Microstructure controlled PbWO4 filler-reinforced flexible silicone rubber for penetration sealing and radiation shielding in nuclear fusion facilities

Flexible silicone rubber (SR) composites doped with different reinforcing fillers are prepared for nuclear fusion facility penetration sealing and shielding against neutrons and gamma rays. Scanning Electron Microscope (SEM) reveals that micron spindle-shaped PbWO 4 fillers have much smaller particle sizes and more uniform size distribution. The experimental results indicate that the thermal resistance and mechanical performance of the spindle-PbWO 4 reinforced SR are superior to the other composites, with the maximum decomposition temperature of 490.1 °C, tensile strength of 0.92 MPa and compressive strength of 5.32 MPa. Moreover, the spindle-shaped PbWO 4 filler significantly reduces the thermal expansion behavior of the composite, which is more conducive to improving the thermal stability. This is attributed to its restraining effect on the thermal vibrations and relative displacements of the polymer chain of the matrix. Due to the ultraviolet absorption ability of PbWO 4 , the tensile strength loss of the PbWO 4 filler-reinforced SR after 60 days of accelerated ultraviolet aging is significantly less than the other composites. SuperMC simulation demonstrates the superior synergistic neutron and gamma ray shielding capability of the spindle-PbWO 4 /B 4 C/SR composite and its effectiveness in reducing secondary gamma ray generation. At a thickness of 15 cm, the spindle-PbWO 4 /B 4 C/SR composite respectively achieves shielding rates of 93.13% against 252 Cf neutrons and 82.76% against 137 Cs gamma rays, and it exhibits optimal shielding parameters ( Σ  = 0.167 cm −1 , μ m  = 0.080 cm 2 /g and μ  = 0.117 cm −1 ). The spindle-PbWO 4 /B 4 C/SR composite offers the best radiation shielding and meets the mechanical and airtightness requirements for sealing fusion device penetrations.