Chernobyl Nuclear Accident Congressional Hearings Transcript

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Answer 17
(continued): forced cooling. As predicted, the fuel and sodium coolant
temperatures initially increased until the combined effects
of thermal expansion and natural coolant circulation shut the
reactor down.
In the loss-of-heat-sink test, power to the secondary cooling
system was turned off while the reactor continued operating.
Again, the reactor shutdown without operator action as a
result of the self-generated negative reactivity feedback
characteristics of the system. Further analyses and
confirmatory testing will be conducted to assure that
operator action, if attempted, could not defeat the safe,
inherent self-shutdown capability of the system. The strong
negative reactivity feedback exhibited in these tests are due
to a combination of the high heat conductivity of the metal
fuel and the thermal inertia of the large volume of pool
sodium in the EBR-II.
Advanced LMR's being developed by DOE are utilizing these
features. Work is also continuing in support of these
advanced concepts to develop an improved metal fuel and to
demonstrate new, simpler processes for the metal fuel cycle.
The EBR-II tests demonstrated that liquid metal reactors can
be designed to be self-regulating in protecting operators,
the public, and the financial investment. The properties