ML20050V304

Northeast Utils Probabilistic Safety Evaluation of Scram Discharge Instrument Vol Mods

ML20050V304
Person / Time
Site:	Millstone
Issue date:	01/19/1982
From:	Bickel J NORTHEAST UTILITIES
To:
Shared Package
ML20050V262	List: ML20050V184 ML20050V304
References
NUDOCS 8204150053
Download: ML20050V304 (29)

Text

'

ENCLOSURE 2 NOR'INI!AST IFFII.FFII!S

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w. wm.,. c..,e.rw. ewa.

P O Box 270

'I~[.'s'..[$d... (.C:..'74

.s, HARTFORD. CONNECTICUT 06101 (203) 666-6911 c.s, L

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1 NORTHEAST UTILITIES Il PROBABILISTIC SAFETY EVALUATION 0F SCRAM DISCHARGE INSTRUMENT VOLUME MODIFICATIONS l

l l

l DR. JOHN H. BICKEL i

SENIOR ENGINEER SAFETY ANALYSIS /PRA UNIT 8204150053 820211 PDR ADOCK 05000245 p

PDR

WHY PROBABILISTIC SAFETY EVALUATION PERFORMED:

• IDENTIFY DOMINANT SOURCES OF S.D.I.V. TRIP FAILURE

• ASSURE MODIFICATIONS ADDRESS DOMINANT RISKS "0PTIMIZE FINAL DESIGN:

- ASSURE RELIABILITY

- REDUCE UNAVAILABILITY

- MINIMIZE SPURIOUS SCRAMS

• PROVIDE GUIDANCE TO PLANT 18C PERSONNEL

• AVOID IMPLEMENTATION OF INSUFFICIENTLY ENGINEERED " FIXES"

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HOW PROBABILISTIC SAFETY EVALUATION PERFORMED:

BASE CASE S.D.I.V. DESIGN DEFINED FAILURE MODE / EFFECTS ANALYSIS PERFORMED FAULT TREE MODEL DEVELOPED t

MINIMAL CUTSET LISTING OBTAINED

• COMMON CAUSE FAILURE EVALUATION

• RANKING OF DOMINANT FAILURE MODES THEN:

• PERTURBATIONS IN BASE CASE DESIGN EVALUATED

• EFFECTS OF MODIFICATIONS > STUDIED i

• 0PTIMIZED DESIGN CONFIGURATION OBTAINED t

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o PROGRAM Mtt tsfour e - A T.uu.3, WNCTtnNAL LEVEL BEFORT NO.

DIACRAM SYSTEN ftt AttoE Pf eit C reoy PREPARED BT h [ N'(' M SUBSYSTDI S D I V.

FIGUEE I t

CHECKED BY EQUIPMENT PePauf. Auf)

DATEsejes/slREY.01

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Inherent Ef f ect Component Failure Symptoms, Local Effects Method of Compensating on No.

Name Mode Cause and Dependent Failures Detection Prowlsion RPS Reestk e 3

aAAq u A L CLOSED OPERmru81 FAlts To LOSS OF (CVE L StastTCH SdKV(IL L A MCC

- Rt huwoAu1 Hg Hg MONE vAtut c6stocc At TtA inst 372-az r a go.7eok,,)

t.Div Lcutt AAm st F s -tav toSG ot HI SDIV Lf W(L ALAR 4

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1 tevtt enits oPru Etic trt sc4L Contacts srocious Hi SDeV truc t AL Ac as sH soiv AtAc ar

-n e ao u e Assi He HI WohJE (7 : g h,)

w it c H enou ctosen

+ Ait oec u soiv tevet AvicA4 so 2 - 8 2 F t

- S ura v E lttA NCE j

LEVE L F AILG 'lo opt >J

-(t(CTdt eC A L Lol.S OF HIGH spsV LEV (L A.Atat - Rt houDAuf Hf He

• RE BUNf)A>Jr He H8 N ouE z.083h St=J IT C H 6tVtDa HI SDeV C8NT ACT S STeCeN SheV tivtL ALAR &4 ShsV toutt ALAt ag 8F SbiV L f ut t IO d

• S 2F l LIVf L bat t F tr> A1 Srscgg couisNu65 5o INC R.E AM (e = T208 rs) 4 uptuont.

