Probabilistic assessment of the impact of bottom sediment on doses to humans from a groundwater-mediated radionuclide release in a farm-lake scenario

Abstract

Radionuclide transport with groundwater flow and subsequent doses to people are an aspect to be studied when assessing the long-term safety of geological nuclear waste repositories. A scenario where the radionuclide release migrates through a three-layer sediment structure of a lake in a farming environment is presented in this paper. The sediment column consists of deep (till), intermediate (glacio-aquatic sediment) and top layers (clay). The radionuclide release is assumed to enter the deep sediment layer from a bedrock fracture system at a rate of 1 Bq yr−1. The main objectives of the paper are to investigate the most contributing parameters, especially linked to the sediment layers, to the overall dose estimates for humans. The sensitivity analysis was conducted in two phases where the Morris method was used for screening and the Extended Fourier Amplitude Sensitivity Testing and Sobol’s methods were used for estimating total-order indices. The studied radionuclides, 36Cl, 135Cs, 129I, 94Nb, 237Np, 90Sr, 99Tc and 238U, exhibit differences in how the sediment layers affect the concentration in the lake water used for drinking, irrigation and watering cattle and subsequently the dose conversion factors for humans through ingestion, inhalation and external radiation.

Feasibility of neural network metamodels for emulation and sensitivity analysis of radionuclide transport models

“… Sr is not transported as easily as Cs, but plants growing in contaminated soil can take up small doses of both Sr and Cs 8 , 9 . In numerical simulations of groundwater, such as in 10 , 11 , Sr and Cs mainly decay in the transportation phase, while part of the Sr dose will stay in deep sediments and a fraction of both radionuclides could contaminate plants and animals. For example, Cs tends to be absorbed by mushrooms, while Sr tends to be spread to agricultural vegetables 11 .…”