Proposed Modification to the Plutonium Systemic Model

The currently accepted biokinetic model for plutonium distribution within the human body was recommended by the International Commission on Radiological Protection in publication 67. This model was developed from human and animal studies and behavioral knowledge acquired from other known bone-seeking radionuclides. The biokinetic model provides a mathematical means of predicting the distribution, retention, and clearance of plutonium within the human body that may be used in deriving organ, tissue, and whole body dose. This work proposed a modification to the ICRP 67 systemic model for plutonium that incorporated the latest knowledge acquired from recent human injection studies with physiologically based improvements. In summary, the changes included a separation of the liver compartments, removed the intermediate soft tissue-to-bladder pathway, and added pathways from the blood compartment to both the cortical and trabecular bone volumes. The proposed model provided improved predictions for several bioassay indicators compared to the ICRP 67 model while also maintaining its basic structure. Additionally, the proposed model incorporated physiologically based improvements for the liver and skeleton and continued to ensure efficient coupling with intake biokinetic models.