Research on Natural Rubber Based Flexible Neutron/Gamma Shielding Materials

With the development of science and technology, all kinds of nuclear radiation rays are more widely used, and the demand for radiation protection is also increasing. Moreover, with the deepening of radiation protection application scenarios, radiation protection materials need good environmental adaptability, mobility and wearability. Therefore, in this paper, two kinds of neutron/gamma composite shielding materials, B₄C/Bi/NR and Gd₂O₃/Bi/NR, were prepared by using natural rubber, which has excellent mechanical properties, as the matrix, bismuth as the gamma-ray shielding body, and boron carbide (B₄C) and gadolinium oxide (Gd₂O₃) as neutron-absorbing materials, respectively. A neutron test device was built with ²⁵²Cf as neutron source and ³He counting tube as detector to investigate the neutron shielding performance of the shielding materials, and the experimental results were verified by MCNP (Monte Carlo N Particle Transport Code), while the ²⁵²Cf shielding performance of the composite shielding materials was investigated by using MCNP simulation. High-purity germanium (HPGe) detector and universal testing machine were used for gamma shielding performance test and mechanical properties test, to study the filler type (B₄C and Gd₂O₃) and filler content on the composite shielding material gamma shielding performance and mechanical properties of the performance changes of the difference. The results show that the shielding performance of B₄C/Bi/NR and Gd₂O₃/Bi/NR against neutron ²⁵²Cf fission neutrons (slowed down by 12 cm thick polyethylene) increases gradually with the increase of B₄C and Gd₂O₃ fillings, while the shielding rate of Gd₂O₃/Bi/NR against neutrons tends to be stabilized when the Gd₂O₃ content is higher than 40 phr. The experimental results are mutually verified with MCNP. It is found that the transmission ratios of ²⁵²Cf fission neutrons within the composite homogeneous materials all satisfy the exponentially decreasing law, and the composites have the best shielding ability for ²⁵²Cf fission neutrons when the B₄C and Gd₂O₃ fillings are 80 phr, and the neutron reaction cross sections of B₄C/Bi/NR and Gd₂O₃/Bi/NR are 0.265 cm⁻¹ and 0.267 cm⁻¹, respectively. In addition, the shielding performance of B₄C/Bi/NR against 59.5 keV gamma rays decreases with the increase of B₄C addition, whereas the shielding performance of Gd₂O₃/Bi/NR against 59.5 keV gamma rays is enhanced with the increase of Gd₂O₃ content. The mechanical properties of the natural rubber decrease with the addition of B₄C, whereas the addition of appropriate amount of Gd₂O₃ (20 phr) helps to enhance the natural rubber’s. Gd₂O₃/Bi/NR composites have good neutron/gamma shielding properties and mechanical properties, which have potential applications as hybrid radiation field shielding materials.