Safety Classification and Design Rules for Barriers in the Nuclear Power Demonstration Disposal Facility

Abstract

The Nuclear Power Demonstration (NPD) was as a 20 MWe prototype CANada Deuterium Uranium (CANDU) Pressurized Heavy Water Reactor which operated from 1962 until 1987, as a prototype CANDU nuclear power generating station and a training school for nuclear generating station operating staff. The NPD is currently in the Storage with Surveillance phase under a Waste Facility Decommissioning Licence issued by the Canadian Nuclear Safety Commission (CNSC) to the Canadian Nuclear Laboratories (CNL). In-situ disposal has been identified as the decommissioning strategy for the NPD reactor. In-situ disposal means immobilization and isolation of solid radioactive waste at its original site. The in-situ disposal will result in creation of a waste disposal facility: the Nuclear Power Demonstration Disposal Facility (NPDDF). The design of the NPDDF comprises several physical barriers between the waste and the environment. Some of the barriers are existing features through the design of the NPD reactor facility and some are engineered barriers which will be constructed as part of the NPD closure project. As part of the evolving activities for the NPD closure project, a process is developed in accordance with Canadian and International Atomic Energy Agency (IAEA) regulatory documents to classify the barriers (with respect to their importance to safety) that will provide containment and isolation of the waste to ensure long term safety and the protection of workers, the public and the environment. Barriers are typically designed to the appropriate standards that are commensurate with their safety importance. This paper describes the methodology developed to classify the multiple physical barriers in the NPD Disposal Facility and determine their design rules.