ctoSEn ortstalo t. talts to

-LOG 5 of LE vf L 5tosit H

- So tV(s tLAs u

- RC60N Das saf Hi HI N64 E vetve cesroer. asset it sT lo t-arr e

9. no s,,,)

saiv te uct Atata stri-Lv

- (OSS of H8 Sbst/ L(WL A L A d? M g

n4ANUAL c t.a s e D O N C4f*C FAILL 10

-LoS"> 8F LEUEL St.s eTC H

.su Rv( s tta oJ C E RE DuNDANT RPS LoS$ OF '/al

,,, e,oig tevet si.,new,, c s ie,e

<e 5* *" ** ice 'e sT so.2 - 32 ai gw,go s,,,I P2. -t2 Bi,Ei,os ca ranet a ry vAtvc

-Los s os,^^ C uauuC' H e sh'V r2 Ai-ov otve L.

n.c su rut i. sees g,

(f u t t.

FA3LG opt u ELECTRsC AL touTA(T1 - Septiod s *A* C HAu nst, t.

He

-h" cHAasuc t. RPS RCDoupAuT' Re5

'4,RPS toGac s.o.Tc H

.,,u ctose e

. 4 L cre s, soiv trutt,cic wie tic.H r cHamiaets woi sie At itLit h 3nt-62 A g e

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%e PRNRAM grLCf od 1 - A.W.3" FUNCTIONAL LEVEL REPORT NO.

SYSTEM FRCTos? PR0it.c Tio ha DIACRAM SUBSYSTEM S. D l V.

F'C'Of f I CHECKED BT EQUIFMENT PeFIwG AwD DATE se/se /F8 REV. 8I ens 1R uneu1 AfidM (anoa1H sepE) f inherent Effect Component Failure Sygtoes. Local Ef f ects Method of Compensating on No.

Name Mode Cause and Dependent Failures Detection Provision RPS Reserko 7

LevF L FA6LS to oPtN

" t LC fT8 tic AL Co me1 A1 Loss of'A" CHAu wet He SDav

.suttutstLAuce Rfhuu04uf set str Loss oF 8/q (T, =.083 brs)

~

Sav eTc 4 6 Vtu HI s pev C18C ic LEVE L Tee P e=PUT 10 RP5 (8 5 720hrg )

HI SblV LEVEL % 1(Nei of EPS TerP 3o2-82Al LEUCL

- St at t. FLo A T CTIC LE 10 2 9 2 BI, C', 01 C AFAfi't siy E

uAwuAL CLOSED OPL 8t# 80 fL I Alts io

-toss op trutL stui tc H Neof s LL AN(E 8tf buu DAuf RP5 LeSS OF '/g wALVt g4 syn,4 g 3, is g to2 - 82A1 (o. jpo s,,,)

He sbsV (J\\sa 5t.,eftur5 og RPg ingp 82 Al-LV Tt s i

-Loss or*A'CHAMMfL HI SblV 302-B2 81, C l,01 MPARitary ofufL TR P surut 1o RPS

'l MANUAL CLOSED oP(C A1 oft I AltS TU

- LoS S OF Lf0(L $tgeTCl4 SO f2V(t LL A NC s:

Rf DoubAut R PS Loss of 'S THis VALyg 35 VAL V E-RE STDR 6 Of If dC lo2-%2F8 Hg SDfV Lf 0(L $4.stTdy of gpg Tggp opLy g[gggg OwtV-3 MAINit NAN ( e Loss OF HI son / L(UEL AL Af A4 82 QQ Di WOMy M% WTWN

- LoE S of Liust Stue T C H To ALLOW FLUSH 1%

OF lyygggg,,q p

- L o S S of" A" (*HA n u( L HI 50tV LE Ut L ifter INPUT 10 ft P.5 L t4E S.

10 nap uAL CLoSGD OP( ft ATOR. I AILL 10

• loc S o f Le uG L s t., e TC H

' SuRVfit L AkJCC It.f Du aJ04 ht? 8 CPS LOSS OF '/v THis VALue s5

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'Z - R? F e sai cosV trv(L hiTrain op gpg 7 gip og4tif CLOSED VALVE cs s.TDrzf /d'36 C d

't,)[ *,! 1} '"3,i',*[c'u '*"

so 2. s z ni, C., es

.AvAsit Ty oueiu6 sHurbown Luiv-3 MswitwAme Jo2-R2 As 10 ALLOLW FLLJEHl46

-LDs5 oh *A'CHAu tJCL sin Sb8V Of tMLTRUMCNT Lf Ut t 'EtP e4Put 1b R PS L8 ME S.

