Uncertainty from the Food Chain Module

his report describes the analysis of the uncertainty in the model predictions resulting from uncertainty in the values to be assigned to the input parameters describing transfer of radionuclides along food chains. The main aim of this part of the study was to identify the input parameters whose uncertainties make large contributions to the overall uncertainty; the parameters identified would then be included in the final analysis of the uncertainty in the whole system. Uncertainty analysis involves specifying probability distributions for the values of each of the parameters involved, sampling sets of values from those distributions and propagating them through the model to derive information on the uncertainty in the model prediction. Those parameters whose uncertainties make major contributions to the overall uncertainty can then be identified using correlation coefficients between the input values and the model outputs. Earlier expert judgment studies have provided distributions on the values of the parameters describing the behaviour in food chains of those nuclides that make major contributions to the doses following reactor accidents.