The water treatment process generates water treatment secondary waste. It is necessary to develop a method to reduce the amount of such waste. In addition, it is necessary to develop a water treatment method that facilitates solidification process.

The running cost of adsorbents has become an issue, and the development of better adsorbents is desired. In particular, at present the lifetime of adsorbents for iodine is three to four times shorter than that of adsorbents for other nuclides. Another problem is that it is difficult to select adsorbents for iodine because iodine takes various chemical forms.

The plan is to reduce the amount of stagnant water in the reactor building between FY2022 and FY2024 to about half of what it was at the end of 2020, and to “lower the water level after confirming the properties of the stagnant water in the R/B”, and “design and install equipment for removing alpha-nuclides contained in the stagnant water, after understanding their properties. The issue to be addressed is investigation of specific methods for separating and removing alpha-nuclides contained in stagnant water.

Considering during debris retrieval (especially during processing), the nature of contaminated water (nuclides, chemical forms, etc.) is likely to change significantly from the current state, it is desirable to have a water treatment technology (soluble alpha-nuclides removing technology, etc.).

In particular, it is desirable to investigate and develop a technology for removing radionuclides that exceed the treatment capacity of the ALPS.

In investigating water treatment facilities for fuel debris retrieval, it is important to investigate an overall picture of how to share functions with the existing treatment facilities for building retained water (SARRY, ALPS, etc.) to create an appropriate configuration.

During fuel debris retrieval, contaminated water containing a large amount of fine particles is generated due to cutting and other processing, and the α-nuclides contained in the fuel debris may exist in various forms, including fine particles, ions, and colloids. Since the water quality of such contaminated water depends on the method of cutting and other processing, it is difficult to estimate the water quality when the fuel debris retrieval method has not been determined. Thus, issue is created such as the water treatment system during fuel debris retrieval must have a complex equipment configuration to accommodate a wide range of water quality and various forms of α-nuclides.

High-salinity contaminated water contains a large amount of Na and Cl ions, which reduce the adsorption performance of zeolites, etc. Therefore, it is necessary to develop an efficient adsorbent.

It is necessary to investigate the optimal water treatment system for such a situation. In this case, it is important to make the system optimal and efficient in view of safety improvement, cost reduction, and waste generation reduction, etc.

It would be good to be able to not only efficiently collect but also decontaminate and incinerate the collected materials. For example, they could be achieved by remotely spreading resin or strippable paint, etc. on the floor and peeling off. In this case, the spraying agent such as resin needs to be radiation resistant. In addition, care must be taken to avoid collapsing waterways due to the spread of resin or other matter.

Since the sludge contains high concentrations of Cs-137, a removal measure needs to be considered from the viewpoint of measures to reduce worker exposure doses, maintainability, and secondary waste.