The tritium extraction technique considered for a fusion reactor with a self-cooled Pb-17 Li blanket includes the permeation of the tritium into a Na or NaK intermediate loop and the precipitation as tritide in a cold trap. Tritium is recovered by thermal decomposition under vacuum. Basic kinetic studies of the thermal decomposition of sodium hydride are presented using different types of hydrides. The temperature range investigated was between 280 and 420 °C. Using fine NaH powder, the rate constants agreed well with those from other authors. For NaH crystals, the rate constants were lower by one order of magnitude and were similar to those obtained previously for coarse NaH powder.