Uplift and erosion scenarios must be analysed since these natural phenomena are expected to be inevitable at most districts in Japan. It is increasingly important to enhance the confidence in uplift and erosion scenarios even if these processes occur far into the future, since performance assessment cut-off times have not yet been defined. In this context, this study specifies uplift and erosion scenarios considering uplift and fluvial erosion based on Japanese geological and topographical characteristics and describes a conceptual model focused on a comprehensive fluvial erosion process that were based on generalisations of field observations. A series of bounding analyses have been carried out to define parameter conditions to satisfy hypothetical dose criteria considering various uplift and erosion rates and transmissivities. The results based on the conservative assumptions show that there are some cases that satisfy the hypothetical dose criterion in each phase for the likely scenario (base scenario: 10 μSv/y), which is a targeted dose suggested by the Nuclear Safety Commission for sub-surface disposal. All cases are below 300 μSv/y, which is the targeted dose for the less-likely scenario (variant scenario) as well as the dose constraint for radioactive waste disposal by the International Commission on Radiological Protection. The discussion also provides that a loss of inventory in the engineered barrier system by accelerating release of nuclides does not significantly decrease the doses in later phases due to inherent attributes of the repository system, i.e. multiple barriers and multiple safety functions. In principle, the influence of uplift and erosion should be reduced by appropriate site selection and design, to the extent possible; to ensure that sufficient nuclides decay while the repository is deep underground.

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