A contamination map revealing radiation levels at about 150 places in the Fukushima No. 1 power plant was released Saturday by troubled Tokyo Electric Power Co.
The beleaguered utility, known as Tepco, updates the data periodically to help its workers navigate radiation hazards at the crippled nuclear plant in Fukushima Prefecture. The power plant lost its cooling systems when it was hit by the mega-quake and tsunami on March 11.
The updated maps and data on areas near the four crisis-hit reactors are also sent to the Economy, Trade and Industry Ministry and the Nuclear and Industrial Safety Agency and posted at its crisis center in the prefecture.
One finding acquired from the map’s data as of Wednesday night is that a piece of concrete debris near the No. 3 reactor was emitting a nearly lethal 900 millisieverts per hour of radiation.
Many of the locations, including a pipe being used to remove highly radioactive water from a reactor and rubble scattered by several hydrogen explosions on the premises, gave off radiation readings of about 100 millisieverts per hour.
Another piece of debris next to the No. 3 reactor is giving off 300 millisieverts per hour, while the surface of a pipe sending highly toxic water to a nuclear waste disposal facility is radiating 75 to 86 millisieverts an hour, the map showed Another pipe near the facility was giving off radiation readings as high as 160 millisieverts, it said
The legal limit on the amount of radiation a worker can be exposed to has been raised to 250 millisieverts for the crisis. It takes less than 17 minutes to hit that limit when working in an environment being exposed to 900 millisieverts per hour.
Tepco has started using remotely controlled equipment to remove debris at some of the reactors and is expected to take six months to complete the task. At the same time, it is searching for secure facilities in which to store radioactive runoff from its emergency reactor-cooling operations.