ML19329E334
| ML19329E334 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 04/06/1976 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8006120643 | |
| Download: ML19329E334 (1) | |
Text
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f UNITED STATES NUCLEAR REGULATORY COMMISSION
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REGION lli 799 ROOSEVELT ROAD GLEN ELLYN. ILLINOIS 60137 April 6, 1976 Coi.sumers Power Company Dockat No.
ATTN Mr. Stephen H. Howell Docket No. 50-330 Vice President 1945 West Parnall Road Jackson, Michigan 49201 Gentlemen:
Enclosed is IE Bulletin No. 76-05 which requires action by you with regard to your power reactor facilities with construction permits.
Should you have questions regarding this Bulletin or the actions required of you, please contact this office.
Sincerely yours, James G. Keppler Regional Director Enclosures IE Bulletin ho. 76-05 THis DOCUMENT CONTAIMS bec w/ encl:
IE Central Files POOR Q AUTY PAGES J
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Local PDR OGC, Beth, P-506A Ronald Callen, Michigan Public Service Commission Dr. Wayne E. North Myron M. Cherry, Chicago 5
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April 6, 1976 IE Bulletin No. 76-05 RELAY FAILURES - WESTINGHOUSE UFD RELAY 3 DESCRIPTION OF CIRCUMSTANCES:
'Three defective Westinghouse (W) type BFD relays were identified during recent testing of the Reactor Protection System at the H. B. Robinson Unit 2 facility. One relay had an open circuit
-failure and the others had excessive opening times.
The relays which failed were W type BFD with coil style 503C428G21 rated for 125/130 ~ volts dc (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 that the three relay failures were caused by overheating of the relay coils.
It was found that the overheating may result in coil insulation breakdown or melting of the coil solder joints, either of
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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. Manufactura of relays with these i
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 Eproblem can be obtained from Westinghouse Nuclear Service
.j Division, Pittsburgh, Pennsylvania 15230.
4 ACTION TO BE TAKEN BY LICENSEES AND PERMIT IIOLDERS 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
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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 W nervice letter, doncribe the actions planned if relays of the type and style doncribed in the attached W aervice letter are in uce or planr.ed for use f u nafety related systems at
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your facility.
3.
With regard to Item 2 of the attached W service letter, if the opening time of any older style BFD relay exceeds 30 milliseconds, the component should be modified or replaced promptly with a relay which is more suitabic for the application.
4.
With regard to Item 3 of the attached W service 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 submitted describe the means for maintaining steady state temperature below 212 degrees F.
Reports for facilities with operating licenses should be submitted within 30 days after receipt of this bulletin, and reporLs for facilities with construculon permits should be submitted within 60 days after receipt of this bulletin.
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 NRC 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 Of fice.
(GAO Approval B-180255(R0072), expires 7/31/77)
ATTACIIMENT:
Extract from service letter:
BFD RELAYS 1
4
g EXTRACT FROM WESTINC110USE SERVICE LETTER:
BFD RELAYS During receng periodic testing at an operating nuclear power plant, three defective BFD (dc) relays were detected during testing of Reactor Protection logic circuits.
One relay coil had failed open and the other two demonstrated abnormally long drop-out times. These failurcs appeared to be due to overheating of the relay coils, resulting in coil insulation breakdown, or sufficient heat-induced deformation to adversely affect relay drop-out characteristics.
The relays which fa' led are Westinghouse type BFD, (deleted),
i with style 503C428G21 coils. These coils are visually identifiable by their varnished cloth cover outer layer (as opposed to 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 rated 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 in coil degradation.
Manufacture of these relays was discontinued in late 1973, and they-were superseded by BFD style 5069A95, with style 1259C71Gl9 coils. These new coils are visually identifiable by the molded outer form.
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The new relay can be used to replace the old, with all operational s
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 suaceptibility to overtemperature degradation.
The new coils are dimensionally not suitable for mounting on the old relay.
Therefore, replacement of the entire relay is required.
Additional testing is being initiated to reaffirm a higher level of reliability of this new relay.
In order for Westinghouse to complete our investigation cf this matter and establish a final recommendation, all operating plants are requested to provide the following information as soon as possible.
Attachment A 1 of 2 l
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. 1.
Advise normal de bus voltage; bus voltage during battery equalizing charge; normal duration of equalizing charge; and normal frequency of equalizing charge.
2.
Conduct relay drop-out time measurements (in milliseconds) of all BFD relays which provide reactor trip functions or safeguards initiation, and which.are energized during 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 next 30 days.
5.
Westinghouse recommends that equalizing charging 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 9*
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