ML20071A484

Rev 1 to Accumulator Sys, Draft Chapter to PRA

ML20071A484
Person / Time
Site:	Indian Point, 05000000
Issue date:	04/17/1981
From:	PLG, INC. (FORMERLY PICKARD, LOWE & GARRICK, INC.)
To:
Shared Package
ML20071A408	List: ML20071A429 ML20071A431 ML20071A433 ML20071A435 ML20071A438 ML20071A443 ML20071A447 ML20071A454 ML20071A461 ML20071A467 ML20071A484 ML20071A488
References
FOIA-82-626 PRA-810417-07, NUDOCS 8302240167
Download: ML20071A484 (14)

Text

.

• - 'Fj: Lard, LO-s an: Garrick, Inc. IND:AN PO:N! PRA

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A.1 1.1TRS)):TI31 T',e a :unulator syste.1 is evaluat?d in the context of a large loss of conl ant a::ident (~ 00;) uhere t,e pressure in the core d?:reases suffi:ient1/ to allo i injection due to tne higher pressure nitrojan in ea:5 of t5e ac:u.,;1 stor tan %s. 59::ess is defined as the injection of three a::uaulators into t1e three inta:: legs given a LO:A has o::urred -

on t52 fourt.1 Teg.

T32 i,al /sis was :a ried oJt under the follo sing conditions: '

e R l37 is available e ile safe;ineds a:tuation signal is pr?sent.

I,a a::alulat0F s/sti3 does S ! d!p2,d on ele:tri: pcN3r to function, tie ef ore, on1 o,3 cal:ul ation was requir2d for all states of electri: -

po s2r.

I., t5? event trees, the ac:u,ulator systen is incorporated witn the lo.i pressurs i,j ?:tio, syste a (LPI3). 30:5 are required for su::?ssful emergen:y coolant inje: tion. e A.2 RIS).T5 sale 1 saa,a-izes the results of this analysis and compares it to the

!!A5d-1400 results. T'1e mean unavailability of the systea is

1. 31 x 10-3 T.ie probability distribution for the ac:uaulator system unavailabilit/ is sho in in Figure A.

The analysis has revealed the following dominant contributors to systen uns eail abili ty :

4ean e 'totor-operated valves 1.23 x 10-3 (74.21)

e Cie

k valves 4.15 x 10-4 (25.6;)

A.3 0010' JSI313 -

The check valves and the .13Vs are the dominant contributors to accu.nulator unavailability on demand. The tank level, ;12 pressurs, and piping failures are insignificant coapared to the check valves and

43Ys. The resulting aean unavailability on demand (1.61 x 10-3) represents the loss of an/ one of the three intact 1,egs, assuming the LOCA o

curred on tne fourth leg.

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B. SYSTEl1 DESCP.IPTICil B.' SYSTEtt FUt!CTIO!!

For e large LnCA, the acconulator systen provides enough veter to initiete recovery of the enre in the intervel of tine before the LPIS starts to provide flove,'ebout 25 seconds af ter the LOCA. ,

B.2 SYSTEl' C0!!FIGURAT Cl2 A block diagran end e sinplified Pt,lD for the systen are sbovn in Figures ' erd 2. Success of el' . threo accenuletnrs on the intact injection legs is recuired for successful initiction of core recovery. .

B.3 SYSTE!1 OPEPATICtl Phen a nec'ien or large break occurs in the reactor coolant systen, the accrnulator tents discharge to initiete recovery of the reector core.

Urlile the previous systens ubich recuire punps for irjection, the accenu'ete- tert s are pessive, end irjectior occurs uben the reector.

coelert systen pre:sure drops below the nitrogen gas pressure (nonira'1y 610 tc 62C pr.ig) in the tant:. One tart. is provided for each reactor coclart cold leg pipe, end all- the tants are ide-tical.

A nininen borated veter volene of 800 to 815 cubic feet is naintained in tha tarl:s at all tines. Two. level sensors provide control roon reedouts o' the leve'. lov erd high level-alerns occur phen the tent level fellt or rises by nore than a set enount' from the opereting condition. -

• lFer tF= reectn* coo'ent pressure fal'r belev the accmu'etor pressere, the bo-atec veter f1ces through the notor-ope-ated isolation velve (PE/A-3), ubich is norne'ly deenergized oper end receives en npen safegnerds actuation signal. These velves have redundent DC positior indication in the CCP. vben AC pover to the velves is deenergized. Flov

, then contiones through the tro chect; valves and into the cnid leg piping of the reactor coo' ant systen.

!!itrngen gas is nonivelly nainteined in the tenF et 610 to 6?C psic and

is noritored by two press 6re sensors that provide a control ronn display of tbc pressure. An alarn occurs if the pressure falls or rises by more than e set anount from the romal pressure.

