THE INCORPORATION OF PLUTONIUM AND NEPTUNIUM IN ZIRCONOLITE AND PEROVSKITE

The incorporation of Pu and Np in one zirconolite and a number of pero vskite formulations has been investigated under oxidising and reducing conditions. The Pu valence in both perovskite and zirconolite was fou nd to vary independently of the crystal chemical design by altering th e annealing atmosphere, from Pu4+ in air to Pu3+ in 3.5% H-2/N-2. For both atmospheres, only tetravalent Np was found in the zirconolite. Te travalent Np was observed in perovskites fired in air, but trivalent N p was stabilised in suitable perovskite formulations annealed under a reducing atmosphere. A trivalent Np phosphate, NpPO4, was also prepare d under reducing conditions. (C) 1998 Elsevier Science S.A.