Microcomputer Monte Carlo electron transport codes for beta skin dose calculations

The adaptation of a one-dimensional Monte Carlo election transport program (called ZEBRA) for use on microcomputers in a program called Eltran2 is described. The purpose of this adaptation was to reduce the cost of the Monte Carlo calculations. Eltran2 has, in turn, been modified into a two-dimensional program called Eltran3 for computing the dose from a point or a disk source to a cylindrical target. For Monte Carlo calculations, theoretical beta energy spectra are calculated based on the Fermi beta decay theory. The calculated average energies of spectra agree with the values in related publications to within 6%. An extended study has been done using Eltran2 and Eltran3 to facilitate the design of, a beta/gamma skin dose monitor. The programs calculate the effects of angular distribution of source electrons and the radial distribution of the hot particle dose. It is found that the hot particle dose averaged over a live skin area of 1 cm² significantly underestimates the real dose value at the very small area just under the hot particle by a factor of about 1000