The frozen soil barrier wall at the Fukushima No. 1 Nuclear Power Plant of the Tokyo Electric Power Company (TEPCO) was built at a cost of 34.5 billion yen. Initially, TEPCO had planned to finish the work by 2021, but five years have passed since the freeze, and a large amount of contaminated water continues to be generated, with no prospect of even reaching zero. The ice wall, which will cost hundreds of millions of dollars to maintain every year, will enter long-term operation without sufficient verification. (Kenta Onozawa)
Freezing soil with cooling liquid, annual maintenance cost of billions of yen
The freezing wall was built to prevent groundwater from the mountains from entering the buildings where highly radioactive materials such as melted nuclear fuel (debris) remain after the accident. Freezing began in March 2004, and the entire area was frozen in nearly two years. The annual maintenance costs, including electricity for freezing, cost more than one billion yen when the system was first introduced, and TEPCO is bearing the cost.
From December 2007 to January 2009, there were a series of problems with cooling liquid leaking from a total of five frozen pipes. According to TEPCO, all of them are located under the road near the reactor building, and it is highly likely that the vibration of passing vehicles caused fatigue damage to the metal parts.
TEPCO, which had not envisioned long-term operation of the plant, had been repairing problems only after they occurred, but from this year, it has set a frequency for replacement of parts and will prepare replacement parts in advance. A spokesperson said, “The frozen earth wall is effective and will be used continuously. However, from this year, the frequency of replacement will be set and replacement parts will be prepared in advance.
Groundwater through gaps, limited effect
”In March 2006, TEPCO announced that it would build a freeze-earth wall at the Fukushima Daiichi Nuclear Power Plant.
In March 2006, TEPCO announced an estimate that the frozen soil wall prevented about 95 tons of groundwater per day from entering the buildings. Without the wall, the amount would have been 189 tons per day, and the company stressed that the amount had been halved.
However, there is a lack of evidence for the estimate, as it was based on an evaluation of the period when there was little rainfall, and it does not distinguish between the effects of other measures, such as the pumping up of groundwater by sub-drainage wells around the building. Toyoshi Sarada, chairman of the Nuclear Regulation Authority (NRA), has declared that “the main role of groundwater countermeasures is to pump up the sub-drainage.
At the press conference when the calculations were released, Naohiro Masuda, who was the chief decommissioning officer of TEPCO (now president of JNFL), stated clearly that “we will continue to verify” the effectiveness of the frost wall. However, the spokesman now avoids explaining, saying, “It is difficult to show the effects of individual measures.
Calls from the Regulatory Commission for an alternative plan
Initially, the government and TEPCO had set a goal of stopping the generation of contaminated water by around 2009. However, they still do not know where the groundwater is coming from.
The amount of contaminated water, which was 490 tons per day in FY2003, was reduced to about 140 tons in FY2008, but zero was not achieved, and the goal was set back to 100 tons in 2013. TEPCO said, “We will continue with the current measures until 2013. After that, we are still studying.
The cost of maintaining the frost wall will be covered by the electricity bills paid by consumers to TEPCO. In the regulatory commission’s study group, there is a strong opinion among experts that “from the viewpoint of cost-effectiveness, the frozen soil wall should be abandoned and steel plates or concrete walls should be embedded. In response to this opinion, TEPCO simply replied, “We are considering it,” and even 10 years after the accident, there is no end in sight to the contaminated water measures.