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Contaminated water with high concentrations of radioactive materials has been generated as a result of the accident at TEPCO’s Fukushima Daiichi Nuclear Power Station (Fukushima Daiichi NPS). It is currently being treated to remove radioactive materials, and after being treated, it is referred to as “ALPS treated water”. An expert committee named “The Subcommittee on Handling of the ALPS treated Water (the ALPS Subcommittee)” has been studying how to deal with ALPS treated water. This article highlights salient points of the report which was submitted by the ALPS Subcommittee to the government on February 10, 2020.

What is “ALPS treated water”? What do we do with it as it is still being continuously generated and stored on-site?

Our previous articles presented basic and updated information on the contaminated water at Fukushima Daiichi NPS as well as measures in dealing with it. Contaminated water countermeasures have been conducted based on our three basic principles, namely “1. Preventing leakage of contaminated water, 2. Redirecting groundwater from contamination sources, 3. Removing contamination sources”. The water treatment, conducted under No.3 of these principles, is to reduce risks associated with radioactive materials contained in contaminated water. Multiple pieces of equipment are used for purification. The most efficient among them is the “Multi-nuclide removal equipment (known as the Advanced Liquid Processing System = ALPS)” that removes 62 kinds of radioactive materials. Water treated by ALPS is referred to as “ALPS treated water”.

ALPS treated water is currently stored in tanks on site at Fukushima Daiichi NPS. As it is being generated continuously, the amount of ALPS treated water is constantly increasing. In order to install as many tanks as possible, land has been secured and tanks have been arranged in the most efficient manner. Based on the current tank construction plan, however, the tank capacity is assumed that it reaches its full capacity around summer of 2022.

How to deal with ALPS treated water is one of the most significant challenges toward the decommissioning of Fukushima Daiichi NPS. The ALPS Subcommittee has held a series of meetings since November, 2016, where experts discussed comprehensive measures considering not only technical aspect but also countermeasures for reputational damage.

The ALPS Subcommittee met 17 times over three years. As an outcome, it compiled a report on February 10, 2020, as a reference to be used for decision making by the government of Japan regarding appropriate disposal of ALPS treated water.

The salient points of the report submitted by the ALPS Subcommittee

The salient points of the report are set out below:

“Coexistence of reconstruction and decommissioning” is a basic principle. The disposal of ALPS treated water forms a part of the decommissioning process.”

The report refers to the basic principle of “coexistence of reconstruction and decommissioning”. From this viewpoint, disposition of ALPS treated water needs to be completed until the completion of the decommissioning. On the other hand, additional reputational damage should not be caused by a hastened disposition of the ALPS treated water.

“Secondary treatment must be conducted for the ALPS treated water that does not satisfy the regulatory standards, to ensure that it meets the standards before disposal.”

Approximately 70% of ALPS treated water currently stored in tanks contains radioactive materials (other than tritium) with the concentration exceeding regulatory standards for discharge. The reason for this is that when treatment for purification started, efforts were focused on suppressing additional radiation leakage on the boundary of the NPS (on the boundary of the surrounding land) in order to meet the regulatory standards. That being said, as long as the insufficiently-treated water is kept in tanks, it conforms to the regulatory standards. In the case of releasing to the environment, further purification (secondary treatment) must be conducted through equipment such as ALPS.

“Discharge into the sea and vapor release have been conducted and recognized as feasible methods.”

The following five disposal options were studied.

1. Geosphere injection
2. Hydrogen release
3. Underground burial
4. Vapor release
5. Discharge into the sea

The report states that the first three options, namely geosphere injection, hydrogen release and underground burial, have various difficulties in consideration of regulations, technologies and time. Consequently, it advises that vapor release and discharge into the sea, both of which have preceding practices, are the remaining practical options.

To be specific, vapor release was once utilized by an overseas nuclear reactor that suffered an accident although the amount released was different from the amount Fukushima Daiichi NPS will have to release. Under normal circumstances, a nuclear reactor conducts ventilation in a strictly controlled manner. However, in Japan there is no example of vapor release in order to dispose liquid waste. Furthermore, some of the nuclides contained in ALPS-treated water are expected to remain unreleased as solid material forming radioactive waste, despite the fact that the total quantity of nuclides released into the atmosphere will decrease.

Discharge into the sea is also a proven method. Nuclear facilities around the world, Japan included, discharge radioactive liquid waste into the sea, etc. after proper dilution to meet the regulatory standards in respective countries. Discharge into the sea requires simpler equipment than that for vapor release, and therefore it is easier to monitor the process to ensure safe disposal. Nevertheless, it must be noted that the amount of water and amount of tritium to be released will not be equivalent to the amounts that had been released under normal circumstances before the accident.

“The impact of the radiation to human health as a result of the discharge would be no more than 1/1000 of natural exposure.”

The subcommittee also studied radiation effects to be caused to humans by both discharge into the sea and vapor release.

The study is based on the assessment model published by the “United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)” for a comparison of disposal options. Calculations based on this model indicate, for both discharge methods, that if all the ALPS treated water currently stored on-site is discharged in one year and even if this is repeated every year after, radiation effects would be no more than 1/1000 of natural exposure in Japan (2.1 mSv/year).

“In deciding the disposition of the ALPS treated water, the government of Japan must also compile a policy for countermeasures against reputational damage.”

It is necessary to take all possible measures against reputational damage. It is also essential to work out a disposal method which ensures public safety. Secondary treatment of radioactive materials other than tritium is a prerequisite for disposal. In addition, due consideration must be given to the opinions of the parties concerned in determining the time to start disposal, the amount and duration of disposal, and the concentration of radioactive materials to be released.

The report also recommends that additional measures be taken to help minimize reputational damage, including confirmation of the concentration of radioactive materials before disposal, and emergency shutdown procedures prepared in the cases of abnormal figures detected by radiation monitoring or malfunctions of disposal facilities. Enhanced monitoring of the surrounding environment and clear and thoughtful dissemination of important information are also required.

In addition to all measures listed above, the report further requests for appropriate risk communication, precise information, and that financial measures also be taken for preventing, minimizing and compensating for any reputational damage.

“Decisions should be made by the government with the opinions of a wide variety of parties concerned taken into consideration”.

The report concludes with the following remarks:

In line with the above remarks, the government is currently holding Meeting as Opportunities for Receiving Opinions attended by the parties concerned including local community and national associations related to economy, tourism and distribution. Additionally, the government invites opinions in writing from the general public. (The closing date for submissions has been extended until July 31, 2020 with a view to receiving as many opinions as possible.) The government will decide its basic policy after hearing a wide variety of opinions though these opportunities.

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Nuclear Accident Response Office, Electricity and Gas Industry Department

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Research and Public Relations Office, Policy Planning and Coordination Division, Commissionerʼs Secretariat