Abstract <p>Na-alumophosphate glass (NAP glass) and glassy-crystalline matrix samples containing simulated HLW components and ²³⁷Np, ²³⁹Pu, and ²⁴¹Am radionuclides were prepared. The leaching of americium, neptunium, and plutonium from the glass and glassy-crystalline matrix in the presence of bentonite acting as engineered safety barrier was performed. In the experiments with the glassy-crystalline matrix, the concentrations of the leached radionuclides in simulated groundwater increased relative to the experiments with the glass. In the course of leaching, with time the radionuclides underwent redistribution in the matrix–groundwater–bentonite ternary system, with radionuclide accumulation on bentonite. The radionuclide distribution coefficients on bentonite were determined from the data obtained; they appear to be close to those obtained in sorption of the radionuclides onto bentonite from simulated NAP leachate.</p>