ML20084C686

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Ro:On 710720,control Rods Associated W/Scram Solenoid Groups 1 & 4 Partially Inserted During Spurious Trip.Reactor Pressure Spike Caused Steam Voids in Reactor to Collapse
ML20084C686
Person / Time
Site: Dresden Constellation icon.png
Issue date: 09/08/1971
From: Hoyt H
COMMONWEALTH EDISON CO.
To: Morris P
US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML093630339 List:
References
4037, NUDOCS 8304080160
Download: ML20084C686 (9)
v • d • e


Text

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Rr.rORT O. rGLLO'.li.NO SPURICM RT.ACYOR Oi 1r :' 1.. Q..' s ,,,,,, c. ms, u t,, .,. t.. 1 Deat W. Forrt iLion t' 3l 00Curr0d during '!hiG }"6 Tor tw ic ,t , ar t u j sun : o Unaec t e,- of tb c: m n : tion sv tco. The condition j cate.ca a part h1 coa' rot : .e

o i] e nny, a spurious teac
ar ri ica uit in a r ely renalted in a

. col :n l scrar :ic,n. TSis part .1 co > r Rang donitor trip and a t urhiru t r ip, uh i ci. ; ve ca v l T P A C l O :. :: C ralh i I A,

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i The ienctor u in -h> c.m .r. and operr. ting at MM rIW,,Jn l _ July 20, 1971, fu.vria re t<3 c. i : min cream line radi:2 tion o { mn f i or va:. In proccer. wit: cr.:t r a 1 :- "A", "B", and "C" tuonitorn viy:nl w" then s ir.u la t e d u ti f mt orliy cr;-lat e.. / i. q . : (. of Reactor Protect ion :syaten to th " D" r u n i t o c_a.w,". <.m:i t..d m . mnl curveillarce procedurec e pecte, f ol; - (RPS) Chainml h, } turning, the re s e t: cuitch to tha the ep,r., t or be ct.n - re the r.' group 263 positton. Ho ihn ima to - the mitch to the group 1M s spurious trip occurred position but, i>efcte he r. a che.i t h. ps.s ition, a 4 and cleared on the "C" ste'. I nt. ', t ioa monitor in RPS Channel A. Because the Channel B nroup 2a 2 rer m zon p ids had already been reset, only t he c ir,h t y-e i g h t (R_ ) ed 9 nraccLued with scran solenoid groups 'IT?.TM~@ n itsrLing.. The cperntora re.et notion then completed to tbc g r ou p 16', p o s i t i.on. At ' point tha ,roun. Ih'. rods ceased i n r.e r t their 1 mo t ! on a f t e r r.:wi n. app o.; i.ne 1 y F (6i c.o t che s from their original j poaitions. This ro) in ne n.: c n e.:c.:e. c Orop in electrical load fror. l 406 tr.'e to 320 1Me. I 4 i t.:UPY SENT C.CiCN__' _J'M p,, 7 y 8304080160 710823 PDR ADOCK 05000237 i S PDR

,. _ ~ _ _- Dr. Pe ter /.. Morr 's Sep tet:;ber 8, 19 71 9 e i o The tur5;n ce.. 31 in:. d Jun ( c. ra in ta ir. t urb ine *h+ottle

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he, rer.titiut fr a the

,t p id, pre c, o t e.. - s?O p ;i, /, r w so: al i,; w n, caused ateam voids in the pa r ial ci mm e of t h., t u?, i.,o " r t,t tate.- icyni dacrease of approri-renet er en coi.npse teault.,, r,atcly 70 incn:s. The 1.: d s n..

n t ' in t o t b r-

" r u n c a t." n.od e to level then incr.. sed rapI"ly rr31;a t eactor wier inwl. . i The renc ror p c.nure rti':e (960 puig) and tripped the tu rb in.. no bl. M' the rofd cjn; M t.t ~ u. nc nton vnlves recui.ted in void courtd o., col le p.,o m r! A.' M :!! d !. r.c: fl' .crnn. 1. a.nr ka B. !:r.c t or Pr n -n i s,.,. The " S it A<' 'it; in inJtpe Mont logic Chanaals A cnd B. Each ci eb

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'Fr m. asar operated ah:' one t;nnual. operated 4 ub e.', 4,i r .,;a- ,.7m Subchannals A-1, A-2, B-1, end mr elny, a scram t ulny an.d p!. lot T.-2,re equi;.3 n with a w, a n l cerno valve solenoids ( : u.3 & ac;. rer.cter centrol rod hydralle control unit). Two nubcicua.:t s ':-1 brn a ncnual ceran rush butico in pl,u.. or the sen cor a.r; u: ce l..y. Yh con.:rol coa.tv 'L S i n t.o f our nently equal groupc, [ c.

