A series of accidents occurred Wednesday at the disaster-hit Fukushima No. 1 nuclear power plant, 230 km north of Tokyo, with the radiation level at the site briefly surging in the morning.
The radiation level reached 10 millisievert per hour at the plant’s main gate at 10:40 a.m. (0140 GMT), forcing 730 workers at the plant to temporarily evacuate, the government’s Nuclear and Industrial Safety Agency said, adding that it was probably due to radioactive substances emitted from the damaged No. 2 reactor in the plant.
However, the radiation level fell to 6.4 millisievert at 10:45 a.m. and to 1.9 millisievert at 11:20 a.m. and the workers resumed emergency efforts on preventing a fuel rod meltdown by cooling the No. 1 nuclear power plant’s No. 1, No. 2 and No. 3 reactors in the plant.
There are six reactors in the Fukushima No.1 nuclear power plant, all designed by US giant General Electric.
Radiation above 250 millisievert is said to cause health problems such as a temporary reduction in the number of white blood cells. A single dose of 1,000 millisievert causes temporary radiation sickness such as nausea and vomiting, and a dose of 5,000 millisievert would kill about half those receiving it within a month.
Meanwhile, a fire broke out again in the troubled No. 4 reactor, which was already posing the risk of leaks of high-level radioactive materials, but flames were no longer visible about 30 minutes later, the power station’s operator Tokyo Electric Power Co. (TEPCO) told a press conference.
According to TEPCO, a worker spotted flames at around 5:45 a.m. near the northwestern corner of the building that houses the No. 4 reactor. It was the second time a fire has broken out at the No.4 reactor.
Separately, white smoke was observed from the No. 3 reactor around 8:30 a.m.
“There is a possibility that the No. 3 reactor’s containment vessel is damaged,” Chief Cabinet Secretary Yukio Edano told a press conference, suggesting that radioactive vapor may be spreading outside.
But, the top government spokesman said the government has no immediate plans to expand the evacuation area of within 20 km from the plant.
Cooling function of the plant was damaged by Friday’s magnitude 9.0 earthquake and tsunami, forcing the operator to pour seawater into reactors and let out radioactive air into the atmosphere to bring down heat and pressure.