A theoretical study of the H-abstraction reactions from HOI by moist air radiolytic products (H, OH, and O (3P)) and iodine atoms ( 2P3/2)

C. Hammaecher (1) , S. Canneaux (2) , F. Louis (2) , L. Cantrel (3)

1 UCL - Université Catholique de Louvain = Catholic University of Louvain
2 PC2A - Physicochimie des Processus de Combustion et de l’Atmosphère - UMR 8522
3 IRSN - Institut de Radioprotection et de Sûreté Nucléaire

The rate constants of the reactions of HOI molecules with H, OH, O ( 3P), and I (2P3/2) atoms have been estimated over the temperature range 300-2500 K using four different levels of theory. Geometry optimizations and vibrational frequency calculations are performed using MP2 methods combined with two basis sets (cc-pVTZ and 6-311G(d,p)). Single-point energy calculations are performed with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (pertubatively) electron excitations CCSD(T) using the cc-pVTZ, cc-pVQZ, 6-311+G(3df,2p), and 6-311++G(3df,3pd) basis sets. Reaction enthalpies at 0 K were calculated at the CCSD(T)/cc-pVnZ//MP2/cc-pVTZ (n = T and Q), CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p), and CCSD(T)/6-311++G(3df,3pd)//MP2/6- 311G(d,p) levels of theory and compared to the experimental values taken from the literature. Canonical transition-state theory with an Eckart tunneling correction is used to predict the rate constants as a function of temperature. The computational procedure has been used to predict rate constants for H-abstraction elementary reactions because there are actually no literature data to which the calculated rate constants can be directly compared. The final objective is to implement kinetics of gaseous reactions in the ASTEC (accident source term evaluation code) program to improve speciation of fission products, which can be transported along the reactor coolant system (RCS) of a pressurized water reactor (PWR) in the case of a severe accident. © 2011 American Chemical Society.

Mots clés: Severe accident; Single-point energy; Source terms; Temperature range; Theoretical study; Transition state theories; Abstracting; Accidents; Calculations; Fission products; Iodine; Pressurized water reactors; Quantum chemistry; Rate constants; Severe accident; Ab initio; Basis sets; CCSD; Computational procedures; Coupled-cluster methods; Electron excitations; Elementary reaction; Experimental values; Final objective; Geometry optimization; H-abstraction; Highly-correlated; Iodine atoms; Literature data; Moist air; Radiolytic products; Reaction enthalpies; Reactor coolant systems

Domaines: Chimie

C. Hammaecher, S. Canneaux, F. Louis, L. Cantrel. A theoretical study of the H-abstraction reactions from HOI by moist air radiolytic products (H, OH, and O (3P)) and iodine atoms ( 2P3/2). Journal of Physical Chemistry A, 2011, 115 (24), pp.6664-6674. ⟨10.1021/jp202760u⟩. ⟨hal-02954947⟩