r. q i and 6 control rods are ccineved identiftou
h G ruq ;

1, ., a by Chaunni "A " r e sa n ICS/., 108. 10 % an61 Channel "B" rel ays 1083, are ccrnat'd by Channel "A" 100; and lluS. Crtup z nn. 3 c u relm lOdC, luit; an0 1000 sd. .. n " 3" relays 10HD, 10 W and 109D. (Sce rigure 163). l !, cer.u require tlt. c C;cc.en! "A" und a Channel "L" screta l relay aunt oc de-energic.et c r.r.. wt t he n o pilot scrnm ulve solenc,J d o - on tN centro; red hydtni;.e cou ce ....t to de-enerni: c. A trinir:um of fear ncri.i relays, rvo b cach ch tne '!., t.mc de-energir.e t o achieve a s e r.nc i.e.: a G: cap 1 ar.d 6 plut. rroep 2 c'1 3 scram relay in Channel A" coincident with a Cra.;p i.. J ** plus a Group 2 and 3 relay in Channel "B", 1 I c.ccomplished through th.1 re.s e r l Re c e t t ii.;; cha cc.'. al c reiny circuit chown f u F ige u , lhe operator unes a alngle renet nuitch 1 ar. shown in Figura 3 f or t M r..ne:. cicenit. When the recet switch is in the center position, all vr;.tch e m a nc are opea. When the suitch is t nperated to the right, sc rua rel: Der cent.rol rod Groups 2 and 3 in j Chann21a "A" sud "n" ere react (re - energiz ed. ) When the cultch is operated to t h lef t, scren relnya for control rod groups 1 and 4 in Channel A and j D are renet. l A reset circuit ia provided and is no arranged t hat following a ceram ninnni f re r. Cha tr.21 '. T ". Cate c 10 second tirae delay before the r.crom relava can he ri.-et. T:. t m.. d;1a" in provided to allow time for the i control roI!.s t'o envn their Cui'. travc.l bNore the scram relays can be ret.et. This prevents stopping, the cot. trol rado in an interraediat.c penition in the core for a cerr.m. I 1 3

1 i i i 1 Dr. l'e t er A. Mo Se p t erahe r 8, 1971 t e 1 < s. i; tea v.t hwt t I 4e delay becanne a half i A 1 a t. f rc ri 4 I i n e i t,r-d o ' n n m ;rra ce c' .0 c. a. l l noin a 11/./4 T., C nd b dc re r.e t rA nyn. The 114 releys are A ihy rmt 4:O.W1 v 1 w cm, Unen fbe 114 minfc c o n r.c. ' '. are enneg1/ d the:r cont rc t ; c i < < '. misi. r r,1v tha scran relay thereiy i

reim, ta LNir
tmel enerr, zM position. When the l

re t uctil af. the cc.. re: :. t raitch is t e j e, c <: d, + !!L 1- 'm de-emery,be (see figure 3) but the i m '.ml-in contacts (ace ffp,ur. 2). s re c 11, c.w rc. b '.. c o' cerc re li : f 4 j h 114 r.1w: a tir m: a brough th" re:.c r switch (303 devJce) } mul either th, I?7 rMay cea tt oc b I?? r e tt.y centacts ( r.c a fiv, ore 3). l Enorg4 ia;. throgh 'he 125 r. U rent r e.t r p*vait-jurediate retettian (nr, pernii!td for a hm1f se:

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',, u i n, thtour,h tbe 122 relay contactn j

