Here, we reviewed the fundamental properties of metal hydrides, focusing on zirconium hydride, which is a material used to make the neutron reflec­tors of fast nuclear reactors, as well as titanium hydride and yttrium hydride. We discussed the hydrogen content and temperature dependence of
the elastic modulus, hardness, electrical conductivity, heat capacity, and thermal conductivity of zirconium hydride. Values of the physical properties of zirco­nium hydride (8-ZrH166) are summarized in Table 3. Such data are very important and valuable for the utilization of metal hydrides as materials for neutron reflectors in fast reactors.

References

Table 3 Physical properties of zirconium hydride (S-ZrHi. ee) Lattice parameter (nm) 0.47782 Young’s modulus (GPa) 132 Shear modulus (GPa) 50 Bulk modulus (GPa) 124 Vickers hardness (GPa) 2.67 Heat capacity (for S-ZrH158) (J K-1 mol-1) 39.4 (at 367 K) 54.8 (at 708 K) Electrical conductivity (x106Sm-1) 1.47 (at 293 K) 0.95 (at 673 K) Thermal conductivity (Wm-1 K-1) 16.7 (at 286 K) 18.5 (at 663 K)

The data for the lattice parameter, Young’s modulus, shear modulus, bulk modulus, and Vickers hardness were obtained at room temperature.

2.11.4 Summary

This chapter has provided a basic outline of neutron reflectors for nuclear reactors from the perspective of materials science, beginning with an overview of the properties required for neutron reflectors, proceeding to an outline of the production and processing methods for Be and metal hydrides as representative reflector materials, and then to a description of their basic properties. The outline of metal hydrides has focused on zirconium hydride, which is currently used mainly in fast reactors, and has described the influence of temperature and hydrogen concentration on the basic properties of zirconium hydride. The data provided in this chapter are considered to be extremely important and valuable in regard to the use of Be and zirconium hydride as neutron reflectors.

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