The fabrication process of the gadolinia-doped fuel is almost the same as that of the UO2 fuel. The gadolinia-doped fuel fabrication line must be sepa­rated from the UO2 fuel to prevent gadolinium from contaminating the UO2 fuel fabrication line.

2.15.4 MOX Production

The utilization of plutonium in reactors is essen­tial for the establishment of the nuclear fuel cycle. It is already being used in LWRs and research and development (R&D) has been continued to utilize plutonium more efficiently in FBRs. MOX fuel is often selected as FBR fuel because of its excellent burn-up potential, high melting point, and relative ease of commercial fabrication and also because LWR fuel fabricators already have extensive experi­ence with UO2 fuel fabrication. Furthermore, oxide fuel has good irradiation stability, and proven safety
response using a negative Doppler coefficient that mitigates over-power transients.42’43 These advan­tages must be weighed against the disadvantages of oxide fuel, such as lower thermal conductivity that leads to fuel structuring and enhanced swelling’44 reduced compatibility with sodium,45-47 low fissile atom density, and the presence of two moderating atoms per one metal atom. Based on a balance between the advantages and disadvantages, various fabrication processes for MOX fuels, including the conversion processes for plutonium oxide, were developed more than 40 years ago and are still applied. Major processes utilized in the conversion of plutonium oxide and MOX fuel production are summarized here. Their details have been described in the literature.2’б’27’29’42’48 Plutonium emits a-particles with energies higher than 5 MeV, and all operations from powder han­dling to end plug welding after pellets are loaded into a cladding tube are carried out in glove boxes. In order to prevent plutonium inhalation accidents during fuel fabrication, these glove boxes have an airtight structure and their interiors are continu­ously kept at negative pressure. Furthermore, as described in Section 39.2.2, gamma and neutron shielding is required for these glove boxes to reduce radiation exposure.49