Design and Numerical Simulation of a Lead Oxide Mass Exchanger for Oxygen Control in Liquid Lead-Bismuth Coolant Nuclear Reactor

In this work the design of a PbO oxygen mass exchanger with built-in heater has been supported by the use of the commercial CFD code Ansys CFX. The original concept design came from a Russian mass exchanger adopted in LBE cooled nuclear reactors. This new design aims to be adopted as a reliable and effective oxygen delivery supply for the LBE cooled facilities. The built-in heater approach was chosen, among the others, because it is possible to control the oxygen delivery to the system by controlling both the inlet mass flow rate and the heater power. Moreover, it is able to provide a re-circulation flow from the outlet to the inlet of PbO spheres packed bed in order to avoid the poisoning of the lead oxide surface by dissolved metallic impurities in the LBE circuit. The oxygen concentration at the inlet can be kept high enough by the recirculation flow to prevent the poisoning of the PbO surface. The oxygen mass transfer in LBE through the PbO mass exchanger and the effect of re-circulation flow on the oxygen concentration are simulated and discussed. Differently from the currently in use mass exchangers, it is also possible to interrupt the oxygen release without needing any external system. Sensitivity studies have been performed in order to assure the stability of the obtained results. Some parametric studies have been performed as well in order to define the working operation boundary conditions. The developed CFD model and the performed simulations provided a robust design of an oxygen control system, based on PbO mass exchanger technology.