via mainichi.jp / November 23, 2014 / Tokyo Electric Power Co. (TEPCO) has decided to bury a trench at the crippled Fukushima No. 1 Nuclear Power Plant using concrete after an effort to completely stop the flow of radiation contaminated water failed, it has been learned.
TEPCO reported its plan to the Nuclear Regulation Authority (NRA) on Nov. 21, and the NRA approved it, saying that the plan can at least reduce the amount of contaminated water remaining in the trench.
Around 5,000 metric tons of contaminated water is standing in the ocean-side trench of the Fukushima plant’s No. 2 reactor. TEPCO initially had planned to stop the flow by freezing the contaminated water at the point where the reactor building and the trench meet, after which it hoped to remove the water from the trench. However, the plan failed as the water was insufficiently frozen, and the company gave up on completely removing the contaminated water.
According to the new plan, TEPCO will begin pouring concrete that can be used under water at the end of November while draining contaminated water inside the trench. It will see if the flow of the water stops after burying the deepest part of the underground tunnel.
It is concerned that this process may leave some contaminated water in the concrete, but TEPCO has estimated that only 1-3 percent of the water will remain in the material.
The length of the underground tunnel is about 60 meters. A TEPCO representative said that the company has never buried a tunnel that long, but it will carry out the plan with great care.
Meanwhile, there are some 6,000 tons of contaminated water in the seaside trench of the No. 3 reactor. TEPCO plans to bury it with concrete like the No. 2 reactor trench by January next year, and then freeze soil around the basement areas of the Nos. 1 to 4 reactor buildings as part of efforts to prevent ground water from flowing onto the premises of these structures.