A model for void-induced back reaction between radiolytic products in NaCl

A kinetic model is formulated for the chemical reaction between radiolytic sodium colloids and gas bubbles, which are brought into contact with each other during the exposure to ionising radiation by the growing voids. The reaction starts with the evaporation of Na atoms into the void due to the localized heat release caused by reactions between chlorine molecules colliding with the colloid surface. It is shown that this exothermic and autocatalytic reaction leads to a sudden temperature increase inside the void, which gives rise to thermoelastic stresses in the surrounding matrix. Tangential stresses might exceed the threshold stress required for localized cleavage of the matrix resulting in crack formation and mechanical instability of NaCl under high dose irradiation. (C) 2002 Published by Elsevier Science B.V