title: Thermochemistry of Ruthenium Oxyhydroxide Species and Their Impact on Volatile Speciations in Severe Nuclear Accident Conditions.
abstract: Literature thermodynamic data of ruthenium oxyhydroxides reveal large uncertainties in some of the standard enthalpies of formation, motivating the use of high-level relativistic correlated quantum chemical methods to reduce the level of discrepancies. Reaction energies leading to the formation of all possible oxyhydroxide species RuOx(OH)y(H2O)z have been calculated for a series of reactions combining DFT (TPSSh-5%HF) geometries and partition functions, CCSD(T) energies extrapolated to the complete basis set limits. The highly accurate ab initio thermodynamic data were used as input data of thermodynamic equilibrium computations to derive the speciation of gaseous ruthenium species in the temperature, pressure and concentration conditions of severe nuclear accidents occurring in pressurized water reactors. At temperatures lower than 1000 K, gaseous ruthenium tetraoxide is the dominating species, between 1000 and 2000 K ruthenium trioxide becomes preponderant, whereas at higher temperatures gaseous ruthenium oxide, dioxide and even Ru in gaseous phase are formed. Although earlier studies predicted the formation of oxyhydroxides in significant quantities, the use of highly accurate ab initio thermodynamic data for ruthenium gaseous species leads to a more reliable inventory of gaseous ruthenium species in which gaseous oxyhydroxide ruthenium molecules are formed only in negligible amounts.
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: Faoulat
authors.initials: F
authors.lastname: Miradji
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: François
authors.initials: F
authors.lastname: Virot
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: Sidi
authors.initials: S
authors.lastname: Souvi
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Cantrel
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: Florent
authors.initials: F
authors.lastname: Louis
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSN-RES and §Laboratoire de Recherche Commun IRSN-CNRS-Lille1 'Cinétique Chimique, Combustion, Réactivité' (C3R), Cadarache , Saint Paul Lez Durance 13115, France.|UMR 8522 - PC2A - Physicochimie des Processus de Combustion et de l'Atmosphère and ∥UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, CNRS , F-59000 Lille, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Vallet