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UlilTED STATES,1CURRENTEVENTS

CUCLEAR

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.

REGUI.ATORY

PGMER RE. . ACTO... .RS. . ... 'comssiorr..(.. -

- -. .. . . ..<

. ..*

THIS CCMPTLATION OF SELECED DDITS IS PREPARED TO O!55 EMIT: ATE*

"-

* ~.*INFORMATION 'CN OPERATING EXPERIDCE AT NUCLEAR POWER' FLANTS IN ATIMELY MANNER AhD-A5 OF A FIIED DATE. THESE EVENTS ARE SELECTED FRC:4

;*! .

i~~PUCIC"ZRFURMATICN 500RCZ5.'' KRC MS,* QR 15 TAKII;G CONTI!3UCUS ACTIDH-TE"~'.

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! .*CN TRESE ISSUES A5 APPLICABLE. FRCM AN IN5pECTICH AMD ENFORCIMENT,j

, LICENSING AND EENERIC RDIEW STAT;DPODG'. - .J-- -

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. ...

i 'i ..: 1 SE?iEE - 310CiGERIc)7

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$ ' ?" " .#'

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!-. (PUBUSHED DECEMBER ISA.

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. OPERATcR ERRcR. ~ .. .-.

On .1anuary 11. 1977 while the Fort Catheun Station Unit 1 was.

.

oparating, water from the Refueli::g lia.ar 5:srage Tank was pu= ped- : ..

ints the con sin =ent through the c:ntain= ant spray header due *: an*

opera:Cr error..e . . . . .

, ,: , , . . ,. ..I During the perfer=ance of a quartarly test of the safety injec' tion;

and containmant spray pusss',5 *the operat:r ncticed an increase in ..,

,the contain=ent svep level approxicately tan =inutes aftar the*

. ..

low pressura safety injectica p=== had been started... ....., .

Appr==i=ately ~ . '3300 ga1 Tons er water had been pu= ped to the centain=ent. Ah ut one.

. , * * * minute 1atar the ventilation isola:ica actuation signal was received.-

dii. At this time.the opera't:r.reali:ed he had failed to follow the sur- N.

veillance precedbres an,d had left the discharge valve of the low head ,'... * ~~'~-

safety iojecti:n pump epen,. .He ic adiately secured the pump.---

.' , .4 , ..

The Re, actor Ccolant.5ystem was checked for leakage and enntair. ant. .

entry was c.ada approxt=ately one hour later'." Inspection revealed . . . .

i *that a discha e fremithe contain=ent spray nc :les had occurred.*

..

A few minutes ..

|ater power reduction"was started. A secsad centair.=an- . . . .

ca:ry was made about an hour later, after c:ntain=ent air samples " " ' '-

confir=ed that a full face mask would provide adequate respiratsry*

protectica for the levels of radicactivity in the building. A; . . . . ..

- detailed inspection revealed no serious deficiencies and no ele:tricai . . . . .

* *

. ounds; the power reduction was terminated at a power level cf 85!..gr . .'

._ _ .. . .

Although the operator had not followed the pr:cedure and the discharse.*

valve was open, the contain=ent spray header isolation valve (*c-3*3)..

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and the low pressure safety infection to containment spray header* ,

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cress-connect valve (HCV-335) should have prevented the event. The"

g(. t ,' electric / pneumatic c:nvertar en HCY-345 had failed and both red and . . " .. ..r

-,- .- --- -- green .poMtion'. indication.1.ights..were on. indicating the, valve was.. . .'* h * * - *

~ ~~ partial.1y operr. -Prior-to the-event- the-auxiliary 4usld'.ng Equipment. "*."*~.*Ci,' ?,,r - *

- Operator had sken 1cical chh651*3f *the' valve in an stta=pt to *-

';~ .c mpletaly cl.ose the valve. After about 1/2 inch of stas travel. the .

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. .'.. ; - *

-operetar removed the valve piri~anif**tle' s1ve went back *to its previous -*w ----*

y.;.D .c. ;,2 . .....posihcin'"II'Te'1 Ended'by'the 'va1yy pasttioner. The third valve (MCV-335)* ',",,"~.

