Meltdown Caused Nuke Plant Explosion: Safety Bodyhttp://e.nikkei.com/e/fr/tnks/Nni20110312D12JFF03.htmTOKYO (Nikkei)--The Nuclear and Industrial Safety Agency (NISA) said Saturday afternoon the explosion at the f*kushima No. 1 nuclear plant could only have been caused by a meltdown of the reactor core.
The same day, Tokyo Electric Power Co. (9501), which runs the plant, began to flood the damaged reactor with seawater to cool it down, resorting to measures that could rust the reactor and force the utility to scrap it.
Cesium and iodine, by-products of nuclear fission, were detected around the plant, which would make the explosion the worst accident in the roughly 50-year history of Japanese nuclear power generation.
An explosion was heard near the plant's No. 1 reactor about 3:30 p.m. and plumes of white smoke went up 10 minutes later. The ceiling of the building housing the reactor collapsed, according to information obtained by f*kushima prefectural authorities.
At a news conference Saturday night, Chief Cabinet Secretary Yukio Edano discounted the possibility of a significant leak of radioactive material from the accident. "The walls of the building containing the reactor were destroyed, meaning that the metal container encasing the reactor did not explode," Edano said.
The amount of radiation detected inside the plant after 4:00 p.m. slightly exceeded the dose people can safely receive in a year, according to information obtained by the f*kushima prefectural government.
The No. 1 reactor shut down automatically soon after a massive earthquake hit the area Friday, but its emergency core cooling system failed to cool the reactor's core sufficiently.
NISA is affiliated with the Ministry of Economy, Trade and Industry.
This whole description is very reminiscent of THREE MILE ISLAND< HARRISBURG< PENNSYLVANIA in 1979 I think it was. Same playing it down. There, as I described in my earliest post today, a partial Melt-down occured leaving a dangerous Pile of Fissile Uranium that had melted down out of thier ZIRCONIUM alloy fuel-rod assemblies, at the bottom of the reactor 'sump' underneath the containment 'pressure vessel', or inside it. There are pressure walls, double containment and stuff ... I forget.
Anyway, there is a Pyramid affair at the bottom of these sumps to prevent meltdown materials from accumulating into criticality masses. The explosions were big enough to lift the lid off the floor in the reactor room like at Chernobyl, reports say, so yes, I'd still summarise a pretty big, but partial meltdown. But by the way the Jap Corps are playing it down, like the NRC did at Harrisburg, the damage was significant and they won't release the full story for a while if they think they can get away with it ....
Now they are pumping Sea-Water in, which would have taken a lot of calculations as to rates, pressures, and risks of steam explosion 'excursions' they will have it safe, but with voluminous quantities of heavily contaminated sea-water.
But better in the water than in the atmosphere.
I'd say the danger is now over for that one, unless another quake hits...
