Plutonium carbide nuclear fuels

Plutonium breeder LMFBR fuels, 6, 926 Plutonium carbide nuclear fuels, 6, 928 Plutonium complexes, 3,1131-1215 cupferron, 2, 510 Plutonium(III) complexes... 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

The oxides of uranium and plutonium are now widely used as nuclear fuel, while the carbides and nitrides of these elements possess promising qualities as the fuel of the future. 

The binary systems actually and potentially important as nuclear fuel include oxides, carbides, nitrides, phosphides, and sulfides of uranium, plutonium, and thorium. An increasing amount of detailed information is becoming available on the phase equilibria of these compounds, but the relations existing between the composition (especially nonstoichiometric) and the vapor pressure (or activity) of each component are known only for a limited number of systems. 

Another promising uranium compound that can be used in nuclear fuels is uranium carbide that has a high melting point and better thermal conductivity than the oxide and in addition does not form oxygen when radiolyzed. Uranium nitride can also be used, but formation of from N could be problematic. In addition, other uranium compounds that can be used as a fuel in a nuclear reactor, ranging from aqueous solutions to molten salts that are brought to a high temperature in order to keep them in a molten state. MOX of uranium and plutonium also serve as a nuclear fuel in some reactors. 

In a typical fast breeder nuclear reactor, most of the fuel is 238U (90 to 93%). The remainder of the fuel is in the form of fissile isotopes, which sustain the fission process. The majority of these fissile isotopes are in the form of 239Pu and 241Pu, although a small portion of 235U can also be present. Because the fast breeder converts die fertile isotope 238 U into the fissile isotope 239Pu, no enrichment plant is necessary. The fast breeder serves as its own enrichment plant. The need for electricity for supplemental uses in the fuel cycle process is thus reduced. Several of the early hquid-metal-cooled fast reactors used plutonium fuels. The reactor Clementine, first operated in the Unired States in 1949. utilized plutonium metal, as did the BR-1 and BR.-2 reactors in the former Soviet Union in 1955 and 1956, respectively. The BR-5 in the former Soviet Union, put into operation in 1959. utilized plutonium oxide and carbide. The reactor Rapsodie first operated in France in 1967 utilized uranium and plutonium oxides. 

Plutonium, instead of is a main contributor to the nuclear reactions in FRs where mixture of plutonium and uranium is used as fuel. Simple metallic fuel is a candidate to achieve better FR core performance than oxide fuel due to its higher fuel density, which has been employed in the LWR. Carbide and nitride fuels are also considered. 

Only two plutonium-only fuel forms have been tested for any length of time in a nuclear reactor (1) PuAl4 dispersed in aluminum and (2) Pu02 embedded in carbon and sealed in a silicon carbide shell (TRISO-coated PUO2). The INEL has examined these and a few advanced solid fuels that have not been tested. The current fuel choice is the Pu-Al composite. 

---