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ccetting the scrca telay (tu. rc-tj u i rM Jor a
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l 4 j %c 12 5 /. and b re i w (su finore 4) ure not energized for a l J half nernu !m t t N:,.;ra c: q d icr a full cernn. When energized (full l se rr m) tLe 12 5 r.2 L; < cor. t rie r .s u e rn h:e the 122A r.nd h t itre delay relnyn, j Win:n the 122 reiny enntc;ta cleae airer. t eu second t.f.mc delav the reset l re a, (1V) arc m ed to et tb sciam teiays. 1 1 f C. _A_m_.: l_v.:1.._. o..f._ Me.n..e n i } Duri ; corv :lli. m t e.u ne,, a Main stean 1.ine Itadia r ton 4lonit or i 1 "f:" dieh chmenergized scran relnys 108F, i r,enenr um, ope t r. t.d on C.n: : Croups 3 n td 4, ra.d IN91, Ga up ? Ind 3 (see Figure 1 subchannel D-2). The Ch.n. s 1 "/." : n t a y.: rem ine.! ere rn ; wd and, therefore, there was no moven.ar. of the control roda. Yh t. i: c half scran condit ion. The test s j was cuxpicted and the operr.un w.rc rectoring the RPS t.o normi by recetting t b o r,c r ra ralsyn. Malay 10lU u:t-n.. y t (re-encrgized) by cperating the l Neet w;. ch in Figure 3 to the r i.p.h t to reset :he Groups 2 and 3 scram r elr.yn and re-cac cg o e r M i c ucr. c. rolencidn. The operator was in the i process of r.oi tan t he tc aer L 'o the Icft reuct positicu when a Main S t an:a Lin. nadint.icn Mcait: a Ce nc i "/ " generated a spurious trip. I 1 l This spuricun trip de-nnerg.inou rcram relnyc 103 E and 1.08G l in CSannel "/." (fNe Fintn e i rabchene.,1 A-2). Scram relay 10ff in Chanuct. l "B" brid not yoc been reset.atd, th refute, the pilot scrota valve solenoids l de-energinnd and ;aitlated incertica of Groupe 1 and 4 control rods into the cere (cer n) hacause their A & B rcram solencids were de-energized. l The Groups 2 aos 3 control roda did not nerara since only a Channel "A" t j Groupa 2 nnd 3 acrata relay (10fG) and scram solenoids were de-energized. The channel "B" Groups 2 nad 3 acrran relay (10Sil) tripped during curveil-lanco t eating, had already ban race t. At thic tiire relays-10E3, 108F, and 108G vere de-energized. Relay 125n vna energized and time delny relay 1223 was timing out. Relay 125A could not be unerp,ined becnuse relny 10811 had been re-energized. (See fi6urca 3 6 's.) ---ee4+--m---* ir w eyr-i-m r www wwu.pw,- r rweuw v erra1a.-vrw-y Myrvrmr=-'T'Tw r y w www syve 1.sv--st- ,, vywy-ggg w m + vgw w g-me ve-*Meywg

O September 8, 197L u - A. W rriu Dr. Peter 2n actinn by turniog ihe g d M > t ' s e *, .mr cenaf ull y o r.c rnir ed r ese r G.t t t th~n m The op., a: a !LL-D i.- o, Channel "A" nod the i & !. p t,r o.:p r A ay 10'c ' 164. This left the miten it, a nd r e m m.r;;We d ..c r at > "A" gcups r e l a y L U.4 w h

  • M ruaids in C uvi? rw! Chanel"D" p,rnaps 1 6 4 de-ids de-ena ;:iz.cd.gl f

~/. pilm oc.; ' "A" iud Lat h Ch.:tu :i "/ " and "B" seleno ll

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centrol reda were fully p r cci rre"? i ' : cre a cn intermedinte posttien In f the Thic re. .ov. ncat k in e t c.ppi o;; t he m and renul; a g intern dfate ponition in the coreThe 1 cod re the c.,rt i hs re s,.,. a ~, t op,, 4 ;; I c;.2 d. All l M b, o renoi med J o a cqq,N -%ut' dub ic. t urn caused a hir,h fina 9ernn. l tr.i. vhutdo m the reactor. 'are " r. a ju v we r. s i i ly, a t' I e t.n t re : r # i,c c I, l I and Cencral .c_.o..n -..s w n a u by Com:aonvaalth Edison 3. i A i cvit., M the hPS circuitry Elect ric L ; a'. i r ci t. ' ;h i t f a ilure s Juna f or.:n r a decinned and no component r 1 1. D. - revit I i occureci. r ulth n rcr r. d;..cv wed herein could only occuwith a short 1 cr. one channel coincident 2. The e.r t. d occurrin.; precicely as i ;3 partin3?v recet~~_.._,a._.__-ser:ond chcnnel. t et of duris u, n dria

he process of completing the res j

at tre the opp 3, tor _is Jo.

channel, W..

the tvip on tb t f unct ion l A trip on both channals cculd override the recesuitch held in a l with the reset 3. and go to co~.plcrica evenA r.ect was cuccessfully performed en to verify this. r react po s it i ca. Dec r. den linit d2 on July 23, 1971 opera te and the RPS provides the necessary The unit is unfe to protect.Lon to cafely shutdown the react.or. 4. l d have cach t The Srne lun Rev1cw ): card and Nuclear Iteview Bo l I revie. rad the f.equance of eventr. end ana ys i j t / conclusloas. c' e / J J (/ I i ,t' s( f/ *e.- ? ! ? lx r . s; II.1:. lloyt l I l Superintendent 1 I l I i 11 Kit:do t i f d I i i i f i I f s i i.

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