ML-1 was an experimental reactor built as part of the US Army Nuclear Power Program. Unlike the other seven reactors of this program, it did not use a steam turbine, but instead used a nitrogen coolant under several atmospheres of pressure to drive a closed-circuit gas turbine.
The concept failed to live up to expectations, and was abandoned with the closure of ML-1 in 1963 after several major refits and with only a few hundred hours of testing completed in all. However a similar concept has more recently been proposed as part of the PBMR proposal.
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