Sto TC H coCUelLLANCE 8tt Do u0 A ut-R F's

,t/ss os f/9 I'

@MuAL CLo S E D OF8 R 4 f o ff F AILC 70

• Lo ES OF L( uf L n

Loss or g c"uAuns t.

(e<Tros,<3)

H' 50'" t

• V E L '"" "' ' 'F CPS 1"'P v4 tut cessora at rs c so2-t2 '

Hf SDev T*2 - R2Al, Cs, DI mPa tut:1y F2 G s - uv 1e-ST se us t. Isie ewf ui 'Io R P.S i

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i PROGRAM unustoM i - A.T,h,5, FUNCTIONAL LEVEL REPORT NO.

LIACRAM PREPAREDBYhhbitN SYSTEM RE Actou PgoTyc1eo u fl6DatE I SUBSYSYDt

5. D. I. V.

CHECitED BY EQUIPMENT Pf PtwG AND DA g le/re[gf REV. Of susf r/pue N1 Alie )

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Inherent Effect Component Failure Symptoms. Local Effects Method of Compensating on No.

Name Mode Cause and Dependent Failures Det ec tion Provision RFS Remarks 32 LfutL IAsL5 OPf pJ gtECTftlC At LOAeT A LT f S pulleou s HB SDIV Liut L R *'S

~*ff CH444fL 8205 R(bDUD AU T (PS e/2 CPS Lo(e'C Sto e fc q froAi cooSEb erp, g, opgy cg.mu ust*g* Tar s(*

1R *(*

Lar.sof cusaJuf LS M* F ygep ADffcTFb gog.gggg 1

al tilt 6 L F AILS To OP(6J

-fLfC T R BC AL (aMT ALE LOSS OF

'fl* CleAquet HI 50lv

-SURVEeLL4pcf RE DO U D Auf C PS LOSS or '4 (Tg=.Ddhes)

S tw a f f H f.svf u HI SDay STIC iL u vfl 1fteP e n, Pu t its RPS (O

• 720 hrs)

H8 SO'V LIVI L 'b"'## OF RPS Tfts P 102 -82131 t tVE L

~ 83ALL ftO AT STic it.3 10 2-ft2 4 8, C 8, DI capa gg,g,, yy l'd M A HU AL CtOSCD oPERAfee FAgLS TO

.t OSS of bf VE L St.> I T C H sorLUE 8 L L A u CE.

si c no sv0A uf RPS toss of '/8f UALVE RI Sf8 R t Al lE (4 3* E ' 8E 8' (O s 720 hrs) gg SDiv Livf(, St.ittar or gp51gep 5281-LV tt sg-

- Loks of- "f%* C H Au we L HI Sbe V HA C e, h e em LIVt t TE s p lu Pu t 1'o C P.5 15 unravAL C. LOSE f)

OP6tz Af 0(2 ( AlL S 10

-LOSS Of LIVfL Sta3 81 f l4

$d R Vfit L A NC E stt Du up Auf APS Loss of '/2 THIS VALvr is M*D8 VALV E aLEsmac Mlle 14 8 SblV gg'ytt SwlTthof RPS 1R.8P ONLy CLostb

' L*

• S O f 84 ' sO'v L t u b ' "'4 R A' 302 g2 ct,DI DF Afttu T7 DURlu(, SHUTbOW4 U6J gV-1 MAluTENAract

. Lo k S o f L(tst L stoeTCHf 5 b AllDbf FLUSHIAJ6 3o 2 - 112 41, fle

. to s s a t *Aa Aup"ff cH4ubtL OF (*JSTRup(NT" HI GblV LE UFL.1Rt P iMPUT T LI AJES.

To KPS S

M A *JOA L CLO S E D 08'LRAloft FAlts To

-Lo65 8 F LIVet. itneticW

$0ftVkiLLAWe Re 0U AJ Ca ut gp$

to S S OF '/2 1HIS VALUE 85 b2-W8 yg g gy Lg uit A ggreg3 og. gp$ yltar cutty (,tosg, D V4 'E Eds reatE th ie r2

'o B 51 AN LkJ eV-)

ggguig,,gugg

97. pg c e, p, (A P4 838 LIT'f,

DU(llNG SHtlTO Was IO ALLolo flUSHlu6 Jog. W 2 Al, f(I

-Lass of 'A Aub

• 6" C HAnlNtL OF IuSTRtJkf ul' til %iv LAVt t 18t er* Itsfif75 l Juts, te f(PS

• 9

i PROGRAM MIL L Frod I - A.T.W.$.

