Consecutive washing of simulant sludges from the BiPO4 (Cycle 3), Redox, and PUREX processes shows less than 4.5% of sorbed Pu(III/IV) or Pu(VI) is mobilized 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% dissolution of Pu(II/IV) or Pu(VI) from all simulants and dissolution of Nd(III), Cr(III), and Fe(III) (where present) from BiPO4 simulants. The dissolution of Pu(III/IV) and Pu(VI) from BiPO4 sludge simulants by strongly chelating media is accompanied by dissolution and reduction of Mn(IV) to a Mn(III) complex. Details of radioanalytical and spectroscopic investigations of sludge simulant washing are discussed in the context of understanding actinide behavior during alkaline leaching of radioactive sludge wastes.