On 29 March 1979, a major accident occurred at the Three Mile Island nuclear power station in Pennsylvania, USA.
A leaking coolant led to overheating, but the signals were wrongly interpreted by staff, who temporarily shut off the emergency coolant designed to prevent just such an incident.
Experts said that little radiation had escaped into the environment, but a potentially explosive bubble of hydrogen gas inside the crippled reactor posed a new threat of nuclear disaster.
If it exploded, the reactor’s container could have been breached, releasing large amounts of radioactivity.
The State Governor, Richard Thornburgh, recommended the evacuation of children and pregnant women living within five miles of the plant.