ML16341C661

Forwards Revision 1 to IE Bulletin 80-19, Failures of Mercury-Wetted Matrix Relays in Reactor Protective Sys of Operating Nuclear Power Plants Designed by C-E. Written Response Required

ML16341C661
Person / Time
Site:	Diablo Canyon
Issue date:	08/15/1980
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Crane P PACIFIC GAS & ELECTRIC CO.
References
NUDOCS 8009030278
Download: ML16341C661 (8)

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UNITED STATES NUCLEAR REGULATORY COMMISSION REGION V 1990 N. CALIFORNIABOULEVARO SUITE 202, WALNUTCREEK PLAZA WALNUT CREEK, CALIFORNIA94596 August 15,

'980 Docket

!Io

, 50-275 0-323 Pacific Gas and Electric Ccmoanv 77 Beale Street San Francisco, California 94106 Att ntion:

.'1r. Philip A. Crane, Jr.

Assistant General Counsel ig SL'BJECT:

IE BULLETIN NO. 80-19, RE'/ISION 1 - FAIILR S OF 'MERCURY-HE) IED

.'4ATRTX REI AYS IN REACTOR PROTECTI'/E SYSTE!IS'F OPERATING NUCL AR PO',IER PLANTS DESIGNED BY COMBUSTION EIHGItIEERI,'IG Enclosed is Revision 1 to IE Bulletin i'Io. 80-19.

The revision merely clarifies the areas of concern; therefore, the actions including dates of reports required by you wi th respect to your nuclear power facility are not changed.

In order to assist the HRC in evaluating the value/impact of each Bulletin on licensees, it would be heloful if you would provide an estimate oi the manpower expended in conduct of the review and preparation of the report(s) required by the Bulletin.

Please estlMat2 separately the manpower associated with corrective actions necessary ollowing identification of problems through the Bulletin.

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

Sincerely, Encl osures:

l.

I Bulletin 'Io 80-19 Revision 1

2.

List of Recently issued IE Bulletins

/

..'lt/H'.

otic'Iken / ~

/Director cc w/enclosures:

E.

B. Langley, Jr.,

PGaE M. Raymond, PGKE R.

Ramsay, PGhE, Diablo Canyon ppi) igI )pl IIn pI;I~US,!Ii,- j~.! j jgpog Sooooso

UllITED STATES

, <<'IUCLEAR REGULATORY CQ<<MMISS IO'I OFFICE OF Il'ISPECTIQH A<<'IP E<<IFQRCE<<v!EHT

'.IASHI."IGTOI'I, D.C.

20555 SSIHS

<<'Io.: 6820 Accession

<<'lo.:

8006190052 Auaust 15, 1980 IE Bulletin <<'lo. 80-19 Revision 1

FAII.URES OF >~!ERCURY-'iIETTED AVIATRIX RELAYS IH REACTOR

. ROTECTI'/E SYSTE<<IS OF OPERA) IHG <<'IUCLEAR PO',!ER PLA<<ITS DESIG<<'lED BY CONBUSTIO<<'I EHGIlIEERIHG BACKGROU "lp:

This bulletin addresses the ailures of mercury-wetted relays used in the logic matrix of the reac.or orotective system (RPS) of nuclear oower olants designed by Combustion Enaineering (C-E),

Except or Arkansas luclear One Unit 2 and Palisades, both of which use dry-con"act matrix relays, ihe HRC understands that ail other ooeratina 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 Mestiake 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, althougn the dry-contact relays used at Palisades have performed wi houi a failure since they were installed, they are not available

=or the other operating nuclear power plants designed by C-E.

OPERATIC!G EXPERIEHCES AHD E)/ALUATIO)I:

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 viere "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 trio di erent tests).

Because of the re-dundancy vii thin the

RPS, no reported event viould have prevented a reactor trio;

however, the build-up of coincident "failed-closed" failures of certain sets of relays could result in trip failures for of,-normal events.

