ML19322C503
| ML19322C503 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/08/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001170832 | |
| Download: ML19322C503 (1) | |
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ACRS CONCERNS THI -2 INCIDENT ' t
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What assurance do we have that the THI event will not haooer a t a nothe r :.......=.
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B&W reactor tomorrow?
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.=iid The initiating event (loss of condensate and feedwater pumps) is an
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anticipated transient, i.e., it is e:(pected to occur and may occur
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4E~ iF tomorrow.
However, the severity of the consequences in the THI-2 2.;_.
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incident was caused by multiple circumstances and actions which are ti-.c.:.
addressed by the April 5,1979 IE Bulletin 79-05A.
The purpose of M"M
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that Bulletin is to prevent recurrence of the contributing circumstances. i.s and actions thereby preventing recurrence of the incident.
The Bulletih 5'
requires licensees to:
review their procedures and operator actions
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and determine that they are adequate to prever;. a sim0 =r incident
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particularly with regard to termination of HPl flow and tripping of 5
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RCS pumps and with regard t; reliance placed on pressurizer level indicators in determining operator actions; ' eview containment isolationi..;.iii E..=iaii.
singals to determine tnat proper isolation will be provided; and E. ~5
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assure that adequate auxiliary feedwater flew will be provided by observing specific requirements provided in the bulletin regarding
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auxiliary feedwater systems operability and availability when the b :-
plant is at power.
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There has been much discussion of this accident as a B&W oroblem.
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What makes this accident unioue to B&W PWRs?
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Is there anything unfoue about the TMI containment isolaton features?
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MW EE55' Five other operating B&W designed plants have similar designs as THI, pgll[
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however, the actions described by the Bulletin will preclude a similar
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p The large majority of other operating plants have containment isolation. 7.g 7:~N 3
systems that by design would have prevented flooding of the Auxiliary
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Most plants utilize safety injection as a signal to initiate containment isolation in addition to 5~
containment pressure.
SI was initiated 2 minutes for these other p.)~
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.$c operating plants at that time, rather than at 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> as was the case
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at TMI.
Therefore, little radioactivity would have been released.
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What is the sincie basic difference in the olant designs of other
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at IMI1
.lW We currently believe that the single most important difference in-
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.otherl PWR designs is related t'o the location of the pressurizer and f]:3 E:E=
Irouting of its. surge line.
BWRs of course do not have a pressurizer."
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Other types.of PWR desiIs locate the pressurizer and surge line so =
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(reactor system level is measured.-
The TMI design requires operator g?_}.
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interpretation of a number of instruments to properly identify reactor,-. l..
coolant system level.10ther designs lend themselves to more direct 55 f
imeasu'rement.
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