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

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 con-
sists 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.