FUNCTIONAL IEVEL 4

REPORT NO.

DIAGRAM SYSTf24 KE ACT0ft PROTFcTled SUBSYSTf21 S. D. L. V.

Fl6URE I gg,C,,,,,

EQUlfHENT PIPING AMD DATE II/se/rf REV. of inswumt u1 Alina (aeoniu 5:06) l Inherent Ef f ect Component Failure Symptoms. Local Ef f ects Method of Compensating on No.

Name Mode Cause and Dependent Failures Detection Provision RPS Remarks 47 MewoAL ClosCD rM RA10'E FAILG To -loSL Of LE VE L StolTC NC E

• S O R U( lL LA N C E RE btsMDAut Ap3 Loss of '/2 lHis VALWF 85 os-RPs TRae ONLY(WLEb VALVE Rt Sto R C Af M R 302-E2CI,DI He sbib-LEU 6L Uuiv-2 AA AIMTEN A NC C

- Loss oF T* Aub "D*' C84A8JUEL 5tassitHES 702-8/ A{qMA8tt T7 DURING sHOTDOUM He SDiv LEuLt 1ftlP 1490T5 g,4tgggg pgggggg,4 oF fuSTEUA4s MT

- oss o hfuG L Sta TCif r

L8 C.

i 3 og. S'Lt l

-Loss of Hi Hi SDtv LEVE L ALAga4

-Loss of condR8L E*DWITHCChet Pft4 Hir13 7 IB M ANU AL Clos E D oFYRA foe FAILS To -Loss of LEuf-L StasTC HE S 50 RUE f LL A NCE, RE*DOHDAuf RPS LOCS OF' Yt THIS VALUE 83 VALVE Restorzt Arit ra so2-R2Cl, DI HI SDfV L6UEL OF EPS 1Rs P ouLy CLoCE D Les i v-2 MaluTEN ANCE

-LD55 0F "C." A ND

• ff C HA NMil

%s t TCHE s92-12A(@ CAPARItIQ Oufttu6 GHOTDOWM til EblV LEurt 1f21P tw PUTS To Au otJ I-LU5Hlh6 lo R PS of lNLTRUMauT-

-Loss av LEUCL 5La s tC H

'*UlC-

'202-S 2 L-I

-toss oF Hi HI SDIV LEUEt_

AtDEfW

- LOE5 oF coutflot ROD LAsil!6 DRAWS 982cH a n g T

'S M ANU AL C t.oCF p OFY 82A1 ort f ALLS 70 -LOGS of LCUC L CausT(H

- 5 W f2 bf l L LA FJC f RL DL)pDAut-RPS t.05% of Ms

"#LDI RE STo4 L AF1 C fl

'fo 2-F2 C l E O

• 72o krd He stuV LEVE L.

OF ICPS Ilhf ti t t e-Ulv gegy

_ Log g op C" CH AUM(L WI stosT(th C LA PA ft#L eTy SD:V 13 W L 'Trce P s uPt>1 302-22 41,81, DI

'la R P.S

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PROGRAM A4tLLSTour I-A.Tfn.S.

RTNCTloNAL LEVEt, REPORT NO.

DIACRAM SYSTDI,@Tott PatoTKT884 Fl6ute 1 y

stuststat S.D l.V.

EW i m MT Ptn 46 anD DATEti/g/ff REV.ol

1. NM fl0M t b1 Alto N lue 81Ff_HQE )

Inherent Effect Component reflure Symptoms, Local Effects Method of Compensating on No.

Name Mode Cause and Dependent Failures Detection Provielen RPS Reserks

• "claduwst. R95 Rf DUMOA AJT R PS V2 RPC tmic (7,,,= 8 krs) 20 LEVEL FAILS OP(M (LfcTeacAt (eaeTActs s PO Riot > 5 til SDIV LEVEL RPS c.

