EVALUATION OF METHODS FOR THE ASSAY OF NEPTUNIUM AND OTHER LONG-LIVED ACTINIDES IN ENVIRONMENTAL MATRICES

Inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis (NAA) have been investigated as alternatives to alpha-spectrometry for the low-level determination of Np-237 and other actinides in environmental matrices. ICP-MS in particular, has been shown here to offer suitable sensitivity, precision and accuracy compared to the other techniques, with considerably faster sample throughput relative to radiometric and activation approaches. Added advantages of ICP-MS are found to include the abilities to determine other long-lived actinides simultaneously and to quantify Pu-239:Pu-240 ratios. The neutron activation analysis approach was found to be particularly prone to interference especially from uranium nuclides.