Approach to operational safety in the Japanese HLW repository project

The safety of a repository for vitrified high-level radioactive waste (HLW) has two aspects: operational safety of activities during the period extending from construction to closure of the repository and long-term safety following closure of the repository. In Japan, 40,000 waste packages are scheduled to be disposed of in a deep repository over an operational period of approximately 100 years. As the implementer, the Nuclear Waste Management Organization of Japan (NUMO) is responsible for maintaining operational safety during this period. Such operational safety is envisaged as being a key concern on the part of the general public. NUMO adopts a structured approach to developing robust and flexible repository concepts (RC) in a transparent manner, considering the stepwise progress of the HLW repository project in Japan. One of the design factors for development of RC is operational safety. NUMO plans to manage a hierarchical structure of design factors relating to operational safety using a requirements management system. This paper presents the approach to achieving NUMO's goal of operational safety, from construction to closure of the repository, taking into consideration the special features of the HLW disposal project in Japan. (author)