The steps for recovering
uranium and transuranic elements are simplified, and the generation of waste
solvent and waste materials is suppressed.
Spent nuclear fuel is dissolved in
nitric acid (S100) and the resulting solution is subjected to electrolytic oxidation so that U, Np, Pu, Am is oxidized to VI using Ce as oxidation catalyst. The solution is cooled, and nitrates of valence VI thereby deposit as crystals and are separated from the
mother liquor (S104). The
mother liquor is heated and concentrated (S114). The mixed crystalline deposit is dissolved in
nitric acid (S106),
uranyl nitrate is deposited alone by cooling (S108), and the crystals are separated from the U, Np, Pu, Am
mixed solution (S110). The
uranyl nitrate is dissolved in
nitric acid (S112), and the heated and concentrated
mother liquor is added to it to prepare another
mixed solution. This
mixed solution is then subjected to electrolytic oxidation to oxidize the remaining U, Np, Pu, Am to valence VI, and the solution is cooled so that U, Np, Pu, Am are coprecipitated with
uranyl nitrate as crystals, and can be separated from high level radioactive
effluent (S118).