Fabrication and characterization of LiH ceramics for neutron shielding in space reactor systems

Lithium hydride (LiH) is a neutron shielding material for space nuclear reactors, but research on its preparation, processing, and functional integration remains limited. This study systematically investigates the preparation process and properties of LiH ceramics to evaluate their potential application in neutron shielding systems for space reactors. Green bodies were prepared via cold pressing and sintered at 500°C, yielding highly dense (98%) ceramics with closed pores, uniformly distributed grains (3–5 μm), stable microstructure, and no significant cracks. Mechanical testing revealed compressive strength reaching 180.67 MPa and flexural strength of 35.21 MPa at the optimal sintering temperature. Thermal performance tests indicated that the ceramic's thermal conductivity exceeded that of the green body and exhibited a decreasing trend across a broad temperature range from room temperature to 500°C, demonstrating stable and predictable thermal behavior. Both MCNP simulations and experimental measurements using a 252 Cf neutron source confirm that thin-layer LiH ceramics achieve over 90% shielding efficiency for low to medium energy neutrons and demonstrate significant shielding effects for fast neutrons. Comprehensive analysis indicates that LiH ceramics can simultaneously achieve high density, excellent mechanical and thermal properties, and outstanding neutron shielding capability. This provides reliable process guidance for the design and application of shielding materials.