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 C-14, 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 C-14 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 C-14 fixing phases has been estimated.