Cement solidification method for radioactive waste and solidification product

Cement comprising Ca, Si and Al as the main ingredient with the Ca content being in the predetermined range is hardened such that voids of the cement hardening products in solidification products is less than 20% by volume. For this purpose, operation conditions such as water/cement ratio, hardening time for the mixture of hardening material and wastes, addition of organic polymers, etc. are determined. Further, for preventing the formation of soluble ingredient Ca(OH)2, the CaO content in the cement is defined as greater than 0.62 x C (SiO2) + 0.27 x C (Al2O3) and less than 1.87 x C (SiO2) + 2.20 x C (Al2O3), where C (SiO2) represent the silicon content (wt%) converted as the weight of SiO2 and C (Al2O3) represents the aluminum content (wt%) converted as the weight of Al2O3. Thus, cement solidification products with less leaching of radioactivity can be obtained and increase of the leaching amount of the radioactivity upon water immersion can be prevented. (T.M.)