Materials research for the isolation and disposal of irradiated fuel

The Canadian Nuclear Fuel Waste Management Program is concentrating on an assessment of the disposal of radioactive fuel wastes from CANDU reactors in a deep, hard-rock vault. The principle underlying the safety of this disposal concept is the provision of a series of engineered barriers intended to supplement the natural isolation from the geosphere. These barriers include a durable waste form (either irradiated UO2 fuel bundles, or solidified reprocessing waste if a CANDU fuel-recycle option is eventually adopted), containers to provide isolation for significant periods, and buffers and backfills to inhibit diffusional and advective transport. The present paper describes progress in some of the research programs to evaluate potential container materials and how this relates to the design, fabrication and performance testing of fuel-waste containers. This paper has described some of the materials research activities relevant to the isolation and disposal of irradiated fuel waste in a deep, underground vault. Reasonable progress has been made on the testing and analysis of various container designs, with encouraging results. Generic and applied materials studies are underway to predict the long-term performance of container materials in a disposal vault, and to demonstrate the technology to reliably fabricate containers and to assure their quality. Many of the research activities are maturing quite rapidly, and likely options for container materials and fabrication techniques are becoming more evident