Numerical study on coolant flow and heat transfer characteristics and particle deposition behavior in LFR fuel assemblies

The liquid lead-bismuth eutectic(LBE) is highly corrosive to structural metal in the LBE-cooled fast reactors (LFRs). Typically, oxygen injection is used to form an oxide layer on the surface of structural components, which significantly reduces the corrosion caused by LBE. However, the oxygen injection process can lead to the formation of Fe3O4 particles that are carried along with the coolant. These particles may deposit on the surface of the fuel rods, potentially causing localized heat transfer deterioration and posing a risk to reactor safety. This study employs the DPM model and RBF mesh deformation method to, for the first time, perform particle deposition calculations for full-size fuel assemblies of LFRs. The results indicate that, particles smaller than 40 mu m are more likely to deposit within the fuel assemblies because of buoyancy. Deposition is more significant at the inlet section of the assembly, and as the flow field becomes fully developed, the particle deposition rate in the outlet section gradually decreases, with the particle concentration dropping from 3.0 x 10-5 kg center dot m- 3 to 2.6 x 10-6 kg center dot m- 3. At a flow rate of 0.2 m/s, the minimum deposition rate is 3.1 x 10-8 kg center dot m- 2 center dot s- 1, which is 43 % of the deposition rate at 1.6 m/s. The effect of temperature on the deposition rate is not very significant; when the coolant temperature rises from 550 K to 800 K, the deposition rate only increases by 10.6 %, which provide a theoretical foundation for optimizing fuel assemblies and designing anti-blocking mechanisms.