Determination of plutonium in environmental samples by AMS and alpha spectrometry

Environmental samples from nuclear weapons test sites at the atolls of Mururoa and Fangataufa (French Polynesia, south Pacific) have been analyzed for their content of plutonium isotopes by applying the independent techniques of decay counting (Alpha Spectrometry) and accelerator mass spectrometry (AMS). Here, we propose the combination of both techniques which results in a maximum of information on the isotopic signature of Pu in environmental samples.

Plutonium was chemically separated from the bulk material by anion exchange. ²⁴²Pu was used as an internal standard for both AMS and alpha spectrometry. The samples for alpha spectrometry were prepared by micro-precipitation with NdF₃. After alpha spectrometry, the samples were reprocessed for AMS. Pu was co-precipitated with Fe(OH)₃ and finally, solid samples were prepared. At the VERA (Vienna Environmental Research Accelerator) facility, the various Pu isotopes were separated by their isotopic masses and quantified by the AMS technique.

A good agreement of the results obtained from the AMS measurements was found with those obtained from Alpha Spectrometry. Overall, the data agree on average within 10% of each other. Isotope ratios for ²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu can be extracted from our investigations. Alpha spectrometry delivers data for the ²³⁸Pu and the combination of ^(239+240)Pu concentrations in those samples. In addition, the AMS technique provides information on the individual concentrations of ²⁴⁰Pu and ²³⁹Pu.