Absorbed fraction sensitivity to changes in size of the ICRP nose model

The Human Respiratory Tract Model of ICRP Publication 66 is used for calculations of dose in the extrathorathic (ET₁) airways. Scaling for age and body size is included in determining the mass of the target tissue (basal cells) in ET₁ but is not included in deriving the absorbed fraction for particulate radiation. For dose calculations, it has been assumed that all absorbed fractions for particulate radiation published in ICRP Publication 66 are independent of age and body size. Therefore, these absorbed fractions are applied to calculate specific effective energy values not only for the Reference Worker but also for non-adults with noses of different sizes. In this note changes to the size of the cylinder model of the anterior nose in ICRP 66 are made by varying the surface area, the cylinder radius, and the thickness of tissue beyond the target region (basal cell). The energy deposition (absorbed fractions) in the target region (basal cells) is calculated using the MCNP4B (Monte Carlo) code to study the effects of these changes on the predicted absorbed fractions within the cylinder model.