Work began in earnest on April 19 to transfer some 25,000 tons of highly radioactive water, found in a trench and in the basement of the turbine building at the Fukushima No. 1 nuclear power plant's No. 2 reactor, to a waste treatment facility on the premises.
Work began in earnest on April 19 to transfer some 25,000 tons of highly radioactive water, found in a trench and in the basement of the turbine building at the Fukushima No. 1 nuclear power plant's No. 2 reactor, to a waste treatment facility on the premises.
The contaminated water in the basement of the turbine building, linked to the trench, is hampering efforts to restore the power supply to cool down the reactor. The radioactive water in the trench at the No. 2 reactor could also flow out in 10 to 20 days unless removed.
On April 19, about 100 tons of contaminated water from the trench were transferred by the first night, with Tokyo Electric Power Co. planning to move about 10,000 tons in all in the first phase into the waste treatment facility. The first one-quarter will be removed under close supervision using a single pump, and the number of pumps will later be increased to three. The pumping out of the trench is expected to be completed around May 14.
Workers are taking the utmost care with the contaminated water, which contains radiation of more than 1,000 millisieverts per hour at the surface, because leakage could contaminate the surroundings and expose them to high levels of radiation.
TEPCO installed an approximately 800-meter-long hose to the central waste treatment facility for the transfer operation. For most of its length, the hose runs through the interior of turbine buildings for the No. 2 through No. 4 reactors, to prevent outdoor workers from being exposed to radiation and also to contain potential leakage within building interiors. Parts of the hose that run outside were either fixed on both sides with steel parts or installed in gutters to avoid being dislodged by aftershocks.
Hose junctures were also tied with metal fittings and wires and wrapped in plastic bags made of material that is radioactive absorbent to reduce the chance of leakage.
To reduce the risk of transferred radioactive water leaking out of the waste treatment facility, cracks and openings in the facility were repaired and sealed, and the quake resistance of the building was reconfirmed. The level of contaminated water in the treatment facility will also be set at about 50 centimeters below that of groundwater for safety.
The waste treatment facility has a full capacity of 30,000 tons, but the decision to use only part of its full capacity below groundwater level has made it impossible to transfer the 25,000 tons of contaminated water all at once.
TEPCO says that the transferred water will undergo purification to lessen its radioactivity level, and will then be stored in other tanks or be reused to cool down the reactor core. For purification, installation of a water treatment system that removes radioactive materials by settling them out or using zeolite to absorb cesium, is being considered.
In the meantime, 100 tons of what appears to be groundwater that leaked into the basement of the No. 6 reactor turbine building has been transferred to a condenser, TEPCO sources said April 19.
Anne Lauvergeon, chief executive officer of Areva SA, a major French nuclear technology provider, told a press conference in Tokyo on April 19 that she had a timeline of late May in mind to start the purification of contaminated water at the Fukushima No. 1 nuclear plant at TEPCO's request.
Areva will use its technology to decontaminate 50 tons of toxic water per hour. Lauvergeon explained that radioactive materials could be removed by mixing chemicals into contaminated water and that radioactive concentrations could be lessened 1,000 to 10,000 times.
(This article was written by Takashi Sugimoto and Eisuke Sasaki.)