Many tanks sit at the site of the Fukushima Daiichi Nuclear Power Plant, filled with water that has been processed by the so-called Advanced Liquid Processing System (ALPS, also described as a multi-nuclide removal system). The system treats a mix of cooling water from fuel debris as well as groundwater that has flowed into the reactor and turbine structures. As of October 2019, already more than 1.16 million cubic meters of treated water were being stored in 960 tanks.
In February 2020, the government’s Subcommittee on Handling of ALPS Treated Water released its report of discussions about how to handle the contaminated water, concluding that the release into the ocean and atmosphere were realistic options.
The total amount of tritium was estimated at 856 trillion Becquerels. About 80% of the liquid stored in the tanks exceeded ocean discharge regulatory standards[1] for 62 radionuclides other than tritium.[2] TEPCO says that if it release the contaminated water to the sea, it will perform secondary treatment to ensure contamination concentrations are below the regulated limits.
The Ministry of Economy, Trade, and Industry says that nuclear plants around the world are discharging tritium and there is almost no impact on health. But despite what METI says, there certainly are problems. For example, even if the amount of radioactive energy in tritium is very low, there are impacts when organically bound tritium is absorbed into living cells, and DNA is damaged when tritium replaces hydrogen in DNA and decays into helium.
Toyoshi Fuketa, chairman of the government’s Nuclear Regulation Authority, has repeatedly stated that dilution and ocean release is the only realistic option to deal with the ALPs contaminated water. But although realistic alternative proposals have been made for land-based storage, the authorities have not given them fair consideration.
42 of 44 speakers at hearings opposed ocean discharge
METI held briefings and hearings on August 30 and 31, 2018 in Tomioka, Koriyama, and Tokyo regarding how to deal with the ALPS treated water. Forty-two of the 44 persons who spoke at the hearings stated clearly that they were opposed to ocean discharge. Most poignantly, speakers from the fishing industry, including Tetsu Nozaki, head of the Fukushima Prefectural Federation of Fisheries Co-operative Associations, spoke about the devastating impacts any ocean discharge would have on the fisheries which had been revived so painstakingly since 2011. Many speakers pointed out the dangers of tritium and said the treated water should be in long-term tank storage on land.
After the hearings, Mr. Yamamoto, chair of METI’s subcommittee, stated that it would include “tank storage on land” as an alternative plan. However, there has been virtually no discussion about this option.
Proposals for land-based storage ignored
A technical committee of the Citizens’ Commission on Nuclear Energy (a citizen-based think tank that also includes many technical experts in the field of large industrial plants) submitted proposals to METI regarding land-based storage using large tanks, and also mortar solidification technology. [3]
The large tank storage proposal involves constructing large dome-shaped tanks with a capacity of 100,000 cubic meters each, equipped with water seal vents. The site for the large tank storage is to be chosen from among the future sites of (now cancelled) reactor units 7 and 8, a soil dumping area, or an area at the back of the Fukushima Daiichi site, after obtaining local consent. The proponents said that it would be possible to store about 48 years’ worth of new ALPS-treated water by constructing 20 tanks on an 800 x 800 meter site and also, by gradually replacing existing tanks on the existing site with larger ones.
The supposed disadvantages, as claimed by TEPCO, were that large tanks were not any more efficient than regular tanks in terms of site usage, that there was the risk of rainwater mixing with tank contents, and that there would be a large discharge in the event of damage to a tank. The subcommittee report simply used the explanation from TEPCO without further questions or discussions on these points.
It is well known that large tanks already have a track record of being used around the world to store oil and other liquids. A dome-type design would avoid the risk of mixing with rainwater. And proposals for large tanks included the installation of protective berms to prevent accidental discharge.
The mortar solidification proposal is a method already used in the disposal of contaminated water at the Savannah River nuclear reservation in the United States (South Carolina). Contaminated water is solidified into mortar by being mixed with cement and sand, then the mortar is poured into concrete tanks and stored partially underground.
Yasuro Kawai (former plant engineer), who was involved in preparing the proposal for the Citizens’ Commission on Nuclear Energy explained it this way: “The advantage is that solidification allows you to eliminate the risk of discharging radioactive substances into the sea. But the disadvantage is that mixing contaminated water with cement and sand reduces the volumetric efficiency by a factor of about four. Even so, with an 800 x 800 meter site, there is enough space using mortar solidification and storage for about 18 years’ worth of contaminated water at this site.”
Is there really a lack of space at the existing site?
The discussions about the Fukushima Daiichi site are still incomplete. Subcommittee members posed various questions. For example: “Looking at the Fukushima Daiichi Nuclear Power Plant site usage, can’t you install tanks with the same capacity as existing tank capacity on the north side of the site where there is currently a contaminated soil storage area?” “If the site is not big enough, why not expand the Fukushima Daiichi Nuclear Power Plant site?” If large tanks can be also installed on the soil dumping area on the north side of the site, an estimated 48 years’ worth of treated water can be stored in the future. Regarding the soil now accumulating in the contaminated soil storage area, TEPCO explains that it ranges from a few to several thousand Bq/kg in radioactive levels.[4] If that is true, it is not correct to say that the soil cannot be moved off-site.
As for the potential to expand the site for storage tanks, the subcommittee’s secretariat stated that it would be difficult to get local community consent.[5] Obviously, it is very important to provide an explanation to the community and obtain local consent, but it is premature to conclude that it is too difficult to expand the site without having actually made any effort.
Local fishermen are ramping up their fight against the narrative that was biased in favor of discharging contaminated water into the sea. Tetsu Nozaki (Fukushima Prefectural Federation of Fisheries Co-operative Associations) has repeatedly stated his organization’s to the proposed ocean discharge. In February 2020, the Ibaraki Coastal Region Federation of Fisheries Cooperative Unions also submitted a formal request that the government not permit the discharge of contaminated water into the ocean. Ibaragi Prefecture’s governor, Kazuhiko Oigawa stated, “I want the government to reconsider this from step one.”
[1] The sum of the ratios of actual concentrations to regulatory standards for radionuclides. For any discharge to satisfy regulations this should be less than 1.
[2] Document published by TEPCO, November 18, 2019.
[3] Citizens’ Commission on Nuclear Energy, “Comments on the handling of ALPS treated water,” October 3, 2019.
[4] TEPCO remarks at the 15th ALPS Subcommittee meeting.
[5] Document 4 at the 16th ALPS Subcommittee meeting