ML20085M746

RO 50-267/75/2A:on 750115,both Secondary Coolant Loops Appeared Isolated Simultaneously by PPS Action.Caused by Design Error.Capacitors Added Across Collector Load of Output Buffer Transistors

ML20085M746
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/17/1975
From:	Brey H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
RO-50-267-75-2A, NUDOCS 8311090194
Download: ML20085M746 (6)

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P. O. Tox 361, Platteville, Colorado 80651 A','1 \ ! i 'W?-

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June 37, 1975/.O I j,].~,:' ' V, . J,

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lir. E. Morris novard, Director ./f

            ?:ucicar Eerulatory Comiguion                                  '\r 9%                ~ h) '

F.egion IV Of fice of Intrection ..nd Enforcerent

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FI! AL IIH" :'1 FICATIC; Or F dim:. l'6$.. _... hoih recondary coolant loons appmred t o It isninted ninul tmiecunly by PPS act ion. i m ation 7.6. Thin is identi t ivit es au ruu,ocil rvcnt, per po r,rrnph C 3 imd non-rout t oe report s. l l l Ci.11TIONS PR10R I;outine ShutJain l Tu OCCURRET:CF. , _ _ Steady State Po'.ter Itoutine 1.oad Changa 110t Sliu dovn _, j Other (spec.i fy) X Cold Shutdown Kefuc33ng Shutdown l Routine Start up 5 9 e

   *           '                                                                                                                                      l' age 2 The i cij or plant. par.-     tbrs at. t he t ira: of t.1m event were as follw :

l'e.te r PTlt , g _ _ _ 1 L't h F.I.rCT , 0 f;L'e Secor.:!arj Coolant Prc: sure 1500 p t. f.c Ternper.1 t u re 200 F fl o.e 150,010 t/hr. Prl: .iry Co:.lant P. car.u re ~ 150 psit Temperatu .. M5 'F Core la!.ct 100 ' F Co re- Co t.. e t l Fl e' __ _ 0_ _. h/ht. 0 g a b 'l

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D!: Sci: 1Pf f G : Dr O ct.C : 1:

        "the L c;     I and Loop 2 lielina Circulat ort, uere operat int; at scif-turbining condition.         The f eeduater f lo.e t o f.he 1.oop 2 st cari ; enerators was isolated.

The Joe;- 1 ute.au nenerator had 150,000 t/hr. of fjo.. t.he beartu;; cat er a: ctre.ulator for 1.oop 2 should be It van de t et uiund that. lucrea :J n; :he llel.inu Ci rculat or tested f or acce..t ahic cyrat .instruc.ntation ion prior to had becn set up t o mon ! Lor t.he Speedr. After the recordby. perf emunco of thin t.est .both bearin;; vater pumps vero tripped for one I!elium Circulot.or auxillaty loop and t he tuo inch;eca coanted 'down The and Loopvere aut o-- 2 shutdeun isolate.1 f ree the ato:t] inries , per nore".1 Pps act inn.

• sinnt.1 uns received and the proper alar' <, and act ions occurred .

problems rete Short.. l y (5 ninutos)follu...in:; t he Loop 2 accumulator test,eac cubsequently

                                                                .This probict er.}crienced with the buffer hellun syst m.v t ern ined to be due t o valve ponit J Tho  11ecct or Opervt or shut do"n the Loop,1 11oliu.n ci rc ulat ors and ret urr. valves.

in an ordarly r:aar.er. Thit uns done and all PPS actions and indicatione appeare: normal. ntor not be;; ai the process of returnin;; the Loop 2 Helin', The Ib actor 0; When t he buf fe: helium trips Circulators to the self turbJning conditicn. and berrin; water trips ven cleared on one helier circulator the Loop 2 This is non.:a1 bec. ur e shutde:. cicared and initiated Loop 1 shutdu..n alar . the J f ret an t 1.th Jodout r;tc (Jn the PPS) was clonrod of a Loo ~ 2 trip cud tho Lecp 1 trip was not now leched out. (uith The l oop 2 re. lie- circulatorri belo;; stcrted nou cxpr.rienced proh]ct L' hen th.f r. eceu! : d the bvf G.r helien system) and uc're r:? nun 11y shut. Th bdoen. shenld no'; have harpe.Td, the PPr initiated a Leop 2 shut- dot n r i m Actual Jeap because the l oop 1 secondary coo 3 ant loop.use already chut d e.tn . isolation did not occur but appeared t o havu happcaed as indicated by the

    -       annonicator synten.

