20 Août 2014
August 20, 2014
Tokyo Electric Power Co. (TEPCO) has revealed a plan to review its ambitious scheme to create an ice wall in the entire section between a turbine building and an underground trench at the crippled Fukushima No. 1 Nuclear Power Plant to block radioactive water from flowing from the reactor building into the underground tunnel.
TEPCO, the operator of the Fukushima nuclear power station, had planned to remove contaminated water from the trench near the No. 2 reactor building after creating an ice wall to stop the inflow of contaminated water. But because the utility failed to completely freeze the water in the section between the turbine building and the trench, it will take an additional step of filling chinks in the ice with filler material.
A total of 11,000 metric tons of contaminated water has accumulated in the trenches built near the No. 2 and No. 3 reactors facing the Pacific Ocean, and the utility is to first start work to remove contaminated water from the trench for the No. 2 reactor. If the utility fails to remove contaminated water from the underground tunnels, it will not be able to proceed with a project to freeze soil and create a wall of ice around the four reactor buildings. Therefore, whether the additional measure is effective or not is likely to vastly affect measures to reduce radiation levels of water at the wrecked nuclear complex.
TEPCO has been trying to create the frozen wall since April by installing underground pipes to circulate coolant, but the work has not been done as originally planned. The company started to add a total of about 415 tons of ice and dry ice at the end of July, but it could freeze only 92 percent of the water in the section between the turbine building and the trench. Therefore, TEPCO judged that there were chinks at four locations in the frozen section at least. TEPCO officials say the speed of the water flow through the chinks increased, making it difficult to freeze water there.
At a meeting of experts from the Nuclear Regulation Authority (NRA) on Aug. 19, TEPCO showed a plan to seal chinks with filler material such as special cement. NRA officials are concerned about whether TEPCO's plan will have an adverse effect on the entire "ice wall" project. TEPCO will proceed with its original plan to install more refrigeration equipment. The utility will then decide whether to go ahead with the additional step after confirming the status of the operations again as soon as early September or mid-September.
NRA Commissioner Toyoshi Fuketa said, "The situation needs to be firmly confirmed because it could affect subsequent measures."
August 20, 2014(Mainichi Japan)