Biokinetics of a Uranium Octoxide-Bearing Aerosol Formed in a New Laser Enrichment Process: Implications for Human Exposure

Abstract

This study forms part of a programme of work to investigate the biokinetics of uranium in aerosols formed during laser isotopic separation at a new uranium enrichment processing facility (Ansoborlo et al., 1994). These aerosols can consist of UO2, Umetal and U3O8 in different proportions and contain an ultrafine component. A previous study (Henge-Napoli et al., 1994) identified an aerosol consisting of 85% UO2/Umetal and 15% U3O8 with up to 20% of the activity associated with an ultrafine component. The ultrafine fraction was shown to consist of small clusters of 0.1 um particles. This material had similar absorption characteristics to the default values recommended in the International Commission on Radiological Protection (ICRP) Publication 66 (ICRP, 1994) for compounds with moderate absorption rates (Type M). Workers can be exposed to two different types of uranium aerosols which in normal conditions are a mixture of UO2+Umetal. However, due to the high pyrophoricity of uranium metal, a fire could ignite which would alter the initial composition. Although considerable information exists on the biokinetics of U3O8 (Stradling et al., 1989) there is a paucity of data available on aerosols formed during uranium fires. The aim of this study was to use material-specific physiochemical data and biokinetic data, obtained from animal experiments, to provide a basis for deriving dose limits and assessing monitoring procedures. The study employed the most recent recommendations, models and methodologies of the ICRP ICRP Publications 60 (ICRP, 1991), 66 (ICRP, 1994), 68 (ICRP, 1994) and 69 (ICRP, 1995). All computer codes used were developed specifically to implement the latest ICRP models.