Deterministic Performance Assessment for a Conceptual Repository for Low- and Intermediate-Level Wastes in Korea

The release of radionuclides from the conceptual low- and intermediate-level radioactive waste (LILW) repository in Korea is analyzed by establishing a multicompartment model. The model takes into account the vault-array configuration consisting of multiple waste types, multimember radioactive decay chains, and radionuclide transport through the water-unsaturated regions and water-saturated aquifer. Observations of the repository performance have been made with the radiological exposure dose rates and with the radiotoxicities in the environment.

Numerical results show that, among all the radionuclides in the waste, ¹²⁹I is the predominant contributor to the overall peak exposure dose rate. The peak exposure dose rate of ¹²⁹I can be affected by a migration distance in the geosphere and the vault-array configuration. Reducing the initial inventory of ¹²⁹I stored in the waste vaults or spreading its release over a longer time period by modification of the engineered barrier system would effectively reduce the exposure dose rate because the release rate of ¹²⁹I from the repository is reduced.

The total radiotoxicity in the environment is dominated by ¹²⁹I at early times and by ²³⁸U and its daughters after 10⁶ yr. Because of the long half-lives of these nuclides, the radiotoxicity in the environment is insensitive to the vault-array configuration or to the transport distance in the geosphere.