²⁴¹Am: 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 ¹³⁷Cs for γ-ray or β-particle emitters, ⁹⁰Sr/⁹⁰Y for pure β-particle emitters and ²³⁹Pu for α-particle emitters to calibrate their measurement instruments. However, the use of ²³⁹Pu presents challenges, including the necessity to destroy the filter to determine its traceable activity and associated uncertainties with liquid scintillation counting. ²⁴¹Am 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 ²³⁹Pu in α-particle measurements. The ASNR's ICARE¹ test bench, a unique facility in Europe, is utilized to produce reference filters with ²⁴¹Am of a defined AMAD.² The reference activity of these filters is measured via γ-ray spectrometry on a CEA/LNHB reference HPGe³ spectrometer. ²⁴¹Am provides accurate activity determination with minimal uncertainty. The final calibration comparison on a gas-proportional counter with two PTFE⁴ membrane filters, one with ²³⁹Pu the other with ²⁴¹Am, confirm the advantages in using ²⁴¹Am 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 ²⁴¹Am for α-reference filter can significantly enhance the reliability of radioactive contamination monitoring while avoiding practical challenges associated with ²³⁹Pu.