Looking back more than a year after the event, it is clear that the Fukushima reactor complex, though nowhere close to state-of-the-art, was adequately designed to contain radiation.

WSJ: The Panic Over Fukushima

Mr. Edano said another reactor in the same complex, one that was not operating at the time of the quake, was on fire Tuesday morning.

WSJ: Japan's Nuclear Crisis Escalates

Tuesday's explosion at the No. 2 reactor in the Fukushima complex, 150 miles north of Tokyo, for the first time raised the possibility that the key containment structure of the unit, which protects the reactor vessel and keeps dangerous radioactive materials from leaking out, had been damaged.

WSJ: Japan's Nuclear Crisis Escalates

In 1986, the fourth reactor at the Chernobyl nuclear complex in the Ukraine exploded and caught fire, spreading a radioactive cloud across Europe in the world's worst nuclear disaster.

CNN: Saturday,

One of them, Rear Admiral Simon Lister, is in charge of this complex programme, and as he took me round the cramped corridors, past the nuclear reactor and down into the sweaty machine rooms, he acknowledged this was a prototype and there was always going to be some "teething" issues.

BBC: HMS Astute recovers from shaky start