Radiolysis of the magnesium phosphate cement on γ-irradiation

•The γ-radiation induces the water decomposition contained in cement to give hydrogen.•At absorbed doses up to 4 MGy, the formation of a detonating gas mixture is excluded.•Hydrogen formation does not lead to swelling or destruction of the MPC.•At high absorbed doses the mechanical strength of material is maintained.•The MPC is stable to radiation and can be used for capsulation of radioactive wastes. The effect of γ-radiation on the chemical transformations and stability of the phosphate cement (MgHPO4·3H2O) was studied. It was shown that exposure to 60Co γ-radiation is accompanied by hydrogen formation upon radiolysis of water. Oxygen is detected in trace amounts (less than 1% relative to hydrogen). In the region of absorbed doses of 4–5 MGy, the yield of hydrogen is approximately 0.055 ± 0.005 molecules/100 eV. At high doses, hydrogen accumulation reaches a stationary level. An empirical equation describing the dose dependence of hydrogen accumulation was obtained: VD = V∞(1−e−kD), where VD is the volume of released hydrogen (cm3/g) at the absorbed dose D (MGy) and V∞ and k are process parameters equal to 0.73 ± 0.05 cm3/g and (0.17 ± 0.01) MGy−1, respectively. Hydrogen formation does not lead to swelling of magnesium phosphate cement and does not change its mechanical strength even at high doses. The results can be useful for evaluation of the activity level of radioactive wastes that can be encapsulated into this matrix.