Toward an usage of americium-241 for filter calibration

Abstract

In nuclear safety and environmental studies, it is necessary to measure the activity of aerosols collected on filters. The calibration of these filters' measurement chains currently involves producing a reference filter with a controlled deposit of aerosol marked by a specific radionuclide. In France, commonly used radionuclides include 137Cs for gamma or beta emitters, 90Sr/90Y for beta emitters, and 239Pu for alpha emitters. However, using 239Pu presents several issues, notably the destruction of the filter required to determine its traceable activity and the associated uncertainties. The challenge of this project is to propose a radionuclide enabling non-destructive, SI-traceable measurement while retaining the reference filter. The proposed radionuclide is 241Am, which is both alpha and gamma-emitting and allows for precise non-destructive measurements. Reference filters are produced on the IRSN’s ICARE test bench with calibrated aerosols tagged with 241Am. The reference activity of theses filters is measured by gamma spectrometry on CEA/LNHB reference counter. A series of tests confirmed that 241Am provides accurate activity determination with minimal uncertainty. Consequently, adopting 241Am can significantly improve the reliability of radioactive contamination monitoring while avoiding practical challenges associated with plutonium.