Radiolysis of the magnesium phosphate cement on γ-irradiation

Abstract

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.