The use of solid angle for alpha detector efficiency in 226Ra analyses of soil samples

In the frame of proficiency tests organized by IAEA and IRMM, the specific activity concentration of radium-226 in soil has been measured. The BaSO4 co-precipitation technique has been used. Normally, in this method, the detector efficiency of the alpha spectrometer is determined using a 226Ra source with known activity. As an alternative to using a 226Ra standard, we calculated the detector efficiency from the relative solid angle subtended by the detector on the soil samples. The accuracy of this method depends on the uncertainty of geometrical properties and the distribution of activity within the source. An uncertainty budget is provided. The method was applied successfully in the intercomparisons. - Highlights: ► Modified radiochemical extraction procedure for 226Ra analysis in soil samples. ► Solid angle calculation method was used for detector efficiency. ► Modified procedure was successfully tested in intercomparisons.