Thermal Design of a Metal Hydride Storage Bed, Permitting Tritium Accountancy to 0.1% Resolution and Repeatability

Tritium storage beds at the International Thermonuclear Experimental Reactor are likely to use uranium as a getter material with a total inventory of 150 g T₂ at 75% stoichiometric composition of UT₃. We propose a storage bed design directly extrapolated from the Joint European Torus uranium beds, which already have a ²³⁸U inventory of 4.284 kg. Three alternative approaches to implement calorimetry for in situ tritium inventory accounting are discussed. The favored solution uses a microporous thermal insulation operating in a hydrogen atmosphere. This design is shown to meet all operational and safety requirements. The accuracy of calorimetric assay to ±0.1% requires only the measurement of a temperature difference to ±0.1 K and stabilization of the ambient reference temperature of 300 to ±0.1 K.