ML19338C523

Forwards IE Bulletin 80-19, Failures of Mercury-Wetted Matrix Relays in Reactor Protective Sys of Operating Nuclear Power Plants Designed by Combustion Engineering. Action Required by Facilities W/Ols or CPs

ML19338C523
Person / Time
Site:	Grand Gulf
Issue date:	07/31/1980
From:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:	Stampley N MISSISSIPPI POWER & LIGHT CO.
References
NUDOCS 8008180062
Download: ML19338C523 (1)

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0 JUL 311983 In Reply Refer To:

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Mississippi Power and Light Company ATTN:

N. L. Stampley Vice President of Production P. O. Box 1640 Jackson, MS 39205 Gentlemen; Enclosed is IE Bulletin No. 80-19 which requires action by you with respect to your nuclear power facility (ies).

In order to assist the NRC in evaluating the value/ impact of each Bulletin on licensees, it v-=ld be helpful if you would provide an estimate of the manpower expended i-conduct of the review and preparation of the report (s) required by the Bull'cin. Please estimate separately the manpower associated with corrective actions necessary following identification of problems through the Bulletin.

Should you have any questions regarding this Bulletin or the actions required by you, please contact this office.

Sincerely, h

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Y James P. O'Reilly Director l

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Enclosures:

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IE Bulletin No. 80-19 2.

List of Recently Issued IE Bulletins cc w/ encl:

C. K. McCoy, Plant Manager l

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, f, 3 e, 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 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., 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

• 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.

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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e IE Bulletin No. 80-19 Enclosure July 31, 1980 RECENTLY ISSUED IE BULLETINS Bulletin Subj ect Date Issued

, Issued To No.

80-18 Maintenance of Adequate 7/24/80 All PWR power reactor 4

Minimum Flow Thru Centrifugal facilities holding OLs Charging Pumps Following and to those PWRs Secondary Side High Energy nearing licensing Line Rupture Supplement 2 Failures Revealed by 7/22/80 All BWR power reactor to 80-17 Testing Subsequent to facilities holding OLs Failure of Control Rods to Insert During a Scram at a BWR Supplement 1 Failure of Control Rods 7/18/80 All BWR power reactor to 80-17 to Insert During a Scram facilities holding OLs at a BWR 80-17 Failure of Control Rods 7/3/80 All BWR power reactor to Insert During a Scram facilities holding OLs at a BWR 80-16

. Potential Hisapplication of 6/27/80 All Power Reactor Rosemount Inc., Models 1151 Facilities with an and 1152 Pressure Transmitters OL or a CP with Either "A" or "D" Output 4

Codes 80-15 Possible Loss Of Hotline 6/18/80 All nuclear facilities With Loss Of Off-Site Power holding OLs 80-14 Degradation of Scram 6/12/80 All BWR's with an Discharge Volume Capability OL 80-13 Cracking In Core Spray 5/12/80 All BWR's with an Spargers OL I

80-12 Decay Heat Removal System 5/9/80 Each PWR with an OL Operability l

80-11 Masonry Wall Design 5/8/80 All power reactor facilities with an.

i OL, except Trojan J

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