Determination of americium in plutonium based nuclear fuel materials: An assessment of different methodologies

Determination of americium (Am) is one of the requirements of chemical quality assurance of plutonium (Pu) bearing fuel materials. Though many methods are published for determining Am at picogram to femtogram levels in environmental and biological matrices, yet a few of them are used routinely for Pu based nuclear fuel samples. This paper gives a brief summary of the different analytical methods available and presents results of our experiments on the determination of Am in Pu bearing fuels using gamma spectroscopy. The methods utilizing gamma emissions from 241Am and Pu isotopes are fast as they do not involve chemical separation of Pu and Am, do not require an accurate knowledge of the efficiency values of the detector systems and are not dependent on the availability of a radiometric standard for 241Am. In addition, for aged Pu samples containing large amounts of 241Am, there is no need for dilution and this reduces the volume of analytical radioactive waste solution. Future requirements of reference materials to validate different methodologies for determining Am isotopes are also highlighted.