ML19322C324

Forwards Description of Analytical Work Supporting Vendor 177-Fuel Assembly Plant Safety,Per 790424 Meeting W/Nrc & 177-Fuel Assembly Plant Owners

ML19322C324
Person / Time
Site:	Crane
Issue date:	04/25/1979
From:	Taylor J BABCOCK & WILCOX CO.
To:	Mattson R Office of Nuclear Reactor Regulation
References
TASK-TF, TASK-TMR NUDOCS 8001160846
Download: ML19322C324 (6)

Text

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Babcock &Wilcox

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P.O. Sw 1260. t.yw.wsrg, Ve 2 8'/

Te*, phone. (8041.184-5111

[ April.2'5,1979

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Dr. Roger J. Ma ttson, Directtr Division of Systens Safe ty Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.,

20555

Dear Dr. Mattson:

In.the NRC, Staff meeting with B4W and its 17 7 - Fue l As semb ly l

plant owne rs art Tuesday, Ap ril 24, 1979, 84W agreed to describe the scope and status of certain additional analytical work to support the cont.inued safe operation of these plants.

The attachment documents this information.

We intend to provide this inforna tion to you on or before Friday, May 4, 1979, and suggest that a detailed technical presentation of the information be made to the appropriate Sta f f engineers at that time with follow-up meetings as deemed necessary.

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i Ver truly yours, A

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James H. Tayto Mana ge r, I.ic ens in g JHT:dsf Attach.

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ATTACHP'ENT MALYTICAL. WORK TO BE SUBPflTTED TO THE STAFF IN SUPPORT OF 177-FA PLA

.MAY 4,.1979

'.f Analysesifn this area concern themselves minly with the prediction of[

. System behavfor. following alloss of main feeMate'r' or other events that r=sult in a loss of feedwater and a$ delayed estabitshment of auxif fary reedwater.

The analyses can be df vfde.d into two genersi types:

(a)

Initfal system response which is capable of predicting primry

, system reactions until such time as two-phase effects become signf ricant.-

Work in thf s area wi11 primarify utilf ze the CA005 comuter cnde.

This code is capable of modeling the inf tf ai 8 to 10 minutes of such trans f en ts.

jb) 1.ong tem system response which can deal with primry system evaluation following the estabif shment of two-phase conditions In the r= actor coolant system.

These latter analyses will primrfly utfilze CRAFT code and can be carried out until final resolution of the incident is estabitshed.

From our review of anticipated transients, we will provide analyses of those transients whf ch place the greatest constraint on the actfons' of the auxfilary feedwater system.

For these analyses, we will then girovide calculations detailing the scenarios which may result fron delayed auxilfary fee +.<ater actuation.

The delays will be considered f rr a range from norm 1 actuation to no actuation at alt.

The speciffe analyses shown in the following pages will be documented and submf tted to the Staff.

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7 AFT Analyses (Small Break or Enended Time, 0 Break, Analyses) s itatus Description of Analyses Result / Expected Result f.ength of Evaluation Done

1. Stuck open PORV, RC pumps Some two-phase conditions at Approx, 1000 s on, nomal auxiliary feed-selected areas within the RCS water and 2 HP! System will be encountered. Natural trains actuated, circulation could be estab-11shed at any time provided, RC punps went terminated.

Reactor core covered at all 8

times with no temperature excursion.

Done

2. PORV stuck open, RC pumps Very sistlar for Case 1.

The Approx. 1000 s -

on, normal auxiliary degree of two-phase accumula-feedwater.1 liPIS train tion in the RCS is signifi-cantly higher.

The return to a subcooled ustem is delayed but tha natural cir-calation would be established at any time the RC puaps could.

be terminated.

Done 3.IPORV. stuck open.?RC pushs Significant steam accumulation Approx. 1000 s jon.. normal aux 111ary. feed-la the RC system such that if

i. water, }iPl;llaltaa to 200

, RC pumps were teminated af ter isps.

an extended time tne collapse

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1 of the two-phase fluid and the separation of water and steam l

would ae expected to _ uncover l

tne core causing severe core

, danuge.

i 5rogress

4. 'THi-2 ' actual tnns te'nt.

