How useful is the icewall?

4 Mars 2018

March 2, 2018

TEPCO defends Fukushima ‘ice wall,’ but it is still too porous

http://www.asahi.com/ajw/articles/AJ201803020042.html

THE ASAHI SHIMBUN

The “frozen soil wall” erected around the crippled reactor buildings at the Fukushima No. 1 nuclear power plant at huge taxpayer expense appears limited in keeping groundwater from flowing in.

Tokyo Electric Power Co., which operates the plant, said March 1 that 95 tons of radioactive water has been reduced a day on average between December and early February because of the underground barrier.

“Contaminated groundwater was cut in half due to the wall,” a TEPCO official said.

TEPCO estimated that the volume of polluted groundwater would have amounted to about 189 tons if the ice wall had not been in place during that period.

The utility also said the amount of polluted groundwater was reduced by about 400 tons a day now due to combined measures, such as the wall and wells pumping up water, compared with before such measures were taken.

But Toyoshi Fuketa, chairman of the Nuclear Regulation Authority, has insisted that the wells, not the wall, are the “key” to controlling the groundwater, voicing skepticism about the role of the ice wall.

The utility is proceeding with work to reinforce the wells.

The 34.5 billion yen ($322 million) frozen soil wall project began in 2014 to lay out the 1,500-meter-long underground wall around the No. 1-4 reactor buildings.

A large number of pipes were inserted to a depth of 30 meters to circulate liquid with a temperature of minus 30 degrees through them to freeze the surrounding soil.

It was designed to prevent groundwater from flowing into the plant and mixing with highly radioactive water in the basements of the buildings.

TEPCO’s recent assessment of the effectiveness of the frozen soil wall came after temperatures around the structure dropped to below zero following work that began last August to freeze the remaining final section of the wall.

But experts pointed out that the utility’s assessment is based on figures only when there was little rain.

The water volume rose to 1,000 tons or so a day in late October when two typhoons struck the area.

TEPCO believes that the surge at that time is largely attributable to the downpours from the typhoons.

Heavy rain accumulated in the basement after flowing down holes in the ceilings caused by hydrogen explosions during the 2011 triple meltdown.

It costs more than 1 billion yen a year in electricity fees to keep the wall frozen.

The company plans to remove all the groundwater from the buildings by 2020 so that it can begin work to decontaminate the facilities later.

(This article was written by Masanobu Higashiyama and Yusuke Ogawa.)

TEPCO estimates 'ice wall' reduces contaminated water by 95 metric tons per day

https://mainichi.jp/english/articles/20180302/p2a/00m/0na/009000c

An underground wall of frozen soil surrounding the stricken Fukushima No. 1 Nuclear Power Plant that blocks groundwater from flowing into the plant has cut back on the amount of radiation-tainted water that is generated by an estimated 95 metric tons a day, plant operator Tokyo Electric Power Co. (TEPCO) announced March 1.

This marks the first time a provisional calculation has been made on the efficacy of the "ice wall" on its own.

The 1.5-kilometer wall comprises approximately 1,500 pipes that have been buried 30 meters underground surrounding the nuclear plant's No. 1 to 4 reactors, through which a liquid with a temperature of minus 30 degrees Celsius is circulated to create a wall of frozen soil.

TEPCO used computers to estimate the flow of groundwater, concluding that having the ice wall reduces the amount of contaminated water that is generated by 95 metric tons, or half of what would be produced if the wall did not exist.

At the same time, according to the utility, by the winter of 2017, when the construction of the ice wall was almost fully completed, the amount of contaminated water that was generated had dropped by approximately 380 metric tons per day compared to the winter of 2015, when the freezing process of the wall had not yet begun.

The effects of the ice wall at the Fukushima plant are believed to be limited compared to the process of pumping groundwater upstream and releasing it into the Pacific Ocean, and introducing a subdrain system in which water is drawn from wells around the reactor buildings. Not only did it cost 34.5 billion yen from public coffers to build the structure, maintaining the ice wall will cost 1 billion-plus yen per year. The Nuclear Regulation Authority had been doubtful about the cost efficiency of the project from the outset.

"It has become clear that the ice wall, on its own, has the effect of reducing contaminated water," a TEPCO representative said. A government panel of experts will deliberate the validity of the power company's estimate.

When the construction of an ice wall was given the green light in May 2013, the Japanese government was fighting to win the bid for the 2020 Summer Olympics, and presented the wall as a trump card in controlling the ever-increasing volumes of radiation-tainted water. It was a way for the Japanese government to show the rest of the world that it was leading efforts to suppress further generation of contaminated water, and gave the government an excuse to pump public funds into the cleanup of a disaster caused by a private company.