Effect of supplementary cementitious materials on the degradation of cement-based barriers in radioactive waste repository: A case study in Korea

This study focuses on investigating the chemical degradation characteristics of cementitious barriers used in low- and intermediate-level radioactive waste repository by reactive transport modeling. The impact of the blending with supplementary cementitious materials (SCMs) in the barriers on the chemical degradation was evaluated to find the optimum barrier design. A number of different barrier designs were examined by replacing ordinary Portland cement (OPC) by SCMs (i.e., fly ash, silica fume, and blast-furnace slag). The simulation results showed that silica fume blended barrier has better durability against chemical degradation by rainwater compared to fly ash or blast-furnace slag blended barriers. In addition, the chemical durability of silica fume-based barrier increased with increasing replacement level up to about 20 %. It seems that the amount of formed calcium silicate hydrate (CSH) in the initial cement-based barrier highly affects the overall chemical durability. The newly developed reactive transport model demonstrated its capability for understanding the barrier performance and investigating the optimal design of the barrier system.. Authors: Kim, Min-Seok [Korea Advanced Institute of Science and Technology (KAIST), Daejeon (Korea, Republic of); Korea Radioactive Waste Agency, Gyeongju, Gyeongsangbuk-do (Korea, Republic of)]; Han, Sol-Chan [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000190313657); Yun, Jong-Il [Korea Advanced Institute of Science and Technology (KAIST), Daejeon (Korea, Republic of)]. DOE Contract: AC52-07NA27344. Subjects: 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 36 MATERIALS SCIENCE; Cement mortar; Concrete; Long-term durability; Radioactive waste processing and disposal; Reactive transport modeling; Supplementary cementitious material; Vault type radioactive waste repository