Interaction between Molecular Iodine in a Gas Phase and Paints Aged in a Nuclear Power Plant

Abstract

The interactions of gaseous molecular iodine with painted surfaces aged in French nuclear pressurized water reactors (PWRs) were carried out in an experimental facility consisting of a molecular iodine generator, a mixing chamber, a sampling chamber, a specimen holder, and a gamma-counting probe [Cristal NaI(Tl)]. The same experimental facility was used to precisely measure the gaseous molecular iodine interactions with epoxy-painted coupons conditioned by two artificial hydrothermal treatments, either by heating at 130°C in a dry atmosphere or by heating at 130°C in a saturated water atmosphere. Then, a kinetic model was developed to represent these experimental results.This paper examines if the previous kinetic model can be used to interpret the gaseous molecular iodine interactions with aged paints. With the rate constant values found for the artificially conditioned paints, the kinetic model agrees with experimental results. Moreover, for the three studied temperatures (95, 110, and 125°C), the values of initial adsorbed water concentration onto the paint and the adsorbed water concentration in equilibrium with the steam of the carrier gas are intermediate between the values found for the two artificial hydrothermal treatments.Finally, a kinetic model is available, allowing the evaluation of precise assessments of the gaseous molecular iodine interactions with aged epoxy paints in the case of a severe PWR accident.