Abstract
The external exposure to gamma rays from a radioactive cloud, i. e. the cloudshine, is an important exposure pathway. A computer code, AIRGAMMA, was developed to calculate quickly the cloudshine doses by interpolating normalized doses provided on the basis of the Gaussian plume model. The normalized dose is defined as the dose on the ground when a gamma-emitting nuclide is released at a rate of 1Ci/hr or the amount of 1Ci and the wind speed is 1m/sec. The code approximately takes account of depletion of the dispersing materials for calculation of the cloudshine doses, but ignores effects of the building wake and the mixing layer on the cloudshine doses. The interpolation of the normalized dose would not cause errors larger than 1% for most of the cases. The time for calculation of a dose is less than 2 msec on the computer FACOM-M380. The applicability of the approximations mentioned above is discussed in this report.