?.T -?. in the incident had.a leakage problem that had been previously identiftet - -* -

...*

but no corrective action had been tahan.-_. * ~*-'*

'.~

W[ . ' ' '.i The pneuaatic relay on valve NCV-345 was replaced and valve HCV-335

. *, . . .: *

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S. 3 .' ' ~ ; repaired. Valve HCV-344 and HC7-345 are now required to be placed '

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; in the tast mode-prior to operating the low pressure safsty injection ...

b. .* --

. . pump or contain spray pump for testing. This mode along with verift-*f'.

.. * ' ~ -

i catica of an. annunciator will ensure that both of tha* *Tr, * id*thi fully cloied position prior to pump operation.ge valves are - , " _

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YAI.YE HA!.TUNCTIONS........; -..

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[_, -| 1. Primary system Cepressurisation-

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,. ,,.

~ r/ ' ~...f on September 24,197J, Davis tesse pruelear Power Station Unit=. . *

*

~ No.' 1 experienced a depressurization wnen a pressurizer power.

'

reitef valve The React:r Coolant ,*System (RCS) f. ailed in the.open position...

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pressure was reduced''f.-om 2255 psig to 875 psig in*- - -

approximately t'wenty-one (21) minutes. At the beginning of"5-this eveny, 's't'eam was being bypa'ssed to the condenser and the

*. **

. . reactor thermal power was at'2E3 HW, or 9.5::. Electricity " ' .-

"

'*

was not being generated. The*following systems malfunctioned "".- *

., during the transient: * - - - - ~-,,, * ~ **

#.' * , . .* ~ .

Stelun'anCF*Hwater Rupture Control System (SFRCS).4 a. e *

% - *

. . "b. 'Pr,essurizer Pilot Actuated Relief Yalve..t .- .** .

'- '

. , c. No. 2 Staam Generator Auxiliaiy Feed Pump Turbine Governor.;,

~

The event was initiated at 2134 hours, when a spurious ** half-trip"?

oc:urred in the SFRC3. resulting in closure of the No. 2 Feedwater ."*,. .-"- *

Startup Valve and-loss of flow.to No. 2 Steam Gemarator. Approxi-- --

.

fJ " '

' mately one minuta later. los level in the No. 2 Steas Generator.

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caused a. fun.5FRCS . trip, . closing the Main Steam Isolation Yalves-- - - - -,

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( (MSIY). ThelossofheatsinkforthereactorcausedtheRC3*temperature, pressure, and pressurizar level to rise.-

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. - - - .... .... -.*

Th -.1.

' '~ 'ee RC5 oressure ihc/hased to the pilot actuated reTTef valve ~ *-..

s tpisnW2255-)sig) and the valve cycied open anB closed r.ine.

times in rapid succession, failing to close on the tanth opening.Meanwhile, the reactor opdrato'r cbserved the pressurizer level --

increase and manually tripped the ' reactor about one minuta after .-;# MSIVclosure'(tGominviesinto'thetransienj:). At this point-

. . . .

the RC5 pressure was approximately 2000 psig and decreasing -- -

.-" "~ "~~ white-the pressurizer level had reached.its maximum initial,

.; rise of about 310 inches. The RCS pressure continued to decrease *

*

due to the open relief valve and upon reaching 1620 psig a;pr:xi '. -

';- mately three minutes into the transient, actuated safety Features ~~-

.: including high pressure (water) injection and.contain=en: isola: ion. -

< . .* *

Appror.imately five minutes-into the transient the rupture dis:' *; on the pressurizer quench tank, which was receiving the RCS **

blowdown, burst. 'lurs' ting of the ruptura dis: was aggravatedby the actuation of cantain=ent isolation, which had isolated,

'' *** 'tne quench tank cooling systeni,' resulting in expedited pressuri-

'

.-

zation of the quench tank. -

.

**

The RCS continued to blow dcwn'through the open pressurizer.

