Increase in Radiation from Japanese Nuclear Plant

The explosion that shook Unit 2 of the accident-stricken Fukushima Daiichi nuclear power plant in Japan might, unlike the explosions at Units 1 and 3, have damaged the reactor containment. The reactor vessel itself is unharmed, but the bottom of the concrete containment building surrounding the reactor may be damaged, increasing the risk of radioactivity being released.

The storage pool for spent nuclear fuel at Unit 4, which was already shut down at the time of the accident, is also reported to have been on fire. The fire, likely caused by yet another hydrogen explosion, has now been put out, but radioactivity was released into the atmosphere.

Japanese authorities report that radiation levels are now high enough to damage human health and doses of up to 400 millisievert per hour have been reported at the accident site. The highest allowed dose for radiation workers is 50 millisievert per year.