Chernobyl Nuclear Accident Congressional Hearings Transcript

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QUESnON_l. (Continued) 3 -
For U.S. pressurized water reactors, a significant portion of the
area of the primary reactor system consists of thousands of steam
generator tubes, which at many reactors are cracked and/or
corroded. A rupture of those tubes represents a containment
bypass release 'scenario in that the secondary side of the steam
generators is isolated from the environment by relief valves, not
a containment structure. In U.S. boiling water reactors, the
primary core coolant path exits the containment structure. In
both types of U.S. plants, there are piping connections to the
primary reactor system which exit the containment structure and
which have design pressures far below that of the primary system
piping. Thus, U.S. reactors have built-in containment bypass
pathways. This is not to say that each core meltdown in a U.S.
plant would result in substantial offsite releases.
With regard to the Soviet Union reactor designs, I agree with the
Commission that their plants have different designs than U.S.
plants. However, there appear to be some interesting similarities
in the design bases which were used here and in the Soviet Union.
In the attached response to Question C.4 (which was provided to
the Commission by the NRC staff as background information for a
Congressional hearing in May), the staff wrote that the Chernobyl
reactor and portions of the inlet and outlet piping were
surrounded by a "vault" with a design pressure of 27 psi which was
in turn connected to a pressure suppression pool. This
information provided the basis for my previous comments on the
Chernobyl and U.S. containment designs. The NRC staff is now