Multi-Physics Model Development for Polonium Transport Behavior in a Lead-Cooled Fast Reactor

Po-210, a highly toxic element with strong volatility, is one of the main source terms of a Gen-IV lead-cooled fast reactor (LFR). Therefore, the radioactive safety caused by Po-210 has become an important topic in LFR-related research. In order to simulate the behavior of Po-210 in an LFR, this work developed a multi-physics model of an LFR from the perspective of radioactive transport. Considering the effects of nuclide decay, cover gas leakage, containment ventilation, and Po aerosol deposition, a comprehensive simulation was carried out to evaluate the sensitivity of those effects on the Po-210 distribution in detail. Preliminary results indicate that during normal operation, most of the Po-210 in the LBE exist in the form of PbPo, and around 10(-9) of Po-210 could evaporate from the LBE into the cover gas, and then further leak into the containment. In addition, even if the leakage rate of Po-210 in the cover gas into the containment is maintained at 5 parts per thousand per day, due to the deposition of Po aerosol, the Po-210 contamination on the inner surface of the containment is still below the radioactivity concentration limits.