Fusion waste requirements for tritium control: Perspectives and current research

The successful realisation of energy production through the fusion of deuterium and tritium will necessarily lead to the generation of waste contaminated with tritium. Not only will some of the tritium fuel permeate into components of fusion reactors and their wider fuel cycle, but tritium will also be generated directly in materials exposed to the high neutron fluxes via nuclear break-up reactions. Motivated by predictions from fuel-retention modelling and nuclear transmutation simulations, which demonstrate the potential scale of the tritium contamination challenge, UKAEA is exploring different solutions for detritiation, including acid etching/dissolution and thermal (melt) treatments, leveraging the experience gained from handling the waste materials generated during the operation of JET. The high mobility of tritium poses a challenge for waste storage and containment. Knowledge of how tritium permeates through different materials under different conditions is critical for ensuring the environmental safety and regulatory compliance in the design and operation of waste-disposal containers, waste storage units and waste transportation systems. A low-temperature permeation rig has been designed and commissioned to measure the permeation of tritium at low temperatures through different materials; primarily investigating candidate materials for waste boxes, but which could also be deployed for tritium containment in low temperature regions of a fusion power plant, such as on the walls of a reactor hall. The experience of establishing and operating experimental tritium rigs and handling tritiated waste from JET is invaluable for the future fusion industry, while there is optimism that the experimental research trials will steer fusion waste strategy by designing waste containers and barriers that minimise the spread of tritium contamination or provide efficient detritiation solutions.