3. Materials used for their nuclear properties

3.1 Fuels

Uranium, in oxide form, is most commonly used as fuel, usually enriched in its fissile isotope ²³⁵ U. Other uranium- or plutonium-based compounds (carbides or nitrides) could be considered, but comparison of the various physical and employment properties generally favor the choice of oxide. UO ₂ was chosen because of its very high melting temperature (2,845°C), which guarantees large margins in accident situations, and for its inert nature towards water. On the other hand, its thermal conductivity is low, below 2 W · m ^–1 · K ^–1 at 1,000°C.

As the ^...