[en] In a tritium processing device for processing fuel exhaust gases mainly composed of hydrogen isotope gases and off gases exhausted from a neutron particle heating device, an oxidation promoting means for oxidizing the whole amount of the hydrogen isotope gases, a condensation/liquefaction means for condensating/liquefying processed regeneration steams and a storage means for recovering and storing the liquefied water are disposed. Since the whole amount of hydrogen isotope gases are oxidized, coagulated liquefied and stored, tritium generated in a plasma container by a deuterium plasma reaction is removed, thereby enabling to reduce the releasing amount to ordinary environment with no influence on public safety. (N.H.)