EFFECT OF SOURCE ENCAPSULATION ON THE ENERGY-SPECTRA OF IR-192 AND CS-137 SEED SOURCES

The effect of source encapsulation on the energy spectra of Ir-192 and Cs-137 seed sources, both with stainless steel and with platinum encapsulation, was determined from results of Monte Carlo simulation. The fractional scatter dose around these sources has also been determined from Monte Carlo simulation. The platinum-encapsulated Ir-192 source exhibited greater attenuation of the primary spectrum, as expected, and, consistent with this greater attenuation, exhibited more scattered radiation. Significantly less scatter was seen with the Cs-137 source than with either Ir-192 source, as is consistent with the higher-energy photons from Cs-137.