This evaluation is being mac'e to 3

bes t' es tima te prediction.

' oemonstrata the capaollity of the BAW evaluation accel to predict LA avents at TMI-2.

Significant yoid fractions

1 i

's atus Description of Analyses Result / Expected Result length of Evaluation j 1

within the RC system will dev-elop during the first hour i

and 45 minutes for which RC T

pumps were on.' Termination i

of the A loop punps at that time I

will result in'a steam and. water separa tion... A serious amount of.

j Tcore uncovery resulting in i

severe core damage' will. result.

It is our intention to carry the analyses through core uncovery and to provide

[

approxinute core neatup times a

to the point of core damage.

2 2

Done

5. 07 f t,.02 f t and for the.07 ft and.02 ft Approx. 2000 s 2

2 2

.01 ft small breaks small breaks significant ACS at the pung discharge voids, exist however the core without auxiliary will never uncover an,d no

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feedwater actuation cladding temperature excursion j

for 20 minutes, no will result.

RC purros and 2 ilPI

?

2 2

systems These.07 ft.02 ft evalua-tions were performed for 1

i 30 niinutes with no auxiltary i

feedsater and no auxiliary i

feedwater would be required at

)

any tl.ne after a successful

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resolution of the transient.

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.The.. 01'it small? breat is th'a.

lmost llat ting of'these transients

! and requ f res.actua t lon - of e l ther.

, auxiliary feedwater or JPI' by, D3 minutes to prevent core Encovery,and the..petential t

aor core da.uge.

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LMr l Anal' iis {Cht'd)

J Status Description of Analyses Result / Expected Result t.ength of Evaluation in progress

6. A loss of offst te power and Significant void formation in the Approx. 3000 s loss of main feedwater eval-primary system but re-establish-uation with manual inttiation acnt of natural circulation would of HPI at 20 minutes, no RC be automatic with the establishment pumps, no auxillary feedwater, of auxillary feedwater.

'This evaluation will also be per, formed considering further delays in actuation of HPl in order to identify the longest delay possible to prevent core uncovery.

Done

7. A small break in the steam This_ evaluation models the results Appeos. 3000 s space of the pressurizer of ofa[stuckopenPORV. Evaluation 1.052 in.

differs from those thewn in items 1

~

2 and 3 in that the initiating event is a small break with no RC pumps available, normal auxiliary feedwater and one HPI.

Small degree of steam formation in the RCS.

Natural circulation can established, no core uricovery or temperature excursion.

Incident can be terminated at almost anytime througn securing the block valve.

e in progress

8. References to conipleted small A listing af small break LOCA analysis break LOCA analyses and models.

licensina suomittals.wnten provide furtner clarification to small break, concerns will tie furnished.

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.... ; m s.6 w,

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M-5t tus Description of Analyses Result / Expected Result length of Evaluation _ j I

within the RC system will dev-i elop during the first hour i

and 45 minutes.for which RC i

pumps were on. Termination l'

of the A loop punps at that time i

will result in'a steam and water separa tion. A serious amount of core uncovery resultin() in b

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severe core damage will result, l

it is our intention to carry the analyses through core I

uncovery and to provide lr approx 1nute core heatup times to the point of core damage.

2 2

Done

5. 07 ft,.02 ft and for the.07 ft and.02 ft Approx. 2000 s 2

2 2

.i

.01 ft small breaks small breaks significant RCS at the pump discharge voids, exist however the core without auxiliary will never uncover an,d no feedwater actuation cladding tenperature excursion

)

t for 20 minutes, no will result.

RC pumps and 2 HPI 2

2 systems These.07 ft.02 ft evalua-I tions were performed for i

30 minutes with no auxiliary i

feedwater and no auxiliary i

feedwater wuld be required at i

any Lt.re after a successful l-resolutica of the transient.

1 1

The.01 f t' smil brea c is the most li.nf ting of'these transients and requires actuation af ef tner auxillary feedwater or ciPI Dy i

20 minutes to prevent core

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uncovery and the potent 1JI i

for Core ddi,nage.,

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