Self-thermal sustainability

Am undergo fission with thermal neutrons of these isotopes and Pu are the most important as they are most readily obtainable. Other heavy nuclei require fast neutrons to induce fission such neutrons are much more difficult to control into a self-sustaining chain-reaction. 

In early 1941, 0.5 )-lg of Pu was produced (eqs. 3 and 4) and subjected to neutron bombardment (9) demonstrating that plutonium undergoes thermal neutron-induced fission with a cross section greater than that of U. In 1942, a self-sustaining chain reaction was induced by fissioning 235u... 

The result of high temp stability testing shows that at a temp of 150—200° under a press greater than lOOpsi, NPN will undergo a self-sustained thermal decompn yielding a gaseous mixt comprised primarily of carbon monoxide... 

The sustained decomposition of a substance without introduction of any other apparent ignition source besides thermal energy and without air or other oxidants present. Autodecomposition is the result of a thermal self-decomposition reaction for given initial conditions (temperature, pressure, volume) at which the rate of heat evolution exceeds the rate of heat loss from the reacting system, thus resulting in an increasing reaction temperature and reaction rate. 

A material that will undergo an exothermic, self-sustaining or accelerating self-reaction (decomposition, polymerization or rearrangement) when heated to a specific temperature for given conditions of pressure, volume, composition and containment. Thus, the self-reaction can be initiated by thermal energy alone. 

Self-sustaining thermal decomposition of NPK fertilisers is apparently possible if crystalline potassium nitrate is present from a exchange reaction of ammonium nitrate [1], Almost pure fertiliser grades of ammonium nitrate are legally restricted in some countries because of its instability [2],... 

The thermal DeNO system removes NO in practical systems because the NH2 + NO initiates a significant chain branching system, thereby allowing the overall reaction sequence to be self-sustaining. Following the general scheme in Table 8.2, the conversion of NH3 to NH2 occurs principally by reaction with OH ... 

Thermal runaway is an event that occurs when the battery electrode s reaction with the electrolyte becomes self-sustaining and the reactions enter an autocatalytic mode. This situation is responsible for many safety incidents and fires associated with battery operations. 

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... 

Three types of polymeric materials are used inert polymers, active polymers, and azide polymers. No exothermic heat is produced when inert polymers are decomposed thermally. On the other hand, exothermic reactions occur when active polymers and azide polymers are decomposed. Self-sustaining burning is possible when active polymers and azide polymers are ignited. 

Typically, ATR reactions are considered to be thermally self-sustaining and therefore do not produce or consume external thermal energy. In fact, since ATR consists of the combination of an exothermic reaction (CPO) which produces heat, with an endothermic reaction (CSR) where heat must be externally generated to the reformer, the balance of the specific heat for each reaction becomes a very distinctive characteristic of this process. This makes the whole process relatively more energy efficient since the heat produced from CPO can transfer directly to be used by CSR. However, other exothermic reactions may simultaneously occur, such as WGS and methanation reactions. 

The silicon reduction process is not thermally self-sustaining and, therefore, is done in an electric arc furnace ... 

Deflagration to detonation transitions for either the composite or HPDB (High-performance double-base) proplnts have not resulted from the use of mild thermal initiation even when strongly confined. It was generally observed that porous beds of material are required to provide compressioned heating that ultimately develops into a self-sustained deton, as was proposed by Andersen ... 

By local heating of an explosive by a heat source in the form of a flame, spark, etc. A localized thermal impulse creates a local zone in which reactions start to occur and then propagate through the rest of the explosive due to their self-sustaining character. 

Of the fast neutrons produced in fission, some of them will be moderated to thermal energies and will induce other fission reactions while others will be lost. The ratio of the number of neutrons in the next generation to that in the previous generation is called the multiplication factor k. If the value of k is less than 1, then the reactor is subcritical and the fission process is not self-sustaining. If the value of k is greater than 1, then the number of fissions will accelerate with time and the reactor is supercritical. The goal of reactor operation is to maintain the system in a critical state with k exactly equal to 1. The extreme upper limit for the multiplication factor would correspond to the mean number of neutrons per fission ( 2.5 for 235U(n,f)) if each neutron produces a secondary fission. 

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