Assessment of the dose equivalents delivered by the main radionuclides involved in the operation of nuclear plants

The internal exposure of workers is characterized by an exposure of the body protracted after the intake. In order to describe this exposure in term of likely potential detriment, ICRP has defined two concepts in its publications 26 and 30: 1/ Committed dose to organs and tissues associated to a limit for non stochastic effects and 2/ Effective committed dose to the whole body associated with a limit for stochastic effects. Dose equivalents have been calculated after these concepts for 38 radionuclides; they are expressed as a function of the intake route for a unit concentration per second in inhaled air and for a unit ingested activity. Two kinds of factors are considered in the assessment of the delivered doses. The physiological and metabolic factors are quantified in models describing the radionuclide behaviour in the body as a function of their physical form and their physico-chemical nature. The dosimetric factors are concentrated in the formulation of the effective specific energy which considers the concept of source organ and target organ. Particular calculations have been made for radionuclides in the gaseous state in order to take into account the complex exposure involved