Japan has 55 nuclear reactors with an installed capacity of about 50 GW and which are responsible for about a third of Japan’s electric power generation.  In Japan, as in the Czech Republic, nuclear power is considered to be an essential, strategic source of electric power.

The recent earthquake, the largest ever recorded in Japan, has had limited impact on Japan’s nuclear power plants.  The International Atomic Energy Agency (IAEA) has reported that four nuclear power plants Fukushima Daiichi, Oganawa, Fukushima Daini and Tokai Daini closest to the earthquake epicentre near Sendai have shut down as they are designed to do in an emergency.

Fukushima Daiichi

A cooling function at Tokyo Electric Power’s (TEPCO) Fukushima Daiichi nuclear plant failed.  At last report water levels in a reactor were continuing to fall, and some 2,000 residents within a 3 km radius of Fukushima Daiichi have been asked to evacuate the area.  Reportedly the US offered to provide additional coolant, but apparently it was not needed.

“Japan’s nuclear safety agency said pressure inside one of six boiling water reactors at the Fukushima Daiichi plant had risen to 1.5 times the level considered normal. Hours after the evacuation order, the government announced that the plant in northeastern Japan will release slightly radioactive vapor from the unit to lower the pressure in an effort to protect it from a possible meltdown.

“Chief Cabinet Secretary Yukio Edano said the amount of radioactive element in the vapor would be “very small” and would not affect the environment or human health. “With evacuation in place and the ocean-bound wind, we can ensure the safety,” he said at a televised news conference early Saturday.

After the quake triggered a power outage, a backup generator also failed and the cooling system was unable to supply water to cool the 460-megawatt No. 1 reactor, though at least one backup cooling system was being used. The reactor core remains hot even after a shutdown.”  Source

The company is bringing in mobile generators to restore the power supply, but pressure inside the containment of Unit 1 continued to increase.

According to the IAEA Japanese authorities have informed the IAEA’s Incident and Emergency Centre (IEC) that officials are working to restore power to the cooling systems of the Unit 2 reactor at the Fukushima Daiichi nuclear power plant.  Mobile electricity supplies have arrived at the site.

Japanese officials have also reported that pressure is increasing inside the Unit 1 reactor’s containment, and the officials have decided to vent the containment to lower the pressure.  The controlled release will be filtered to retain radiation within the containment. 

Saturday morning Tepco said has said it has lost the ability to control pressure at the No. 1 and 2 reactors.

Onagawa

A fire was reported at the Onagawa nuclear power plant, but it has since been extinguished according to the IAEA.

There has been no release of radiation at any of the plants.