Abstract
In the radioactive waste disposal system, cement materials have been used as (1) structual materials in disposal facilities, (2) solidifying materials for enclosing radioactive nuclides, and (3) internal filling mortar for the space between the waste and the concrete. One of the important features of cement materials is its ability to establish a high pH in the water within the repository. A high pH is beneficial because in this condition the solubilities of many radionuclides, especially TRU,in aqueous solution are low. It is necessary to maintain the high degree of sorption of radionuclides based on the high pH-for the long term safety of the system. Then the important thing is to gain a reasonable evaluation of the pH within the repository. Atkinson et al. have presented a method of evaluating pH in the leaching groundwater from cement. They predicted the dissolution property of cement based on a simplified model using equilibrium data for the CaO-SiO2-H2O system. In the present report, we explain the Atkinson proposed method of evaluating the pH in the repository. Our studies on solubility of cement hydrate are also discussed.
