Leveraging Neutronics to Monitor Mass Transfer Corrosion in Lead and Lead-Bismuth Cooled Reactors

Corrosion phenomena in heavy liquid metal cooled reactors primarily result from dissolution and mass transfer of alloying elements such as nickel from the structural materials to the coolant. We propose and preliminarily demonstrate an approach to passively monitor nickel dissolution in lead and lead-bismuth cooled reactors based on the effect of mass transfer on the neutronics. We support this suggestion with parametric simulations that demonstrate the effect of nickel transfer on reactivity in a modified TRIGA Mark-III reactor with steel cladding and lead coolant. Simulations of a uranium sphere show that nickel contributes a negative effect on the reactivity in the fast spectrum through parasitic absorption which is stronger than its effect on moderation. Transfer of nickel from the cladding to lead in the modified TRIGA reactor model results in removal of some of the nickel from the active core and significantly increases the total reactivity.