Absolute counting of 103Ru

Abstract The absolute measurement of 103 Ru activities is complicated by adsorption in the source of the soft electrons associated with the decay. It is shown that 103 Ru in an equilibrium source of 103 Ru- 103 m Rh can be measured to better than ±2 per cent by sandwiching normal 4π-sources between known thicknesses of aluminium absorber and counting in a 4πβ-γ coincidence counter. The method can be used for resolving the components of mixtures of 103 Ru and 106 Ru in fission products.