Comparison for the simultaneous determination of 237Np and Pu isotopes between TEVA and TK200 resin

Abstract

A reliable and stable method was developed to accurately analyze neptunium (²³⁷Np) and plutonium isotopes in environmental samples using ²⁴²Pu or ²³⁶Pu as a tracer. Key parameters, including the valence adjustment conditions and the stabilities of Pu and Np in the different resins, were investigated using TK200 and TEVA resin. It was found that Pu and Np could be efficiently extracted simultaneously using TK200 resin under the optimal loading conditions (6-12 M HNO₃) with the addition of 0.01-0.12 M NaNO₂ for valence adjustment. These isotopes were subsequently stripped out using a solution containing 0.1 M HCl, 0.05 M HF, and 0.01 M NH₂OH·HCl. The separation efficiencies of Pu and Np were >93%, and the chemical yield ratio between Np and Pu was maintained steady at an average of 1.00 ± 0.03 (n > 50) under the optimal conditions. The analytical method was validated by analyzing environmental soil samples spiked with known amounts of ²³⁹Pu and ²³⁷Np standard solutions or certified reference materials. The measured values of ²³⁷Np, ²³⁹Pu, and ²⁴⁰Pu obtained by inductively coupled plasma tandem mass spectrometry were consistent with their International Atomic Energy Agency literature values within a 95% confidence interval. These results confirm the reliability and high analytical precision (<6%) of this developed method using Pu as a non-isotopic tracer for monitoring the chemical yield of ²³⁷Np. The developed method can also be used for environmental pollutant monitoring and for tracer studies of the ²³⁷Np and Pu isotopes.

Keywords: (237)Np; Environmental soil; Pu isotopes; TEVA; TK200.