This was to be the ultimate solution for controlling groundwater infiltration in the basement of damaged reactors where it mixes with highly contaminated cooling water. With a total cost of 34.5 billion yen (298 million dollars) paid by Japanese taxpayers, this unprecedented government project was to confirm the Prime Minister’s assertions to the Olympic Committee in 2013 that the situation ” Is under control “.
Begun in June 2016, soil freezing around the four damaged reactors was expected to limit groundwater infiltration and leakage of contaminated water. Since the areas with the strongest phreatic currents did not freeze, TEPCO had to pour concrete in certain areas. But the results have been slow and TEPCO was always demanding more time for the project to prove itself. According to the Asahi, the Nuclear Regulatory Authority, the NRA, seriously doubts the effectiveness of this technique, which it now considers as secondary. Media actions are not enough.
Indeed, according to the NRA, despite the low rainfall, the amount of water pumped in the basements of the reactors and in the contaminated groundwater around the wall does not drop enough. It therefore considers that the solution goes through pumping, not the wall. In response, TEPCO is committed to doubling its pumping capacity to 800 m3 per day in groundwater in the fall.
The NRA also authorized complete soil freeze upstream of the reactors, although it did not block downstream flows.
According to the soil temperature maps published by TEPCO beginning December (www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161208_01-e.pdf) or more recently (www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161222_02-e.pdf) some portions were still not frozen upstream. According to the latter document, TEPCO always injects chemicals into the soil where it does not freeze. It also gives the planning of future work. It will be necessary to wait until February 2017 to obtain the complete freezing upstream.
Soil freezing over such a distance for years is a very complex technology to implement. TEPCO reported a leak of the coolant discovered last December 19th without the cause being known. (www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161222_02-e.pdf)
As the company recalls, the primary purpose of these operations is to reduce groundwater infiltration in order to slow down the increase in the stock of contaminated water in tanks at the site.
According to the Asahi, before the soil was frozen, TEPCO pumped on average 300 m3 per day of contaminated water in the basements of the reactors in addition to the water injected for cooling. This became now 130 m3 per day, which is still more than the 70 m3 per day targeted.
The latest data published by TEPCO show an increase to 176 m3 per day at the end of December, to which must be added the too contaminated or salt groundwater to be treated directly and which is therefore mixed with the water in the basements. The latter is down to 58 m3 per day. The total reached 234 m3 / day. The impact of soil freezing is not obvious on this graph. (www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161226_01-e.pdf)
It should be noted that TEPCO injects a hundred cubic meters of water into each of the three accidented reactors daily to cool the fuel. And this water, very contaminated, leaks to the basements. TEPCO’s latest report shows a partially treated contaminated water stock of almost one million cubic meters, to which 60,000 m3 of reactors and 9,156 m3 of liquid waste are added. (www.tepco.co.jp/en/press/corp-com/release/betu16_e/images/161226e0201.pdf)
In addition, TEPCO has installed sensors at the port exit in front of the rugged power station to continuously measure the concentration of cesium and total beta in seawater.(http://www.tepco.co.jp/en/nu/fukushima-np/f1/seawater/index-e.html)
Translated from french by Dun Renard (Hervé Courtois)