ML20037B255
| ML20037B255 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 04/06/1976 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009100727 | |
| Download: ML20037B255 (1) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION REGION til 799 ROOSEVELT ROAD l
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o April 6, 1976' IE Bu'lletin No. 76-05 RELAY FAILURES - WESTINGHOUSE BFD REL/sYS DESCRIPTION OF CIRCUMSTANCES:
Three defective Westinghouse (W) type BFD relays were identified during recent testing of the Reactor Protection System at the j
H. B. Robinson Unit 2 facility. One relay had nn open circuit failure and the others had c::cessive opening times.
The relays which failed were W type BFD with coil style 503C428G21 rated for 125/130 volts de (plus or minus 10%). These relays are normally energized from the 125 volt de bus and, therefore, will be subject to 140 volts de during battery charging operations.
The relay manufacturer has determined thet the three relay failures were caused by overheating of the relay coils.
It was found thit the overheating may result in coil insulation breakdown or melting of the coil solder joints, either of which may lead to an open circuit failure.
Also, the overheating may result in deformation of the nylon coil sleeve in which the plunger travels, and this may adversely affect the relay opening time.
The defective coil style 503C428G21 may be identified by its-varnished cloth outer cover. Manufacture of relays with these coils was discontinued in 1973, and they have been superseded by coil style 1259C71G19.
This later coil style may be identified by its molded outer form. Portions of a W service letter containing information about these relays is attached to this bulletin.
Further instructions regarding this relay problem can be obtained from Westinghouse Nuclear Service Division, Pittsburgh, Pennsylvania 15230.
ACTION TO BE TAKEN BY LICENSEES liND PERMIT HOLDERS For all power reactor facilities with an operating license or construction permit:
1.
If you have received the attached W service letter, describe the actions taken regarding corrective measures to resolve the relay problem as discussed in the attached W service letter.
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IE Eulletin No. 76-05 April 6, 1976 2.
If you have not received the attached U r.orvice letter, describe the actions planned if relaya of tht type and style described in the attached W service letter arc in use or planned for use in safcty related systenc at your facility.
With regard to Item '2 of the attached W service letter, if the opening time of any older style erd relay exceeds 30 milliseconds, the component should be modified or replaced promptly with a relay which is core suitable for the application.
4.
With repard to Item 3 of the attached W scrvice letter, if the temperature of the relay coil is found to exceed 212 degrees F during operation, provide a means for reducing this temperature.
In the report subritted describe the means for maintaining stecdy state temperature below 212 degrees F.
Reports for facilities with operating licenses should be submitted within 30 days after receipt of this bulletin.
and reports for facilities uith constructica pcraits cheuld be submitted within 60 days after receipt cf this bullctin.
Your report should include the date when the above actions were or will be completed.
Reports should be submitted to the Director of the NRC Regional Office and a copy should be forwarded to the HRC Office of Inspection and Enforcement, Division of Reactor Inspection Programs, Washington, D. C.
20555.
Approval of NRC requirements for reports concerning possible generic problems has been obtained under 44 U.S.C. 3512 from the U. S. General Accounting Office.
(GAO Approval B-180255(R0072), expires 7/31/77)
ATTACIDfENT:
Extract from service letter:
BFD RELAYS 4
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EXTRACT FROM WEST 1NGliOUSE SERVICE LETTER:
BFD RELAYS L
During recent periodic testing at an operating.nm : ar power plaat, three detective CFD (de) relays were detecteu during testing of Reactor Protection logic circuits.
One rejay coil ~ had failed open and clie other two demencerst ed abnormally.
long drop-out-tince.. ~Thece failures appecred to be due to
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overheating of the relay coils, resulting in coi! liisulation breakdown, or sufficient heat-induced. deformation'to adversely affect relay drep-out characteristics.
The relays which failed are Westinghouse. type BFD, (deleted),
with style 503C428C21-co12c. -These coils are.isually identifiable by their varnisied cloth cover outer layer (as opporcd te molded coils). These control relays are used in de application only.
Type BF (ac) relays, and AR or ARD relays are not involved.
Even though the relay coils are-rcted at 125-130 volts dc+ 10%.
and suitable for. application.where occasional battery equalization charging condition of 140 volts appear on the de bus, a design review has confirmed that the elevated. temperature developed during elevated voltage operation is sufficient to cause accelerated aging of the relay, and can result la coil degradation.
Manufacture of these relays was disccatinued in late 1973, and they were superseded by BFD style 5059A93, with styJe 1259C71C19 coils. These new coils are visually identifiabic by the molded outer form.
The new relay can be used to replace the old, with all operational characteristics being equal to, or better than, the old.
In addition the new coil, having a different class insulation should provide a higher level or reliability through less susceptibility to overtemperature degradation.
The new coils are dimensionally not suitable for mounting on the old relay.
Therefore, replacement of the entire relay is required.
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Additional testing is being initiated to reaffirm a higher level of reliability of this new relay.
In order for Westinghouse to complete our investigation of this b matter and establish a final recommendation, all operating plants are requested to provide the following information as soon as possible.
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Advise normal de bus volta;,c; bus voltane duri bittery equal!.in;; charne; normal duration of eat tJ :.
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an 1 norn;al f requency of equali; in;; ci.;:r,,.
2.
Conduct relay drop-out time measurements (in r.illiceconds) of'all P,FD relays which provide reactor trip functioco or saf e;.uards initiation, and uhich are energized durin; normal operation on the de bus which is subjected to battery equalizing potential..
3.
Advise ambient temperatures of relay racks housing the relays in question.
4.
Testing of relay drop-out times should be repeated if equalizing charging is required within the nc>:t 30 days.
5.
Westinghouse recommends that equalizing chargir.; on the de bus should not exceed 140 volts, and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> duration.
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Attachment A 2 of 2 j
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