Corrosion assessment for spent nuclear fuel disposal in crystalline rock,using variant cases of hydrogeological modeling

This paper presents a corrosion assessment of copper spent nuclear fuel disposal canisters in crystalline rock,using hydrogeological modeling.A simplified approach is considered,to avoid complex and time-consuming computer simulations.This simplified case is presented as a base case,with changes in the hydrogeological parameters presented as variant cases.The results show that in Taiwan’s base case,decreasing the hydraulic conductivity of the rock or decreasing the hydraulic conductivity of dikes results in a shorter transport path for sulfide and an increase in corrosion depth.However,the estimated canister failure time is still over one million years in the variant cases.

Modelling of the Hydrogeological Behaviour of the Tassette Aquifer: Study of the Possibilities of Exploiting This Aquifer as an Alternative against the Limestone Problem in the Commune of Thies

Senegal’s drinking water supply comes on the one hand from groundwater and mainly from Maastrichtian and Paleocene aquifers. The Tassette area included in the Thies region has such potential that the Paleocene is currently exploited to cover a certain part of Dakar’s important water needs. In addition, the city of Thies is itself confronted with the problems of limestone present in its drinking water and generally creating problems of scaling pipes. A water transfer is therefore a possible option to deal with this situation. This study will consist of modelling the Tassette aquifer to determine if it will cover Thies’ water needs over a period of 20 years. To assess the responses of the groundwater to pumping at this level and the changes that may occur, a numerical hydrogeological model is necessary. In order to have a better overview of the area, boreholes and piezometric tests were carried out, highlighting the different characteristics of the aquifer and the water it contains. Based on these, the model was developed according to a mesh system and more precisely by discretization and simulation according to the finite difference method from the Visual Modflow Flex software. The results observed for this modelling show that the city of Thies cannot be supplied as a whole. This mining model also causes brackish water intrusion. On the other hand, the additional withdrawal of a certain quantity of water compared to the current situation does not have as great negative impacts and would still partially meet the expectations of this modelling.

Evolution and modeling of mine water inflow and hazard characteristics in southern coalfields of China:A case of Meitanba mine

In this paper,the hydrogeological characteristics in the southern coalfields of China are first briefly outlined.Then,taking the Meitanba mine as an example,the evolution and modeling of mine water inflow are studied.Finally,the hazard characteristics related to mine water and mud inrush are analyzed.The results show that the main mine water sources in the Meitanba mine area are groundwater,surface water and precipitation.The evolution of mine water inflow with time indicates that the water inflow is closely related to the development of karst structures,the amount of water from rainfall infiltration,and the scope of groundwater depression cone.The mine water inflow increases with time due to the increase in mining depth and the expansion of groundwater depression cone.Using the big well method and following the potential superposition principle,a hydrogeological model considering multi-well interactions has been developed to predict the mine water inflow.Based on the monitored data in the Meitanba mine area over a period of nearly 60 years,it is found that with increasing mining depth,the number of water and mud inrush points tended to decrease.However,the average water and mud flow rate per point tended to increase.

Integrated Numerical Simulation of Water Resources in Crystalline Aquifers at KouéWatershed Scale(Western Cote d’Ivoire)

The present work applied the HydroGeoSphere (HGS) model in humid tropical area to Koué watershed scale to simulate flows in porous and fractured area of crystalline aquifers. It integrates rainfall, physiographic, fractures, hydraulic drilling and hydrodynamic data. The simulation of flows in porous area concerned 5 test zones. The input database of the model is implemented on a triangular grid in porous area using Gridbuilder software and interactive block grid in fractured area. In order to use the model in these two environments, boundary condition was set. The infiltrations rate of the earth layers is estimated in the order to 10-5 ms-1. The model simulates the pumping with a good reproductivity of the drawdown profiles of groundwater at the drillings. The storage coefficients vary between 9.9 × 10-4 and 2 × 10-3. The hydraulic conductivities vary from 8.5 × 10-6 to 2 × 10-5. 73.9% of the drillings studied has a high hydraulic conductivity and shows a strong drawdown of the groundwater table. The study of the static levels of the ground water allowed indicating the distribution of the water resources in the drillings: 57% are deep in the first 10 meters, 36% between 10 and 20 m, and 7% in the higher level to 20 m deep in the earth.

Surface Flood and Underground Flood in Xiangxi River Karst Basin： Characteristics, Models, and Comparisons

Xiangxi River Basin, located in western Hubei Province in central China, is a karst ridge-trough area with an inhomogeneous and complicated distribution of water resources. This paper compares the characteristics of surface and subsurface floods in this karst basin, utilizing a one-parameter Darcian model and the traditional exponential model. The observed hydrographs and inferred water components are strikingly similar for surface and subsurface floods. The Darcian model and the exponential model are based on different views of the flood generation process, with the former fitting the entire hydrograph with a single time constant, and the latter fitting only the recession limb with multiple time constants. Due to the anisotropy and heterogeneity of karst media, a combination of physical and chemical techniques including the use of 3S（remote sensing, geographical information system, global positioning system） method is proposed for an enhanced hydrological investigation to assess and characterize karst water resources in mountainous areas.