Preventing release of radioactive fission products is a major concern in the design, construction, and operation of a nuclear plant. Therefore, mechanical strength plays an important role in selecting reactor materials. High mechanical strength is desirable because of its possible degradation due to radiation damage and the need to contain the radioactive liquids and fuel.

Summary

The important information in this chapter is summarized below.

Material Properties Considered for Selection Summary

Machinability is the ability of a metal to react to mechanical deformation by removing chips, with respect to the amount of metal effectively removed and the surface finish attainable. This property is important when selecting parts that require very close tolerances and very smooth surfaces.

Formability of a material is its ability to withstand peripheral expansion without failure or the capacity of the material to be manufactured into the final required shape. This property is important when selecting materials that have to be made into specific shapes by such means as rolling or bending and still retain their required strength.

Stability of a material refers to its mechanical and chemical inertness under the conditions to which it will be subjected. This property is important when selecting materials environments such as high temperature, high acid, high radiation, and high pressure environments.

Fabricability is a measure of the ease with which a material can be worked and made into desirable shapes and forms. This property is important when materials are required to have very complicated shapes or forms and require very close tolerances.

Ductility is essential for materials that are subject to tensile and compressive stresses. Ductility is important in the construction of reactor vessels.

Availability is the ease with which material can be obtained and its cost.

Good heat transfer properties are desirable for the boundary between the fuel and the coolant. These properties are desirable for heat exchanger tubes, fuel cladding, etc.

Cost is an important factor in selecting plant materials.

FUEL MATERIALS

Nuclear plants require radioactive material to operate. Certain metals that are radioactive can be used to produce and sustain the nuclear reaction. This chapter discusses the materials used in the various nuclear applications. The student should refer to the Nuclear Physics and Reactor Theory Fundamentals Handbook prior to continuing to better understand the material in this chapter.

EO 1.3LIST the four radioactive materials that fission by thermal neutrons and are used as reactor fuels.

EO 1.4STATE the four considerations in selecting fuel material and the desired effect on the nuclear properties of the selected fuel material.