Plant MaterialsDOE-HDBK-1017/2-93FUEL MATERIALSFUEL MATERIALSNuclear plants require radioactive material to operate. Certain metals that areradioactive can be used to produce and sustain the nuclear reaction. This chapterdiscusses the materials used in the various nuclear applications. The studentshould refer to the Nuclear Physics and Reactor Theory Fundamentals Handbookprior to continuing to better understand the material in this chapter.EO 1.3LIST the four radioactive materials that fission by thermal neutronsand are used as reactor fuels.EO 1.4STATE the four considerations in selecting fuel material and thedesired effect on the nuclear properties of the selected fuelmaterial.Overviewof MaterialTypesThe reactor core is the heart of any nuclear reactor and consists of fuel elements made of asuitable fissile material. There are presently four radioactive materials that are suitable for fissionby thermal neutrons. They are uranium-233 (233U), uranium-235 (235U), plutonium-239 (239Pu),and plutonium-241 (241Pu). The isotopes uranium-238 (238U) and thorium-232 (232Th) arefissionable by fast neutrons. The following text discusses plutonium, uranium, and thorium asused for nuclear fuel.PlutoniumPlutonium is an artificial element produced by the transmutation of 238U. It does exist in smallamounts (5 parts per trillion) in uranium ore, but this concentration is not high enough to bemined commercially.Plutonium is produced by the conversion of 238U into 239Pu according to the following reaction.23982U + 1on 23992U 23993Np 23994PubbThis reaction occurs in reactors designed specifically to produce fissionable fuel. These reactorsare frequently called breeder reactors because they produce more fissionable fuel than is used inthe reaction. Plutonium is also produced in thermal 235U reactors that contain 238U. Plutoniumcan be obtained through the processing of spent fuel elements. To be useful as a fuel, plutoniummust be alloyed to be in a stable phase as a metal or a ceramic.Rev. 0Page 5MS-05
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