SLw1C H 0 ftc At CLOSL b gr A g t o P( 4 C HAN Nt t "C" Tf71P TRIP LU HT gig gggy Ltygg ggsp stulTC N 6 s NO T 102.- E 2 C I AFf etle b 21 (EUEL FAILE To or(M -ElfC1 RICAL coa,1A(Ti LoSC of "C" C H Aunt L Hi SOiV TO 82VCIL L A NCE REDUwDAuf RPS tess oF '/4 (Tp ot3 hn)

" '# K-LFurL1eop s oeu r la R. PS (8 = F20 brs) utsnavLLv(t,

<* RPsTfsP StoTcet

vtu pi soeu 8^ R ' ' " ' ' '

• si-in Hem 3n-cA',8'. '"#d" ' Y soz-sace uueL De 22 MANu4L ct.asa b ortRaioR FAILS to - L o ss of LFUfL StalTf H suRUC f L L ANCE ftt Dou D4uT cps Loss o/'/4 vAlyn agggg g pg. u gz 3o2-stg c g gg,170 % s)

He SDeV LEUEL.

w gps, y,p U CI T(S T*

-Lo s s, of "c"CHA M ME L HI SDiv stull(We s 3a2 32Al, capAgita ry Leu (L -tale iuPuT 10 RPS Gt, Di i

I 23 unnuAL ctosgn cesanTore FAILS To -Loss oF LEVEt. % eTC H SUtutett ANCE RL DUMDnMT RPS LOSS OF 'l4 THis tIALVE 01 unLME ge s; ton g A f'TE e 302-92 DS 9g sgg ggggt,,

og gps ingr eMLSl CLOLEb unav-Lt MAsuTgunuct

- t os s af "V tH AMN6L HI SDW w aTC HG s 102-9240, L APA BlL s TY gu,tg4 guyggg,9s, LfvEL TelP suPOT 1a RPS gg, ca 1t,4LL

,u, Q5,n(,

- Loss of L6urt stalTCH

'3o2-B2El of 8miTRUMAeT

-Loss op H He SDiv Lf utt

i. s ue s,

Alf9 R M

-LMS$ (f (ob1 Rot 82o0 weiltDKAio4 F70HIBli i

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FUNCTIONAL LEVEL PROGRAM A41LL S70 W l-A.Tig,$.

ltEPORT NO.

SYSTEM Rf Agon PRolettis AJ DIACRAM SUBSYSTDt 5.D A V.

Fl6t>RF I

'"EFARE ET(

CHECRED BY EQIIHENT Fil%46 AMD DATE is/es/s s REv. os t us1 Rout uTSiiro luomite Sit 4)

Inherent Effect Component Failure Symptoms. Local Effects Methc,d of Compensating on No.

Name Mode Cause and Dependent Failures Detection Provision RPS Remark e 24 uAnust coosth or>e R A tofz. FAlts 18

~LoS5 oF LCU6L ItonTC H SURUCILL AME RE DONDouT R. P. S. (pss or '/9 ines VALyc s.t VAVE g g s, tog g AfTER 307-12D I

&41 SblV Lf Vf t-O F RPa ~1 RIP outy CLDI6b L N IV - 'l Man u1E NANCE

.-Lo E S O F D* C HA NNEt, Hi IOM swinHe5 Toz.82Al, (AP4Riuly NR'% EHUMU U vrL lillP tNPUT 10 RP5 fil, c l

-LoS5 of leu (L flogT(H bAR N W HW6 3o2 - 8 Z t-i OF lusTR O ME NT

-Lo5S OF Hg HC SDtv LCull.

t,ngg, At AR M

-LOSS et cont Rot rod WIT 18924W vntesHin g 1 35 M AwuA L CroSED OPERATOR FAILS 10

- LOSS of LGUE L StonTC64 Jucuu t.L A NC E Rf Du M DAUT RPS Lose of '/4 vAtuC Rz none Af tt R 3o2 -112Dt g).720 % )

HI 8;D'" LEVf' o f RP1 N8F v 2 DI-UV TE ST-

-LOSS of"O"(HAnuft He SDIV st., s icHe 5 ;o2 12 A', c.4PAu f t:1y LtUt L 1 RIP thPUT TO RPS 8', C8 2.(>

L(UEL F4ILS OPE M (LEC.T Rl(4L CavTA(n Spurious HI SDIV LEUrt. RPS "D* CH44ue L R Ps att poucAuf RPS e/1 EPilo6it (Tg e g y)

Stas eTC H FHoM C loGt D Fw gt op( y CHAMW(t.*D" 7 Rep TRIP LsGHT He SDn1 L EU E l-TRIP 3o2 - F2 Ds StonTCH6i NOT" A VVEC Tt b 27 Livtt FAILS in cre N Et(cioc4L CouTAis Loss CF " D" CHA MOf t. 48 ifWV ~ SOCUl it LA MCC ReDuuD4ur RP5 toss. o* '9 (T,m.otikrs)

Sn.s i tc H Geyce) pg SDsV sT iC K tJufL ~1REPGMOUT 10 KPS (0 :32cges)

Hg sbsu LEVEL of RP5"ItiP 3e 2_- 12 DI LEULL isAt t H o 4 T GT K tt 5to s tT Hes Wo?-R248, c APA RsL s GI, C f

>f e

~

e p tsto M i-M M '

FtfNCTIONAL LEVEL REPORT NO.

