Thermal neutron shielding properties of rare-earth nickel alloy materials

Abstract

The thermal neutron shielding performance of rare-earth nickel alloys are investigated, specifically focusing on the influence of various rare-earth elements and their concentrations on neutron transmission coefficients. The nickel-based alloy GH3535, with a thickness of 0.5 cm, was doped with mono or binary rare-earth elements. The thermal neutron transmission coefficients were assessed using Monte Carlo simulation methods. Key parameters analyzed included macroscopic absorption and scattering cross-sections, secondary gamma dose, and displacement radiation damage from recoil electrons. The results reveal that thermal neutrons in GH3535 primarily lose energy through scattering, allowing for a high transmission coefficient of 7.24 × 10⁻¹. The incorporation of gadolinium (Gd), a rare-earth element with the largest thermal neutron microscopic absorption cross-section, into GH3535 forms a mono rare-earth nickel alloy, Gd-Ni. The introduction of Gd significantly enhanced the Gd-Ni alloy’s absorption capacity, achieving a transmission coefficient of 2.52 × 10⁻⁶ at 1.50 wt% Gd, with a secondary gamma dose of 2.32 × 10⁻⁵ pSv·s⁻¹. Further doping of binary Gd-Ni alloys with other rare-earth elements, such as samarium (Sm), europium (Eu), and dysprosium (Dy), formed binary rare-earth nickel alloys Gd-Re-Ni and substantially improved shielding effectiveness. Compared to the Gd-Ni alloy (1.5 wt% Gd), the thermal neutron transmission coefficients were reduced by 64.47 % (1.0 wt% Sm), 54.68 % (1.0 wt%, Eu), and 15.13 % (1.0 wt%, Dy). The secondary gamma dose varied with different dopants and Eu notably minimized gamma exposure yielding a dose of 2.29 × 10⁻⁵ pSv·s⁻¹ at 1.0 wt% Eu. Meanwhile, doping with Eu, Sm and Dy reduced the displacement per atom (DPA) in the Gd-Re-Ni alloy, thereby enhancing its resistance to irradiation damage. The study demonstrates that the incorporation of rare-earth elements, particularly Eu and Dy, significantly enhances the thermal neutron shielding capabilities of nickel alloys while reducing secondary gamma radiation and irradiation damage. These findings provide essential theoretical support for the design and application of advanced neutron shielding materials.