In this paper a one-dimensional depth distribution of absorbed doses is found in the semi-infinite tissue-equivalent medium, on the surface of which there is an infinitely thin uniform layer of a mixture of Pu239 prompt fission products. These calculations are made using the method of a “single dose function” based on experimental studies of dose distributions from wide monodirectional beams of monoenergetic electrons. The approximate formula C(E0 - E)2(E + 0.51)2 is used for describing the shape of partial β-spectra. It is shown that at the depth of 0.007 g/cm2, corresponding to the basal layer in the human skin, dose rate is rather slightly dependent (approximately by a factor of 2) on the fission products “age” (varying from 1 day to 1 yr) and consequently on the strongly varying spectral composition of the β-radiation. © 1969 Health Physics Society.
