Fast neutron source

Among other isotopes produced at SRP were uranium-233 for breeder research, cobalt-60 [10198-40-0] for irradiators, plutonium-238 for spacecraft such as V ojager 2in.d lunar research power suppHes, and califomium-252 as a fast neutron source. The accomplishments of Du Pont at SRP are well chronicled (53). 

The fractional loss in energy when a neutron collides with an atom is greatest for the H atom. Thus, by passing a beam of fast neutrons thru a series of samples, of the same material, but with varying moisture contents, a relationship is observed between moisture content and measured thermal neutron intensity. Using a small. radioisotope fast neutron source and a lithium iodide thermal neutron detector, this neutron... 

Two different types of information can be obtained by bombarding soil with neutrons. Fast neutrons are slowed when they interact with water and thus can be used to measure the amount of water present. This type of analysis is most often conducted in the field rather than in the laboratory. Figure 8.2 illustrates the use of a fast neutron source and a slow neutron detector to measure the moisture content of soil. This method depends on the interaction of neutrons with hydrogen and so it is not as useful in soils with significant or highly variable organic matter contents. 

Fission cross section ratios of minor actinide nuclides (Np-237, Am-241 and Am-243) relative to U-235 in the fast neutron energy region have been measured at YAYOl fast neutron source reactor. 

All neutrons born from fission appear (without delay) mono-energetically at u = 0, and fissions are due only to thermal neutrons therefore, the fast-neutron source is... 

The rate of formation of Pu from capture of thermal neutrons in U is N2 02z4>- The resonance absorption is given by an expression similar to the second term in the numerator of equation (4.5), with a corresponding term having to be added to include the fast neutron source from Pu, once this has built up enough to be a significant factor. If we assume that e is the same for and Pu, the resonance production of Pu is then... 

In Vivo Activation Analysis. The use of neutron activation techniques for in VIVO measurement of iodine in the thyroid gland is nowin clinical use, but the measurement of skeletal Ca and other major body elements such as Na, using fast neutron sources, is still subject to many errors if absolute measurement is required. However, there is considerable current interest in this aspect of medical activation analysis. — ... 

Fast-neutron source, which is an assembly of 30 fuel plates arranged in 6 groups of 5 plates each. (See Figs. 23.4 and 23.5.). 

The technologically most important isotope, Pu, has been produced in large quantities since 1944 from natural or partially enriched uranium in production reactors. This isotope is characterized by a high fission reaction cross section and is useful for fission weapons, as trigger for thermonuclear weapons, and as fuel for breeder reactors. A large future source of plutonium may be from fast-neutron breeder reactors. 

The principal source of natural tritium is the nuclear reactions induced by cosmic radiation in the upper atmosphere, where fast neutrons, protons, and deuterons coUide with components of the stratosphere to produce tritium ... 

For the neutron porosity measurement, fast neutrons are emitted from a 7.5-curie (Ci) americium-beryllium (Am-Be) source. The quantities of hydrogen in the formation, in the form of water or oil-filled porosity as well as crystallization water in the rock if any, primarily control the rate at which the neutrons slow down to epithermal and thermal energies. Neutrons are detected in near- and far-spacing detectors, located laterally above the source. Ratio processing is used for borehole compensation. 

Thru 1967, emphasis was given to the use of neutrons as the bombarding source of radiation. Almost all possible neutron reactions were considered including moderation of fast neutrons by hydrogen in the expl, thermal capture reactions, elastic and inelastic scattering of neutrons and neutron activation reactions. These neutron reactions are listed as follows ... 

Another source of overlapping tracks are the knock-on protons produced during fast neutron irradiation of a hydrogenous material. 

Nuclear weapons which usually use nuclear fusion, have far greater yields than weapons, which use only fission, as fusion releases more energy per kilogram and can also be used as a source of fast neutrons to cause fission in depleted uranium. 

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