ML20024B537

Comments on Proposed ANS Paper.Reader Must Work Too Hard to Get Message

ML20024B537
Person / Time
Site:	Crane
Issue date:	01/08/1980
From:	BABCOCK & WILCOX CO.
To:	Labelle D BABCOCK & WILCOX CO.
References
TASK-06, TASK-07, TASK-10, TASK-6, TASK-7, TASK-GB GPU-0294, GPU-294, NUDOCS 8307090097
Download: ML20024B537 (9)

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j jf i t s; j s. i s,. I . ;s s Attached is a proposed ANS paper with required NPCD L. y. approvals for presentation at the 1980 Susser Conference. This is an invited paper for a special session on thetaal-s 'p( $ M. hydraulics and sust he suhaitted to the AMS by January 25 1980.. g 4 l g gygjg, - - r ' e.. i '} t. a. i ) t Attachm.ent j Approval Date i I. A. Vomack i l ..} D. E. Key l = C. D. Morgan .o. ' J. E. Taylor e s I l 1. = 4 0 T - - ~ ~ J B j '_1_ 3 2G 0_6 9 I) C15 8 5 3 5},,.. _ l .r l i.i ~ ' ~ ' ' '

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Free W -- O %M D. W. LaBelle, Manager, Safety Analysis (2117) W as 442.s .. Ca st. File No. or ner. s 1 ~ j ' Su bj. T, Dats ANS Faper Approval Eequest January 4, 1980 e t. gru.s l. .i l .e. e j .l.8 t )

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f 3.. 'l 1 '.,l !.L Attached is a proposed ANS paper with required NPCD '4 -{ l approvals for presentation at the 1980 Summer conference. .'j This is an invited paper for a special session on thermal- + J-N-hydraulics and must be submitted to the ANS by January.25, l 19.80.- e j .j DEL /km r. a j p -I .? t a t l* 3 4 t .]i e + .t Attachment \\ t .4 4-1. } -.1 Approval Data ,r. t (,; E. A. Ucaack ? U 1 D. B. Koy. .,k .i. y C. D. Morgan 'd "a J. E. Taylor i p~ i # 1 i *' r N w g g .4 A 32G' o 6 9 sj l l C15 8538) g [ m. -- s L _ - __j

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4 1, l 1 s .:. t GE AME!1ICAN NUCLEAII SOCIETY i , TECHNICAL GRO UP FOR THER.'.A1.. HYORAUT.!CS + 1 l p 1 i i i.ii.n. .. a. p s e s== .. m us. i. 3. Eevenber 27. 1979 ~~ Mr. Desiel W.,Lage11e

,4 Embcock & Wilcox Company i

e F. O. Box 1260 1 Lynchburg, Virginia 24503 ,,s 3 Dear Mr. LaBelle -' *t .1 The Ther=al-Hydraulics Technical Group will sponsor an -isvited session entitled ~.l " Thermal-Eydraulies: Changes in Machods in Light of THI" at ths.1980 Annual Meeting. This seating will be held June 4-13, 1980 in Las Vegas, Nav na. The invited sassion vill deal primarily with, but not be restricted to, responses to NRC bulletins that have been issued as a result of the TMI-2 incident. 'Je ., invite you to present a paper at this session and would appreciata your partici-j, Patia** ~l

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) ,j A list of the speakers that have been invited to this session is presented below. for your infor= sties. ' Y *Q 'ik.lo .Deo& W. LaBelle Babcock and Wilcox Company ) }- er }

e. Isbert 3reen National Safety Asalysis Center

~~ 3 j e f aul Bergeron Tankee Atocic Electric Company

e. Zoltan Roszteczy W. S. Nuclear segulatory Coc=issica.....

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e. Joseph longo Combustion F.ngineering, Inc.

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• Patrick U.Marriott General Electric Corporation

~ ( .. j e..,,.i.ncent J. Esposito Weetinghouse Electric Corporation V ~ ) s. ] The deadline for submittal of a 900 word sumary describing your presentation la 4 Jannery 11. 1990. If you have any questions, or cannot comply with the January 11 l dead 11as, please call Toa 2ndack at combostion Engissering (203)-688-1911, 1hre===iotr 2731. g .~ y Sincerely yours. ,4 g e .l Dr.1. T. Lahey, Jr. e i Chairman, ANS Technichi Cr, p for ~ Thezzal-Hydraulics l y l .) 8 . Q, IIL:ab y .d. e ,.4 't e -.c-4 i 326\\069:5] C15 8539] ...~. V- " " ' ' ~ ~ * * *

