Chernobyl Nuclear Accident Congressional Hearings Transcript

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• Third, the design appears to be limited to the pressure
suppression of certain specific break sizes and locations,
and does not appear to envelope the full range of
possible accident sequences for which U.S. containments
are analyzed.
• Fourth, the structure does not appear to be designed to
withstand burning or explosion of combustible gases from
zirconium-water reactions or graphite-steam reactions.
The inventory of potential chemical energy in the
RBMK-1000 type reactor is very much greater than in an
equivalent 1000 MWe light water reactor. As previously
stated, the amount of zirconium is between two and seven
times larger than comparable U.S. LWRs . Also, the
RMBK's graphite combustion energy has no equivalent in
light water reactors.
In general, Soviet compar tmentalization appears directed at
limiting the pressures from pipe breaks, not containing
chemical energy or the activity that could be released in an
accident. Again, the comparison of what happened at TMI and
at Chernobyl helps explain the importance of these design
differences. At TMI, very little activity escaped containment.
Most of the small amount of activity that was
released was in the form of gaseous fission products that
present relatively small health risks in comparison to the
particulate fission products that were contained effectively.
As previously discussed, the hydrogen produced at TMI
from the high temperature chemical reaction between zirconium
and water did not result in combustion inside the
reactor coolant system. However, some of the hydrogen did
escape the reactor coolant system via a power operated
relief valve and surge tank relief system. This hydrogen
accumulation eventually resulted in a hydrogen burn and
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