Microhydration of caesium metaborate: structural and thermochemical properties of CsBO2 + n H2O (n = 1–4) aggregates

Theoretical Study of the Monohydration of Mercury Compounds of Atmospheric Interest

The structures, vibrational frequencies, and model IR spectra of the monohydrates of oxygenated mercury compounds (BrHgO, BrHgOH, BrHgOOH, BrHgNO₂, BrHgONO, and HgOH) have been theoretically studied using the ωB97X-D/aug-cc-pVTZ level of theory. The ground state potential energy surface exhibits several stable structures of these monohydrates. The thermodynamic properties of the hydration reactions have been calculated at different levels of theory including DFT and coupled-cluster calculations DK-CCSD(T) with the ANO-RCC-Large basis sets. Standard enthalpies and Gibbs free energies of hydration were computed. The temperature dependence of Δ_rG°(T) was evaluated for the most stable complexes over the temperature range 200-400 K. Thermodynamic data revealed that the highest fraction hydrated at 298 K and 100% relative humidity will be BrHgNO₂-H₂O at ∼5%.

Chemical stability of caesium iodide deposits in air/steam atmosphere

Iodine compounds that may be released in case of severe nuclear accident will have important radiotoxicity if they are disseminated in air. One of the most important iodine species is CsI that is deposited on the surfaces of the reactor coolant system. However, depending on the conditions, CsI can volatilize or react with oxidants to produce I_2(g). Theoretical and experimental studies demonstrate that the oxidation of iodide depends on the temperature and in the presence of oxidants in the gas. It is also slightly influenced by the crystallinity of the CsI particles and the nature of the support. In case of a high temperature deposition, the iodine release started at temperature lower than 300 °C. For the CsI vapour and aerosol depositions, the iodine is detected only at temperature above 450 °C and become very important above 550 °C.