B.4 SUPPOP.T SYSTE!!S l The eccunnletor systen is e pasrive response systen such that, et the ,

tine of injection, no other systens need to oporate. Level and pressure in the accenulators are nonitored during pornal . operation to essure tbc

[ reed' ness of this systen.

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3.5' TES~.-3J1VE*;LAJ:E, A' 3 TE:i:::r'. SPECIFICATI3.1 RE0]ItE:tE' Ts A.:7e:k v 31 v e Ll e 3': test is performed during refueling outige intervals for v3lves 695 A, 3, C, D and 897 A, 3, C, D. Prior to returning to servi:e wh?n 105 press'Jr2 has fallen within 100 psig of the RHR systaa desi;q orassure, a c'1?ck is perfor.ned .to 'terify .that.these valves are in the closed position. Table 2 shows tne components that are test 61.

~

One a::u.7alator can be taken out-of' service for a aaxinua of S hours for

' hot si;;do.in testing.

3.5 :1A!1TE.JA.CE RE7JIRI'1E:1!5 T12 pla7 i s not allowed to operate with an/ at unulator inoperable In a :ase.of reqJired asint293n:2, tne plant is shut down.-

3.7 3? ERAT 33 I'1TER ACTIO:!

e There is no oce-stor intera: tion uit'1 the a::uaul3 tor syste.i during 60-71,. Oce-stio1.

3.3 C3T131 CA'JSE p0TENTIV.

Sin:e t1e sys 27 is basi sily a ' passive systea requiring no a:tuation signals or supoort systems, no significant :onaon cause potential has been identified. .The.only a:tive components are the -che:k valves, whi:5 are required to. ope, on deaa.,d.

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- C. LCG C 1100EL C.1 Tor E','E:US The _ event of "Insufficiert Flov Fron the Accunnlator" is defined in the evert tre* rnt nust be positive before LPIS is regrested. Since the

~

' !10Vs are deenergized open, there is no po'iier requirenent for these sy stens. .

C.2 SYSTEft FAULT TPEE .

The tree for each recuneletor, shnen in Figure 3, is an OP. gate' with tuo cFect velves and en liOY thrt is rornelly deenergized open rod riso receives a srfegurrds actertion signal to oper in case it has beer '

energi:ed cre closed. For a large LOCA, all three eccenu17 tors on good legs nust provide flov to successfully initiate recovery of-the core.

Therefcre, cr: of the nina ve'ves thet frils to ellov f'on vi cruse a "frilere of the accunuletor systen." Other failures of lov tarh level, '

icu tent pressore, and pipe frilure, are riso shoun. Their contribution vill be discussed in the cuantification section.

C.2 FAL".T T:EE CODM:' A':.9 SAS C EVEl:TS The besic events are listed in Table 3 vith the frilure node end nerr fri'ure rete indiceted. Erch of these is e sing'e elenent cutset sirce cry ore frilure frils the systen. The resu't is nine ~ single evert failures thrt resu't in tcp evert fri'ure.

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D .1. ?_ TES~ At!D !!A*t;TE!!A! ICE C0!!TRIEUTIO!!

As disci sseri ir Sectior B.L. tests on the-systen pre dnne at refueling.

Ary neirtenprce on the systen during operatinn cells for a plent sFt'tt'es n, ttere' ore, no unevailebility contribution is considered .fron test crr' nainterance.

D.1.3 HU::An ERR 0n C0!!Tn:EUTI0t

- Since this~ is a passive systen, no hunan interection occi'rs dt' ring norre' nooration.- There# ore, no contriht' tion is allot *d to overt!'

syster uravailibility due tn hunen error.

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f-9 TABLE:2 TEST!r;G REC'J1REVENTS--If1 DIAR; POINT 3 a

Correner.t Testing Che:< Va'ves 597A, B, C, D Cycled every RCS depressurizatio'n*

Chs:s Val.es 595A, B, C, D

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Leak tested every RCS depressur- .

ization*

F.0VE92,B,C,D Cycled every RCS depressurization

" Tested for leakage every refueling; tested to assure closu're every '9 R:: re- essud ization.

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A :umulator Block Diagram ,

Fi ure 1.

. 4 4

8 e

i A

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12

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. o ACCUMULATOR ACCUMtJL atoll ACCllMill.ATOlt ACCUfAtllATOf t 31 .

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$ 894C 0 D. D.O. s 895A 8950 895B 895C 897A 8970 n973 897C LOOP (1) 1.OOP (4) fic 1.O OP (2)

COLO LEG HC LOOP (3)

Y Y COLD LEG Y

RC COI.D LEG

,Y 11C COLD LEG

• D.O.

• Deenergized open.

. Figure 2. Accianulator Simplified PAID

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