DIACitAM e.

SYSTfN (E114C7082 peoTfCTIDM SUBSYSTFN S D.I.V.

CHECKED BY E@tm M 46 AND DATE'l/88[f1 REV. o f e MsT E u S1E NT A1MN Ihl0RTH SIDI)

Inherent Effect Component Failure Symptoms,t.ocal Effects Method of Compensating on No.

Name Mode Cause and Dependent Failures Detection Proviolon RPS Reestk o l

23 MANUAL CloSE D OP6 RAlo e. FAIL S

. toss or LCUFL Sto t1( H

-sutvEs L LANCE arDJuoANT R PS OSC OF %

UALUE h ReETortE AFTEC 3*2-82D' (0:720hrd H CDaV LEVEL.

• RPC lesP t

82 DI - LV TEST

- Loss of

0" cuaaJNFL Hs 508V 5 TcWs 3o2-82%CA PAnit ITy Lfut-L Tsz P supor lo CPS l

2')

MANUAL CLo SE f) oPeRM1ac FAlt s

-LOSS of L(O(t A I T( d

~5pE u t lLt.4 N C E stE 0 u 9 0A u f H I NONe VALvr 5, cestorze Arigrt 302 - B'Z E l (e s ito k.)

50'V LIV'L 4'*E "

l RT.E l-uV 7egr

-Loss oF 14 i HI SDIV LEUEL ALARM

-Loss of tonTRet to D te 1H0t w at rRoHiBir 70 LEVf L FAILE OP(kJ EL(c.TitsCAL CouTAts-SPU8tions H HI SDIV LEVI L HI Hi 50sV ALACA1 RE DuuOANT HI MONC

@a* Shes)

Sw 8TC H Ff2cm Crost-D e Ast oPEN 4(A2 Ag SDeV Lit /f L ALARM 302' UU

- Cow 1frot rod tosTHDG4ivAL moHsBai ACTUA f t 3

'3 :

trUEL FA Ls 1o oP(M -f LECTRaf At Co AMAT LOSS oF Hi HI EDav Lf UEL SoRue st LANC C Gbuuohur Hj NONE NTs.0dkrs)

Sto lit H 6sut N Hi HI AL A b b%

(O'l20h'S)

SDIV LfVfL OLAEA4

'L

- N N"Ol U'M 5

-Loss oF coNTral R.ob WITHDNel 3eg.g'2(g SDIV tt u(L FF oHille T 32 fM A NUA L

(. Loa f b OP( R Alo R f48t 5

- Less oF Hi Hi SDeu LfUf L SDEVf 8LL A NCE RfDouDANT HI NoNE UALUE

'10 'Z t STO R L Ol'1L il OLOR h (Os 120 hss) sOsu t. tut L ALAC At 82e - Lv 16 sr

- to ss or mutm 200 w81HM89A' reoH(r4 T

't e

v

~

SYSTEM OPTIMIZATION CRITERIA:

FIRST PRIORITY:

RELIABILITY OF STANDBY OPERATION I

- FUNCTION ON DEMAND

- DETECT FAILURES VIA PERIODIC TESTING

- PREVENT CONDITIONS WITH POTENTIAL FOR COMMON CAUSE FAILURE SECOND PRIORITY:

AVOID SPURIOUS ACTUATION OF SCRAM LOGIC THIRD PRIORITY:

AVOID EXCESSIVE-ISC PERSONNEL EXPOSURE (ALARA)

- FLUSHING CAPABILITY IN SMALL PIPING

- SHIELDING CONSIDERATIONS

- EQUIPMENT ACCESSIBILITY 4

QUANTIFICATION MODELS USED:

• ANNUNCIATED FAILURE /0N-LINE REPAIR FEASIBLE b)Y hT g

• NON-ANNUNCIATED FAILURE / PERIODICALLY TESTED b )*I h(6-T [/6 7

- RUNNING (S) = TT /6

- DURING TEST

• HUMAN ERROR DURING PERIODIC TEST (9 ) = (H.E.P. )(DOWNTIME)/6

- FAILURE TO RESTORE INSTRUMENT ISOLATION VALVES

' COMMON CAUSE FAILURE ANALYSIS:

" UTILIZED 3-FACTOR APPROACH

?

