Health Physics Society of Japan Meeting, Okinawa, Japan, June 26-27, 2008
Dr. James participated in the 42nd Annual Meeting of the Japanese Health Physics Society, Okinawa, Japan, June 26-27, 2008, where he made two platform presentations and new contacts with Japanese scientists with particular interest in USTUR’s research program.
Using in vivo measurements and urine bioassay to characterize the absorption of inhaled 241AmO2 and evaluate the probability distributions of doses
Anthony C. James (USTUR), Timothy P. Lynch (PNNL), Alan Birchall (HPA-RPD, UK), Matthew Puncher (HPA-RPD, UK)
This paper describes the use of comprehensive urine bioassay and external counting data from an initial 6-y follow-up of an individual who accidentally inhaled
241AmO2 to evaluate: (i) the probability distributions of parameter values characterizing dissolution and absorption of this material from the lungs; (ii) the probability distribution of a parameter characterizing this individual’s rates of transport of intact 241AmO2 particles from his lungs, and; (iii) the probability distributions of this individual’s intake, effective dose and committed tissue dose equivalents. The application of the UK Health Protection Agency’s “Likelihood Weighted Latin Hypercube” (LWLH) method utilizing Bayesian inference with the IMBA Professional Plus software to derive these distributions directly from the bioassay data is described. This is an ongoing U.S. Transuranium and Uranium Registries (USTUR) case study of a healthy volunteer registrant. It is now 12 y since the accidental intake occurred. Plans to test the power of the parametric probability distributions derived from the initial 6-y follow-up to predict future bioassay results and updated probability distributions of doses in this case will be discussed. More general application of the probability distributions of 241AmO2 absorption parameters derived from this case study will also be discussed. [USTUR-0245-08]
Beyond α-spectrometry for actinide determination in human tissues?
Sergei Y. Tolmachev (USTUR), Michael E. Ketterer (NAU), Anthony C. James (USTUR)
We present an overview of the analytical methods for Pu, Am and U isotopic determination in human tissue samples currently used at U.S. Transuranium and Uranium Registries (USTUR), including exploration of inductively coupled mass spectrometry (ICP-MS) techniques. 239+240Pu, 241Am and 234,235,238U determinations by both Sector Field (SF) ICP-MS and α-spectrometry (AS) have been intercompared. For 239+240Pu, activity values derived from ICP-MS measurements were 3% higher than the AS results (for 12 samples). The results of investigating this bias in the ICP-MS measurements using 240Pu/242Pu standards will be presented. With SF-ICP-MS, 241Pu (β-emitter, T1/2 =14.1 y) was measured in 4 samples (with “high” Pu content). However 238Pu was not measurable due to isobaric interference from background 238U. For 241Am, the ICP-MS values were 8% lower than those from AS based on 4 samples analyses. More samples are being analyzed to investigate this 241Am measurement bias. Uranium measurements highlighted significant problems in using AS for low-activity (natural) isotopic determinations. However, for higher activity samples (occupationally-exposed workers), ICP-MS and AS results were in a good agreement. The SF-ICP-MS detection limit for 238U is an order of magnitude lower than that by AS, and SF-ICP-MS accurately measures 236U from anthropogenic uranium. For all isotopes, ICP-MS has the great advantage of rapid analysis (10 min per sample vs. 41 hr for AS). [USTUR-0246-08]