241 Am : A new nuclide for reference α − filter production and calibration

In the field of nuclear safety and environmental monitoring, accurate measurement of radionuclide activity in aerosols collected on filters is of critical importance, particularly in terms of the traceability of such measurements, as they can inform operational decision-making. Laboratories, especially in France, commonly employ radionuclides such as 137 Cs for γ -ray or β -particle emitters, 90 Sr / 90 Y for pure β -particle emitters and 239 Pu for α -particle emitters to calibrate their measurement instruments. However, the use of 239 Pu presents challenges, including the necessity to destroy the filter to determine its traceable activity and associated uncertainties with liquid scintillation counting. 241 Am is an alternative reference nuclide. It can be measured non-destructively while maintaining traceability to the International System (SI) and having properties similar to those of 239 Pu in α -particle measurements. The ASNR’s ICARE 1 test bench, a unique facility in Europe, is utilized to produce reference filters with 241 Am of a defined AMAD. 2 The reference activity of these filters is measured via γ -ray spectrometry on a CEA/LNHB reference HPGe 3 spectrometer. 241 Am provides accurate activity determination with minimal uncertainty. The final calibration comparison on a gas-proportional counter with two PTFE 4 membrane filters, one with 239 Pu the other with 241 Am , confirm the advantages in using 241 Am as nuclide for reference α -filters. The high quality of the reference filter, coupled with the non-destructive nature and high precision of the calibration process, confirms that adopting 241 Am for α -reference filter can significantly enhance the reliability of radioactive contamination monitoring while avoiding practical challenges associated with 239 Pu .