRC
To:	Knighton G, Novak T NRC
Shared Package
ML17083B484	List: ML20209C687 ML20209C692 ML20209C725 ML20209C729 ML20209C734 ML20209C742 ML20209C774 ML20209C779 ML20209C786 ML20209C810 ML20209C853 ML20209C869 ML20209D170 ML20209D204 ML20209D416 ML20209D421 ML20209D450 ML20209D560 ML20209D649 ML20209D703 ML20209D864 ML20209D903 ML20209E021 ML20209E030 ML20209E037 ML20209E052 ML20209E145 ML20209E211 ML20209E268 ML20209E506 ML20209F952 ML20209G177 ML20210E664 ML20210E745 ML20210E799 ML20210E811 ML20210E916
References
FOIA-86-197 NUDOCS 8403090022
Download: ML20209C742 (3)

Text

. -

EflCLOSURE 1

's g3 f./ creug'q, UNITED STATES

! *  % NUCLEAR REGULATORY COMMISSION

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2 i' ""i s l

E WASHINGTON, D. C. 20555 [ * '

m l j

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& W. o NOTE FOR:

T omas M.

George t.

ak nighton " - W~h $rAU FROM: s Schierling hCLE I 6'@A. .

SUBJECT:

DIABLO CANY0fl - FAILURE OF CIRCllIT RREAKERS AND SRURRER

7 13 The following information on the subject was provided to me in a telephone call from Tom Bishop and Harvey Canter of Reofon V on February 15, 1985 - 5 PM.

Electrical Circuit Breaker Failure PG&E recently noticed frequent failures of GE-Magnablast dKV ML 13 breakers There are about 30 such breakers that feed all 3 vital busses, probably many more nonvital throughout the plant.

The failure is in a small teflon bushing in the operating nerhanism. The bushing breaks as result of frequent operation.

PGaE is new replacing teflon bushinos with metallic bushinos. Replacement to be conoleted by about March 10, 1984.

PG&E also noticed poor construction of breakers during current replacement.

Pone welding on breaker components. .

Recion V thinks that failure of teflon bushings was sub.iect n# a Technical Information Bulletin in 1974 Apnerently no action taken by PG&E at that time. Region V is looking into backgrnund.

Issue: Ts above generic? I l

Complete resolution needed before gaine critical? ,

Part 21 cenoliance? f what is qualification of breakers? I

. ?.

Large Snubber Failure PG8E found cracked / broken bolt in large snuhber in Unit 2 steam genaratnr. .

Exact date unknown, maybe February 15, maybe 6 weeks ago.

Manufactured in/by Willis in California.

Such bolt failure apparently also came up in 1976 and action was to be taken.

Failure is attributed to hydrogen intrusion causing embrittlement and failure.

Heat-up of Unit 1, i.e. Mode 4 and 3, scheduled #or February 11 has been '

delayed pending further. investigation by PG&E Issue: Generic problem?

tlas action taken in 1976?

Is this isolated case?

Region V will orovide update on both issues.

k .b-b Hans Schierling 4

TRANSCRIPT OF GE SERVICE ADVICE LETTER 31B.1, FEBRUARY 1977 ENCLOSURE 2

- v' P.81 ,

• In lina uith our policy of keeping us:rs informed cf conditi:ns which could possibly affect breaker operation, the following information is provided on type ML-13 breaker mechanism. , g REPLACEMENT OF TUF-LOC SLEEVE SEARINGS WITH AltMINUM 8RONZE 5LEEVE BEARING 5 ON SELECTED RATING 5 0F MAGNE-8LAST BREAKERS h w

Although these breakers were properly qualified according to all applicable 3- C industry standards, field experience has shown a few cases that involved F R.

R more mechanism than normal used onwear of the Tuf-Loc the following sleeve bearing rated breakers: in M.-13 operating AM-4.16-250-8(*)8 &9 (*)8 -R AM-4.16-350-1(*). AM-4.16-350-2(*). AM 7.2-500-6(*)4. AM-13.8-750-5(*)8 *D and AM-13.8-1000-3H of all current ratings. (*=H. C. L. or F). (These brcakers have a Short Time Momentary current rating of 80.000 llM5 total T. b amperes.) These sleeve bearings are Teflon coated fiberglass.

K Q ,

Although our experience indicates that this condition has almost always been b associated with breakers applied to repetitive duty, such as Gas Turbine . .

Installations or Power House Auxiliaries. it can also be experienced with p any breaker of the previously mentioned types, models, and ratings. @

Evidence of the condition may be indicated in the following ways: y0

1. Excessive play and wear of the bearings in the linkage, pawls, etc.

of the mechanism, and.

2. Difficulty in obtaining and holding the required adjustments.

including the primary contact wipe of the breaker and the mechanism.

To minimize the possibility of a breaker problem and to increase the life of the bearings in the mechanism. particularly. for those used on repetitive duty, we recossend that you promptly and regularly inspect the breaker's contact wipes. You should also consider replacement of the Tuf-Loc bearings with Aluminum 3ronze bearings. The Aluminum Bronze design was qualified and introduced into all new breakers since 1975.

Tha replacement of Tuf-Loc bearings with Aluminum Bronze bearings should ba part of a regular maintenance' program. or where the condition evidences itself. These may be ' ordered through your local General Electric Company Sales Office.

ORDERING INFORMATION

1. Order Cat #0156C9403 G-1 Aluminum Bronze sleeve bearing

. required per breaker.

replacement This will provide kit,the quantity one (1)(21) sleeve bearings -

twenty-one seven different si:es - required for each mechanism.

2. Order one (1) copy drawing 0156C9403. This drawing outlines 'a suggested procedure for replacing the sleeve bearings. -

l 3. Order D50H15 grease. When reassembling parts lubricate l with 050H15 grease as specified in drawing 0156C9403. '

7;; J. 7 . Fceo N.2 C b Md

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