Thermal design of a metal hydride storage bed, permitting tritium accountancy to 0.1%2resolution 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 T-2 at 75%2stoichiometric composition of UT3. We propose a storage bed design directly extrapolated from the Joint European Torus uranium beds, which already have a U-238 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%2requires only the measurement of a temperature difference to +/- 0.1 K and stabilization of the ambient reference temperature of 300 to +/- 0.1 K.