Chernobyl Nuclear Accident Congressional Hearings Transcript

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on the facts and to ensure that correct lessons are identified.
My summary of fundamental design differences will be
divided into three areas: reactor differences, containment
differences, and safety system differences. My point of
comparison will be the U.S. light water reactor.
REACTOR DIFFERENCES
The Chernobyl reactors are light-water cooled, graphite
moderated, vertical pressure tube, boiling water reactors.
These 1000 MWe plants are called "RBMK-1000 '
by the
Soviets. The RBMK reactors are the dominant standard Soviet
design. RBMK-type designs comprise over one-half of all
operating Soviet power reactors and about 65% of their
nuclear capacity.
The first difference between Soviet RBMKs and U.S. LWRs is
the use of graphite as a neutron moderator. The RBMK design
evolved in the Soviet program from earlier weapons production
reactors that used graphite and low enrichment
uranium. U.S. designers selected the light water coolant as
moderator over graphite for power reactor applications for a
number of reasons:
• First, the concerns associated with a potentially
flammable material inside the reactor core are avoided,
along with all the complex support systems that go with
it (moderator heat removal, cover gas, fire protection,
etc. ) .
• Second, the unique physical problems of graphite under
irradiation, requiring annealing of the Wigner energy
effects, are avoided.
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