A NEW PHOTOCHEMICAL REACTOR FOR THE RAPID REDUCTION OF U(VI) IN THE DEVELOPMENT OF MIXED METAL OXIDE FUEL FABRICATION PROCESSES

摘要

Within the UK National Nuclear InnovationProgramme, work has begun on the development of a highPu-content MOx fuel fabrication process which aims toreduce the heavy metal throughput of reprocessing plants.As a contribution to this, a rapid and clean photochemicaltechnique for the reduction of U(Ⅵ) and co-reduction ofU(Ⅵ)/Ce( Ⅳ) (as a Pu surrogate) is under development inour laboratories.By directly utilizing the advantageous photochemistryof U, with isopropanol as a reductant, we report theconvenient photo-excitation and chemical reduction ofU(Ⅵ) upon exposure to 407 nm light energy. Using apurpose built laboratory scale photo reactor, light isdelivered by an ultra-bright 6,000 mW LED array withinan integrating sphere for highly efficient energy transfer tothe U solution. The effect of illumination is immediate withthe successful conversion of 12 g/dm3 U(Ⅵ) in 2 mol/dm3nitric acid demonstrated within 90 seconds. With theaddition of hydroxylamine nitrate as a stabilizing agent /nitrous acid scavenger, this results in the rapid generationof a stable U( Ⅳ) product solution, indicating that theprocess is promising as a viable co-reduction method foruse in MOx fuel fabrication.