Global Sensitivity Analysis of Groundwater-Radionuclide Transport Model from Near Surface Disposal Facilities

摘要

The quantitative assessment of the performance of radioactive waste disposal facilities is an important aspect that needs to be addressed to check its impact on public and the environment. In this paper, near surface disposal facilities (NSDFs), constructed to contain the low level radioactive waste is considered. The performance of these systems is examined by safety assessment models where the concentration of radionuclide migrating from the barrier system to the human habitat through a particular pathway is estimated. The radiation dose experienced by an individual through drinking water pathway is the endpoint of assessment of the model. The contaminant migration is modelled numerically as a three dimensional 1000 x 1000 x 6m groundwater contaminant transport model with a decaying source. The concentration and radiation dose of Carbon (~(14)C) at a distance of 200m from the barrier system are estimated from the model. The uncertainty is considered as an integral part of modelling and the input parameters considered are porosity, hydraulic conductivity, groundwater velocity, distribution coefficient and diffusion coefficient. The uncertainty propagation and quantification is carried out using collocation based stochastic response surface method (CSRSM). To run the simulations for a huge set of input, a code is developed using built-in python interface in the software. Further, global sensitivity analysis is carried out to identify the critical parameters affecting the migration of radionuclide.