Fuel self-sustaining

The inherent safety features and passive operation capability of the SPINNOR and VSPESINOR are targeted to eliminate core meltdown and, therefore, to avoid adverse environmental impacts in accidents. Because their conversion ratio is about one, the fuel self-sustainable regime may be established, in which only fertile fuel material, e.g. depleted uranium, will be consumed to produce energy. If higher breeding ratios become necessary, they could be achieved just by placing an external blanket in the reflector position. 

Flammability Limits There are both upper (or rich) and lower (or lean) limits of flammability of fuel-air or fuel-oxygen mixtures. Outside these hmits, a self-sustaining flame cannot form. Flammability limits for common fuels are listea in Table 27-18. 

Flanumbility limits (or explosion limits) for a flammable gas define tlie concentration range of a gas-air ini. ture witliin wliich an ignition source can start a self-propagating reaction. Tlie minimmn and maximmn fuel concentrations in air tliat will produce a self-sustaining reaction mider given conditions are called tlie lower Jlammability limit (LFL) and tlie upper Jlammability limit (UFL). (The abbreviations LEL and UEL, for lower and upper explosivity limits, are sometimes used.) The flanunability limits are functions of... 

A flame is a thin region of rapid, self sustaining oxidation of fuel that is often accompanied by the release of large amounts of heat and light. Flames are what we most coninionly associate with combustion. One part of combustion science focuses on the different ways flames can be formed and the scientific and practical consequences of each. 

The burning mechanism of composite propellants differs from that described above. There is no exothermic reaction which can lead to a self-sustaining fizz zone. Instead, the first process appears to be the softening and breakdown of the organic binder/fuel which surrounds the ammonium perchlorate particles. Particles of propellant become detached and enter the flame. The binder is pyrolysed and the ammonium perchlorate broken down, initially to ammonia and perchloric acid. The main chemical reaction is thus in the gas phase, between the initial dissociation products. 

Because the isotope uranium-235 is fissionable, meaning that it produces free neutrons that cause other atoms to split, it generates enough free neutrons to make it unstable. When the unstable U-235 reaches a critical mass of a few pounds, it produces a self-sustaining fission chain reaction that results in a rapid explosion with tremendous energy and becomes a nuclear (atomic) bomb. The first nuclear bombs were made of uranium and plutonium. Today, both of these fuels are used in reactors to produce electrical power. Moderators (control rods) in nuclear power reactors absorb some of the neutrons, which prevents the mass... 

Fire is a self-sustaining, exothermic oxidation-reduction reaction. The fire reaction usually involves oxygen which forms the oxides of the fuel. The most important examples in petrochemical and hydrocarbon processing facilities are combustion reactions of hydrocarbons with oxygen. 

Based on conventional thinking, lower temperatures should result in a decrease of thermally produced NO, . However, despite the substantially lower temperatures in the PSR, as shown in Fig. 26.4a, the NO, mole fractions do not significantly differ between the two reactors, except for very fuel-lean mixtures, near extinction of self-sustained flames. Similar behavior was recently observed when radiation from... 

Self-sustaining decomposition or combustion characteristics with higher fuel concentration and lower oxidizer concentration. 

Subcritical Mass when the quantity of radioactive fuel is insufficient to produce a self-sustaining chain reaction Sublimation process where a substance passes directly from the solid to gaseous phase without going through the liquid phase... 

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