ML20084U605

Ro:On 700508,MSIV 2D Failed to Close During Surveillance Tests.Caused by Stuck Operating Pilots.Pilots Replaced

ML20084U605
Person / Time
Site:	Dresden
Issue date:	05/18/1970
From:	Hoyt H COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U585	List: ML20084U605
References
01676, 1676, NUDOCS 8306290140
Download: ML20084U605 (3)

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. Dr.'Teter A. Gorria, Dirch DiViuion of baClor Licec. sing U. 3. Ate:aic 8nargyCeatissiou

'lashinbton, D. C. 20545

Subject:

Lt:en se LPa-19, Dresden Nuclear Power S ta tion, Un1* m2 ,

ciection_6.u.B of Technical Spectficatio_ns.

Dear Dr. Morris:

s T'ais is to report a conditica relating to the operation of the s tation in whica caring aarveillance teats, several taain stea:a isolation valves (11SIV) lailed to closa as specifiad in sect,.on 3.7.D.

I roblera anu Initial Actioy This situatica was discovered at 0:10 a.m. on May 0, 1970.

During the rou;ine surveillance testing as required by section 4.7.D.l.C, d main steau isolation valve 2D would nor close on test. Valve 2B had beau eiosed since April 27, 1970, when, during survuillance testing the valve" '

closed properly but failed to re-open. All other valves cperated actraally .

on routine testing oa May G. At the tine 2D valve failure was observed, the reactor uns suberitical an- at 103 paig pressure. At 10:20 a.ra. '

additional' valve testing una perfonaed in the fast-full closure uude by actuation of tha operating switches. Tuis test showed that 10, 2A, 20 and 2D uould not close in the mode. 10 therefore, was closed by-the test switch (a sprin;; return sultet.) and helci closed by a. jumper on the test su11.ch uiting tenainals. This action provided a closed valve or an operable valve lu each -n steam lead. An orderly shutuovn was also initiated and all withdraua control-rods inaerted by 12:10 p.n. and reactor system cooling uns continued. itcactor l water tenperature was 1950F and the reactor vented at 10:20 p.u. ]

s I catinattva-N Investi",ation of the cause of valve failure was immediately -

in'itia ted. The operating pilots for the outboard valves 2A, 2C and-2D, were found stuck and were rchlaced with new pilots. The 1C operating pilot was

-cleaned and reinstalled.I The manufacturer's representative icvicued at.

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+h ' Dresden, ' tl.e condition of the"three removed pilot valves with General j 1 - '

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v, Dr. l e ter A. I! orris May LU, 19/b

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islectrie uite and engineering petsoaael and 3dicou pernoanel, and observea operation of ti.e 2A IUIV prior to reuoval of the stuck piloc. fue op. ating p ilo t s for valve a PA, 20 a..d 21; were taken back to the t..anufacturer'a plant for d2 tailed inspec tica and ces ting by Lite ueseguerc.

The pilot valve naterial for both she spool and un tinp inner cylinder is 4400 stainless ateal with haruacas of b2 doc!azell-C. The cicarance be cueen these uatin ; pa rts ts oa the o; der of 0.0c015 laches and is air luorleated oy he leakc[;e of coarci air thrcugh the apuol cylinder clearance.

Tue nauuf ac turer of a.a pile' valves; Huna tics , Inc, ran a serie> of tests in 1967 on tne atiec. v2 a gh teg etature oa t;.e pilot valve oprabilit .

, . . . ....o, A n ann..u:a tolerance satve anc a aumau:.' r oleraaee valve .,are ,ma t.eu to sto r and-tyclea for 30 uinaces.  : hen the3 ceoled, the uaxiua..- colerauca va lv a acill operateu; .h; n _a n.ui.. coleta..ca vaiva nack. As a result, in October, 196 7, ducatica cecan auppi f iu, calj nauhaau oleraace pilot valvea Cut nain s team isola tior. valve asace, until October, IN9, uhun their manu-facturing proecsses ere up;,radeu to provide gceater concrol of toaadaea, and straightness anu c:ats inuicated a retara to previcas cia.cualoc.a1 col 2rances could be naue. Tha pilot valves ic: D-2 aua .1-3 sere supplied before Getobel. ,

19a7. Tae manufacctrer la sapp 71 am ali ues pilot valves nauutactared oy ,47 the neu cchnique to replace all de pilc_ valvea f or Dreaden Uaits 2 auf J.