• NET Q ADDED AS CORRECTION TO INDEPENDENT RANDOM FAILURE O cc NET

• FOR COMMON CAUSE LEVEL SWITCH FAILURES f=0.53 SOURCE: FLEMING + RAABE GA-A14568

• CONSERVATIVELY BIASED DUE TO DOMINANCE OF OPERATOR ERRORS IN

-FACTOR DETERMINATION Q

b

• Scu h

etc Ok SENSOR w

= (6.32 x 10-4)2 + (0.53)(6.32 x 10-4) + (6.32 x 10-4)2 (0.53)(6.32 x 10-4)

+

= 6.7 x 10-4

• WASH-1400, SOUARE ROOT BOUNDING WOULD HAVE PREDICTED i

O

= (6.32 x 10-4)2.+ (6.32 x 10-4)3/2 + (6.32 x 10-4)2 SENSOR (6.32 x 10-4)3/2

+

= 1.59 x 10-5

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TOTAL (Qcc)

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12.78%

COMMON CAUSE SENSOR FAILURE DOUBLE VALVING

• dQ)=4.4x10-3 84%

ERRORS CROSS TERMS 3%

'NO COMMON CAUSE COUPLING 0F VALVING ERRORS IS ASSUMED - SHOULD BEf=0.1

CASE I CONTD.

• IF COMMON CAUSE COUPLING OF VALVING ERRORS IS ASSUMED:

- DOUBLE VALVING ERRORS INCREASE TO 98.2%

- COMMON CAUSE SENSOR FAILURES LESS THAN 1%

• SINGLE VALVE ERROR FOUND CAPABLE OF CAUSING REACTOR SCRAM

• SPURIOUS SCRAM PROBABILITY:

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CASE II (REMOVE 8 ISOLATION VALVES) 94 CUTSETS 7

TOTAL

<(0 NET)+$0cc)=3.61x10-3 100%

<(Q ) = 6.7 x 10-4 18.55%

COMMON CAUSE cc I

SENSOR FAILURE DOUBLE VALVING (02)

= 2.8 x 10-3 77.56%

ERRORS **

CROSS TERMS 1.41 x 10-4 3.8%

30% REDUCTION IN UNAVAILABILITY FROM CASE I

• ELIMINATES BASE EVENTS A3, A4, D3, D4 l

• • N0 COMMON CAUSE COUPLING 0F VALVING ERRORS IS ASSUMED - SHOULD BE l

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4 CASE II CONTD.

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• IF COMMON CAUSE COUPLING 0F VALVING ERRORS IS ASSUMED:

- DOUBLE VALVING ERRORS INCREASE TO 97.2%

- COMMON CAUSE SENSOR FAILURES LESS THAN 2.4%

• SINGLE VALVE ERROR FOUND' CAPABLE OF CAUSING REACTOR SCRAM

• SPURIOUS SCRAM PROBABILITY REMAINS:

4.1x156/ MONTH i

t

CASE III (DIVERSE INSTRUMENTS

• IN A,B) 122 CUTSETS

<(0 NET)=3.24x10-3 100%

TOTAL (Q) 0 0%

COMMON CAUSE cc I

SENSOR FAILURE DOUBLE VALVING

([Q)=2.8x10-3 86.4%

ERRORS **

CROSS TERMS

= 4.4 x 10-4 13.58%

I 48% REDUCTION IN UNAVAILABILITY FROM CASE I

• ASSUME USE OF HEATED JUNCTION THERMOCOUPLES

- SIMILAR RESULTS FOR 4P TRANSMITTERS

- MAIN EFFECT IS ELIMINATION OFje-COUPLING

• • NO COMMON CAUSE COUPLING OF VALVING ERRORS IS ASSUMED - SHOULD BE l

d?= 0.1

CASE III CONTD.

