ML19345A438
| ML19345A438 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 04/05/1976 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011210520 | |
| Download: ML19345A438 (1) | |
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I UNITED STATES NUCL
.tl REGULATORY COTMISSION s
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REGloN i 639 P ARK AVENUE KING OF PRUSSI A, PCNNSYLVANIA 19406 g
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i Yankce Atomic Electric Company Docket No. 50-29
[ j Attention: !!r. Robert H. Groce 7
Licensing Engineer 20 Turnpike Road f
I Westborough, Massachusetts 01581
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4 Genticmen:
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Enclosed is IE Bulletin No. 76-05 uhich requires action by you with
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E regard to your power reactor f acility(ics) with an operating license or l
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a construction permit.
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Should you have questions regarding this Bulletin or the actions re-a quired of you, please contact this office.
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A James P. O'Reilly l
E Director 7
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Enclosure:
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l If Approval of NRC requiremente for reports concerning
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possible generic prob 1 cms has been obtained under 44 U.S.C. 3512 from the U. S. General Accounting Office (GAO I
Approval B-180255(R0072), expires 7/31/77).
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H. Autio, Plant Superintendent
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Donald G. Allen, President f
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NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
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DATE: April 5, 1976 F
Page 1 of 3
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P RELAY FAILURES - WESTINGHOUSE BFD RELAYS 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 f
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 de (plus or minus
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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 th a three relay failures were caused by overheating of the relay coils. It t - found that the overheat-n ing 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 everheating 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 dis-continued in 1973, and they have been superseded by coil style 1259C71Gl9.
This later coil style may be identified by its molded outer form.
Portions of a (W) service letter containing information about these relays is l
attached to this bulletin.
Further instructions regarding this relay problem can be obtained from Westinghouse Nuclear Service Division, Pittsburgh, Pennsylvania 15230.
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i IE Bulletin No. 76-05 DATE: April 5, 1976 Page 2 of 3 ACTION TO BE TAKEN BY LICENSEES AND 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.
J 2.
If you have not received the attached (W) service letter, describe the actions planned if relays of the type and style described in the attached (W) service letter are in use or planned for use in safety related systems at i
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 f
30 milliseconds, the component should be modified or
- Et replaced promptly with a relay which is more suitable for the application.
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With regard to Item 3 of the attached (W) service letter,
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if the temperature of the relay coil is found to exceed 212
}g degrees F during operation, provide a means for reducing g;
this temperature.
In the report submitted describe the
- !q means for maintaining s teady state temperature below jy
.it 212 degrees F.
[3 Reports for facilities with operating licenses should be submitted within 30 days af ter receipt of this bulletin, lg J's and reports for facilities with construction permits h
should be submitted within 60 days af ter receipt of this
.?s bulletin. Your report should include the date when the
.pr above actions were or will be completed.
!Mf Reports should be submitted to the Director of the NRC j$
i Regional Office r'd a copy should be forwarded to the
!5,1 NRC Office of Inspection and Enforcement, Division of Reactor Inspection Programs, Washington, D. C. 20555.
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IE Bulletin No. 76-05 DATE: April 5, 1976 Page 3 of 3 j
, ~_s Approval of NRC requirecents for reports concerning poss.ib1.e generic problems has been obtained under 44 U.S.C 35.12 from the U. S. Cencral Accounting Office.
4-(CAO Approval B-180255(R0072), expires 7/31/77)
ATTACHMENT:
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Extract from Westinghouse service letter:
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Attachment A 1E Bulletin No.76-05 DATE: April 5, 1976 Page 1 of 2 EXTRACT FROM WEST 1FCHOUSE SERVICE LETTER:
BFD RELAYS During recent periodic testing at an operating nuclear power plant, three defective BFD (de) 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 failures appeared to be due to overheating of the relay coils, result-ing in coil insulation breakdown, or sufficient heat-induced deformation to adversely affect relay drop-out characteristics.
The relays which failed are Westinghouse type BFD, (deleted), with tyle 503C42SG21 coils.
These coils are visually identifiable by tacir varnished cloth cover outer layer (as opposed to molded coils).
These control relays are u-ed in de application only. Type BF (ac) relays, and AR or ARD relays are not involved.
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Even though the relay coils are rated at 125-130 volts dc !10%, and d
suitable for application where occasional battery caualization charging h
condition of 140 volts appear on the de bu;, a design review has 2
confirned that the elevated tenperature developed during elevated
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voltage operation is sufficient to cause accelerated aging of the relay, and can result in coil degradation.
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Manufacture of these relays was discontinued in late 1973, and they l
were superseded by BFD style 5069A95,' with style 1259C71G19 coils.
l These new coils are visually identifiable by the molded outer form.
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g Attachment A IE Bulletin No.76-05
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DATE: April 5, 1976-E Page 2 of 2
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The new relay can be used to replace the old, with all operational E
characteristic being equal to, or better than the old.
In
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the new coil, having a different class insulation should provide a higher level of reliability through less susceptibility to over-5 temperature degradation. The new coils are dimensionally not suitable
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for mounting on the old relay. Therefore, replacement of the entire c
'd relay is required. Additional testing is being initiated to reaffirm a higher level of reliability of this new relay.
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In order for Westinghouse to complete our investigation of this matter
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and establish a final reco==endation, all operating plants are requested te provide the following infor=ation as soon as possible.
E 1.
Advise normal de bus voltage; bus voltage during battery equalizing
- a charge; normal duration of equali;!ng charge; and nor=al frequency of equalizing charge.
2.
Cenduct relay drop-out time measure =ents (1.' milliseconds) of all EFD relays which provide reactor trip funs-tions or safeguards f
initiation, and which are energized during normal operation oc the de bus which is subjected to battery equalizing potential.
3.
Advise-ambient te=peratures of relay racks housing the relays in-questien.
4.
Testing of relay drop-out times should be repeated if equalizing charging is required within the next 30 days.
5.
Westinghouse reco== ends that ecualizing charging on the dc_ 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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