International comparison of activity measurements of 133Xe

An international comparison of 133Xe activity measurements has been carried out under the auspices of EUROMET (project Nr 304). The project was divided into two stages concerning first the measurement of sealed glass ampoules containing about 40 MBq of 133Xe at BIPM, LPRI, NPL and PTB and second the measurement at LPRI, NIST and NPL of the radioactivity concentration of 133Xe mixed with nitrogen with an activity concentration of the order of 50 MBq mol−1. The experimental techniques employed at each of the participating laboratories are described and a statement of the results and conclusions is provided.