Chemistry, radiation, and interfaces in suspensions of nuclear waste simulants

We focus in this report on three issues that are of central importance in the management of radioactive high-level Liquid waste (HLLW). We show that the only reducing radical that lasts longer than a few ps in typical HLLW, and is capable of generating hydrogen, is NO32-. We measured the lifetime of this species across the whole pH range (3 less than or equal to pH less than or equal to 14) and found it to be shorter than approximate to 15 mu s, before it dissociates to give strongly oxidizing NO2 radicals. We found that it reacts with many proton donors (H+, phosphate, borate, NH4+, amines) in a reaction that is not merely an acid-base equilibrium reaction. Using high-level ab initio calculations we estimate its redox potential and pK(a). We have developed methodologies to study the degradation of organic additives to the HLLW (to CO2 or carbonate) by NO2 Relative rates of degradation of several complexants were determined using competition kinetics and C-13 NMR and proton NMR detection techniques. Direct absorption of the radiation (low-energy electrons as well as photons above the ionization threshold) in NaNO3 single crystal at the solid/vacuum interface led to production of NO, O, and O- as the major products.