Icewall challenges

April 30, 2015

Ice wall project faces challenges

http://www3.nhk.or.jp/nhkworld/english/news/20150430_14.html

Apr. 30, 2015 - Updated 03:05 UTC+2

Underground ice-wall technology to block groundwater has been used for subway and tunnel construction.

But building a 1.5 kilometer ice wall of uniform thickness is unprecedented.

TEPCO will drive about 1,700 pipes into the ground, 30 meters deep, around the reactor buildings. The pipes will be filled with liquid frozen to minus 30 degrees Celsius.

Pipe installation is nearly complete on the inland side of the reactor buildings, where the trials will be held.
But work on the seaside has been hampered by the delay in removing radioactive wastewater from underground utility tunnels.
At present, 300 tons of groundwater flows into the reactor building basement each day, increasing the pool of contaminated wastewater.

The government and TEPCO say the ice wall and other measures could cut the inflow to one-tenth.

But if the level of groundwater falls below that of contaminated wastewater in the reactor buildings, the wastewater could leak out and spread the contamination.

TEPCO plans to control the level of groundwater by adding water through wells that will be dug around the reactor buildings.

A system to pump up groundwater for purification and release into the ocean remains on hold due to local opposition.

TEPCO to begin freezing soil on trial basis

http://www3.nhk.or.jp/nhkworld/english/news/20150430_12.html

Apr. 30, 2015 - Updated 03:00 UTC+2

The operator of the damaged Fukushima Daiichi nuclear power plant will build an underground wall of ice to stem a buildup of contaminated water in reactor buildings.

Tokyo Electric Power Company plans to freeze soil around the No.1 to No.4 reactor buildings to create the 1.5-kilometer-long ice wall. The structure is intended to keep groundwater from seeping into the reactor buildings.

The utility began work on the project last June.
Workers drove pipes into the ground for containing the liquid to be frozen.

On Tuesday, Japan's Nuclear Regulation Authority approved TEPCO's plan to start trials to freeze the liquid at 18 locations.

The government and TEPCO decided to begin the work at noon on Thursday.

If the ice forms as planned, TEPCO will start freezing the liquid at other locations, pending government approval, to eventually create the wall.

The project is unprecedented. It's unclear how long it will take to complete the structure due to a delay in removing radioactive wastewater from underground utility tunnels around the reactor buildings.