Éric Blanchardon has defended his HDR on the 21st November 2012 in Orsay.
Mrs Michèle Gonin, staff delegated to occupational health at EdF
Mr Wesley E. Bolch, professor in University of Florida
Mr Didier Dubois, Research Director in CNRS
Mr Éric Quémeneur, Research Director in CEA
Mr François Paquet, senior expert in IRSN
Mr Éric Simoni, professor Paris Sud University
The exposure to ionizing radiation increases the risk of cancer in proportion to the absorbed dose. The dose is therefore a fundamental quantity of radiation protection which my expert work aims to assess in case of internal radioactive contamination, from the measurement of activity and by the application of biokinetic and dosimetric models. However the variability observed in the doses assessed in intercomparison exercises leads to question the reliability of the models and the conditions of their application. A large part of my research work is therefore dedicated to evaluate the variability of the measurement data and the reliability of the biokinetic and dosimetric models, in order to restrain their associated uncertainty. Still, no matter how accurate the techniques and models, the right tool should be applied in the right situation to obtain consistent results. To ensure the robustness of methods, the quality assurance of results and a better reproducibility of the internal dose assessment procedure, guidelines were written for the professionals in the field. In spite of those guidelines, the results of a recent intercomparison exercise show different approaches to each contamination case, according to different assumptions. Measurement errors and incomplete knowledge of the conditions of exposure and of the underlying biological and physical mechanisms are sources of uncertainty which inevitably propagate to the estimated dose. We quantified this uncertainty to decide whether it was acceptable in view of the situation and of the objective. We believe that a reliable assessment of dose is feasible for risk management purpose. But the assessment of the individual health risk remains an issue, notably because most exposure to ionizing radiation leads to effective doses below 100 mSv, in a range where the relation between dose and risk is unclear. The understanding of risks in this low dose range is the goal of a significant effort in epidemiology and radiobiology. We contribute to this effort through the development of dosimetric models to provide a realistic assessment of the dose received by the subjects of epidemiological studies and animal experiments.