Workers install temporary pressure indicators for the Unit 1 reactor at the Fukushima Daiichi Nuclear Power Station, 3 June 2011.

TOKYO, June 4 (Kyodo) – The operator of the Fukushima Daiichi nuclear power plant said Saturday it has detected radiation of up to 4,000 millisieverts per hour at the building housing the troubled No. 1 reactor. The radiation reading, taken as Tokyo Electric Power Co. sent a robot into the No. 1 reactor building on Friday, is believed to be the largest detected in the air at the plant. TEPCO said it took the reading near the floor at the southeast corner of the building. A pipe runs under the floor, but TEPCO said it found no damage to the pipe. The pressure suppression containment vessel is located under the building and highly radioactive contaminated water generated by the reactor is believed to be accumulated there, TEPCO said, adding, the steam is probably coming from the water. TEPCO said its workers have no plan to work around the area but it will carefully watch developments in the area. On Friday, nine workers entered the building to attach a pressure indicator to the pressure vessel, with the workers exposed to up to about 4 millisieverts of radiation, according to TEPCO. The Fukushima Daiichi plant was crippled by the massive March 11 earthquake and tsunami.

Fukushima’s No. 1 reactor building radiation up to 4,000 millisieverts