Description
Authors (affiliation): 1. Alexander Mauring (Institute for Energy Technology, Norway), 2. Paul Mc Ginnity (IAEA Radiometrics Laboratory, Monaco), 3. Bojan Seslak (IAEA Terrestrial Environmental Radiochemistry Laboratory, Austria), 4. Barbara Nadalut (IAEA Terrestrial Environmental Radiochemistry Laboratory, Austria).
The importance of self-attenuation correction factors in gamma-ray spectrometry has been known for many years. Failing to appropriately correct for self-attenuation can cause relatively large deviations in the calculated activities, especially for low-energy gamma-ray emitting radionuclides, if the sample matrix differs significantly from the standard used for calibration. Although various experimental, empirical and numerical methods of correcting for self-attenuation have been proposed in scientific literature over the past decades, many laboratories struggle to successfully apply self-attenuation corrections as part of their routine analysis. Furthermore, the uncertainty associated with the correction factors is often ignored completely or oversimplified to the point where it may no longer be realistic.
In this work, experimental transmission measurements through the sample material of interest using collimated point sources are combined with the empirical calculation of a simplified chemical composition for the material to compute self-attenuation correction factors at all energies of interest. As the method does not make any presumptions about the chemical composition of the sample, it provides flexibility to estimate self-attenuation correction factors even when the sample material is not well characterized. It also makes it possible to realistically estimate the standard uncertainty corresponding to each correction factor through a straightforward sensitivity analysis process.
Verification of the proposed method using samples with well-defined activity concentrations shows very good agreement to reference values. This, in addition to the practical and straightforward approach of the method, indicates that it is fit-for-purpose and potentially of significant interest to laboratories who need to measure low-energy gamma-ray emitters in a large range of sample materials.
