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Given the inherent variability of natural processes and the uncertainties involved in modelling, presenting modelling results as distributions of probable values would provide a fuller representation of reality than the single values of the deterministic models. <p>This project had two main aims: to develop a probabilistic model or models for use in the assessment of routine discharges of liquid radioactive waste, and to use the model for a sensitivity analysis of the input parameters. It was proposed to create probabilistic versions of two deterministic marine dispersion models (WAT and ADO) to be used in assessing the impact of proposed radioactive discharges as part of the FSA's prospective dose methodology.
Two methods of selecting random numbers from specified distributions for use in the model were evaluated for accuracy: Simple Random Sampling and Latin Hypercube Sampling. The latter was chosen as it provided smoother distribution predictions. Uncertain parameters were identified and the parameter distributions determined, for the entire UK coast, through consultation with CEFAS experts. <p>The distributions were then propagated through the models using Monte Carlo analysis. An assessment of the Sizewell nuclear site was used as a case study for the new models and for comparison with a deterministic assessment of the site. The uncertainty due to the habits survey for this site was investigated.
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Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.