An explosion that took place on Saturday made a wall of the building housing one of the reactors collapse, which might make one or more nuclear reactors melt after the failure of the cooling system.
According to government spokesman Yukio Edano, the metal sarcophagus housing the reactor was not affected by the explosion. He said that radiation levels around the plant have not increased after the blast, but instead are being reduced, as is the pressure inside the reactor.
The evacuation zone around the plant was extended to an area of 20 km and people are asked to leave the zone quickly. Some 51,000 people have been evacuated earlier.
According to the Japanese Meteorological Agency, the wind in the region is weak and facing north-east towards the sea.
The TEPCO (Tokyo Electric Power) company, which operates the station, reported that four employees were injured and hospitalized with fractures and bruises.
Images on Japanese television showed the walls of a building collapsing, exposing the steel structure still standing. Small clouds of white smoke poured out of the plant.
Robert Alvarez, a senior scholar at the Institute for Policy Studies in Washington, said “This is a situation that has the potential for a nuclear catastrophe. It’s basically a race against time, because what has happened is that plant operators have not been able to cool down the core of at least two reactors.”
The problems began in the No1 reactor at the plant located in the town of Onahama (270km northeast of Tokyo), after the 8.9 magnitude earthquake and tsunami that took place Friday. The power supply was cut off causing failure of the cooling system.
The pressure was then accumulated in the reactor, reaching twice the normal level. The Japanese Nuclear Safety Agency had informed the press that “radioactive fumes” were released to lower the pressure. An official of the agency, Ryohei Shiomi, then warned that a meltdown was possible.
Even before Saturday’s explosion, the No1 reactor had already discharged radioactivity. Radioactivity levels eight times higher than normal had been measured outside the plant and a thousand times higher than normal within the central room of reactor No. 1. According Ryohei Shiomi, every hour, the plant emitted a level of radiation that a person normally absorbs in a year.
After the earthquake that struck the north-eastern coast of Japan on Friday, causing a tsunami, the government declared a state of emergency for five nuclear reactors at two plants that have lost their cooling capabilities.