ML19332A715
| ML19332A715 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 07/31/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8009180152 | |
| Download: ML19332A715 (1) | |
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UNITED STATES CENTRAL FILES
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NUCLEAR REGULATORY COMMISSION PDR:HQ REGION IV LPOR
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July 31, 1980 Docket No. 50-267 Public Service Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
Enclosed is IE Sulletin No. 80-19 which requires action by you with respect to your nuclear *pewer facility.
In' order to assist the NRC in evaluating the value/ impact of each Bulletin on licensees, it would be helpful if you would provide an esti= ate of the manpower expended in conduct of the review and preparation of the report required by the Bulletin.. Please estimate separately the manpower associated with correc-tive actions necessary following identification of problems through the Bulletin.
Should you have any questions regarding the Bulletin or actions required by you, please contact this office.
Sincerely, Yb db KarlV.Sehrit
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Director
Enclosures:
1.
List of Recently Issued
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IE Sulletins cc:
D. '4. f4arembourg, Nuclear Production Manager Fort St. Vrain Nuclear Station P. O. Box 368 Platteville, Colorado 80651 L. 3 rey, Manager, Quality Assurance eo09.180gyA l
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'SSINS No.: 6820 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION' 8006190022
-0FFICE OF INSPECTION AND ENFORCEMENT T'
D IS WASHINGTON, D.C.
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. July 31, 1980 IE Bulletin No. 80-19 FAILURES OF MERCURY-WETTED MATRIX RELAYS IN REACTOR PROTECTIVE SYSTEMS OF OPERATING NUCLEAR. POWER PLANTS DESIGNED BY COMBUSTION. ENGINEERING
' BACKGROUND:
This. bulletin addresses the failures of mercury-wetted relays used in the logic matrix of 'the reactor protective system (RPS) of nuclear power plants designed'by Combustion Engineering (C-E).
Except for Arkansas Nuclear One Unit 2 and Palisades, both of.which use dry-contact matrix relays, the NRC understands that all other operating C-E plants use C.P. Clare Model HG2X-1011 mercury-wetted matrix relays in the RPS.
Mercury-wetted matrix relays manufactured by the Adams and Westlake Company were initially used in the Palisades plant;-however, because of repeated failures of these relays, they were subsequently replaced with relays having dry-contacts.
GTE, the manufacturer of these dry-contact relays, however, has k
since-discontinued their production.
Thus, although the dry-contact relays used at -Palisades have performed without a failure since they were installed, they are not available for.the other operating nuclear power plants designed by C-E.
OPERATING EXPERIENCES AND EVALUATION:
To date, operating nuclear power plants designed by C-E have reported.
thirty-one -(31) failures of mercury-wetted relays used in the logic matrix of the RPS.
-Most of the reported failures were " failed-closed" type (i.e., the type that could izdliblt.a reactor trip), and four of the reported events involved multi-ple failures (i.e.,~three relay failures were detected during two tests; two other failures were: detected during two different tests).
Because of the re-dundancy_within the RPS, no reported event would have prevented a reactor trip;- however,'the build-up of coincident " failed-closed" failures lof certain i
sets of' relays could result-in tt1p failures for off-normal events.
The number of' single and multi ple relay failures reported gives rise to two concerns: (1) the total. numbr; of failures yields a much higher random failure rate than that used in other relay failure estimates *, and (2) the number of.
- -Other. relay failure estimates include (1) WASH-1400, " Reactor Safety Study",
NRC; October 1975; (2) IEEE Std 500-1977,"IEEE Guide to the Collection and
' Presentation 'of Electrical,. Electronic, and Sensing Component Reliability Data-for Nuclear Power' Generating' Stations", IEEE,.New York; and (3)'NUREG/
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.CR-0942, " Nuclear! Plant Reliability Data. System, 1978 Annual Reports of
.l Cumulative. System and Component Reliability", NRC.
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'IE Bulletin No; 80-19 July 31, 1980 Page 2 of 2 multiple failures detected suggests the presence of a common-mode failure mechanism.
Such a common-mode failure mechanism could result in the build-up of specific ~" failed-closed" failures which, in turn, could result in antici-pated transients without scram (ATWS).
Thus, the-relatively high random failure rate and the. suggested common-mode failure mechanism, indicate that plants using mercury-wetted matrix relays in the RPS are more susceptible to scram failures than predicted in other studies.
ACTIONS TO BE TAKEN BY HOLDERS.0F CONSTRUCTION PERMITS OR OPERATING LICENSES FOR NUCLEAR POWER FACILITIESi 1.
Review your facility to~ determine whether or not mercury-wetted relays are used in the RPS. If no such relays are used, you should submit a negative declaration to this effect and you need not respond to the remaining items in this bulletin..Your negative declaration shall be submitted to the appropriate NRC Regional Office within thirty (30) days of the date of this bulletin and a copy forwarded to the Director, Division of Reactor Operations Inspection, Office of Inspection and Enforcement, NRC, Washington, D. C. 20555.
2.
-Licensees of operating nuclear power plants using mercury-wetted relays in the RPS-should= increase the frequency of their surveillance tests.
Until further notice, or until the mercury-wetted relays have been re-placed with qualified relays of a different design, surveillance testing of the relays shall be initiated within ten (10) days of the date of this bulletin and repeated at intervals not exceeding ten (10) days thereafter.
Upon detecting a failed relay, the failed unit shall-be replaced with a qualified dry-contact relay or a new mercury-wetted relay.
(The removed relay shall not be reused in the RPS').
3.
Nuclear power facilities which are using or whose design includes the use of mercury-wetted matrix relays in the RPS shall submit either their plans and schedules for replacing the mercury-wetted relays with qualified relays of a different design, or justification for using the mercury-wetted relays.
Responses to this item shall be submitted to the offices listed in' Item 1, above, within ninety (90) days of the date of this bulletin.
Approved by GAO, B180225 (R0072); clearance expires July 31, 1980.
Approval was given under a blanket clearance specifically for identified generic problems.
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IE Bulletin No. 80-19 July 31, 1980 RECENTLY ISSUED IE BULLETINS Bulletin Subject Date Issued Issued To No.
D' gradation of Scram 6/12/80 All BWRs with an 80-14 e
Discharge Volume Operating License (OL)
Capability or Construction Permit (CP) 80-15 Possible Loss of Emergency 6/18/80 All nuclear facilities Notification System (ENS) holding Operating Licenses with Loss of Offsite Power (OLs) 80-16 Potential Misapplication 6/ !7/80 All Power Reactor of Rosemount Inc., Models Facilities with an 1151 and 1152 Pressure Operating License (OL)
Transmitters with Either or a Construction Permit "A" or "D" Output Codes (CP) 80-17 Failure of 76 of 185 7/3/80 All BWR power reactor Control Rods to Fully facilities holding Insert During a 3 ram Operating Licenses (0Ls) at a BWR or Construction Permit (CP)
Sup. 1 Failure of Control Rods 7/18/80 All BWR power reactor to 80-17 to Insert During a Scram facilities holding Operat ng i
at a BWR Licenses (OLs) or Con-struction Permits (cps)
Sup. 2 Failures Revealed by 7/22/80 All BWR power reactor to 80-17 Testing Subsequent to facilities holding Failure of Control Rods Operating Licenses (OLs) to Insert During a Scram or Construction Permits at a BWR (cps) 80-18 Maintenance of Adequate 7/24/80 All PWR power reactor Minimma Flow Thru Centrifugal facilities holding OLs Charging Pumps Following and to those PWRs
' Secondary Side High Energy nearing licensing Line Rupture Enclosure