ML19331D588
| ML19331D588 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/15/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Oprea G HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 8009030268 | |
| Download: ML19331D588 (1) | |
Text
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UNITED STATES g ? ; e c/( gg NUCLEAR REGULATORY COMMISSION b, #/
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REGION IV
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ARLINGTON, TEXAS 76012
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August 15, 1980 In Reply Refer To:
RIV Docket Nos. 50-498/IE Bulletin No. 80-19, Revision 1 50-499/IE Bulletin No. 80-19, Revision 1 Houston Lighting & Power Company ATTN: Mr. G. W. Oprea, Jr.
Executive Vice President Post Office Box 1700 Houston, Texas 77001 Gentlemen:
SUBJECT:
IE BULLETIN NO. 80-19, REVISION 1 - FAILURES OF MERCURY-WETTED MATRIX RELAYS IN REACTOR PROTECTIVE SYSTEMS OF OPERATING NUCLEAR POWER PLANTS DESIGNED BY COMBUSTION ENGINEERING Enclosed is Revision 1 to IE Bulletin No. 80-19.
The revision merely 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/ impact of each Bulletin on licensees, it would be helpful if you would provide an estimate of the manpower expended in conduct of the review and preparation.of the report (s) required by the Bulletin. Please estimate se arately the manpower associated with correc-r tive actions necessary following identification of problems through the Bulletin.
Should you have any questions regarding the revised Bulletin or actions required by you, please contact this office.
Sincerely, 0,,1;/ /
-/-
/.hL O f W{
K. V. Seyfrit Director
Enclosures:
1.
IE Bulletin No. 80-19, Revision 1 2.
List of Recently Issued IE Bulletins
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SSINS No.: 6820 UNITED STATES Accession No.:
NUCI. EAR REGULATORY COMMISSION 8006190052 0FFICE OF INSPECTION AND ENFORCEMENT T~
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WASHINGTON, D.C.
20555 iM 44 an e9 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 d ry-conta cts.
GTE, the manufacturer of these dry-contact relays, however, has since discontinued their production. Thus, althouch 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-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 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 concerns: (1) the total number of failures yields a much higher random failure rate than that used in other relay failure estimates *, and (2) the number of i
- 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/
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 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 sug;ested 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 repe sted at intervals not exceeding ten (10) days thereafter.
The additior.ai 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 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 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 GA0.) Approval was given under a blanket clearance specifically for identified generic problems.
IE Bulletin No. 80-19 July 31, 1980 RECENTLY ISSUED IE BULLETINS Bulletin Subj ect 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 (OLs) 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 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 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 nearing licensing Line Rupture 80-19 Failures of Mercury-Wetted 7/31/80 All nuclear power Matrix Relays in Reactor facilities having Protective Systems of either an Operating 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 Pecmin (CP)
Encloscre