ML20128E052

Provides Summary of Addl Info Presented by GE on Failures of Protection Sys Relays Discovered During Functional & Preoperational Testing,During 700708 Meeting W/Nsp & GE to Discuss Mods of Safe Ends

ML20128E052
Person / Time
Site:	Monticello
Issue date:	07/17/1970
From:	Vassallo D US ATOMIC ENERGY COMMISSION (AEC)
To:	Deyoung R US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9212070459
Download: ML20128E052 (3)

Text

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T C.;2 b - i OUL f 7 R. C. DeYoung, Assistant Director for_ Pressurised Water Reactors, DRL -

THRU D..R.' Muller, Chief, PWR Projects Branch fl DRL i MONTICELLO - UNSAFE FAILURE OF PLANT PROTECTION SYSTEM RELAYS tt At a meeting held on-July '8,1970,1with Northern States Power (NSP) and General Electric (GE) to discuss modifications of safe ends, /

GE also presented additional information on the f ailures of pro-tection system relays discovered during functional and preoperational testing at Monticello. . The latter is summarized in this meno..

Specific information on the relay failures is presented in a-Compliance Inquiry Memorandum, dated June 2,'1970

• Background of Events General-Electric confirmed that the cause of the relay failures was heat bonding of the armature plate to - the.' contact end of the'-

coil pole _ piece. -- During the manufacturing process. primer is.

applied to _the pole pieces as a corrosion' inhibitor and 'mir cured at room' temperature. -The bonding of'some relays _ observed-at Monticello'resulted from: additional curing of the primer, which.

apparently had been incompletely cured during the manufacturing process._ The in-place curing of the primer was promoted by internal heat generated in the coils- during ' initial extended (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or less) energisation __of .the relays.

GE described the apparent reason for the improper curing of the corrosion inhibitor on the. pole pieces of theirelays inntalled at i

Monticello. The manufacturing specification designates a 0.003-inch = layer of primer paint, which is applied with a hand brush ~ . ,

It was discovered that the pole pieces of the relays currently-being manufactured have a f.hicknesalof _ primer paint greater, than 0.003 inch, which apparently.leade'to incomplete curing. . The-reason for-the thicker primer coating _is rather-interesting.

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• Compliance. Inquiry Memorandum, Unsafe Failure of Plant Protection System Relays, H. D. n ornburg to J. P. O'Reilly, June 2','1970.'

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R. C. DeToung We were told that the type of relay in question has been manuf actured and used successfully for about 30 years, with no change in design or manuf acturing process. Until two yeare~ago, the relays were built by the CE Relay Product Department in Philadelphia. The workers at this plant had developed a technique for hand brushing the primer on the pole pieces. Two years ago the manuf acturing operation was moved to Puerto Rico, with no changes in design or manufacturing process of the relays. It now appears that the workers in Puerto _ Rico vere applying the primer in a thicker layer, and this coupled with in-adequate quality control resulted in relay pole pieces with an incompletely cured primer coating. Another point of interest in that in the Philadelphia plant another type of relay being produced there uses uncoated pole pieces of the same material as the relays in question without any adverse effects.

,P,,ropose_d Fesolution CE considered three solutions to rectify the problem for those relays installed in plants without. disconnecting the relay. These are:

a. Remove the paint at the exposed end (contact end) of the pole piece with a small wire brush and vacuum clean the relay box.

b. Remove the spring-loaded armature plate and place a thin layer of Teflon on the surface that contacts the pole pieces,

c. Cure the paint in the field by energizing the relays for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, manually unstick the armature and then operate for an additional 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to test operability.

CE considers removal of the paint as the most adaptable to resolution of this problem in the field. This is proposed not only for Fonticello but for all plants using this type of relay. CE atated that they have tested production relays f rom which the paint was removed, and did not encounter any sticking of the armature after energization.

Many of the relays f rom the same production run, but from which the paint was not removed, stuck upon energitation.

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SURNAME > . . . . . . . . . . . . . .. .... . . . . . . . . . . ., .. . . . . . . . . . . . . . . . . . . . . .

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Form AEC-818 (Rev,9-68) U16ovrRamt mmes crFKg .Hes- o-wa-see

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R. C. DeYoung Our concern is whether all aspects of the problem have been studied comprehensively. Because of the large number of relays used in the protection system, we feel that this matter is sufficiently important \

to warrent a report such that we can be assured that CE and the- '

appiteent have focused on all aspects of the problem. For example, we don't know whether protracted operation of the relays could cause a further problem from curing or flowing of the primer remaining _

on those portions of the pole pieces imbedded in the coil laminations.

Further, we believe that CE should fully describe a check out or test program, not only for the Monticello plant but for all plants-containing the multicontact relays. Also, a control procedure should be set up to ensure that corrective measures have been taken for each relay (with painted pole pieces) installed in an operating plant or in a plant under construction.

Oddnal dgoed ay

.D. 3. Va salla .

D. B. Vassallo, Project Leader PWR Projects Branch #1 Division of Reactor Licensing Distribution:

Docket File RL Reading PWR-1 Reading D. J. Skovholt S. Levine F. Schroeder R. S. Boyd Branch Chiefs /PUR R. W. K1ecker D. B. Vassallo-N. M. Blunt oma .BL.:EWRq,,, ,,,,,,pt : PWp-1 ,

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