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9 / t i } "A New Era for-the Non-LOCA overeocling Events s ig + ] A.'CharaWant, 1. O. Yosburgh, J. J. Cudlin, D. 7. LaSalle. i 'Ihis paper, describes new areas of analytical study which have evolved. the evaluation of poa-LOCA overcooling events since the T31-2 accident t j ,p of March 28, 1979. Overtooling eveets have acquired greater significance aa the. nuclear industry has begun to deal with the frequency cf loss of pressurizee level indication _ and the small break LOCA requirement of a manual EC pe p trip following ECCS actuation on Iow-low ECS pressure. Specific

p. M---- 2 which are being studied relate to the potential for steam voiding f

la the RCS faebuf f ag its method of formation, distribution, eliminatica, and impact ca core cooling, especially during periods of tressition to natural [IO p circulation. I

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- ' contractica 'of the ACS coo.lant liquid volume occurs as a result of tempers-j% b p,gture decreases during an overcooling transient. The pressurizer coupensates ] l 8 for this inventory voltase change v.ith its liquid inventory of approxinately. s. r I j f 3 N 800 ft for a typical SW 177 TA.plaat designi The pressure and temperature l( 4 conditions achieved during the traastent determine the = cunt of the steam g,g and, liquid volume in the pressurizar which is transferred to the ICS and,in J! I; addition to neraal makeup, the actuation of the emerge =cy tore cooling'systez Sf- ~ t=MMg high prassure 'injecti34 s I OWI), low pressure injection (LP1),..or, core \\ flood task (CY*) systems. ~ '~ Tlie severity of the overcooling transient determines the influence of f ( 't j various sech= M a for steam void formation in the RCS. As the pressurizer ( ..] i liquid icventory is lost, the RCS approaches sacuestica and the poteocial exists I i for sceau' void formatioc. La the most elevated regions of the hot less and reactor r ] vessel upper head. The extent' of saturation is further. enhanced by the transfer [t h. of the ptsasuriser steam space into the ACS. The other nachanism walch intro-s g ] duces steam voids-into the ICS is flashing e5 coolant in the hotter regions of. ] j the RCS by localized heat transfer from metal surfaces during periods of rapidly decreasing pressure. For the non-LOCA event, this process is self-y regulating. Ja the staan separates or additional flashing occurs, the pressure j decrease is' the systes lessens even with centinued sys'cas overcooling. 'The .] stesa void wi'l be subsequently compressed and collapsed as' a 'subcaoled state 7; .is r.-eseablia.a. During periods af forced coolant circulation, steam voids, if they are produced, are quickly entrained. They are subsequently swept into the subcooled g.) { 4 y ',t --f } ~ I h ~ I 3 2G' o 6 9 ' 6J C15 8 5 4. 0} --.w .3 j,. g. 1.

...~._._r. .a. 4 i ... g. ' J ', i. -i - .1 4 4 I . *} ,, port, ions of the system and collapsed prior to the buildup of appreciable quality

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-levels in the acs. When forced flow is lost, staan separation from the liquid ~ / 3, g phase is highly probable. Stratified scesa could collect la the upper =ost regions i of sha BCS hot less and reactor vessel upper head. De quantity of staan t ^ .sellected La the het less has the potentia 1 for disrupting transition to astural circulation and resultant core ecoling. 3 l Preliminary analyses have been performed for two overcooling events to provide additional insight fato the potential for steam void fdraation and its - 3 ceasequences. The events studied were a asia feedvateLOGU{ overfeed of the ,stesa generators fo11cving a reactor trip and a d.ouble-ended satan line. break.h d 'I 6. g.D. ".perfeed,c,,a,,se,_g.rnpresen,tative of so anticipated over,coolias transient od-4 f,pt ?. I, p,"f s kish frequency of-occurrence for 34W operating plaats. JThe steam line braak $ [ ',.G Dy 1 ,y cadent is the limitliig~nea-LDCA overcooling., design _ basis accident presented i j in the SAR[3oth events were analyzed from full power with the 34W computer i

• ?l-code TRA?2 No operator or non-safecT grade systaa actions were assumed i

f. 5 -$: A for the first 10 afautes of the ' transient. l 'j k j f', The TRAF2 code was developed as extension of the CRAFT 2 - LOCA model

• t L4 61-3!.6 to permit analysis of transient RCS sad staan gecarator thermal-hydraulie

