Fukushima – a year after the disaster

In the history of civil nuclear technology, 11 March 2011 marks another turning point. After a catastrophic earthquake that triggered a major tsunami, the greatest reactor disaster since Chernobyl occurred at the Fukushima Dai-ichi nuclear power plant on the east coast of Japan. With the plant devastated, the mains electricity grid destroyed and the emergency power supply completely out of action, the cooling systems failed, there were three core meltdowns in quick succession and several hydrogen explo­sions in four neighbouring reactor blocks, while three reactor pressure vessels were destroyed – an event more serious than anything envisaged in nuclear accident scenarios. How could this happen?