Measurements of the disintegration rate of a sample of a radioactive isotope, and of the γ-ray dose-rate provide experimental data for the estimation of the factor referred to as the γ-ray dose-rate in roentgen per hour at 1 cm from 1 mC of the isotope. The experimental values of this factor for six isotopes (24Na, 42K, 60Co, 82Br, 131I and 198Au), based on measurements by four United Kingdom laboratories are given, together with values obtained from calculations based on the decay schemes.
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