It's the worst accident in US commercial nuclear power history. In March 1979, the Unit 2 reactor at Three Mile Island nuclear generating station came half an hour from full meltdown. Two days later, an explosive bubble of hydrogen gas was found in the reactor.

To talk technical malfunction, human error and public response, J Samuel Walker joins Don for this episode. Sam is a former historian of the U.S. Nuclear Regulatory Commission and author of 'Three Mile Island: A Nuclear Crisis in Historical Perspective'.

Produced by Sophie Gee. Edited by Siobhan Dale. Senior Producer was Charlotte Long.

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