Nuclear graphite manufacture

Figure 1. Flow diagram for manufacture of nuclear graphite.

Nuclear graphite is usually manufactured from high-grade coke filler and pitch binder, processed as described earlier in this chapter, and then thoroughly purified by halogen treatment (see Sec. 2.3 above). The highest degree of purity is necessary to attain the required nuclear properties. 

Nuclear graphite grades, their manufacture, microstmcture, and properties ... 

Nuclear graphite is an artihcially produced polycrystalline material with around 20% porosity [12]. The raw materials and manufacture route used to produce nuclear graphite are basically the same as those used to manufacture graphite electrodes and graphite components used in the electronic industry. The raw materials used are a graphitizable pitch or petroleum coke along with a pitch-based binder and pitch-based impregnating medium. 

Aerospace and nuclear reactor appHcations of graphite demand high reHabiHty and reproducibiHty of properties, physical integrity of product, and product uniformity. The manufacturing processes require significant additional quaHty assurance steps that result in high cost. 

Uranium carbide UC (UC2 and U2C also exist) has a melting point of about 2300 °C and is an important nuclear fuel for high-temperature reactors. It is prepared by reduction of UO2 with carbon, followed by pressing and sintering. It can also be made by hot pressing of mixtures of uranium metal powder with graphite at 1000 to 1100 °C. A mixed carbide with ThC is manufactured in the form of spheroids by melting. As the product is hydrolyzed on exposure to air, it is coated with a protective carbon layer. 

Carbide powder is manufaetured by carburization of the metal, metal oxide or metal hydride with nuclear-pure graphite at ca. 2000°C. Carbide powder pellets (see Section 5.5.5.1.5) or beads up to 0.6 mm in diameter are formed and sintered using ceramic process technology. Reaction sintering is commonly used for the manufacture of uranium earbide fuel beads, in whieh uranium oxide and carbon are first mixed then annealed to form the carbide and then are sintered to 90 to 95% of the theoretical density. An... 

Atomic power industry (cutting of spent nuclear fuel pipe) manufacturing and processing of graphite... 

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