In the concept of vertical disposal of high-level radioactive waste, evaluating the influence of groundwater flow into disposal pits on the performance of buffer materials as an engineering barrier is important because the inflow might cause erosion of the buffer materials. In particular, for a rock mass in which fractures control the permeability, it is necessary to evaluate the groundwater behavior around the disposal pit in consideration of fractures in the surrounding rock mass. We develop a lattice-transportation flow (LT-Flow) program that models the rock fractures using a discrete fracture network model and expresses the groundwater flow path using a three-dimensional pipe network. The purpose of this study is to model fractures by assuming a radioactive waste disposal tunnel in the fractured rock and evaluating the groundwater behavior around the disposal pits using LT-Flow. The analysis is conducted under conditions of modeling a single disposal tunnel and five disposal tunnels by assuming disposal panels. The variance in disposal pit inflow due to the distribution of fractures is evaluated quantitatively. Furthermore, the effectiveness of grouting for the disposal pits to control the inflow, and the impact of grouting on other disposal pits or surrounding disposal tunnels are also evaluated quantitatively.
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