Reaction chemistry of plutonium with vanadium pentoxide in molten salts

Vanadium pentoxide, V sub 2 O sub 5 , has been proposed as an oxidant for the stabilization of reduced forms of plutonium within pyrochemical salt residues from plutonium pyrochemical processes at the Rocky Flats Environmental Technology Site because of its large reduction potential and its ability to react via normal solid-state reactions. However, when V sub 2 O sub 5 was used to oxidize actual process residues results were highly variable. This paper discusses the reaction chemistry of PuCl sub 3 , Pu deg and PuOCl with V sub 2 O sub 5 under a variety of conditions, including in the presence and absence of a NaCl/KCl salt matrix. This work is the first systematic study of the solid-state oxidation of plutonium species by vanadium pentoxide. For PuCl sub 3 a greater than or equal to 1:1 V sub 2 O sub 5 :PuCl sub 3 ratio is needed for complete oxidation. Increasing the amount of V sub 2 O sub 5 from 1 to 2 equivalents increases the contribution of side reactions, including reactions of V sub 2 O sub 5 with the process equipment and/or salt matrix, and produces undesirable non-volatile ternary and quaternary vanadium compounds. The oxidation of PuOCl is similar to that of PuCl sub 3 . Greater than a 1:1 V sub 2 O sub 5 :PuOCl ratio is required to achieve adequate conversion of PuOCl to PuO sub 2 . Oxidation of Pu deg by V sub 2 O sub 5 is more complex than the PuCl sub 3 or PuOCl oxidations. Complete oxidation of Pu deg to Pu(IV) in the presence of the salt matrix does not occur with up to 6 equivalents of V sub 2 O sub 5 . However, conversion of Pu deg to Pu(IV) occurs rapidly in the absence of the salt matrix.