By the beginning of work in the 1960s, information on the properties and manufacturing technology of materials for the NRE core (based on zirconium, nio­bium, uranium carbides, and zirconium hydride) was absent or inconsistent. It was known that unlike mono compound of uranium with a low melting point (2,500 K), a fuel based on solid solutions of UC-ZrC and UC-NbC carbides with nearly sto­chastic composition can provide the heating of hydrogen up to 3,000K. Therefore, investigations of solid solutions of uranium monocarbide with isomorphous, highly refractory zirconium, niobium, and monocarbides providing high melting points and compatibility of HREs with heat carriers became the most important material tech­nology direction. The prospects of the development of UC-ZrC-ZrN fuel were also outlined. The manufacturing technology of these refractory materials was based on powder metallurgy methods.

Refractory compounds are characterized by high hardness, elastic modulus, chemical stability, heat resistance and the high brittleness caused by features of interatomic interaction with mixed ionic-covalent type and low dislocation mobility [1-3]. Graphite with low values of hardness, strength and an elastic modulus possess many times higher thermal stress resistance R > 700 K in comparison with carbide compounds.

The first data on the radiation resistance of HREs (integrity, swelling, and strength) at temperatures from 1,000 to 3,100K and neutron flux intensities up to 1015- 1016cm-2 confirmed the expediency of the choice of fuel materials based in solid carbide solutions. It was decided [4, 5] for the first time in the development of a highly reliable construction in machine building to use brittle materials, which required changing construction principles and the established concepts of strength and thermal strength. A new criterion for estimating the bearing ability of thermally loaded products was introduced, which was accepted by the scientific community worldwide [6].

A. Lanin, Nuclear Rocket Engine Reactor, Springer Series in Materials Science 170, DOI: 10.1007/978-3-642-32430-7_4, © Springer-Verlag Berlin Heidelberg 2013