Modelling the transport in the porous layer of oxide films formed on material surfaces in nuclear power plants: A BWR case study

The deposited, porous layer of the oxide film adjacent to the bulk coolant is expected to have an impact on the activity incorporation (mainly by 60Co, which constitutes a major radiation hazard during shutdown maintenance due to its long half-life) into the structural materials of the primary circuit of nuclear power plants. This work aims at describing the steady-state transport of radioactive and other molecular species through the porous film with a mathematical model, and identifying the limiting phases for the rate of activity build-up from high-temperature aqueous solutions. A necessary prerequisite for gaining a lucid insight into the processes taking place in such systems is a reasonable characterization of the electrical atmosphere within the pore fluid, which is bound to greatly affect the transport properties of the soluble constituents therein. A BWR coolant with high-purity water under NWC conditions was selected as a test problem. It is the simplest case available for performing scoping calculations, yet relevant to actual high-temperature systems. A concise outline of a simple conceptualization of this particular transport system along with its mathematical description are given is this report. Preliminary model results are also presented and briefly discussed.