Tritium issues will play a central role in the performance and operation of next-step deuterium-tritium (DT) burning tokamaks and the safety aspects associated with tritium will attract intense public scrutiny. Tritium fuel has been successfully used in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) producing 10 and 16 MW of fusion power respectively. This experience together with focussed laboratory studies, has illuminated the challenges. The orders-of-magnitude increase in duty cycle and stored energy will be a much larger change than the increase in plasma performance necessary to achieve high fusion gain and ignition. Erosion of plasma facing components will scale up with the pulse length from being barely measurable on existing machines to cm-scale. Magnetic Fusion Energy (MFE) devices with carbon plasma facing components will accumulate tritium by co-deposition with the eroded carbon and this will strongly constrain plasma operations. We report on a novel laser-based method to remove codeposited tritium from carbon plasma facing components in tokamaks. The operational lifetime of alternative materials such as tungsten has significant uncertainties due to melt layer loss during disruptions. Production of dust and flakes will need careful monitoring and minimization, and control and accountancy of the tritium inventory will be critical issues. The relevant plasma material interactions are comprehensively reviewed in. Operation of next step experiments will help resolve key tritium issues in the design of a magnetic fusion reactor. Many of the tritium issues in Inertial Fusion Energy (IFE) are similar to MFE, but some, for example those associated with the target factory, are unique to IFE. The plasma-edge region in a tokamak has greater complexity than the core due to lack of poloidal symmetry and nonlinear feedback between the plasma and wall. Sparse diagnostic coverage and low dedicated experimental run time has hampered the development of predictive models. Diagnostic advances are urgently needed to better characterize the plasma edge and wall and improve our predictive capability.
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