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Chernobyl Nuclear Accident Congressional Hearings Transcript

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305<br />

nUESTION FROM CHAIRMAN JAMES A. MCCLURE<br />

Question I?.: Is there room for improvements in U.S. reactor containment or<br />

confinement systems? Could you give us some examples? Where<br />

are the major deficiencies in current containment systems<br />

used in the U.S.?<br />

Answer: Various changes to containment or confinement systems have<br />

been proposed. For example, in PWR plants, some are<br />

advocating changing a standard containment system to a<br />

filtered-vented containment system. In BWR plants, NRC has<br />

proposed four possible changes: hydrogen control for<br />

Mark III systems, containment dry well sprays, provisions for<br />

wet well venting, and inclusion of refractory materials to<br />

direct debris material so as to avoid by-pass of the<br />

suppression pool. But whether such changes are improvements<br />

depends on several factors; such as, does a current<br />

containment provide a sufficient level of safety; is a slight<br />

improvement in safety worthwhile if the cost of the<br />

improvement is very significant; to what degree is added<br />

protection against extremely low probability events<br />

worthwhile if accidents with less severe consequences are<br />

made more probable? Reviews on the adequacy of containment<br />

structures are being made in conjunction with the<br />

NRC/DOE/industry review of the severe accident/source term<br />

issue. Whether there are deficiencies that will need<br />

correction with be identified as part of this work.

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