Plutonium mobilization and matrix dissolution during experimental sludge washing of bismuth phosphate, redox, and purex waste simulants

Consecutive washing of simulant sludges from the BiPO4 (Cycle 3), Redox, an d PUREX processes shows less than 4.5% of sorbed Pu(III/IV) or Pu(VI) is mo bilized during CrO42- dissolution by the 0.01 M NaOH + 0.01 M NaNO2 sluice or 3.0 M NaOH leach solutions to be used for sludge pretreatment at Hanford . Experimental sludge washing with 2.0 M HNO3 results in 5.8-65.5% dissolut ion of Pu(II/IV) or Pu(VI) from all simulants and dissolution of Nd(III), C r(III), and Fe(III) (where present) from BiPO4 simulants. The dissolution o f Pu(III/IV) and Pu(VI) from BiPO4 sludge simulants by strongly chelating m edia is accompanied by dissolution and reduction of Mn(IV) to a Mn(III) com plex. Details of radioanalytical and spectroscopic investigations of sludge simulant washing are discussed in the context of understanding actinide be havior during alkaline leaching of radioactive sludge wastes.