Storage of tritium in the form of metal hydride is a common technique in tritium handling facilities and is generally acknowledged as the only option for the storage of large tritium inventories in future fusion reactor applications. Since accounting for large inventories by the conventional TPVC (Temperature, Pressure, Volume, Concentration) is very cumbersome, it is highly desirable to perform accounting directly by the application of calorimetric methods, for example based on monitoring of temperature rise in the tritium storage container caused by heat of the tritium decay (1.95W/mol.T2). Following an earlier evaluation1 of the JET tritium storage containers by electrical simulation of heat of the tritium decay the viability of the method was proven by adiabatic calorimetry with known tritium inventories up to ≈5900TBq.