• IF COMMON.CAUSE COUPLING OF VALVING ERRORS IS ASSUMED:

- DOUBLE VALVING ERRORS 98.4%

" SINGLE VALVE ERROR CAPABLE OF CAUSING REACTOR SCRAM REMAINS

• SPURIOUS SCRAM PROBABILITY INCREASES:

1.7 x 10-5/ MONTH

- CAUSES:

INCREASED COMPLEXITY SETPOINT DRIFT CALIBRATION ERRORS

- SIMILAR RESULTS FOR OTHER TYPES OF LEVEL SENSORS

" SIMPLICITY OF PRESENT DESIGN IS RELI ABILITY ASSET

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CASE IV (MINIMUM VALVES /4 SETS OF TAPS) 50 CUTSETS 7

(QNET)+bcc)=1.54x10-3 i

TOTAL 100%

COMMON CAUSE (Qcc)

= 6.7 x 10-4 43.5%

SENSOR FAILURE DOUBLE VALVING (Q) = 8.0 x 10-4 51.9%

ERRORS

• CROSS TERMS 4.6%

70% REDUCTION IN UNAVAILABILITY FROM CASE I

'N0 COMMON CAUSE COUPLING 0F VALVING ERRORS IS ASSUMED - SHOULD BE

.B=0.1 l

CASE IV CONTD.

7

• IF COMMON CAUSE COUPLING OF VALVING ERRORS IS ASSUMED:

- DOUBLE VALVING ERRORS 91.5%

- COMMON CAUSE SENSOR FAILURE 7.6%

• SINGLE VALVE ERROR CAPABLE OF CAUSING REACTOR SCRAM:

COMP _LE_TELY ELIMIt[A_TED

• SPURIOUS SCRAM PROBABILITY REDUCED TO 8.1 x 10-7/ MONTH "NUSCO INTENDS TO IMPLEMENT THIS DESIGN i

I

s.

KEY FINDINGS:

7

• CHANGING TO DIVERSE SENSORS HAS TOTALLY INSIGNIFICANT EFFECT ON S.D.I.V. RELIABILITY I

• IRREGARDLESS TO SENSOR TYPES USED, SINGLE VALVE ERRORS CAN DEFEAT TRIP FUNCTION

• DOMINANCE OF HUMAN ERROR IMPACT ON SENSOR FAILURE

- CONFIRMED BY REVIEW 0F OPERATING EXPERIENCE

• 0PTIMUM DESIGN:

7 i

- RETAINS EXISTING SENSORS (SIMPLE, RELIABLE)

- MINIMIZES VALVES TO THOSE NEEDED FOR TEST

- STILL PROVIDES FLUSHING CAPABILITY T0:

REDUCE CRUD BUILD-UP REDUCE RADIATION EXPOSURE

• KEY PROBLEM TO BE ATTACKED:

I

- OPERATIONAL Q.A. DURING TESTING

- NOT EXOTIC LEVEL SENSING DEVICES OF UNKNOWN RELIABILITY E

y+

WHAT PROBABILISTIC SAFETY EVALUATION HAS ACCOMPLISHED:

• DOMINANT SOURCE OF S.D.I.V. TRIP FAILURE IDENTIFIED

- FAILURE TO RESTORE ISOLATION VALVES FOLLOWING MONTHLY TESTING ~

• NUSCO MODIFICATIONS NOW ADDRESS DOMINANT RISKS

- NUMBER OF INSTRUMENT ISOLATION VALVES REDUCED TO MINIMUM

- REMAINING VALVES ABSOLUTELY NECESSARY FOR TESTING AND MAINTENANCE

• S.D.I.V. CONFIGURATION OPTIMIZED

- UNAVAILABILITY REDUCED

- SPURIOUS SCRAM PROBABILITY REDUCED

• NEED TO IMPROVE TESTING Q.A. IDENTIFIED TO PLANT IEC PERSONNEL

- KEY PROBLEM:

REDUCING DOWNTIME FROM VALVING ERRORS l

- SEVERAL OPTIONS BEING EXAMINED

- INCORPORATION OF PROCEDURES FOLLOWING HARDWARE INSTALLATION l

l l

.t MEETING

SUMMARY

DISTRIBUTION:

D6 6 50-245

~

A 3

4 g

NRC PDR s

LPDR p

b NSIC ORB #5 RF RECElVED 1

b pg 1 7 ISOS "

D. Eisenhut G. Lainas Tn H. Smit 5

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0 ELD D'

OI&E

/4 6

ACRS (10)

~

H. Silver J. Tsao A. Thadani Paul Blasioli, NUSCO John Bichel, NUSCO Bhaman Stefi, SAI Paul Amico, SAI Robert Liner, SAI

.