Abstract Tritium inventory build-up is a safety and economic issue for next step fusion devices and power plants. JET with a beryllium wall and tungsten divertor brings a unique contribution on fuel retention and recovery in a metallic device, as it has operated with deuterium, tritium and deuterium-tritium plasmas. This paper documents the JET fuel retention programme, results and lessons learned, focusing on the tritium, deuterium-tritium campaigns and tritium clean-up in 2023. Fuel retention results from gas balance and Laser-Induced Desorption with gas detection using Quadrupole Mass Spectrometers (LID-QMS) are discussed. Gas balance has shown that there is no significant isotopic dependence of in-vessel global fuel retention, however a faster decrease in outgassing rate has been observed with increasing mass, likely associated with the difference in concentration and depth profile of tritium and deuterium. LID-QMS data has provided new local in-vessel fuel retention data demonstrating capability for measuring fuel retention, monitoring changes in fuel retention during an operating period as well as providing direct measurement of increased near-surface fuel concentration due to diffusion of hydrogen isotopes to the surface at elevated baking temperature and removal of fuel by inner strike point heating.
Widdowson et al. (Fri,) studied this question.
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