Solidification of high level waste using magnesium potassium phosphate compound

Compound samples based on the mineral-like magnesium potassium phosphate matrix MgKPO4 x 6H(2)O were synthesized by solidification of high level waste surrogate. Phase composition and structure of synthesized samples were studied by XRD and SEM methods. Compressive strength of the compounds is 12 +/- 3 MPa. Coefficient of thermal expansion of the samples in the range 250-550 degrees C is (11.6 +/- 0.3) x 10(-6) 1/degrees C, and coefficient of thermal conductivity in the range 20-500 degrees C is 0.5 W/(m x K). Differential leaching rate of elements from the compound, g/(cm(2) x day): Mg-6.7 x 10(-6), K-3.0 x 10(-4), P - 1.2 x 10(-4), Cs-137-4.6 x 10(-7); Sr-90-9.6 x 10(-7); Pu-239-3.7 x 10(-9), 241Am-9.6 x 10(-10). Leaching mechanism of radionuclides from the samples at the first 1-2 weeks of the leaching test is determined by dissolution (Cs-137), wash off (Sr-90) or diffusion (Pu-239 and Am-241) from the compound surface, and when the tests continue to 90-91 days-by surface layer depletion of compound. Since the composition and physico-chemical properties of the compound after irradiation with an electron beam (absorbed dose of 1 MGy) are constant the radiation resistance of compound was established. (c) 2018 Korean Nuclear Society, Published by Elsevier Korea LLC.