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Three Mile Island by J. Samuel Walker, University of California Press, $24.95, £16.95, ISBN 0520239407 Reviewed by Rob Edwards

A FEW seconds after the accident at the Three Mile Island nuclear reactor in Pennsylvania began, more than a hundred warning lights were flashing in the control room. “I would have liked to have thrown away the alarm panel,” one of the duty operators, Craig Faust, said later. “It wasn’t giving us any useful information.”

Water pumps, the turbine and the reactor had all unexpectedly shut down. But none of the blinking lights told the operators what they needed to know – that cooling water was leaking from the reactor core through a valve that was stuck open. If they had realised that, they could have stopped half the core from melting and prevented the worst nuclear accident in the US.

J. Samuel Walker’s lucid account of the accident, Three Mile Island, which happened 25 years ago this month, is riveting because of its detail. It shows how the companies, the regulators and the government all initially played down the risks, then had to eat their words. It gives a graphic insight into the chaos and confusion of the five-day crisis.

There was, for example, conflicting advice on whether local people should be evacuated. In the event, about 144,000 people moved out. Walker, the official historian of the US Nuclear Regulatory Commission, points out that if the full extent of the core meltdown had been known at the time, hundreds of thousands more would have been told to go.

He also suggests that Three Mile Island proved both sides in the nuclear argument wrong. The industry had underestimated the risk of a core meltdown, while critics had exaggerated its consequences. Part of the melting core, it turned out, had solidified at the bottom of the reactor vessel, helping to prevent it from breaking and releasing a massive amount of radioactivity. A catastrophe was avoided – but only by luck.