An exact solution of gamma dose from ground-level plume

Predictive models for estimating the gamma dose from radioactive plumes or puffs play important roles in the siting and operation of nuclear facilities such as power reactors and fuel reprocessing plants. The traditional model for calculating the long-term absorbed dose from a continuous plume uses the sector-averaged Gaussian plume model to predict the concentration as a function of height at any distance downwind. The model is given in the form of two integrals, I1 and I2, that account for the dose from the uncollided gamma radiation and from the buildup of scattered radiation, respectively. In this paper, analytical solutions are presented to the I1 and I2 integrals in these models. These solutions show that the semi-infinite, Gaussian cloud model predicts lower absorbed dose rates than the semi-inifinite, uniform cloud model. The difference is significant when μsigma/sub z/ is small. Because the Gaussian cloud model is based on a more realistic concentration distribution than the uniform cloud model, the absorbed dose calculations based on the former model should give more accurate estimates of the longterm averaged absorbed dose