AbstractDesorption behavior of D2O or H2O, as a simulant of HTO, from the iron surface covered with thin iron oxide, film was studied by electron stimulated desorption (ESD) and photon stimulated desorption (PSD). When the iron was irradiated with electron or photon, water and hydrogen molecules were desorbed. Desorption behavior of water and hydrogen molecules depended on the incident energy of electron or photon. We discussed desorption mechanism of water and hydrogen molecules by electron or photon irradiation. It was found that the electronic excitation process contributes to desorption. Based on these results, tritium decontamination by ESD and PSD was evaluated.