Chemistry Department Colloquium

The development and deployment of next generation nuclear reactor technologies is necessary to meet ever increasing world energy demands. Time-resolved picosecond electron pulse irradiation techniques are being used at the Brookhaven National Laboratory (BNL) Laser Electron Accelerator Facility (LEAF) in a variety of studies designed to understand the impact of ionizing radiation on nuclear fuel cycle components, such as molten salt coolants and fuel matrices, and next generation extractants for the selective recovering of valuable materials from used nuclear fuel (UNF).
First, I will discuss the utilization of the BNL LEAF for the elucidation of the primary radiation-induced mechanisms underpinning the speciation and transport of iodine/iodide in high-temperature molten chloride salt matrices, as iodine is a volatile high-yield fission product with potential biological impacts. The absorption spectra and kinetics for the decay of the solvated electron (es–), the dichloride radical anion (Cl2•–), and the iodine-chlorine radical anion (ICl•–) were determined as a function of potassium iodide concentration and irradiation temperature (400–700 °C). Measured for the first time in this work, these rate coefficients and Arrhenius parameters are essential for the development of predictive multiscale computer models of iodine speciation in molten salt systems.
In the second part, I will cover the impacts of ionizing radiation and lanthanide ion complexation on the reactivity of N,N,N′,N′-tetraoctyl diglycolamide (TODGA), a promising extractant for the separation of the trivalent actinide ions from lanthanide fission products in UNF reprocessing technologies. Through the use of picosecond electron pulse irradiation techniques, the reactivity of the dodecane radical cation was shown to increase when TODGA is complexed with several lanthanide ions. Density functional theory calculations show that this is likely due to the presence of co-extracted nitrate anions within the metal ion complexes, affording relative radioprotection of the coordinated TODGA molecules. It is therefore important to study the radiation chemistry of next generation extractants in the absence and presence of their targeted metal ion complexes to fully understand their radiolytic robustness and any potential impacts this may have on their performance.