Radioactivity standardization in South Africa

South Africaʹs national radioactivity measurement standard is maintained at a satellite laboratory in Cape Town by the National Metrology Laboratory (NML) of the Council for Scientific and Industrial Research. Standardizations are undertaken by a number of direct methods utilizing liquid scintillation counting (LSC). The successful application of LSC to the 4πβ–γ coincidence method is reviewed. The activity unit is maintained through radionuclide specific calibration factors relating to a pressurized re-entrant well type ionization chamber. A comparison is made between normalized factors given by the manufacturer and deduced factors obtained by a method used to transfer calibration factors from the International Reference System of the International Bureau of Weights and Measures based on the NMLʹs own absolute standardizations.