Developing a database for Cs-137 radioactivity concentration and assessing residual levels in surface soils of Quang Ninh, Hai Phong, and Lang Son provinces

The radioactivity concentration of Cs-137 was determined in 826 soil samples collected from Hai Phong, Quang Ninh, and Lang Son. The residual levels of Cs-137 have also been assessed and compared with previous publications to obtain a trend in Cs-137 in the surface soil. The actual measured average of the residual level of Cs-137 in the soil samples collected in this study was 236±146 Bq/m2, while the value calculated using the publishedexperimental formula was 407±77 Bq/m2. The impact of Cs-137 deposition from the Fukushima nuclear accident (2011) in this area is confirmed to be negligible.

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

210Po, 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 210Po has become an important topic in LFR-related research. In order to simulate the behavior of 210Po 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 210Po distribution in detail. Preliminary results indicate that during normal operation, most of the 210Po in the LBE exist in the form of PbPo, and around 10–9 of 210Po could evaporate from the LBE into the cover gas, and then further leak into the containment. In addition, even if the leakage rate of 210Po in the cover gas into the containment is maintained at 5‰ per day, due to the deposition of Po aerosol, the 210Po contamination on the inner surface of the containment is still below the radioactivity concentration limits.