Summary

In this TLP, the process of nuclear fission has been described, thus explaining the common choices for nuclear fuel used commercially. Materials selection for the major components of a nuclear reactor have also been explored, including:

• Moderators, and how they work best when they consist of light nuclides with relatively low absorption cross-sections.
• Control rods, which require high absorption cross-sections, and how the same nuclides found in control rods, e.g. boron, can act as poisons significantly reducing the efficiency of a reactor if found elsewhere, such as in moderators.
• Cladding, which experiences much stronger radiation fluxes and extremes of temperature than any other structural material in the reactor, and so must be able to withstand these conditions.

Concepts such as neutron cross-section and neutron flux have been explained, and this allowed mechanisms of radiation damage inside structural steels, and the consequences of this, to be discussed.

Radiation materials science is a mature field, but there any many challenges for materials to permit more efficient operation, improve safety and reliability and reduce costs. As this TLP has shown, the basic mechanisms of damage caused by low levels of radiation are now well understood, but the much higher levels of radiation such as those that will be experienced in the new experimental fusion reactor, ITER, have yet to be satisfactorily contained. This TLP has given only an introduction to some of the important phenomena.  To learn more, consult the Going Further section.

Test your understanding of this TLP by answering some of the questions in the next section.