Radiation and Chemical Stability of a Magnesium-Phosphate Matrix for 14C Immobilization

The results of manufacturing, studying the radiation and hydrolytic stability of a magnesium-potassium phosphate (MPP) matrix, are presented, which is being developed for the purpose of immobilizing 14 C, a product of processing mixed uranium-plutonium nitride fuel. Samples of MPP matrix containing 20 and 40 wt % calcium carbonate as a waste form fixing 14 C were irradiated with accelerated electrons with energies up to 2.5 MeV to doses of 10 6 , 10 7 and 10 8 Gy. It was found that the destruction of the target phases begins at a dose of 10 7 Gy up to their complete decomposition after the accumulation of a dose of 10 8 Gy. A significant increase in the leaching rates for all studied cations from radiation-damaged samples after a dose accumulation of 10 8 Gy has not been established; the duration of the geological storage of the matrix until complete decomposition of the main 14 C fixing phases has been estimated.