Rapid determination of 237Np and Pu isotopes in water by inductively-coupled plasma mass spectrometry and alpha spectrometry

A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of Np-237 and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry. U-238 can interfere with Pu-239 measurement by ICP-MS as (UH+)-U-238 mass overlap and Np-237 via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4-6 h, and can also be used for emergency response. Pu-239, Pu-242 and Np-237 were measured by ICP-MS, while Pu-236, Pu-238, and Pu-239 were measured by alpha spectrometry.