Operational surveillance model for actinide exposure

While ICRP publications 30, 35 and 54 provide possibilities for interpreting the results of faecal excretion measurements for cases of acute or chronic inhalation, no data are presently available for use in direct surveillance of workers chronically exposed to an actinide inhalation hazard over a limited period. Using metabolic data applicable to a single inhalation taken from ICRP publications 30 and 54, the authors propose a faecal excretion model based on the hypothesis that workers are submitted to a constant daily exposure level. The cumulative faecal excretion curves determined from this model by convolution calculations are presented for exposure to 239Pu (Classes W and Y, 1 μm AMAD) for variable time periods. Practical application of the model to a group of workers assigned to conditioning waste products containing plutonium involved faecal excretion measurements during the exposure period, followed by control measurements after the end of the exposure. The measurement results expressed in terms of inhaled activity were analysed according to the duration of the exposure to validate the proposed theoretical model. The results were then compared with the ambient atmospheric measurements for the work stations by analysing the filters on the aerosol sampling system. The authors discuss the correlation between these static physical measurements and the proposed individual radiotoxicology survey. (author)