* * *

power relief valve and the quench tar.k rupture disc cpening suntil.prir.ary ecolant saturation pressure was reached, ab::: .

. six minutes into'the transient. The fo:- ation of steam in t'

the RCS caused an insurge of water into the pressurizar. This -*

.insurge and the high pressure water injection then res : red*

pressurizer level to about 310 inches after nine minutes into--.

the transient. ... .( * ''-

... ,* . .- . .

Xpproximately thifteen minutes into the transient, the s'ec:ndary****

side of' the No. 2 Staam Generst:r went dry. Abcut fcurteen 4.; minutes inte-the transient, the operators noticed the 1cw level*

''- ' condition and found that the auxiliary. feed pu=p was operating

at reduced speed. Manual centrol of the auxiliary feed pu=p *

was started and watar level restored to the No. 2 5:aam Generator.-.

,

At approximately 21 minutes into the transient, the operat:rs*

discovered that the pressuri:er power reTief valve was stuck- . . . . ....o Blowdown.via this valve was stopped by closing the bicek

~ *"*v' pen.,Nes-ttrminatiniI.he reactor vessel dep' essuri:atien. . The "-- *alv'e r

RCS pressure recovered to normal and c.o.c.id_o.wn of the sys:F fol15 dei- - "-- -

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..* The reas:n for the spurious " half-trip" of the ITats has n:t yet

(c been determined. An extensive investigation revealed several -

-

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'~ ^ -~~-' loose connectionir at terminal boards, but nothing conclusive.. .. .

.

t yInvestigati.,i1..ti t ,, ' g{;E73 g, p,g3y.g;,. pilot aetuated ---

relief valve revealed that a "close" relay was missing from the "~

- - " * * * - controb circuit. This missing relay would nor= ally provide a )-

-- - - - 7 ' seal-in* circuit which would hold the valve open until the . . " ' '

:* pressure-dropped to 2205 psig. Without the relay the pcwer relief . '"- !-

; valve cycles open and closed each time the pressure of the RC3-

"

went above or below 2255 psig. The rapid cycling of the valve -

.

, .caused a failure of the pilot valve stem, and this failure caused

: the power relief valve to rs=ain open. .8 .

'

It was determined that the auxiliary feed pump did not go to full.

j speed because of " binding" in the turbine governor. . ,

The transient was analy' red by the't:555 vendor and 'detar=ined to be'

' - * within the design parameters analyzed for a rapid ce;ressu.-i:ation...

,

~With eihe'tica of the above noted calfunctions, the pla.t functionedp. - .

* as designed and there was no threat to the health and safety of thegeneral public.1-3-

. . -~~~ * 2. Feedwater Isolation Yalves. . . ..

, ....

On two occasions hi July, at the Trojan nuclear plant, a hydraulic~.

. .~

feed =ater isolation valve failed to c1cse upcn receipt cf a close- -

signal. .All other equip =ent required to operate, func.icned'- ~- " -"n6r a11y.. ...

.

b '

" "- The first failure.* July 6,1977, had been attributed to an"-

.Timproperly assembled solenoid in the hydraulic actuater.*5

Investigation of'the second failure indicated that b:th events" * ' ? "---- - -

were dus 10 a lack of, sufficient hydraulic pressure.- .,

-

| %*

. . .. .-

|Fai' lure of the valve is close.was caused by the pressure regulater

*'liiking and failing to close down te regulate the pressure. This|

.

caused the hydraulic system en .he valve .o be drained d:ner. ts --

-

a point that the valve would not operate. Inspec.ica of the.

regulatsr revealed that a locking screw on the regulat'er adjusting ,

knob was loose and would allow the knob to vibrate t: any pcsition.- ..-=r. - ., .1.'ith,the.regdTats:: ic;r:perly set -it-would-nct clos.e cowr.. : .. _._.

regulate pressure and would allow ~the hy2fai Tic fluft to' drain;- "''# ~ -.

before* tee hydraulic operator could function. A similar proble='.

was discovered on two other valves, although the maladjustmentwas not sufficient to prevent these valves frem operating.~

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