The selection of a repository site will be undertaken via a three-stage process based on the “Final Disposal Act” and involves the selection of Preliminary Investigation Areas (PIAs), the selection of Detailed Investigation Areas (DIAs) and the selection of a repository construction site.

In 2002, NUMO initiated open solicitation of municipalities nationwide, seeking areas to carry out a literature survey as the first step in selecting a final disposal site, however no survey has yet been carried out. Considering this situation, the Japanese government decided to carry out nationwide scientific screening in order to identity municipalities which could be suitable for a literature survey, if accepted.

The site selection procedure specified in the Final Disposal Act consists of three steps, namely literature survey, preliminary investigation and detailed investigation.

NUMO will compile reports on the investigation results at each stage of the process and will hold explanatory meetings. The opinions of local people expressed at these meetings will be made known to the relevant prefectures and municipalities together with NUMO's views and selection will proceed on the basis of respecting local opinions, obtaining stakeholder agreement and securing the government approval.

The government has stipulated that, when approving each stage of the site selection process, the opinions of the municipality mayors and the governors of the prefectures concerned must be listened to and respected. Selections that oppose these views will not take place.

Following the selection of a repository construction site, the disposal facilities will be designed and a safety evaluation will be undertaken; construction will only begin after a safety review by government experts.