Radioactivity standards for 192Ir brachytherapy sources

Absolute radioactivities of brachytherapy 192Ir metallic sources of single pin and hairpin types are nondestructively determined with a microcalorimeter. In order to convert the complete decay energy evolved from the sources into thermal energy, a radiation absorber made of tungsten is used. Overall uncertainties of the activity determinations are estimated to be ±3.1% for the single pin source and ±4% for the hairpin source at the level of 3σ.