Comparison of Observed and Predicted Air Concentrations and Ground Deposition Rates from Resuspension of 137Cs from Contaminated Ground Surfaces
C. W. Miller
Decommissioning and environmental restoration activities at any site contaminated with radioactive material can result in resuspension of radionuclides into the atmosphere from the site, potentially exposing both workers and the public. Evaluation of the potential health impact of resuspension from clean-up operations will probably require the use of mathematical modeling. A simple, stochastic model was used to calculate expected resuspended air concentrations and subsequent deposition rates from the unintentional deposition onto the ground of 137Cs from a teletherapy machine in Goiânia, Brazil, in 1987. Predicted air concentrations and deposition rates were compared with values measured 20.5, 23.5, and 32.5 months after the initial deposition. Based on soil concentration measurements at the contamination site, the ratio of the 50th percentile predicted to observed values for a height of 1 m at these three measurement times was 0.6, 1.6, and 0.5, respectively. The corresponding predicted-to-observed ratios for a height of 3 m were 0.9, 1.8, and 0.8. The predicted-to-observed ratios for the 50th percentile total deposition rates at a height of 1 m of the resuspended material were 0.6, 2, and 2.5 for the same three periods, respectively. The 95% credibility intervals for all predictions were much larger than those for the observations. If properly used, this model could be useful in evaluating the potential health impact of clean-up operations at contaminated sites.
This abstract was presented at the 35th Annual Midyear Meeting, "Decommissioning and Environmental Restoration", Controlling Dose 2 Session, 2/17/2002 - 2/20/2002, held in Orlando, FL.