Tokyo Electric Power Co. plans to move the radioactive water from one of the reactor buildings at the Fukushima Daiichi nuclear power plant and treat it on site, the company said.
In a statement, TEPCO outlined a plan to take about 10,000 cubic meters of contaminated water from the turbine building of reactor unit 2, and move it to a treatment plant that will be built on site. The water treatment equipment will be supplied by AREVA, the French nuclear power plant company.
The water in the turbine building is a combination of the water ordinarily present in the reactor and the tons of water used to cool the reactor down after a tsunami knocked out the generators that powered the pumps. TEPCO has continued to pump water in to the reactor, at a rate of about 168 metric tons, or 44,000 gallons per day.
Even with AREVA's assistance, implementing the plan will take about two months, TEPCO said.
Contamination of the water, according to TEPCO, is mostly iodine-131 and cesium-137. Iodine-131 has a half-life of about eight days and the cesium's is about 30 years. Iodine and cesium are particularly dangerous because even though iodine decays quickly, it concentrates in the thyroid. Cesium dissolves easily in water and is thus absorbed by several different tissues.
Contamination levels are at 3 billion becquerels of cesium per liter of water and 13 billion becquerels of iodine per liter. The legal limits for radioactive cesium in Japan are 200 bequerels per liter, while for iodine it is 100 becquerels per liter.
Radiation exposure inside the plant for workers is expected to be high as they try to extract the water. TEPCO said radiation exposure will likely be about 0.011 millisieverts per hour surrounding the building where the water is stored. Nuclear plant workers at Fukushima are limited to doses of about 250 millisieverts per year. It would take two years to reach that limit at the exposure level TEPCO is planning for -- if one is outside the building. The radiation dosage from working around the water itself is expected to be much higher than that.
Robots sent in to two other damaged reactors buildings, No. 1 and No. 3, found levels of 49 and 57 millisieverts per hour, respectively. The levels in reactor No. 1 are enough to kill a person after about eight days of exposure. Radiation dosages are cumulative, so the amount of time a workers spends in the area has to be limited.