~, ? 5: j ,d h@)0. f. #, y, a code,of the FLAss (3) genre in which integra.ce d e.g behavior during depressurizacion of the secondary rystes. As such TRA?2 is .I j gi JN d.h and somencua. conserystion equations are se,1ved am, first order ordinary differea- . f i tial equations for a user-input network of control volumes and flow paths. '} unique " feature of TRAP 2.is itshetailed stesa generator mode)l,M, ich permits sub-F I '{ 'stantial ripresedenio@, via incraased noding, of both primary and secondary P generator regions and portions of the secondary systen piping. i, As advantage offered by TRAP 2 and cod similar type bilbty.' A relatively cearse spatia sati]oaa be utilized for portions of the r seconda ystem piping wherelatiuid properties are approximately uniform. c' ",,j } Axial er tions in heat transfer and fluid, state is,the generator ragions,- .i 4 which can strongly influence che, overcooling transient, may be staulated by a acre detailed noding. A wide variety of boundary and initial conditions can be y smalysed without the difficulties of. scaling of ten encountered using analog 4 sethods. These. advantages in. flexibility, however, can be offset by the re I d quired computacian ti=e. yce large steam line break cases, e cia.e 1 execution time to real cine is approximately 30 to 1. . e practicality o 1 ,9 * ~ using TRA22 and similar codes for transients of long dura - - - - - _. a d} major deficiency in currest sta:e-of-the-art methods. 9 ~l*- s a 1 'l f I g- ~ z .w C15 8 5 4_.l)' .j f 326 0697} l g,7 .ai t

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. The NFW overf aed study showed that pressurizer liquid inventary could be / I-lost for about 50 seconds during the transient. As the pressticizer emptied ' a a p the EFI was actuated. The makeup flow of the HFI was sufficient to keep up / with the overcooling contraction of the RCS. Steam void formation did not f ( l occar in the RCS, irrespective of whether forced flow or natural circulation conditinas maisted. Thase results are consistent with dac2 obtained for Ag+ m f transients of a similar nature which have occurred at Bh operating plants. j e design basis SLB accidhresulted in stema voiding in the upper regions i l. f the ACS hot legs. This amounted to worst case steam void 1=g predictions for I Steam void-t yk 3 3 .d. one het les of about 400 ft and about 50 ft in the.other hot leg. ( occurred almost exclusively in the loop with the affected steam generator. l H ', 12 the affected steam generator is on the loop vich,the pressuriser, emptyinsp + Other. sensitivity

• . the pressurizer contributed to the steam void formation.

.,scudies were performed for ass'essnect of the time of loss o'f forced RC riow. and , ( afagle failures of a steam relief valve and the EPI on the extent of staan void formation. In all cases analyzed, core flow was saintained. The bulk core region 'b .- resined subcooled throughout the transient. [ 4 ..y These analytical scudies confirs the adeguacy of core cooling during these transient and accident conditions for ch'e current system design. The results, g l ej however, also support the desirability for Improvements in analytical methods and f j [3 operational plant safety, and additional acrengthening of the dgfense-in-depth approach for the current systen design.' A major cirjective of this continuing .J g{ [, [ -design evaluation is the reduction la frequency which the operator or plant j ] design must respoed to coaditions such as loss of 7eassurizer level indication, lose of pressurizer liquid inventory, RC pump trip, and steam void formation is ~ p. the RCS. k this reaso3 it is believed that these analytical studies herald '{ k the beginning of a new era of syscan design and analysis for non-LOCA overcooling ?' + n events. ? References i 'i 1 J. J. Cudlin, P. W. Daggett,'" TRAP 1 - TC 2AN Program f' r Digital SLiula- .a 1. o l tien of the Transient Beha'rior of the once Through Steam Generator and ] Associated R' actor Caolant Systen", BAV-10128, Sakcock and Vilcoz, e -l Lynchburg, Yitsinia (1976). j 2. J. J. Cudlin, R. A. Hedrick, and R. C. Foltz, C2MT2 - TORT 2AN Program ?1 1 43,. for Digital si=ulation of a Multinode React'or Plant During Loss of Coolant", ?. ]l} g MV-10092, Sabcock and Wilcox, Lynchburg, Virginia (1975). l 3. S. C. Margolis and J. A. Redfield, "FIASH: A Program for Digits 1 Sinulation 1 i .I of the ' Loss of Coolant Accident". VA?0-7t-5%, Vestinghouse Electric Corpora-tion (1966). 7 --- a "r = J -{ n I C15 8 5 4 2j-326'Wo 6 9 8) -4 J- ..p. --m ,- ---._ .~ __'- -:.5. _ .}}