DOE-HDBK-1017/2-93PROPERTIES CONSIDERED WHEN SELECTING MATERIALSPlant MaterialsFormabilityComponents may be formed by processes such as rolling or bending, which may causesome parts of the metal to expand more than others. Formability of a material is itsability to withstand peripheral expansion without failure or the capacity of the materialto be to manufactured into the final required shape. This becomes important in selectingmaterials that have to be made into specific shapes by such means as rolling or bendingand still retain their required strength.DuctilityDuctilityis the plastic response to tensile force. Plastic response, or plasticity, isparticularly important when a material is to be formed by causing the material to flowduring the manufacture of a component. It also becomes important in components thatare subject to tension and compression, at every temperature between the lowest servicetemperature and the highest service temperature. Ductility is essential for steels used inconstruction of reactor pressure vessels. Ductility is required because the vessel issubjected to pressure and temperature stresses that must be carefully controlled topreclude brittle fracture. Brittle fracture is discussed in more detail in Module 4, BrittleFracture.StabilityStabilityof a material refers to its mechanical and chemical inertness under the conditions towhich it will be subjected. Nuclear plants have a variety of environments to which materialsare subjected. Some of these environments, such as high temperatures, high acid, highradiation, and high pressure, can be considered extreme and harsh; therefore, the stability ofthe materials selected for service in these areas is a major consideration.Corrosion mechanisms can become very damaging if not controlled. They are identifiedin Module 2, Properties of Metals. High corrosion resistance is desirable in reactorsystems because low corrosion resistance leads to increased production of corrosionproducts that may be transported through the core. These products become irradiated andcontaminate the entire system. This contamination contributes to high radiation levels aftershutdown. For these reasons, corrosion resistant materials are specially chosen for use inthe primary and secondary coolant systems.AvailabilityThe availability of a material used in the construction of nuclear plants refers to the easewith which a material can be obtained and its cost.MS-05Page 2Rev. 0
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