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Calcul de constantes d'équilibre impliquant des produits de fission dans le circuit primaire, an atmosphère mixte vapeur-hydrogène


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Titre de la revue : Nuclear Technology Volume : 163 N° : 2 Pagination : 245-251 Date de publication : 01/08/2008

Type de document > *Article de revue

Mots clés > accident grave, calculs de quantum chimiques, chimie de l'iode, RCS

Unité de recherche > IRSN/DPAM/SEMIC/LETR

Auteurs > CANTREL Laurent, GEDEON Ondrej, KLUVANEK Peter, LISKA Marek, MACHACEK Jan

Date de publication > 01/08/2008

Résumé

Behaviour of iodine fission product if of prime importance for short term radiological consequences in a severe reactor accident. Iodine speciation in the reactor coolant system (RCS) is commonly predicted with severe accident code devoted to the transport and deposition of fission products and structural materials, as for instance SOPHAEROS module of ASTEC. In these codes, chemical equilibrium is assumed to be reached instantaneously whatever are the conditions. Some thermodynamic data are still uncertain due do lack of experimental Data. Quantum chemical calculations can be an appropriate tool to estimate equilibrium constants in a first step and maybe later to determine some kinetic constants for further implementation in such kind of codes to better assess iodine chemical behaviour. This paper is an attempt to calculate some equilibrium reactions for relevant reactions which are susceptible to impact iodine chemistry. The accuracy obtained for such calculations depends a lot of the basis set used and moreover relativist effect has to be taken into account for heavy atoms like iodine or caesium to get reliable predictions.