NUMO published its Safety Case in February 2021 and released its English version titled "The NUMO Pre-siting SDM-based Safety Case" in November of the same year. Currently it has been undergoing an international review by the Organisation for Economic Co-operation and Development / Nuclear Energy Agency (OECD/NEA) to verify its technical reliability. As part of this international review, a workshop organized by the International Review Team (IRT) was held in Tokyo from June 20 to 24, 2022, in accordance with the guidelines set by the OECD/NEA for international reviews. During the workshop, the IRT deliberated on NUMO’s Safety Case, and on the final day, the chair of the IRT presented an interim summary of the review's findings in the public session. The public session was attended by not only NUMO but also by over 50 individuals who applied for participation either in person or online through the event invitation.

The interim findings of the review indicate that the Safety Case adheres to international standards for safety cases and adequately fulfills its role in the current phase of the project, demonstrating the feasibility of geological disposal in Japan. Additionally, recommendations were provided for the stepwise development of the safety case in line with the progress of the project.

The final report of the review, along with its Japanese translation, is scheduled to be published on the OECD/NEA website around autumn 2022.