ML19308B979

Discusses Small Break Analyses Resulting in Reactor Coolant Pump Trips,Auxiliary Feedwater Actuation & Control of Liquid Level on Secondary Side of Steam Generator at High Levels. Recommends Reactor Coolant Pumps Powered Case Analysis

ML19308B979
Person / Time
Site:	Crane
Issue date:	12/11/1978
From:	Rosalyn Jones BABCOCK & WILCOX CO.
To:	Cartin L BABCOCK & WILCOX CO.
References
TASK-TF, TASK-TMR NUDOCS 8001170720
Download: ML19308B979 (2)

Text

W THE BABC0CK & WILCOX ' COMPANY POWER GENERATION GROUP lo l

L.R. CART!!;. I!~IGRATIC?

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R.C. J0 :ES. ECCS A'!ALYSIS (2066) kO. w>us.a a s eas.s l

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File No.

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ALL l

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Date l

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__ SMALL 3REAK A':ALYSES '.?ITd RC PUXpS ?OWERED DECEMBER 11, 1978 l

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l iPresently approved small break analyses have all been perfor:ned assuming l

'that.offsite power is lost coincident with reactor trip. This results in I

[ tripping of the RC pumps, actuation of auxiliary feedwater, and control j

of the liquid level on the secondary side of the SG at high levels.

Should offsite power re=ain available during the transien:, the RC pumps vill remain powered and the ICS will control the secondary side water level to i

approximately 30 inches by throttling the =ain (or auxiliary) feedwa:er control valve. 'Because of the importance of the SG water level to mitiga: ion of small breaks, ECCS recommends an analysis of the RC pumps powered case.

In =aking this reco==endation, ECCS has perfo=ed a review :o determine what previous analyses are available with the RC pu=ps powered and also has made an engineering assess =ent of what vould happen under nhis situation.

No previous analyses could be found. However, 1: is expected that if any were perfor=ed, they were not done at break si:es of interest.

With the RC pu=ps powered, it is expected that natural circulation would be main-tained for a longer period of ti=e and would aide syste= depressuri::a:1on.

Also, maintainance of the system flow would decrease Tho: after reactor trip and would resul: in a lower pressure for system flashing to occur. However, these positive influences would be offset by the decreased ability of the SG to condense steam, fellowing the loss of natural circulation, due to the lower SG level control.

It is also expected that, with the RC pe=ps running, a " steam pocket" vill not form in the cold legs and lower quality fluid will exit through the break and thus shorten.the ti=e for the syste= :o reach the

" boiling pot" mode of the ::ansient. An unknown fac:or at this time is whether or not the steam generated in the core vill _ separate in the hot. leg

!U-band or be carried down into :he.SG and_ condensed,. !!his may be an~1=-

[portantfactorfor.shovi.sgthattheRCpumpsrunning.caseisbetterthanthe lpresent_ assumption of tripping the RC pumps.

ECCS proposes :ha: the i= pac:

of this phenomena be examined in a sensi:ivity s:udy.

Asillustra:edabove,[itisnot.obviouslyclearthatleavingtheRCpumps.

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[ running _resultsinanenhancedECCSsituation.'

Ehus, ICCS reco== ends an l

analysis be perfomed to examine this case.

ECCS proposes tha this j

analysis be run on the 205 yA plants for the following reasons:

1 8001170[,2O

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RC Jones to LR Cartin Page No

Subject:

5.all Break Analvses k*ith RC Pu os Powered Dec. 11. 1978 1.

ne present 205 FA s=all break topical (3AL*-1007/.) assu=es heat re= oval typical of that for the 177 FA plants. Berefore, a co=parison of the

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pu=ps on case to BAW-10074 vill provide an assess =ent of the i= pact on i

the 177 FA plants.

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There presently exists an FAC =odel on the 205 FA plants.

3.

The new SG =odel in CRAFI has been exercised on the 205 FA plants.

This =odel = ore properly accounts for SG perfornance during the tran-sient for the 205 TA and VEPCo plants.

Cc=parison of the pu=ps on case to recent 205 FA plant studies vill provide infor=ation on the i= pact for 205 FA and VEPCo plants.

It is expected that this work could be scheduled into the ECCS Unit workload

'now because of slippage in the NRC s=all break standard proble= and the 205 FA s=all break work.

It is esti=ated that this work vill require 300 =h and 10 CDC hours and a span ti=e of 3 =onths. 'Niru Shah will be the con-tact in ECCS for this issue.

If any questions arise, please contact hi=,

or call =e on extension 2066.

RCJ/lc cc:

B.M. Dunn E.W. Swanson

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