ML19332A721
| ML19332A721 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/31/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| GL-80-70, NUDOCS 8009180160 | |
| Download: ML19332A721 (1) | |
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UNITED STATES CEiiTRAL FILES
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Ei NUCLEAR REGULATORY COMMISSION PDR:HQ l M)A i
REGION IV
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3 611 RY AN PLAZA oRIVE. SUITE 1000 IIC ARLINGTON, TEXAS 76012 NSIC me July 31, 1980 4
Docket Nos.
50-313 50-368.
Arkansas Power and Light Company ATIN:
Mr. William Cavanaugh III Vice President of Generation and Construction P. O. Box 551 Little Rock, Arkansas 72203 Gentlemen:
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Enclosed is IE Bulletin No. 80-19 which requires action by you with respect to your nuclear power facilities.
In order to assist the NRC in evaluating the value/ impact of each Sc11etin on licensees, it would be helpfu.L if you would provide an estimate of the nanpower expended in conduct of the review and preparation of the reports required by the Bulletin.
Please estimata 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, f.
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[ 1-Karl V. Seyffit Director
Enclosures:
1.
II Sulletin No. 80-19 2.
List of Recently Issued IE Sulletins cc:
James P.-0'Hanlon, Plant Manager Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72301
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SSINS No.: 6820 UNITED: STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8006190022 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
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July 31, 1980 ep
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,23 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 iu 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-
.ple failures (i.e.,4three relay failnres were detected during two tests; two l
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.
i 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 tha'n 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 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 OF CONSTRUCTION PERMITS OR OPERATING LICENSES FOR NUCLEAR POWER FACILITIES:
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.
l Approved by GAO, B180225.(R0072); clearance expires July 31, 1980.
Approval was given under a blanket clearance specifically for identified generic problems.
l
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_e IE Bulletin No. 80-19 July 31, 1980
-RECENTLY ISSUED IE-BULLETINS
-Bulletin 1 Subject
.Date Issued Issued To No.
80-14 Degradation of Scram 6/12/80 All BWRs with an 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 6/27/80 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 Failu:e 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 Eto Insert During a Scram facilities holding Operating at a BWR Licenses 1(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 Enclosure