ABSTRACT
The leaching behavior of calcium from cement monoliths through rock was experimentally measured and calculated using a model considering clogging caused by the precipitation of secondary minerals. It is suggested that the calculation model can be simplified to reasonably predict the alteration of cement materials under moderate conditions resulting from chemical reactions. To improve the practicability and credibility of the long-term performance assessment of a radioactive waste repository, it is important to investigate both detailed and simplified modelling approaches and to balance these approaches considering the level of understanding of the mechanism of the alteration reaction and the computing capability. It is also suggested that moderate conditions are effective for improving the credibility of the performance assessment and reducing uncertainty.
