ML19331D471
| ML19331D471 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 08/15/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 8009030047 | |
| Download: ML19331D471 (1) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION 3Ih oj REGION I t
631 PARK AVENUE
' C/
/
KING OF PRUSSIA, PENNSYLVANIA 19406
++..+
August 15, 1980 Docket Nos. 50-443 50-444 Public Service Company of New Hac:pshire ATTN:
Mr. W. C. Tallman Chairman and Chief Executive Officer 1000 Elm Street Manchester, New Hampshire 03105 Gentlemen:
Enclosed is Revision I to IE Bulletin No. 80-19.
The revision merely clarifies the areas of concern; therefore, the actions, including dates of reports required from 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 estimata 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 corrective 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, 8 y e H. Grier Director
Enclosures:
1.
IE Bulletin No. 80-19, Revision 1 2.
List of Recently Issued IE Bulletins CONTACT:
D. L. Caphton cc w/ encl (s:215-337-5266)
JohnDeVincentis,ProjectManager
.8 0 0 9 0 3 o oq7
1 l
l SSINS No.: 6820,
UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8006190052 OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 August 15, 1980 IE Bulletin No. 80-19 Revision 1 FAILURES OF MERCURY-WETTED MATRIX RELAYS IN REAC1 ; PROTECTIVE SYSTEMS OF OPERATING NUCLEAR POWER PLANTS DESIGNED BY COMBUSTION ENGINEERING BACKGROUND:
1 This bulletin addresses the failures of mercury-wetted relays used in the logic matrix of the reactor protective s designed by Combustion Engineering (C-E)ystem (RPS) of nuclear power pla 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 sinec iney 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).
Beenuse 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 fo.
tres yields a much higher random failure rate than that used in other relay failure estimates *, and (2) the number of i
x 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.
A
,.-.-__----._-,m.,
IE Bulletin No. 80-19, Revision 1 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 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:
i 1.
Review your facility to determine whether C.P. Clare Model HG2X-1011 R
R rercury-wetted relays are used in the logic matrix of the RPS.
If b
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 o?erating facilities using the above relays in the logic R
matrix of the DS should increase the frequency of their surveillance R
tests. Until further notice, or until the mercury-wetted relays have been replaced with qualified relays >f a different design, surveillance testing of the relays shall be initir md 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 R[
of the RPS is required by the Technical Specification. Upon detecting a RU 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, blanket clearance 1980.
for renewal pending before GA0.) Approval was given under a specifically for identified generic problems.
S IE Bul.letin No. 80-19, Revision 1 August 15, 1980 RECENTLY ISSUED IE BULLETINS Bulletin Subject Date Issued Issued To No.
80-20 Failures of Westinghouse 7/31/80 All holders of a Type W-2 Spring Return power reactor OL or to Neutral Control Switches CP 80-19 Failures of Mercury-7/31/80 All holders of a Wetted Matrix Relays power reactor OL in Reactor Protective or CP Systems of Operating Nuclear Power Plants Designed by Combus-tion Engineering 80-18 Maint2 nance of Adequate 7/24/80 All holdus of a Minimum Flow Thru PWR power reactor Centrifugal Charging Pumps OL or CP Following Secondary Side High Energy Line Rupture Supplement 2 Failures Revealed by 7/22/80 All holders of a BWR to 80-17 Testing Subsequent to power reactor OL Failure of Control Rods or CP to Insert During a Scram at a BWR Supplement 1 Failure of Control Rods 7/18/80 All holders of a to 80-17 to Insert During a Scram BWR power reactor at a BWR OL or CP 80-17 Failure of Control Rods 7/3/80 All holders of a to Insert During a Scram BWR power reactor at a BWR OL or CP 80-16 Potential Misappifcation of 6/27/80 All holders of a Rosemount Ire., Models 1151 power reactor and 1152 Pressure Transmitters OL or CP with Either "A" or "D" Output Codes I
80-15 Possible Loss Of Hotline 6/18/80 All holders of a With Loss of Off-Site Power power reactor or fuel facility OL connected to the Emergency Notification l
System l
80-14 Degradation of Scram 6/12/80 All holders of a Discharge Volume Capability BWR power reactor OL or CP
.