Concrete No.2 and No.3 seaside trenches

November 22, 2014

After failures, TEPCO to use special cement to prevent contaminated water leaks

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201411220029

THE ASAHI SHIMBUN

The operator of the crippled Fukushima nuclear plant plans to fill in trenches on the coastline in yet another attempt to prevent highly contaminated water from pouring into the sea.

Under the plan, approved by the Nuclear Regulation Authority on Nov. 21, Tokyo Electric Power Co. will inject a special cement mixture into the seaside trenches of the No. 2 and No. 3 reactors while pumping up radioactive water accumulating in them.

The special mixture does not absorb water so it can spread more easily along the bottom of the trenches, displacing the tainted water.

The new method will allow radioactive materials to remain in the surrounding soil, but TEPCO decided to employ the technique because it puts high priority on preventing massive amounts of highly contaminated water from leaking into the ocean.

This spring, TEPCO tried to stop the water influx at the trench for the No. 2 reactor by freezing the junction of the turbine building and the trench, but the operation was tough-going.

The company then attempted to stop the water inflow with a cement mixture, but was unable to do so completely.

(This article was written by Tsuyoshi Nagano and Hiromi Kumai.)

_TEPCO to bury Fukushima plant trench with concrete to control radioactive water

http://mainichi.jp/english/english/newsselect/news/20141122p2a00m0na015000c.html

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.

November 22, 2014(Mainichi Japan)

Tepco fails to halt toxic water inflow at Fukushima No. 1 trenches

Kyodo

http://www.japantimes.co.jp/news/2014/11/22/national/tepco-fails-to-halt-toxic-water-inflow-at-fukushima-no-1-trenches/#.VHCmDsl5B1s

Tokyo Electric Power Co. admitted failure Friday in its bid to halt the flow of toxic water into underground tunnels alongside the ocean at the Fukushima No. 1 plant and said that it will try using a specially developed cement instead.

,000 tons of highly radioactive water have accumulated in the tunnels, trenches dug to house pipes and cables that are connected to the reactor 2 and 3 turbine buildings of the wrecked facility, according to Tepco.

There are fears that this toxic buildup, which is being caused by the jury-rigged cooling system and groundwater seepage in the reactor basements, could pour into the Pacific, which is already being polluted by other radioactive leaks. Groundwater is entering the complex at 400 tons a day.

Extracting the toxic water is a critical step in Tepco’s plan to build a huge underground ice wall around the four destroyed reactors to keep groundwater out.

Initially, Tepco sought to freeze the water in a section of tunnel connected to the No. 2 reactor building. This was intended to stop the inflow and allow the accumulated water to be pumped out. The utility said it took additional measures that also failed.

On Friday, Tepco proposed a new technique for the tunnels: injection of a cement filler especially developed for the task while pumping out as much of the accumulated water as possible.

Under the new method, however, it would be difficult to drain all of this water and some of it would be left behind, endangering plant workers, Tepco acknowledged.

Nevertheless, a Nuclear Regulation Authority panel of experts green-lighted the new strategy at a recent meeting. Some of the experts argued that Tepco should stick to the original plan and draw out all of the water. Others said giving up on it may hamper the construction of the ice wall.