Japan : Nuclear scare grows with an orange flash and a violent blast

Via The Guardian :

" Health concerns as hydrogen explosion at Fukushima 1 nuclear power station injures 11 and destroys containment building

Japanese engineers fought to save three reactors from meltdown at the stricken Fukushima 1 power station as they battled a series of frustrating setbacks that saw workers struggle to pump seawater into the reactors in a desperate attempt to cool the overheating nuclear cores and make them safe.

The day began with an orange flash and a violent blast that destroyed most of the containment building around reactor 3, causing debris to fall back inside and on to the structure housing the reactor. The blast was caused by a build up of hydrogen that was produced when superheated steam in the core reacted with zirconium alloy cladding that surrounds the reactor's fuel rods.

Tepco, the company that operates the power station, said 11 people were injured in the accident, one seriously. A similar explosion blew the top off the reactor 1 building on Saturday morning.

Early this morning there was another explosion, this time at reactor 2. Early reports suggested that there might have been some damage to the containment vessel after pressure dropped, but there was no immediate word of any damage to the reactor itself, the country's nuclear safety agency said.

Despite earlier assertions from Tepco that the steel containment vessels surrounding the reactors were undamaged in either of the two earlier explosions, Naoki Kumagai, an official at Japan's Nuclear and Industrial Safety Agency (Nisa), said: "It's impossible to say whether there has or has not been damage."