Simulation of Kr-85 transport at Savannah River

The AIRDOS-EPA computer code uses a modified Gaussian plume equation to estimate air concentrations from the release of up to 36 radionuclides and couples these results with the terrestrial model developed in US Nuclear Regulatory Commission Regulatory Guide 1.109 to estimate the annual dose to the general public. One year of weekly average 85Kr concentrations observed at 13 sampling stations around the Savannah River Plant have been used to validate the atmospheric transport portion of AIRDOS-EPA. The predicted annual average concentration at each station exceeded the observed value in every case. The average overprediction factor was 2.4 (range 1.4 to 3.4). Pearson's correlation between pairs of logarithms of annualized observed and predicted values was r = 0.93. As the averaging time of the prediction decreases, however, the uncertainty in the prediction increases. For example, the monthly values show more scatter than do annual or seasonal values. When seasonal observed and predicted values were compared, the authors found increasing agreement as they compared spring, summer, fall and winter values