Correccive Ac'. Lea 17ur t.c r s te u.apee doa and ci cuiaa of all pilot valves ucce eu..uucted to assn e aucqeace uitial clearance an- .~ re e d o:. o f cc van m t .

J.fler reas sei.U l f , all u.e lbi'/ 's .Je . a o!.erata- Jaci3 Iacterily in both tita test and fa;c op rai g . cedes au- cini. 3 ieaud a b2 p_vpcr.

Ce crective ac tiva vaa ta'.;c. co cecuce pilot valve operaciac '.cnpera-

.ures co. isis ting of add hg insulativa _o ao: ajsten. coupcaeata in ch2 area of the valvaa. In actitica, c.e outboaru valvas (u. _ch experieuecc hi ;ner t ar.daient a ir tet.p a ra t arc ,haa tua inboa w valves) t.ere proviued w..th coila n

i,.oagh which cov.,.ing ;a;er can be circulateu,, inis cooling rio- will aa applied if the valves enceau .h ; t.caufac turera recosaeaoed limit of 175'p.

Toese pilot cooliu; cotls surrounding tha pilot valves we e covered with insulation to reaintain pilot. valve teapecatuces lo.cr than previously enperienced.

I'j0 d i l e.r-[.nA..a l h. . TJJt.i.n '.; i_r.0 ; _% .

A n e ., m e s t ing prceecure vaa estcollahua to exercise tae II3IV to the Call cloaau po;icien. This teac p uceuare vill provide in E:r.c.a tica assurtag full closare operacica or LL2 valves througnout the 757. puuer tes tiu;; phase 1

ot tue startup cests vari % ohich ac.eady state temperatures of the valve; <

alll oc accieved. .xpericace bained d ria-g this perlou will ,oc utillneu i to evaluate che va lve ceutic.g progrma and define any futu e corrective censures  !

or Leu ting valch n.ay be required. l la additloa to test and fast closure actuatica anJ timing of the ValVea Co;np1Lted afCer inup0ction as noted ahoVe, test!QL; by the ned procucure haa been condocted under hot operatia!; conditions following i

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z. o o Dr. Pe ter A. ho. cis h,ty 16, 1J /U l Unic 2 reactor startup at C: 30 1 . ic . on itay 11, l9 '/ 0, Valvo pe r i~oa aauce j d.: ring, all tea in,; sub;equent to cort ee t.a e act ion ha n been un t ia f ac t o t t, .

l Datea of these Lesco and pilet valve tempe atures ace aa follow:

} S/lJ/10 900F 5/11/70 125"F O

! 5/12/7) 142 oF

{ 3l l.' / id 14.> oF ,

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Thuse ulva teiage ra tures are obtain d by tenporaq thetuccouplea l l installed oa cae inbcard aat one ca.ooard pilot valve represauta ivu of cl1 pilot valva a . ...ah i ; .. u a',r aujacent to tim cacaoard pilou vatve is l

wz L12a02 F of tua ne.:a1 t_u;. era :.ut e icaelf inuica tin; that ;iie added la sala c ion haa cone aa alfac._ve jo ot liniciu;; ' valve tem; era ture. Inboare vaiva j area terapara care la ne ara il,: aooat LOC F. The coolin3 unter to th; oacuoard j MSIV pilot valve co olia;; co ils 1.a s au t. acea appliad, since valve c uap e t a t u t e a

! have been well below 173 F withoat suppler.uu ta ry coolint;.

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Siacerely yours, ,,

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