Micro Ion Source Program NA22 Plutonium Detection Portfolio Final Report

Abstract

Under DOE Idaho Operations Office Contract DE-AC07-05ID14517 iv SUMMARYThe purpose of the micro ion source program was to enhance the performance of thermal ionization mass spectrometry (TIMS) for various actinides and fission products. The proposal hypothesized that when ions are created at the ion optic center of the mass spectrometer, ion transmission is significantly increased and the resulting ion beam is more sharply focused. Computer modeling demonstrated this logic. In order to prove this hypothesis it was first necessary to understand the chemistry and physics governing the particular ion production process that concentrates the emission of ions into a small area. This has been achieved for uranium and technetium, as was shown in the original proposal and the improvement of both the beam transmission and sharpness of focus were proven. Significantly improved analytical methods have been developed for these two elements based upon this research. The iodine portion of the proposal turned out to be impractical due to volatility of iodine and its compounds. We knew this was a possibility prior to research and we proceeded anyway but did not succeed. Plutonium is a potential option, but is not quite up to the performance level of resin beads. Now, we more clearly understand the chemical and physical issues for plutonium, but have not yet translated this knowledge into improved analytical processes. The problems are that plutonium is considerably more difficult to convert to the required intermediate species, plutonium carbide, and the chemical method we developed that works with uranium functions only moderately well with plutonium. We are of the opinion that, with this knowledge, similar progress can be made with plutonium.The breakthrough with uranium has come from development of what has been named the micro porous ion emitter (PIE). Many iterations of PIEs were developed and tested prior to settling on a particular formula. This formula is a 50/50 blend of rhenium and platinum powders initially held together with melted hot glue and extruded into a very small diameter rope. This rope is sliced into very thin pieces that are positioned in the exact center of a rhenium mass spectrometer filament. The filament is then heated in a vacuum to first evaporate the hot glue and then to melt the platinum to alloy with the rhenium powder and filament. This mixture/formula results in a highly porous micro structure consisting of the rhenium/platinum alloy bonded to the rhenium filament. A water soluble ion exchange resin is wicked into the PIE and dried. The sample is then wicked into the PIE so that the element can absorbed onto the resin. The solution is allowed to sit in the PIE long enough for the element to absorb onto the ion exchange sites of the resin and then dried. The sample is then ready for analysis.Three articles will be published in the International Journal of Mass Spectrometry; one is published, the second is accepted and the third has been submitted and is in review. The first appeared in the Septe...