Monitoring of personnel with internal contamination by 241Am: comparison of observed data with biokinetic models

A group of initially 7, now 4 individuals with internal contamination by 241Am has been monitored for more than 10 years. The contamination was due to Am oxide powder serving as the starting material for various products. Sometimes the Am had been converted to the nitrate. The contaminated individuals have been measured in vivo on a whole-body counter, with low-energy radiation detectors positioned near the skull. Urine and stool samples have been analyzed by radiochemical separation and alpha spectrometry using 243Am as the yield monitor. Existing observed data were compared to the ICRP biokinetic model and Legget's model. In the majority of cases, where the time from the intake is longer than 15 years, the excretion rate is lower (or content in the skeleton higher) than as predicted by the models. The urine-to-stool excretion activity ratio is in accordance with the model