The number of storage tanks for contaminated water and other materials has continuously increased at Tokyo Electric Power Company Holdings Inc.'s Fukushima No. 1 nuclear power plant in Japan, and space for still more tanks is approaching the limit.
Behind this is the fact that a way to get rid of treated water, or tritium water, has not been decided yet. The government and TEPCO will have to make a tough decision on disposal of tritium water down the road.
At the Fukushima No. 1 nuclear plant, groundwater and other water enters the reactor buildings that suffered meltdowns, where the water becomes contaminated. This produces about 160 tons of contaminated water per day. Purification devices remove many of the radioactive materials, but tritium — a radioactive isotope of hydrogen — cannot be removed for technical reasons. Thus, treated water that includes only tritium continues to increase.
Currently, the storage tanks have a capacity of about 1.13 million tons. About 1.07 million tons of that capacity is now in use, of which about 80 percent is for such treated water.
Space for tanks, which has been made by razing forests and other means, amounts to about 230,000 square meters — equivalent to almost 32 soccer fields. There is almost no more available vacant space.
Efforts have been made to increase storage capacity by constructing bigger tanks when the time comes for replacing the current ones. But a senior official of the Economy, Trade and Industry Ministry said, "Operation of tanks is close to its capacity."
TEPCO plans to secure 1.37 million tons of storage capacity by the end of 2020, but it has not yet decided on a plan for after 2021. Akira Ono, chief decommissioning officer of TEPCO, said, "It is impossible to continue to store [treated water] forever."
Tritium exists in nature, such as in seas and rivers, and is also included in tap water. The ordinary operations of nuclear plants produce tritium as well. Nuclear plants, both in Japan and overseas, have so far diluted it and released it into the sea or elsewhere. An average of 380 trillion becquerels had been annually released into the sea across Japan during the five years before the accident at the Fukushima No. 1 nuclear plant.
Bottles that contain the treated water continue to be brought one after another to a building for chemical analysis on the grounds of the Fukushima No. 1 nuclear plant. The tritium concentration of the treated water is up to more than 1 million becquerels per liter, which is more than 10 times higher than the national standard for release into the sea — 60,000 becquerels per liter. But if diluted, it can be released into the sea.
Regarding disposal methods for the treated water, the industry ministry's working group compiled a report in June 2016 that said that the method of release into the sea is the cheapest and quickest among five ideas it examined. The ideas were (1) release into the sea, (2) release by evaporation, (3) release after electrolysis, (4) burial underground and (5) injection into geological layers.
After that, the industry ministry also established an expert committee to look into measures against harmful misinformation. Although a year and a half has passed since the first meeting of the committee, it has not yet reached a conclusion.
At the eighth meeting of the committee held on Friday, various opinions were expressed. One expert said, "While the fishery industry [in Fukushima and other prefectures] is in the process of revival, should we dispose of [the treated water] now?" The other said, "In order to advance the decommissioning, the number of tanks should be decreased at an early date."
The committee plans to hold a public hearing in Fukushima Prefecture and other places to hear citizens' opinions on methods of disposal.