Methods for Uncertainty and Sensitivity Analysis : Review and recomendations for implementation in Ecolego

In this paper we review several uncertainty and sensitivity methods available in the literature and provide recommendations for implementing some of these methods in Ecolego. Predictive models used in the assessment of protection of the environment from ionising radiation present some extreme characteristics that make uncertainty and sensitivity analysis a non-trivial task. Those characteristics constrain the number and type of methods that are useful. The uncertainty methods selected in this work are based in Monte Carlo techniques or in other words they are probabilistic methods. These are found superior to deterministic methods in the context of radiological risk assessments and environmental protection. The Simple Monte Carlo sampling and the Latin Hypercube sampling were the sampling approaches selected to make uncertainty analysis. In respect to sensitivity analysis, the global methods were preferred over the deterministic or local methods. Global sensitivity analyses (GSA) are sampled-based analyses and again the Simple Monte Carlo and the Latin Hypercube techniques are necessary to allow their implementation in Ecolego. MatLab codes of the recommended methods were delivered 2004, in a CD to the Swedish Radiation Protection Authority (SSI)

Assessing doses to humans in the Posiva safety case

In Finland, Olkiluoto Island has been selected for constructing a spent nuclear fuel disposal facility. With the approaching licensing step, submitting the application for nuclear construction licence in 2012, all components of the safety case are becoming more site-specific. In order to assess compliance with regulatory requirements, a prospective deterministic dose assessment methodology based on the ICRP concept of assessing doses to the representative person was developed and implemented in the interim safety case 2009, to be further refined for the safety case 2012. To facilitate the assessment of doses to the most exposed people and other people at the evolving site, full dose distributions are derived, comprising the dose to each potentially exposed person in each generation

Study of the uncertainty in estimation of the exposure of non-human biota to ionising radiation

Uncertainty in estimations of the exposure of non-human biota to ionising radiation may arise from a number of sources including values of the model parameters, empirical data, measurement errors and biases in the sampling. The significance of the overall uncertainty of an exposure assessment will depend on how the estimated dose compares with reference doses used for risk characterisation. In this paper, we present the results of a study of the uncertainty in estimation of the exposure of non-human biota using some of the models and parameters recommended in the FASSET methodology. The study was carried out for semi-natural terrestrial, agricultural and marine ecosystems, and for four radionuclides (137Cs, 239Pu, 129I and 237Np). The parameters of the radionuclide transfer models showed the highest sensitivity and contributed the most to the uncertainty in the predictions of doses to biota. The most important ones were related to the bioavailability and mobility of radionuclides in the environment, for example soil-to-plant transfer factors, the bioaccumulation factors for marine biota and the gut uptake fraction for terrestrial mammals. In contrast, the dose conversion coefficients showed low sensitivity and contributed little to the overall uncertainty. Radiobiological effectiveness contributed to the overall uncertainty of the dose estimations for alpha emitters although to a lesser degree than a number of transfer model parameters