Japan’s Nuclear and Industrial Safety Agency said Saturday they believe there has been no serious damage to the container of the troubled No. 1 reactor of the Fukushima No. 1 nuclear power plant, 240 km north of Tokyo, despite a large explosion at the plant, Kyodo News Agency reported.
The officials made the comment after examining the latest radiation data monitored around the facility after an explosion at 3:36 (0636 GMT), it said.
The safety agency earlier said a person at the Fukushima No. 1 nuclear station reported that an explosion was heard and smoke was seen near one of the reactors after a large tremor, according to NHK.
The operator, Tokyo Electric Power Co., said four people were injured.
TV footage shows the outer wall of the building that houses the reactor has disappeared.
The power company said that the ceiling of the building collapsed after an explosion, adding that pressure inside the container of the reactor had been rising after the reactor’s cooling system broke down due to power failure, and radioactive substances have been detected near the reactor.
The hourly radiation from the Fukushima plant reached 1,015 microsievert in its premises, equivalent to the permissible amount of radiation an ordinary person receives in one year.
The plant’s cooling system was damaged after a magnitude 8.8 earthquake hit northeastern and eastern Japan on Friday.
At an urgent press conference in Tokyo, Chief Cabinet Secretary Yukio Edano urged people to stay calm and said the radiation level has been monitored carefully.
The top government spokesman also said the government instructed residents living within a 10-kilometer radius of the No. 1 and No. 2 nuclear plants to evacuate, but it later expanded the evacuation scope of the No. 1 and No. 2 plant to a 20-kilometer radius.
The total number of evacuees near the nuclear plant plus around 210,000 people evacuated in the region at the time when strong aftershocks continued, reached 300,000, according to Kyodo.