Predicted versus measured tritium oxide concentrations at the Savannah River Site

Measured tritium oxide concentrations in air at various offsite locations are compared with concentrations predicted by three computer codes that are utilized at the Savannah River Site to estimate doses to maximally exposed offsite individuals. Annual average concentrations calculated by the computer models were compared with measured average concentrations taken from monitoring data collected over the last 10 y. The computer programs used for the comparison are AXAIRQ, MAXIGASP, and CAP88. The 10-y averaged ratios of predicted-to-measured tritium oxide air concentrations using AXAIRQ, MAXIGASP, and CAP88 are 1.89+/-0.56, 1.70+/-0.48, and 1.40+/-0.39, respectively. The difference in ratios is primarily due to different wind speed averages used within each of the models. These results show exceptional agreement, considering Gaussian plume models typically over predict annual average air concentrations by a factor of two to four.