Execution techniques for high level radioactive waste disposal: VIII Performance assessment of engineered and natural barriers and its application

Abstract

  Scenarios for the geological disposal of high-level wastes were constructed in order to assess the safety of the HLW disposal and the performance of the repositories. The list of features, events, and processes (FEP) related to the disposal and their influence on others, called process influence diagram (PID), were utilized to construct the scenarios. As a result, the scenario involved in groundwater flow can be divided into a reference scenario and alternative scenarios. In addition, the latter are composed of upheaval/erosion, submergence, permanent glacial epoch, permanent interglacial epoch, and higher-temperature inclination with depth. According to the scenario analysis, the performance assessments of barriers were conducted for a sedimentary rock area and granitoid rock area. The results showed that a lower individual dose resulting from the disposal was obtained for the sedimentary rock area because of the higher values of porosity and distribution coefficients in the sedimentary rock area than those in the granitoid rock area. In addition, the dose for the upheaval/erosion scenario gave rise to the highest value.