Time-dependent emission of U from overheated UO2 pellets

The emission of uranium oxides from overheated nuclear fuels proceeds as a function of time. depending mainly on temperature. oxygen potential of the amosphere in contact. and structure and composition of the fuel matrix itself. This Lime dependent emission results in variation of the U-concentration in the released aerosol. The subsequent annealing ("maturation") reactions acting on the aerosol particles are greatly affected bq the emission sequence of the different elements. The maturation phase strongly influences the properties of particles dispersed in thr environment: e.g. the rate of leaching of the particles is particularly sensitive to their "chemical history".