Knowing the chemical speciation of an element in different media is essential for better understanding and predicting its behavior. However, the identification could be difficult for radionuclides at trace and ultra-trace concentrations, for which the conventional spectroscopic methods are barely applicable. Indirect methods combining analytical techniques and radiation measurements appear to be a good alternative for the characterization. The results are usually confronted with the outcome of computational chemistry.
Two examples will be presented to illustrate this approach.
The first one concerns the speciation of astatine (At, Z = 85) in solutions. Indeed, astatine-211 (half-life = 7.2 h, 100% alpha-emitter) is considered as a promising candidate for targeted alpha therapy. A prerequisite is to have a suitable radiolabeling strategy, while the poor knowledge of its speciation and reactivity in solutions hinders the development. In this presentation, the advance in Pourbaix diagram of astatine and astatine-mediated halogen bond will be shown.
The second case concerns the chemical behavior of radionuclides in lead-bismuth eutectic (LBE, 44.5 at% of Pb and 55.5 at% of Bi). LBE is selected as the spallation target and coolant for the accelerator-driven system (ADS). However, the evaporation of radionuclides present in the coolant, originating from the activation of the liquid metal itself and the potential contamination with fission products, is a key issue for its safe application and a significant challenge for licensing. This talk will focus on the behavior of cesium and iodine in LBE; the solubility of CsI in LBE and the identification of evaporated species from Cs&I-doped LBE will be presented.
