Nuclear fuel: composition

Other forms of carbon-carbon composites have been or are being developed for space shutde leading edges, nuclear fuel containers for sateUites, aircraft engine adjustable exhaust nozzles, and the main stmcture for the proposed National Aerospace plane (34). For reusable appHcations, a siHcon carbide [409-21 -2] based coating is added to retard oxidation (35,36), with a boron [7440-42-8] h Lsed sublayer to seal any cracks that may form in the coating. 

Oxides of the actinides are refractory materials and, in fact, Th02 has the highest mp (3390°C) of any oxide. They have been extensively studied because of their importance as nuclear fuels. However, they are exceedingly complicated because of the prevalence of polymorphism, nonstoichiometry and intermediate phases. The simple stoichiometries quoted in Table 31.5 should therefore be regarded as idealized compositions. 

Table 2.1 lists specific radionuclides that may be present in nuclear fuel rods or industrial sources used to construct a dirty bomb. It also lists the radiological half-lives of each radionuclide, whether they are present in fresh or spent fuel rods, and their potential industrial applications. Note that the actual suites of isotopes for given fuel rods will vary depending on the origin and composition of the original fuel mixture. The uranium and plutonium isotopes found in fuel rods may also be found... 

The composition of the ashes from the nuclear fuel (in this case, silicon, characterised by n/p = 1) is a direct consequence of the degree of neutron enrichment allowed by P decay in the time available for nucleosynthesis, which is itself fixed by astrophysical conditions. 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

Though the chemical families retained in the context of nuclear fuel reprocessing are very different, depending on the metallic ion to be recovered and the composition of the initial feed, an attempt to establish a scale of extractants sensitivity toward radiolysis is presented in the following paragraph ... 

Nuclear Fuel Fissionable materials that have been enriched to such a composition that, when placed in a nuclear reactor, they will support a self-sustaining fission chain reaction, producing heat in a controlled manner for process use. 

Solutions. The following solutions were used in one or more of the experiments. With the exception of the distilled water, they reflect the composition of the solutions that may be expected to be present in and around a nuclear fuel waste vault. Their chemical compositions are given in Table II. 

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