ML20024B320

Discusses Possible Solution to Reactor Coolant Pump Status During Small LOCA

ML20024B320
Person / Time
Site:	Crane
Issue date:	05/29/1979
From:	Parks C, Womack E BABCOCK & WILCOX CO.
To:
References
TASK-06, TASK-6, TASK-GB GPU-2444, NUDOCS 8307080397
Download: ML20024B320 (2)

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PRELIMI!u.RY REPORT OF SAFETY CONCERiis

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Analysis perfor ed by ECCS Analysis Unit in January.1979 for the 205FA standard plant.

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ATTACICDIT 1 In the ECCS Analysis Unit's and Plant Design's progress report for January.

1973, the following item was reported as resolution of a concern over the RC pump status during a small LOCA.

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$ mall Break Analysis with t'o less-of-Offsite power - The 0.05 ft break was stuoicc cn Inc 205 f.A. Plants to cctcmine the impact of keeping the R.C. pumps on. Results show a much more rapid loss j

of R.C. inventory relative to a case with tripped R.C. pu:rps. While it has been determined that the li:;uid inventory situation is worse for a pumps rvnning case, hand calculations have been performed which show that, due to the pu=ps running, a forced flow, steam

• '7 cooling situation will exist in the core and will result in cladding temperatures of less than 670F. Thus, the pumps tripped case remains a worse situation for small LOCA evaluations. This position will be documented during February.

Examining this case from the standpoint of being able to withstand multiple s

failures brings about this concern. While the statement above may be true

-7; if the RC pu=;s remain in cperation, the case that was run also shows that 3

the reactor vessel would contain only $550 f t of water in 10 minutes after

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.the break should' t'he RC pu=ps go off line by any means such' as by operator '

action or loss of offsite powei.

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3 Since the RY lower head is,4.900 ft, it would take several minutes just to fill the head with onlyl liPI pump. (RC pressure $1300 psia at 10 min)

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- core temperature transient ' ould probably b'e unacceptable. Rough hand cales w

y ;i Predict a tecperature rise of 300-400 F/ min for the hot pin. Assuming a

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starting cladding temperature of 700F and a 300 F/ min rise, clad temperature POC'=

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would reach 2200 F in 5 minutes. The lower head cannot be filled in 5 minutes.

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d(( j One solution to this problem is to. develop a signal to trip the RC pumps such.

as a low system pressure signal or some new signal such as a low level signal which currently does not exist.

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In any case shculd a trip signal be installed, a great deal of safety and ECCS analyses would have to be perfor: red or re-examined. On the other hand, if the pu ps are not tripped, unacceptable results would prebably eccur if 1

the RC pucps should 90 off line. Further study of this situation is warranted.

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