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Uranium Enrichment, Nuclear Fuels, and Fuel Cycles
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
Plutonium dioxide resembles uranium dioxide in several respects. It can also vary in color from yellow to olive green, depending on the particle size, the temperature, and the extraction process that is used. Just like uranium dioxide, plutonium dioxide is a composite material that has many complex properties. Plutonium dioxide is desirable as a nuclear fuel because the vacancies in the octahedral matrix it forms have enough room to contain the fission products as the Plutonium-239 is consumed. The vacancies in the octahedral matrix provide room for the newly created fission products and still allow the PuO2 matrix to retain its structural integrity. This tends to make plutonium dioxide an ideal nuclear fuel. PuO2 also has a very high melting point (2400°C or 4352°F) and it is dimensionally stable even when the temperature in a reactor core changes dramatically (see Figure 10.30).
Modeling of the P2M Past Fuel Melting Experiments with the Fuel Performance Code FAST-1.0.1
Published in Nuclear Technology, 2023
James Corson, Alice Chung, Steven Muller
The FAST computer code is sponsored by the NRC and jointly developed by the Pacific Northwest National Laboratory (PNNL) and the NRC to simulate the behavior of a nuclear fuel rod during steady-state irradiation, AOOs, design-basis accidents, and dry storage conditions. It models the fuel and cladding thermomechanical behavior, including the transport of fission and decay heat from the fuel to the coolant, fuel and cladding deformation, fission gas release from the fuel to the rod void volume, and cladding corrosion and high-temperature oxidation. While FAST was primarily developed for LWR fuel rods with uranium dioxide, uranium dioxide with gadolinia, and mixed uranium and plutonium dioxide fuel in zirconium alloy cladding, it includes some properties for accident-tolerant fuel materials and capabilities for modeling the metallic fuel used in sodium fast reactors.
Study on Sintering Kinetics of (ThxCe1-x)O2 Ceramic Pellets Prepared via Sol-Gel Method
Published in Nuclear Technology, 2020
Berkan Çetinkaya, Hüseyin Tel, Ahmet Yaylı
In this study, for the investigation of sintering kinetics of thorium-cerium mixed oxide, cerium was used to simulate plutonium. Plutonium, which is dangerous to work with because of its high radioactivity, involves specific precautions and necessitates complex equipment. On the other hand, most countries are deprived of plutonium.6,7 Cerium, a lanthanide series metal, is a common chemical surrogate for plutonium. Cerium has similar physical and chemical properties to plutonium and is a nonradioactive substitute for plutonium for the maintained studies on (Th,Pu)O2 fuel production in many laboratories around the world.8,9 The thermodynamic and crystallographic properties of cerium dioxide are similar to those of plutonium dioxide. It is well known that ThO2 and CeO2 also have the same crystallographic structure (CaF2 type, cubic) and mixed in any ratio, they form solid solutions.7,10
Plutonium-238 Production Program Results, Implications, and Projections from Irradiation and Examination of Initial NpO2 Test Targets for Improved Production
Published in Nuclear Technology, 2022
Emory D. Collins, Robert N. Morris, Joel L. McDuffee, Padhraic L. Mulligan, Jeffrey S. Delashmitt, Steven R. Sherman, Raymond J. Vedder, Robert M. Wham
The heat source plutonium dioxide (HS PuO2) product specification requires the plutonium to contain at least 82.5% 238Pu (Ref. 1). To meet this requirement, the 237Np irradiation flux and time must be limited to convert <15% of the 237Np into 238Pu. Above 15% conversion, the product, 238Pu, is consumed faster than it is created. This is indicated in Fig. 1, which shows the neutron capture cross section for 238Pu (540 b) is greater than that for 237Np (150 b) by a factor of 3.6.