Reliability of Radioactive Transfer Models

Assessment of the radiological impact of planned or existing practices involving the (actual or potential) release of radionuclides to the environment are largely based on the use of modelling techniques which allow prediction of the relationship between environmental levels and releases and the associated radiation dose to man. Models are imperfect means of representing environmental transfer processes, and it is essential to know the reliability which can be associated with the predictions of these models for each and every assessment situation. Such information is necessary in order to establish confidence in model predictions and, in particular, to allow adequate safety margins to be set in the design of nuclear facilities. This knowledge is also a prerequisite to determine release limits or to decide whether further research is justified in order to improve predictive accuracy. Therefore a number of distinguished pilpers have been presented during this workshop which focused both on practical aspects of variability of observations of facts occuring in nature, but also on learned aspects of the science of statistics. It is not very clear, however, whether much insight in mechanisms is gained by such an approach. This insight is probably rather reached by a straightforward judgment of the quality of the primary data and by the willingness to think over carefully the experiments and measurernents before doing them. The book is composed such as to give the reader the chance to quietly study the presented papers in good order.

Session 1: Overview of Model Reliability and Testing Studies.- An overview of the IAEA Safety Series on procedures for evaluating the reliability of predictions made by environmental transfer models.- Verification and validation of NRPB models for radionuclide transfer through the environment.- BIOMOVS: an international model validation study.- Session 2: Transfer Air-Land.- A comparison of model predictions of gaseous dispersion with environmental measurements of 14C around Sellafield, UK.- Calculation model for the impact on soil due to tritium emission into the atmosphere during snowfall.- Confirmation of laboratory results by HT releases under field conditions: HT deposition velocity and reemission rate.- Uncertainty analysis and model validation for a retrospective assessment of thyroid dose resulting from atomic weapons’ test fallout.- An application of a diagnostic wind model to describe atmospheric transport.- Sea breeze wind field prediction in atmospheric dispersion modelling.- Session 3: Transfer in Terrestrial Environment.- A comparison of model predictions and observations of the transfer of 137Cs through the air-pasture-cow-milk pathway.- From model intercomparison to model validation: an example from the BIOMOVS study.- Cesium transport in food chains: comparison of model predictions and observations.- Comparing predictions of two radioecological models with measured values.- Validation of the farmland models for radionuclide transfer through terrestrial foodchains.- Modelling the radiocesium content in milk and comparison with the measured data after the Chernobyl accident.- Particulate transport processes in agroecosystems: validation of predictive models.- The IUR project on soil-to-plant transfer factors of radionuclides: expected values and uncertainties.- Validation of dynamic foodchain models: results of an experimental programme.- Transfer of radionuclides to food plants: root versus foliar uptake.- Session 4a: Transfer in the Aquatic Environment Fresh Water.- Intercomparison of model calculation of the turnover of Ra-226 within an aquatic ecosystem.- Uncertainties associated with estimates of radium accumulation in lake sediments and biota.- Finite element modelling of transport of radium-226 and uranium from Port Granby radioactive waste management site to Lake Ontario.- Biosphere model validation by intercomparison to observed behaviour of fallout radionuclides in the aquatic environment.- Dose assessment and uncertainty with respect to liquid effluent discharges.- Session 4b: Transfer in the Aquatic Environment Marine Ecosystem.- A model performance test for the aquatic dispersion of radionuclides in the North-East Atlantic waters.- Radioactivity of French coast of the Channel due to the release of technetium-99 and iodine-129: modelisation and measurements.- Comparison of marine dispersion model predictions with environmental radionuclide concentrations.- Modelling the behaviour of long-lived radionuclides in the Irish Sea: comparison of model predictions with field observations.- Comparison of models for assessing the radiological impacts of deep-sea disposal of radioactive wastes.- Modelling the sea-to-land transfer of marine discharges from Sellafield: validation against environmental measurements.- Session 5: Transfer in the Biosphere From Waste Repositories.- Comparison of two model approaches for the geosphere/biosphere interface.- The reliability of environmental transfer models applied to waste disposal.- Sensitivity analysis applied to the disposal of low and medium-level waste.- Modelling the radiological impact of release of radionuclides into the biosphere from solid waste disposal facilities.- Session 6: Uncertainty Analysis.- DIVIS: a programme package to support the probabilistic modelling of parameter uncertainties.- The generation of experimental designs for uncertainty and sensitivity analysis of model predictions with emphasis on dependences between uncertain parameters.- Uncertainty analysis for ranking parameters in environmental mathematical modelling.- Reports from Chairmen of Sessions 1, 2, 4a, 4b, 5.- Conclusions.- List of Participants.