The physical properties of the fuel material are primarily of interest in ensuring its integrity
during the manufacturing process. Nevertheless they must be considered in assessments of the
integrity of the core under operating conditions, or the conditions of hypothetical accidents. The
physical and mechanical properties should also permit economical manufacturing. The fuel
material should have a low coefficient of expansion.
It is not possible to fabricate typical refractory ceramics to 100% of their theoretical density.
Therefore, methods of controlling the porosity of the final product must be considered. The role
of this initial porosity as sites for fission gas, as well as its effects on thermal conductivity and
mechanical strength, is a significant factor in the design.
The important information in this chapter is summarized below.
Fuel Materials Summary
Radioactive materials suitable for fission by thermal neutrons and used as reactor
233U and 235U
239Pu and 241Pu
Considerations in selecting fuel material are:
High thermal conductivity so that high power can be attained without
excessive fuel temperature gradients
Resistance to radiation damage so that physical properties are not degraded
Chemical stability with respect to coolant in case of cladding failure
Physical and mechanical properties that permit economical fabrication