- 30 januari 2013
Uranium isotopic abundances in saline media
NUSIMEP-3 Uranium isotopic abundances in saline media
Although NUSIMEP-2 was successful in showing the present status of measurements of isotopic ratios in relatively small amounts of uranium, the samples were clean, i.e. there was no matrix to be removed.
NUSIMEP-3 was designed to provide laboratories with a typical matrix of a saline solution sufficiently concentrated to require removal before measuring uranium. It was expected that the method of handling and chemical separation would be highlighted in this campaign and especially the question of whether clean chemical facilities were essential for measurement of such samples.
Like in NUSIMEP-2 uranium materials were prepared and certified but then after dilution added to a matrix solution of salts making up a typical brine or seawater. The matrix material was previously cleaned from natural uranium. Three solutions with uranium concentrations of 5 ng g-1 (ppb) and one of 2 ng g-1 (ppb) were provided to participants, 100 ng uranium per sample. Participants were asked to measure the isotopic ratio n( 235 U)/n(238 U) as well as n(234U)/ n(238U) andn(236U)/n(238 U), if possible
Some of the main conclusions of this exercise were:
Fewer laboratories participated, probably reflecting the increased measurement difficulties.
The results were more scattered than for NUSIMEP-2 as expected.
A great variety of chemical methods were applied with a large range of handling facilities ranging from high-class clean chemical laboratories to laboratories without special clean handling facilities. Interestingly, the handling conditions did not appear to play a big role in the final results.
The dominance of mass spectrometric methods, especially inductively coupled plasma mass spectrometry (ICP-MS) was well demonstrated.