Les méthodes et les limites de la dosimétrie après contamination interne

Abstract

The methods and limitations of dosimetry after internal contamination.The assessment of absorbed, equivalent and effective doses after internal exposure is based on activity measurement by in vivo counting or bioassay. A dose value is derived from this measurement by means of biokinetic and dosimetric models which describe the behaviour of radionuclides in the body of a reference man and the subsequent deposition of energy. To enforce regulatory dose limits, monitoring programs are designed. The doses can be estimated from the measurement data according to a standard procedure as proposed by the IDEAS group. However, a significant uncertainty is associated with the dose estimate, due to the uncertainties of measurement, to the incomplete knowledge of the conditions of exposure and to the imperfect realism of the models. In addition to this uncertainty, the extrapolation to low dose of biological effects observed at higher dose, the chemical toxicity of radionuclides and the heterogeneous energy deposition make the estimation of the risk following an internal exposure very difficult. As a conclusion, it should be reminded that the effective dose is a tool for the management of radiological protection but not a quantitative indicator of the individual risk.

Assessing internal exposure in the absence of an appropriate model: two cases involving an incidental inhalation of transuranic elements

“…In closing, it should be stated that we must take into account the psychological impact of an evaluation of a committed effective dose over a period of 50 years and provide the employee with all the information necessary in distinguishing between the concepts of risk and effective dose (Blanchardon et al, 2007) …”