In selecting a method, while based on the five perspectives (safe, reliable, rational, prompt, and site-oriented), cost and process should also be used as decision indicators. To this end, evaluation items should be quantified as much as possible, and judgment indicators should be set from a comprehensive perspective.

In selecting a method, it is necessary to develop retrieval scenarios and clarify requirements. The scenarios should be developed based on the preconditions for utilizing the outcomes obtained from the internal survey and technological investigation to be conducted in the future, assuming various outcomes could be obtained. In the clarification of requirements, it is important to investigate keeping in mind the entire Fukushima Daiichi Nuclear Power Plant while paying attention to the interrelationships among the requirements. Currently, a conceptual study is being conducted to select a method for further expansion of the retrieval scale, and by the end of FY2021, the methods are narrowed down for subsequent design investigation.

In order to retrieve fuel debris safely, reliably and efficiently, considering radiation resistant, high corrosion resistance, simplicity of remote inspection and maintenance, have high reliability, high precision, and various troubles likely to occur, it is desirable to develop debris retrieval equipment and devices that meet specifications for a rescue mechanism that does not interfere with subsequent work when trouble had occurred, and can respond flexibly to on-site conditions.

In order to retrieve fuel debris safely, reliably and efficiently, it is desirable to develop an access system corresponding to the debris location, a fuel debris collection system corresponding to the debris condition, and a cutting and dust collection system for fuel debris.

In order to remove fuel debris safely, reliably and efficiently, it is desirable to understand the behavior of dust, fine particles and fumes generated in water and air, and to be able to prevent the expansion of contamination and the diffusion of radioactive material.

In debris processing, it is essential to maintain the clarity of the images provided from the camera so that it is necessary to keep the turbidity of the stagnant water low. For this purpose, it is desirable to inhibit microbial growth without causing any corrosion or other problem.

For fuel debris retrieval, it is necessary to cut, contain and transport in-core structures other than fuel debris to the outside of the reactor, and it is desirable to develop the technology and system for this purpose.

Since in the cut, storage, and transfer of in-core structures other than fuel debris, larger (heavier) objects than fuel debris are handled, the cut, grasp, storage (container), and transfer capabilities are required accordingly.

In order to reduce the effects of radiation on the equipment and devices used in fuel debris retrieval, it is desirable to develop radiation-resistant materials (including electronic circuits) that can be applied to actual sites.

It is desirable to develop a processing including surface processing technology that enable rapid decontamination even when exposed to high contamination conditions.