Uncertainties in workers exposed to random intake of radioactive aerosols

Uncertainties in workers exposed to random intake of radioactive aerosols

The activity of radioactive isotopes intake by workers exposed occupationally to radioactive aerosols can be estimated by bioassays measuring these isotopes in the urine excretion or lung retention and monitoring the area using air-samples to measure their isotopic concentration. This process involves many uncertainties. To estimate the intake a typical assumption is to consider that the daily intake is constant during some periods, but, in fact the   concentration changes.   We have analyzed the uncertainties in the case where the worker is exposed to a random chronic intake. This case represents a real situation that happens in Nuclear Fuel Fabrication Plants where the workers are exposed to the inhalation of UO2.  Part of the uranium measured in the bioassays is due to the natural radioactive background (i.e. part of uranium excreted in the urine is consequence of the diet), and its effect in the occupational intake estimation has been evaluated. These uncertainties have been combined   to estimate the risk to exceed a limit of intake during a period in which a worker is exposed to uranium UO2 aerosols in a specify area. This criterion can be used to establish the bioassay program (frequency of bioassay samples).