Evaluation of nuclide release scenarios for a hypothetical LILW repository

A program for the safety assessment and performance evaluation of a low- and intermediate-level radioactive waste (LILW) repository system has been developed. Utilizing GoldSim (2006), the program evaluates nuclide release and transport into the geosphere and biosphere under various disruptive natural and manmade events and scenarios that can occur after a waste package failure. We envisaged and illustrated these events and scenarios as occurring after the closure of a hypothetical LILW repository, and they included the degradation of various manmade barriers, pumping well drilling, and natural disruptions such as the sudden formation of a preferential flow pathway in the far-field area of the repository. Possible enhancement of nuclide transport facilitated by colloids or chelating agents is also dealt with. We used the newly-developed GoldSim template program, which is capable of various nuclide release scenarios and is greatly suited for simulating a potential repository given the geological circumstances in Korea, to create the detailed source-term and near-field release scheme, various nuclide transport modes in the far-field geosphere area, and the biosphere transfer. Even though all parameter values applied to the hypothetical repository were assumed, the illustrative results, particularly the probabilistic calculations and sensitivity studies, may be informative under various scenarios. (GoldSim, LILW, Nuclide transport, Safety assessment, Scenario).

► A program has developed utilizing GoldSim, by which nuclide transports in the near- and far-fields of an LILW repository, as well as a farther transport through a biosphere under various natural and manmade disruptive events, could be modeled and assessed.
► Illustrations for a normal case and the cases for the drilling of pumping wells in and around a repository site, as well as the effect of degradation of near-field barriers with assumed data, were introduced.
► For imaginary species a colloid-facilitated transported scenario has been also evaluated.