Abstract: The purpose of this study is to develop the tritium trap for LWR fuel element irradiation test with power transient, to purify the ³He gas from tritium produced by neutron capture. Titanium sponge particles were selected as the storage materials. The design of prototype vessel was determined by factors such as the amount of tritium, the titanium-hydrogen reaction, the temperature by the electric heat, the maximum possible pressure of ³He, and helium release condition by the decay tritium. The titanium bed was heated internally to reduce the heat loss, and the primary and secondary containments of stainless steel were applied to prevent the permeation of tritium. Analysis results for the structure, heat transfer, shielding, and confinement of this trap are introduced.