ML19338E309
| ML19338E309 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 08/15/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 8009250458 | |
| Download: ML19338E309 (1) | |
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UNITED STATES
.-J'[ y 3, NUCLEAR REGULATORY COMMISSION CENTRAL FILES
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sit av4N pcazA oRIVE, SUITE 1000 REGION IV LPDR Aq
.e j A AUNGTON, TEXAS 76012 gg7g August 13, 1980 Docket No. 50-267
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Public Serrice Company of Colorado ATTN:
Mr. C. K. Millen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
SUBJECT:
IE BULLETIN NO. 80-19, REVISION 1 - FAILURES OF MERCURY-WETTED MATRIX RELAYS IN REACTOR PROTECTIVE JYSTEMS OF CPERATING NUCLEAR POWER PLANTS DESIGNED BY CCMBUSTION ENGINEERING Enclosed is Revision i to II Sulletin No. 80-19.
The revision ::erely clarifies the areas of concern; therefore, the actions including dates of reports required by you with respect to your nuclear power facility are not changed.
.In order to assist the NRC in evaluating the value/1= pact 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 (s) required by the Bulletin.
Please estimate separately the manpower associated with correc-tive actions necessary following identificatien of problems throu;;h the Sulletin.
Should you have any questions regarding the revised Bulletin or acticus required by you, please contact this office.
Sincere 1' (-
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K. V. Seyfrit i/
Directo;-
Enclosures:
1.
IE Su11ecis No. 30-19, Revision 1 2.
List of Recently Issued II 3u11etins cc:
D. W. Warembourg, Nuclear Production Manager For: St..Vrain Nuclear Stacion
.P. O. Box 368-Platteville, Colorado 8065i L. 3 rey, Manager, QualityLAssurance 8'009250458 g
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- s e, SSINS No.: 6820 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8006190052 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin No. 80-19 Revision 1 Date: August 15, 1980 Page 1 of 2 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 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 inhibit a reactor trip), and four of the reported events involved multi-pie failures (i.e., three relay failures were detected during two teets; two other failures were detected during two different tests).
Because or the re-dundancy within the RPS, no reported event would have prevented a reactor trip; however, the build-up of coincident " failed-closed" failures of certain sets of relays could result in trip failures for off-normal events.
The number of single and multiple relay failures reported gives rise to two (1) the total number of failures yields a much higher random failure concerns:
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, Octobar 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/
CR-0942, " Nuclear Plant Reliability Data System, 1978 Annual Reports of Cumulative System and Component-Reliability", NRC.
IE Bulletin No. 80-19 Revision 1 Date:
August 15, 1980 Page 2 of 2 i
multiple failures detected suggests the presence of a common-mode failure mechanism.
Such a c.ommon-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 OF CONSTRUCTION PERMITS OR OPERATING LICENSES FOR NUCLEAR POWER FACILITIES:
1.
Review your facility to determine whether C.P. Clare Model HG2X-1011 R1 mercury-wetted relays are used in the logic matrix of the RPS.
If R1 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 facilities using the above relays in the logic R1 matrix of the RPS should increase the frequency of their surveillance R1 tests.
Until further notice, or until the mercury-wetted relays have been replaced 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.
The additional surveillance testing applies when operability R1 of the RPS is required by the Technical Specification.
Upon detecting a R1 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 the above relays in the logic matrix of the RPS shall submit either R1 their plans and schedules for replacing the mercury-wetted relaya 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
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the original version of this bulletin, July 30, 1980.
R1 Approved.by GAO, B180225 (R0072); clearance expires July 31, 1980.
(Application for renewal pending before GAO.) 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.
80-17 Failure of 76 of 185 7/3/80 All BWR power reactor Control Rods to Fully facilities holding Insert During a Scram Operating Licenses (CLs) at a BWR or Construction Permit (CP)
Sup. 1 Failure of Control Rods 7/18/80 All BWR power reacter to 80-17 to Insert During a Scram facilities holding Operating 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 l
at a BWR (cps) 80-18 Maintenance of Adequate 7/24/80 All PWR power reactor Minimum Flow Thru Centrifugal facilities holding OLs Charging Pumps Following and to those PWRs Secondary Side High Energy nearin3 licensing Line Rupture 80-19 Failures of Mercury-Wetted 7/31/80 All nuclear power Matrix Relays in Reactor facilicies having l
Protective Systems of either an Operating l
Operating Nuclear Power License (OL) or a Plants Designed by Combus-Construction Permit (CP) tion Engineering 80-20 Failures of Westinghouse 7,31/80 To each nuclear Type W-2 Spring Return power facility in to Neutral control your region having Switches an Operating License (OL) or a Construction Permit (CP)
Enclosure l
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