showing a basic process of a reprocessing method by a fluoride volatility process using solid gas separation according to the present invention this is a reprocessing method in which fluorine or a fluorine compound is subjected to a reaction with a spent oxide fuel to produce fluorides of uranium and plutonium and recover uranium and plutonium as uf 6 and uf 6 puf 6 using a difference in volatility behavior the method of the present invention comprises an hf fluorination step and an f 2 fluorination step in two stages of different temperatures in the hf fluorination step a spent oxide fuel containing uo 2 and puo 2 is subjected to a reaction with a hydrogen fluoride gas whereby uranium plutonium and most impurities in the spent fuel are converted into solid fluorides or oxides to inhibit volatilization the hf fluorination step is carried out by supplying a hydrogen fluoride gas supplied amount 1 1 to 1 3 times the stoichiometric ratio concentration 60 to 90 vol using a fluidized bed furnace operated in the temperature range of 350 to 430 u00b0 c since the hydrogen fluoride gas has a weak oxidizing power a nonvolatile fluoride having a low valence lower fluoride is produced by the.