Cryogenic adsorption of hydrogen isotopes on porous adsorbents is an attractive method for tritium re-covery from helium which conducts as sweep gas of tritium breeding blanket in a fusion reactor. In order to use this method to extract tritium effectively

it is necessary to investigate adsorption properties of various candidate adsorb-ents. In this study isotherms and isotopic effects of hydrogen isotopes on three carbonaceous adsorbents: carbon mo-lecular sieve

activated carbon and carbon nano-fiber have been tested at liquid nitrogen temperature. It was con-cluded that the first two adsorbents could be used for this purpose and the third one was excluded because of its low adsorption capacity. Adsorbent modification using concentrated HNO3 and experimental results of the modified ad-sorbents have also been reported.