Basic Policy to Assess the Adequacy of the Depth of Radioactive Waste Subsurface Disposal

This paper describes the objectives and specific applicational issues of the document authorized by the Nuclear Safety Commission entitled “Policy of the safety assessment of subsurface disposal after the period for active control”, focusing on the policy of assessment for the appropriateness of burial depth. Concerning the burial depth of subsurface disposal, the proposal of 50-100 m from the surface has been made by the Atomic Energy Commission as a sufficient depth to avoid general usage of the underground environment, furthermore, taking into account these circumstances, the above document stipulates the new policy of assessment for the appropriateness of burial depth considering uplift/erosion noted in the safety assessment for long-lived radioactive materials. In the case of considering uplift/erosion, the isolation from the living environment planned in the original scheme will be gradually lost, the disposal facility will come close to the surface and become near-surface disposal in the long term. This paper describes the required roles of burial depth for subsurface disposal considering the long-term evolutional changes, introduces the physical protection capability to human intrusion as one of the protective functions of engineered barriers, and discusses the specific important issues related to the actual application.