An evaluation of nuclide release from a trench-type LILW repository

• A GoldSim template has been developed for a probabilistic safety assessment of a trench-type repository.
• Illustrative evaluations for a comparison among the scenarios are made.
• A sensitivity of shortcut pathways generated due to earthquakes on the nuclide transport was also investigated.

A simple and effective model and a GoldSim (GoldSim, 2006) template program, by which a probabilistic safety assessment of a conceptual trench-type repository for low- and intermediate level radioactive waste (LILW) disposal can be carried out under various nuclide release scenarios, have been developed. To quantify the exposure dose rates due to nuclide release from the trench and transport through the various pathways possible in the near- and far-fields of the repository system under a base case and some alternative scenarios, illustrative evaluations for a comparison among the scenarios as well as a sensitivity of shortcut pathways generated due to earthquakes on the nuclide transport are made and demonstrated. To this end, by changing the conservative base case nuclide release scenario under which all portions of the cap of the trench are failed unconditionally and immediately after a closure of the repository, a total of four other alternative scenarios were separately evaluated for the total exposure dose rates to the farming exposure group and then compared to the base case results. Among them, an earthquake scenario shows a dominant behavior almost throughout the whole time span. To see the influence of all shortcut travel pathways that are assumed to be newly generated by this earthquake scenario, their sensitivities to the exposure dose rates to the farming exposure group were also made and compared to each other.