ML20024B604

Current Events Power Reactors,Operator Error, 770901-1031

ML20024B604
Person / Time
Site:	Crane
Issue date:	12/31/1977
From:	NRC COMMISSION (OCM)
To:
References
TASK-03, TASK-06, TASK-3, TASK-6, TASK-GB B&W-0161, B&W-161, NUDOCS 8307110014
Download: ML20024B604 (4)

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UlilTED STATES

,1 CURRENTEVENTS CUCLEAR REGUI.ATORY PGMER RE.. ACTO....RS....

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THIS CCMPTLATION OF SELECED DDITS IS PREPARED TO O!55 EM

• ~.*INFORMATION 'CN OPERATING EXPERIDCE AT NUCLEAR POW TIMELY MANNER AhD-A5 OF A FIIED DATE. THESE EVENTS ARE S 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-i 'i 1 SE?iEE - 310CiGERIc)7

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. OPERATcR ERRcR

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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.

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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

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3300 ga1 Tons er water had been pu= ped to the centain=ent. Ah ut one

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• minute 1atar the ventilation isola:ica actuation signal was received.

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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,'.

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

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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 l

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) s r

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t and the low pressure safety infection to containment spray header 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

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~ ~~ partial.1y operr. -Prior-to the-event-the-auxiliary 4usld'.ng Equipment.

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

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

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

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

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

but no corrective action had been tahan.

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W[. ' ' '.i The pneuaatic relay on valve NCV-345 was replaced and valve HCV-335 S. 3.' ' ~

repaired. Valve HCV-344 and HC7-345 are now required to be placed l

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

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

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i catica of an. annunciator will ensure that both of tha

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• id*thi fully cloied position prior to pump operation.ge valves are

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YAI.YE HA!.TUNCTIONS

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Primary system Cepressurisation

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~...f on September 24,197J, Davis tesse pruelear Power Station Unit

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No.' 1 experienced a depressurization wnen a pressurizer power reitef valve The React:r Coolant System (RCS) f. ailed in the.open position.

pressure was reducedf.-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

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

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. "b. 'Pr,essurizer Pilot Actuated Relief Yalve.

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No. 2 Staam Generator Auxiliaiy Feed Pump Turbine Governor.

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The event was initiated at 2134 hours0.0247 days <br />0.593 hours <br />0.00353 weeks <br />8.11987e-4 months <br />, when a spurious ** half-trip"

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

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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

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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

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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 aggravated by 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 s

until.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.

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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

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• "*v' pen.,Nes-ttrminatiniI.he reactor vessel dep' essuri:atien.. The "--

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

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4 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 y Investigati.,i1..ti t,, ' g{;E73 g, p,g3y.g;,. pilot aetuated -

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

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- - " * * * - 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.

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With eihe'tica of the above noted calfunctions, the pla.t functioned p

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

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2.

Feedwater Isolation Yalves On two occasions hi July, at the Trojan nuclear plant, a hydraulic

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feed =ater isolation valve failed to c1cse upcn receipt cf a close signal..All other equip =ent required to operate, func.icned

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

.T improperly assembled solenoid in the hydraulic actuater.

• 5 Investigation of'the second failure indicated that b:th events

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were dus 10 a lack of, sufficient hydraulic pressure.

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

• 'liiking and failing to close down te regulate the pressure. This l

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;- "#

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

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

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