The number of s.ngle and multiole 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 ther re)ay rai ure estimates include (') <<lASH-1400, "Reactor Safety Study",

<<'IRC, October

<975; (2)

IEEE Std 500-1977,"IEEE Guide to the Collection and Presentation of Electrical, Electronic, and Sensing Component Reliability Data or.'Iuclear Power Generating Stations",

IEEE,

<<'lew York; and (3)

HUREG/

CR-0942,

".'Iuclear Plant Reliability Data System, 1978 Annual Reports of Cumulative System and Component Reliability", <<'IRC.

IE Hulletin llo. 80-19, Revision 1

August 15, 1980 Page 2 of 2 multiole 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" ",ailures which, in.urn, could result in antici-pated transients without scram (AT'i!S).

Thus, the relatively hioh random failure rate and the suggested common-rode failure mechanism, indicate that plants using mercury-wetted matrix relays in the RPS are more susceptible to scram failures than oredic ed in other studies.

ACTIO/!S

<0 BE TAKE<'! 8Y HOLDERS OF CO!ISTRUCTION PERMITS OR OPERATING LICENSES FOR

<IUCLEAR PO'JER FACILITIES:

Review your facility to determine whether C.P.

Clare Model HG2X-}0 mercury-wetted relays are used in the logic matrix of the RPS. If no such relays are used, you should submit a negative declaration to this feet and you need not resoond to ihe remaininq items in this bulletin. Your negative declaration shall be submitted to the appropriate .'!RC regional office within thirty (30) days of the date of this bulletin and a copy forwarded to the Oirector, Oivision of Reactor Ooerations Inspec:ion, Office of Inspection and Enforcement, l!RC, ':lashington, 0. C.

20555, 2.

Licensees of operating facilities using the above relays in the logic Rl matrix of the RPS should increase the frequency of their surveillance R1

tests, Until further notice, or unti l 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. Tne additional surveillance testing applies when operability R1 of the RPS is required by the Technical Specification. Upon detecting a R'ailed

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. tluclear power acilities which are using or whose design includes the use of the above relays in the logic matrix of the RPS shall submit either Rl .heir olans and schedules for replacing the mercury-wetted relays with qualified relays of a di ferent design, or justification or using the mercury->>etted relays. Resoonses 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, }980. R} Aooroved by GAO, B}80225 (R0072); clearance expires July 31, 1980. (Application for renewal pending before GAO.) Aporoval uas g',ven under a blanket clearance specifically =or identified generic problems.

IE Bulletin Ho. August 15 1980 80-19, Revision 1 RECE!i'TLY ISSUED IE BULLETINS Encl osure Bul 1 etin i'lo. Subject Date Issued Issued To 80-20 80-'19 80-18 Supplement 2 to 80-17 Supplement 1 to 80-17 80-17 Failures of liestinghouse Type W-2 Spring Return to i'leutral Control Switches Failures of i~tercury-Wetted i'iatrix Relays in Reactor Protective Systems of Operating i'iuclear Power Plants Designed by Comous-ion Enaineerina Haintenan'ce of Adequate iiinimum Flow Thru Centrifuga'i Charaina Pumps Following Secondary Side High Energy Line Rupture Failures Revealed by Testing Subsequent to Failure of Control Rods to Insert During a Scram at a BWR Failure of Control Rods to Insert During a Scram at a 8',lR Failure of Control Rods to Insert During a.Scram at a BWR 7/31/80 7/31/80 7/24/80 7/22/80 7/18/80 7/3/80 To each nuclear power facility in your region having an OL or a CP All nuclear power faci1 ities having ei ther an OL or a CP All PWR power reactor facilities holding OLs and to those PWRs nearina licensing All 8'liR power reactor facilities holding OLs All BWR power reactor facilities holding OLs All BWR power reactor facilities holding OLs 80-16 Potential iiisappl ication of 6/27/80 Rosemount Inc., ilodels 1151 and 1152 Pressure Transmit.ers with Either "A" or "D" Output Codes All Power Reactor Facili ies with an OL or a CP 80-15 80-1< Pos s ib 1 e Loss Of Hotl i ne With Loss Of Off-Site Power Deoradation of Scram Di scharge Volume Capabi 1 ity 6/18/80 6/12/80 All nuclear facilities holding OLs All BWR's with an OL

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