Weixiong Chen

In lead-cooled fast reactors, steam generator tube rupture could lead to the discharge of high-pressure steam/water into lead or lead-bismuth eutectic (LBE) and result in several risks to the reactor's safe operation. Due to the differences in the physical properties of LBE and water and limited research in the steam-LBE jet flow, a compressible multi-phase numerical model was set up and used for the investigation of the submerged steam jet in LBE. The jet phase interface evolution pattern was found to be different under different inlet pressures, and the jet structure could travel to neighboring structures in a short time. Moreover, during the initial jet process, there was an initial pressure shock that might have an impact to nozzle itself and close structures along the jet direction. In addition, the (quasi-)back-attack phenomena were both observed, and a pseudo-nozzle structure was found to be responsible for the different patterns of the two phenomena. Those phenomena also brought pressure shock to the tube end, and the condition with an intermediate inlet pressure caused the fiercest pressure shock. Meanwhile, the wave structure at the phase interface was found to be resulted by strong shear flow.

Crosslinked phenolic resin was prepared using hexamethylenetetramine (HMTA) as a crosslinking agent in hydrochloric acid solution. The ablation-heat-resistant material was prepared by a pressure-assisted RTM (resin transfer molding) process with reinforcing material (quartz fibre 2.5D needle-punched fabric/satin fibre cloth/fibre mesh tire) and matrix (crosslinked phenolic resin). The thermal stability of the cured product was studied by a thermogravimetric analyser (TG and DTG). The mechanical properties, heat resistance, and ablation properties of the composites were tested. The ablation morphology, element analysis, and phase structure of the composites were analysed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD), respectively. The results show that the phenolic resin has a lower initial viscosity and a longer pot life at 80 °C, and a higher carbon residue rate (70.18%). The tensile strength of the composites is close to 40 MPa, the tensile modulus is higher than 1.35 GPa, the compression modulus is higher than 10 MPa, and the elongation at break is higher than 1.55%. SiO₂, SiC, and ZrO₂ ceramic phases were formed after ablation, which effectively improved the ablation performance of the composites.