Radiation exposure assessment at using thoriated compounds on the basis of comparisons between measurements of air activity concentrations and urine measurements

Thorium intake could not be excluded while handling thoriated compounds. Dependent on the range and kind of handling, the possibly high internal radiation exposure needs an incorporation monitoring. Urine bioassays or air measurements preferably come into consideration as monitoring procedures. The interpretation of the data obtained by both procedures is afflicted with specific problems. Both the deviations of the real, compound specific biokinetic behaviour from the chosen interpretation model and the real intake mode with the supposed irregular sequence of many single intakes in contrast to the approach of chronic intake prove to be the principal uncertainty with urine bioassays. The influence of the activity from natural sources or the proportion in the urine, due to Ingestion, is negligible compared with faeces measurements. In air measurements the issue of the representativeness of the sampling arises. Is the activity strongly inhomogeneous distributed on the working side, the risk of a under or over-estimation of the exposure exists. One can never exclude sample contamination completely with both procedures. This contribution lights up these difficulties with the data interpretation. Goal of this investigation was to determine as well the results of both procedures can be approximated, in order to be able to detect thus the biased errors better. In a plant, which manufactures thoriated gas mantles, extensive air measurements by means of personal worn and fixed samplers installed at various working sides were carried out. The intakes calculated from this measurements were correlated with those, derived from a regime of quarterly urine measurements through many years. The results correspond quite satisfying. The contribution shows, what is to be considered with the data interpretation. (orig.)