Abstract <p>Samples of magnesium potassium phosphate compound containing boron-containing evaporator bottom simulant after concentrating liquid radioactive waste from nuclear power plants were synthesized. The possibility of solidifying up to 14 wt % evaporator bottom simulant components into a compound containing 15–20 wt % wollastonite was demonstrated. The phase composition of the samples obtained, their compressive strength, resistance to thermal cycles, water resistance, and hydrolytic durability were determined. The integral ¹³⁷Cs leaching rate is 5.7 × 10⁻⁴ g/(cm² day), and the leaching index is 10.7. The quality indicators of the compound obtained meet the regulatory requirements for a compound for solidifying radioactive waste.</p>