The 2003 Coryell Award winner, Michael Briggs from the University of British Columbia was recognized at the NUCL Business Meeting during the Spring ACS National Meeting. Michael did his undergraduate research project under the direction of Prof. Don Fleming and Khashayar Ghandi.

Michael Briggs and Sherry Yennello

Michael’s research involved the study of muonium and muoniated free radical formation and radiation chemistry in sub- and super-critical carbon dioxide. There is a great potential for use of supercritical (SC) solvents (in particular, SC-CO₂) for the extraction of unstable isotopes from nuclear waste. The main concern when handling solvents and reaction vessels after extraction of this waste is their level of radioactivity. When using supercritical solvents such as CO₂, in which UO₂ is extremely soluble, the temperature and pressure of the solvent can be adjusted quite easily to change its density (drastically!). High SC-CO₂ density thermalizes radioactive decay products (radiation) so that they do not reach the vessel walls (or the outside). Using the MuSR technique at TRIUMF, Vancouver, BC, the positive muon was injected into supercritical carbon dioxide at varying densities. Its intra- track spur formation (the degree to which the muon ionizes the solvent (CO₂) and those high-energy electrons travel, thus forming radiation of their own) was closely studied using a MuSR Spectrometer. Better understanding of “spur formation” in supercritical CO₂ allows us to tune its temperature and pressure to the ideal levels for the safe use in UO₂ extraction.