6/4/2011 | Tepco detects 4,000 millisieverts per hour in Fukushima : reactor building No. 1 plant's air radiation highest measured so far

Source: AP via The Japan Times
Date: Saturday, June 4, 2011

Kyodo, AP

Tepco said Saturday it has detected radiation of up to 4,000 millisieverts per hour at the building housing the No. 1 reactor at the Fukushima No. 1 nuclear plant.

The radiation reading, which was taken when 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 so far.

On Friday, Tepco found that steam was spewing from the reactor floor. Nationally televised news Saturday showed blurry video of steady smoke curling up from an opening in the floor.

Tepco said it took the reading near the floor at the southeast corner of the building, under which runs a pipe emitting steam. No damage to the pipe was found, the utility said.

The pressure suppression containment vessel is located under the building and highly radioactive contaminated water generated by the reactor is believed to have accumulated there, Tepco said, adding the steam is probably coming from the water.

The utility said its workers have no plan to work near that area, but it will carefully monitor developments.

Meanwhile, tanks for storing radioactive water were on their way Saturday to the plant.

Tepco has said radioactive water could start overflowing from temporary storage areas on June 20, or possibly sooner if there is heavy rainfall.

Two of the 370 tanks were due to arrive Saturday from a manufacturer in nearby Tochigi Prefecture, Tepco said. Two hundred of them can store 100 tons, and 170 can store 120 tons.

The tanks will continue arriving through August and will store a total of 40,000 tons of radioactive water, according to Tepco.

Workers have been fighting to get the plant under control since the March 11 tsunami knocked out power, destroyed backup generators and halted the crucial cooling systems for the reactors, causing the world's worst nuclear disaster since Chernobyl in 1986. Several explosions have scattered radioactive debris around the plant, and reactors are spewing radiation into the air.

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.

Nuclear fuel rods are believed to have melted almost completely and sunk to the bottom of three reactors' containers, although falling short of a complete meltdown, in which case the fuel would have melted entirely through the container bottoms.

Tepco has promised to bring the plant under control by January, but doubts are growing whether this projection is overly optimistic. The plan calls for a reprocessing system for the radioactive water by June 15, with hopes of reusing the water as coolant in the reactors.