A disposal system for spent nuclear fuel mainly divides into two parts; Engineered barriers include spent nuclear fuel, canister, buffer and backfill and natural barriers mean a host rock surrounding engineered barriers. If radionuclides released from a repository, they can migrate to the ecosystem. Sorption plays an important role in retarding the migration of released radionuclides. Hence, the safety assessment for the disposal of a spent nuclear fuel should consider the migration and retardation of radionuclides in geosphere. Distribution coefficient is one of input parameters for the safety assessment. In this work, distribution coefficients for crystalline rock as a natural barrier were collected and evaluated for the purpose of safety assessment for the deep geological disposal of a spent nuclear fuel. The radionuclides considered in this work are as follows; alkali and alkaline earth metals (Cs, Sr, Ba), lanthanides (Sm), actinides (Ac, Am, Cm, Np, Pa, Pu, Th U), transition elements (Nb, Ni, Pd, Tc, Zr), and others (C, Cl, I, Rn, Se, Sn). The sorption of radionuclides is influenced by various geochemical conditions such as pH/carbonates, redox potential, ionic strength, radionuclide concentration, kinds and amounts of minerals, and microbes. For the evaluation of distribution coefficients, the data from Sweden (SKB), Finland (Posiva), Switzerland (Nagra), and Japan (JAEA) were collected, analyzed, and the recommended distribution coefficients have been suggested.

• Jae-Kwang Lee(Korea Atomic Energy Research Institute (KAERI)) Corresponding author
• Jang-Soon Kwon(Korea Atomic Energy Research Institute (KAERI))
• Jaeun Kang(Pohang University of Science and Technology (POSTECH))
• Wooyong Um(Pohang University of Science and Technology (POSTECH))