Explosion in Japan's Nuclear Plan

An explosion and feared meltdown at one of Japan's nuclear plants on 12 March exposed the scale of the disaster facing the country after a massive quake and tsunami left 1,000 feared dead. The cause of the explosion remains unknown though several employees were injured in the explosion. Damage to the nuclear power plant came as a result of an 8.9 magnitude earthquake, the strongest ever recorded in the country that rocked the nation on 11 March. However, it is said that the reactor cooling systems failed at two plants after the earthquake hit, unleashing a terrifying 10-metre (33-foot) wave that tore through coastal towns and cities, destroying all in its path.

Declaration of Atomic Emergency
After declaring an atomic emergency, the government said that thousands of people living within 20 km (12 miles) of the Fukushima No 1 plant should leave, widening the evacuation zone from 10 km. Nuclear authorities had earlier warned that the Fukushima No 1 plant, located about 250 km (160 miles) northeast of Tokyo, an urban area of 30 million people, 'may be experiencing a nuclear meltdown.' The plant's cooling system was damaged in the quake that hit on 11 March, leaving the government scrambling to fix the problem and evacuate more than 45,000 residents within a 10-km radius.

However, serious damage to the stricken reactor's container, which shields the external environment from the effects of nuclear fission, was unlikely. Operator Tokyo Electric Power confirmed the explosion at the plant 250-km northeast of Tokyo, and that the roof of the reactor building had collapsed, saying this had happened during an aftershock from the quake.

Contingency Measures
The government was taking contingency measures and collecting iodine, which can be used against radiation sickness. Nearby residents have warned to stay indoors, turn off air-conditioners and not drink tap water. The people going outside were told to avoid exposing their skin and to cover their faces with masks or wet towels.

The radiation detected after the explosion was about twice the level at which companies are required to notify the government. The hourly radiation matched the allowable annual dose. When reactors shut down, cooling systems must kick in to bring down the very high temperatures. These systems are powered by either the external power grid, backup generators or batteries.

The fear is that, when this fails, fuel rods that cannot be cooled are exposed to the outside air and release radioactivity. In a meltdown, or severe nuclear power plant failure, the reactor core is unable to properly cool, leading nuclear fuel assemblies to overheat and melt, potentially releasing radioactive materials into the environment.

Japan -- located on the 'Pacific Ring of Fire,' where several continental plates meet and create a string of volcanoes and seismic hot spots -- records 20 percent of the world's major earthquakes. Japan draws about 30 percent of its power from about 50 nuclear plants.