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Pap 4 a . 7 s, (N (0) \v AIt.*r rf C.'.!'SE Ununual m rvice Coud.

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__, Component railure _!;anufacture _ _0ther (rpecify) inntiilatien/ Count. Operator _ Procedure __ cre prevent ed fm, cir ultan( ously icolating, in" Uoth r,eccadary ec.olant loopr te shutde, .i np u t sign 91s, by a "first eeen thee:;b both have Jegi tir Icolat fon of both sy.<.: er . This 1ct i c syst era epo r. '.ed pmr"rly t o prevent.loors of the . isolated as describ seccudar coolantr.J arm action to occur ir; roperly s hc n rentart but allo wd the locp v. , attuptol. existence event 'as caused by Lt.e Subserpmnt inventigntion revealed tbnt t.hs (T1UI.) " Loop shutrio.:a" ci rc;!"a11 u i t s. of a "rac.t" in th PP S I' irs t-i n-Ei t h--1.e cheuthc t "remorn!" of an inhibit . This " race" hns been resolved by delpyi'. I' b ? C011 UI OI c" [Or 3 fiill(MecGr.d.I.y the "[d3!ioD of a CJIMOilCI MCI'D S cc: - . of 11"' l' A l b" i correct t lon!. entw 1y lwfoieh to the buf f er t v:mcintors chich delay thet o "ve r " t be "l'i rat - input. In- ui t h-l.oct cut allov ihe proper nirnal.;ignal vooid be paored t o the corgierentary t he coatradict or , e 4 4

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A':?,1.Ym i. OF ocrt': .': GCI'.: t o recreat e t bc event . A r,crien of operat ione. were p"rf ori'ed t o at t ep.pt Tin evcnt. could im recreated at vi!), a n.1 neveral h intdio fthe t o y,in ndd Irional. Int:it i 1 ir e t brotuth ferent (but sir !! of event r uvi e pe r fm , ? the ni !,nal t ranr1 t sequeues prebler. , Ulriedcly it van concluded that c i.on y.h i s tiren'" vent the the Id;,h cpeed logit circuitry differed by junt preveu: the "/i" lo",1c frem r.uton!!v exelocive "tC" n, orork required to "A" lenic "U" Jor,ic (a 100,3 1 trip in tis contreiicting,the cenple#cntary Jopic and v:ce versa). inhibita a loop 2 trip in the "n" crs Ihe enllect n; Joad of thn output buffcr tr.w i< Cal ac ! t ort, vere cdded acror: long enough to alle; t he prn, - which delayed the renoval of an inhibir cc jmtWi ory rd r,aal Ut'"l', 6 1'csed to *cd the cc - - rir

i :,n D t o "m. t" t he F Wh be l AfI o t >:

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                                                                    'ificaiion, ti,e regner                 '       V:rie.

the co 1b cutav, inpat. u cor rc. a r.e ' o of t. ii - an.I no conflict J r. ne'ic:.irdfcatIoos. or c1:v. no 'nnt -1

           <:eque ees vete g rfarrod, uit 11 % inport ., nt        t-   recor,niae ihet tiic p'robler on1x enifcra(d I ml ~ n f t<

the onlii.tly reqrcnce of: loop (circuletorn and reedwat c)

1. Shutt. Inn doun t!:e let.

e, u n' ba <,ut d xn)

2. Shutt in: doun the 2nd loe,.

r (cire"12 terr pr? roeA re

3. 11ectarting, t he J r.t . loop (c ire t I nt or.s) .

occur, " rc< it ro<1ui ren t 1:.- r .:13 ret Th.- requonce ven!d norm 3.13 r.cve, Um ert bol, n, the cJrcu't down at one point in ti .. Iout conf 'at inc circul a1 orr be rhut ic.11flent loa alloc der,cribed :,er,r<ence i o occ ur el! indicalions. C013'.ECTIVE ACTIOS: Sec " analysis of occurrences" TAILURT. DATA /S1IllUd REP 0;1TfD OCCunnrNCr.S: None PROGR_idO_IATIC IMPACT: j None CODE 1MPACT: None / 0

                                                                                                     <-                    D-i Recor.uended :

M'^M^ p # ^ '\ _ Approved: , _(([tg.d F. U. Swart, H. Larry U'ey Supt. Muc1 car Production Superj ut endent-Operation s Public Service Company

                                 . Fort St. Vrain Uuelcar                                         . of Colorado Generat lun St at lon                                                                         .. . . .}}