Medical monitoring and dosimetric uncertainty concerning actinides: experience feedback and optimisation
Le Guen, B.; Gonin, M.; Bailloeuil, C. Berard, P. Carles, M. Gibert, B.
IRPA-10: 10. international congress of the International Radiation Protection Association Hiroshima (Japan) 14-19 May 2000, T-5-3, P-6a-306;10 refs., 1 tab.
The individual dosimetric surveillance of workers exposed to actinides is intended to ensure that any intake is detected at an early stage and that the associated committed doses are evaluated. The latest ICRP recommendations impose additional internal dose estimation constraints. Difficulty in interpreting the results of surveillance stem from uncertainty concerning the prospective biokinetics of inhaled particles, the actual industrial situation (different workstations and changes in employee positions in companies) as well as the surveillance regime chosen. The authors describe their experience of the surveillance of nuclear fuel cycle workers and the optimisation of dose evaluation. The introduction of work area or workshop monitoring associated with measures to detect collective and individual exposure necessitates an exact knowledge of the actual nature of the workstations and the products handled there, and the fundamental requirement is that the means must match the risks. Collective monitoring can, for instance, be carried out by taking nose blow each time a zone is left, measuring air conditions and characterising workstations, all modes of surveillance which are as close as possible to operational dosimetry, the goal of which is to control exposure by monitoring the actual effectiveness of the radiological protection measures. Individing monitoring combines whole body counting with the monitoring of urinary and faecal excreta, to situate the case of each worker in terms of the dose limits. Three situations in very different industrial sites have thus been analysed, making it possible to substantiate the usefulness and the complementarity of the monitoring procedures adopted. The lower dose limits imposed by the regulations necessitate reducing the factors of uncertainty so that internal doses can be more accurately estimated. The surveillance must be adapted to each individual industrial site according to the actual risks encountered in the fuel cycle, from fabrication to decommissioning of the facilities. This optimisation calls for close collaboration between the radiological protection departments, human-factors engineers and occupational medicine services involved.