Absolute standardization of 22Na by sum-peak and 4πβ-γ coincidence methods

The counting method known as sum-peak can be used in the activity measurements for those nuclides, which present, at least, two photons in cascade in the decay scheme. The simplicity of the experimental set up and the low uncertainty of the standardization make this method comparable to the laborious coincidence counting method. The nuclide 22Na disintegrates predominantly to the 1275 keV level of 22Ne (89.84% beta plus and 10.11% electron capture). A very small fraction (0.056%) disintegrates to the ground state of 22Ne. Its long half-life makes that nuclide one of the most important positron emitter standard available. In this work a solution of positron emitter 22Na has been standardized by the 4πβ-γ coincidence and sum-peak methods in order to check the consistence of these methods. The measurement methods and results are described and discussed. (author)