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Description
The present work describes a method for the preparation and validation of plutonium age dating reference materials [1]. The prepared reference samples can be used to validate experimental protocols for determining the production date of plutonium via the 234U/238Pu, 235U/239Pu, 236U/240Pu and 241Am/241Pu chronometers. The starting material was prepared using reactor-grade plutonium, which was purified using a dedicated method to guarantee high Pu recovery, while maximizing U and Am separation efficiencies. The U and Am separation factors were determined by the addition of high-amounts of 233U and 243Am spikes and their re-measurement in the final product. Th and Np were measured from all aliquots, but it was not aimed for Np/Am or Th/U chronometers.
The age values obtained for the test samples using the different parent/daughter pairs (chronometers) are in excellent agreement and agree also with the known production date. The date of the last chemical separation is known to within one hour, and not biased by any residual daughter nuclides.
The different forms (liquid and solid) and concentrations allow the use of various techniques, e.g. alpha spectrometry, ICP-MS, TIMS or SIMS. The method was demonstrated to be directly applicable for the preparation of a certified reference material (similar to IRMM-1000).
The prepared material is intended for quality control and assessment of method performance in nuclear forensics and safeguards.
[1] Z. Varga, A. Nicholl, J. Zsigrai, M. Wallenius, K. Mayer, Methodology for the preparation and validation of plutonium age dating materials, Anal. Chem. 2018, doi: 10.1021/acs.analchem.7b05204
