Testing of a computer programme for calculating the Sr-85 yield as well as fallout Sr-89 and Sr-90 in a single LSC measurement with detection limits conforming to ISO 11929: Chapter 3

Environmental surveillance of Sr-89 and Sr-90 following an accident or incident with fission material is particularly important. Most analytical strategies require at least two measurement procedures – one to determine Sr-89 and the other to determine Sr-90 indirectly by measuring the daughter Y-90. However, the Sr-89 and Sr-90 can be determined simultaneously and independently of the state of the Sr-90/Y-90 equilibrium by liquid scintillation counting. Modern LSCs allow the recording of scintillation spectra which facilitates the setting of energy regions for optimal counting of a particular radionuclide. The yield was determined by gamma spectrometry of the tracer Sr-85 added in known activity to the sample prior to analysis. This tracer is not present in nuclear fallout. In the event of a nuclear accident, however, the pressure on gamma-spectrometric capacity may limit the capability to carry out the Sr yield determination by this method.