Hydrolytic and thermal stability of magnesium potassium phosphate compound for immobilization of high level waste
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The samples of the magnesium potassium phosphate (MPP) compound have been synthesized during solidification of high level waste (HLW) surrogate. The compound consists of a main phosphate phases Mg1.1Na0.35K0.45PO4 × (4–6)H2O and MgCs0.5Na0.2K0.3PO4 × (5–6)H2O. Differential leaching rates of 239Pu, 152Eu and 90Sr from the MPP compound after heat treatment (450 °C) are 7.8 × 10−9; 1.7 × 10−7 and 8.8 × 10−6 g cm−2 day−1, respectively. The coefficient of thermal expansion of MPP compound—(11.6 ± 0.3) × 10−6 °C−1; coefficient of thermal conductivity averages 0.5 W m−1 K−1. The properties of MPP compound meet the regulatory requirements for solidified HLW.
KeywordsMagnesium potassium phosphate compound High level waste Immobilization Thermal stability Leaching rate Leaching mechanism
The study was carried out through the Russian Science Foundation Grant (Project No 16-13-10539).
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