Tokyo Electric Power Co. said Thursday about 100 tons of highly radioactive water overflowed and spilled from a tank at the Fukushima No. 1 plant.
The utility said it believes that the escaped water did not reach the ocean, as there was no drainage ditch that connects to the sea near the leaked area around the tank, which is in an area called H6.
At the crippled Fukushima No. 1 site, Tepco removes cesium from tainted water that flows into the basements of the crippled reactor turbine buildings daily. The water is put into storage tanks.
Tepco said the water was supposed to go to tanks placed at the E area, which is west of H6, but it went to the tank that was already storing water at H6 and overflowed.
According to the utility, two of the three valves of the pipe that control the water flow to the H6 area were open. Yet even if only the third valve was closed, the water should not have flowed, Tepco said, adding that the valve may be broken. But Tepco also admitted the three valves should have all been closed and is still not sure why two were left open.
While cesium was removed from the leaked water, it contains other radioactive materials, like strontium. Tepco said the level of those that emit beta rays was 230 million becquerels per liter.
The leaked water was among the most severely contaminated that Tepco has reported in the aftermath of the March 2011 disaster at the Fukushima Daiichi plant, when damage caused by an earthquake and a tsunami led to meltdowns in three of the plant’s reactors. Each liter of the water contained, on average, 230 million becquerels of particles giving off beta radiation, the company said. About half of the particles were likely to be strontium 90, which is readily taken up by the human body in the same way that calcium is, and can cause bone cancer and leukemia.
That means the water was about 3.8 million times as contaminated with strontium 90 as the maximum allowed under Japan’s safety standards for drinking water. It also showed levels much more radioactive than a worrisome groundwater reading that Tepco announced earlier this month. That reading — five million becquerels of strontium 90 per liter — which was detected at a location closer to the ocean than the latest spill, prompted criticism of Tepco because the company waited five months to report it publicly.
Critics have assailed the company since the accident, saying that it has been slow to acknowledge problems at the stricken plant and that it has disclosed too little information about the conditions inside. Even so, the government has left the company largely in charge of the cleanup work there.
Tepco has struggled to deal with the hundreds of tons of groundwater seeping each day into the plant’s damaged reactor buildings, where it is contaminated by the melted nuclear reactor cores. To keep the radioactive water from running into the Pacific, the company must pump it out of the reactor buildings and store it in rows of huge tanks it has erected on the plant’s grounds.
So far, Tepco said, about 340,000 tons of water have accumulated in the tanks, enough to fill more than 135 Olympic-size swimming pools.
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