Neutron properties, 2

C06-0044. Compute the speed of a neutron that has a kinetic energy of 3.75 x 10 J (see inside back cover for neutron properties). 

Table 3. Calculated neutronic properties for various Oklo-like ores. ...

Groves received the news acidly. He had ordered Compton to run CP-3 at full power full time to look for just such trouble. Ever the optimist, Compton apologized in the name of pure science the mistake was regrettable but it had led to a fundamentally new discovery regarding neutron properties of matter. He meant xenon s consiuning appetite for neutrons. Groves would have preferred to blaze trails less flamboyantly. 

Sphere critical mass is piotted as a function of Pu concentration in homogeneous solutions in Fig. 1. The excellent neutronic properties of polyethylene as compared to water are attributable to an increased Iqrdrogen atom density, and the replacement of oxygen by more of the better moderator carbon. The other materials are similar to water, or are less neutronically favorable. 

Determine the critical equation for a one velocity spherical reflected reactor which has the following specifications (1) a homogeneous active core of radius a (2) a spherical shell reflector of thickness h — a the neutron properties of which are, in general, different from those of the core (3) an infinitesimally thin spherical shell of absorbing material at the core-reflector interface this absorber has the property that it transmits a fraction a of all neutrons incident on either face. 

Attempts to alter the GT-MHR fuel cycle to produce plutonium with an isotopic content suitable for weapons material would be difficult and readily detectible. This would require frequent refuelling and use of fuel loadings that differ substantially from normal fuel loadings, with corresponding differences in neutronic properties. The safety and operational requirements of the GT-MHR will require strict compliance with requirements for fuel handling and placement in the core to insure core power and temperature distributions are within the limiting conditions assumed in the safety analysis. The fuel accountability and inspection requirements would preclude the major alterations in the fuel cycle required to produce the desired plutonium isotopic content, and would preclude diversion of spent fuel for clandestine reprocessing. 

The optimization of the graphite reflector thickness is described in Sect. 4.1. The material selection is based on cost, weight, and neutronic property considerations. An important aspect of the SSR reflector is... 

With an objective to illustrate the difference in fuel temperatures of the low thermal conductivity and high thermal conductivity fuels, a thermal power distribution inside a reactor core was calculated based on the neutronic properties of a fresh and symmetric core of a pressure channel (PCh) supercritical water-cooled reactor (SCWR). 

BeO is a metallic oxide with a very high thermal conductivity. BeO is chemically compatible with UO2, most sheath materials including zirconium alloys, and water. In addition to its chemical compatibility, BeO is insoluble with UO2 at temperatures up to 2160°C. As a result, BeO remains as a continuous second solid phase in the UO2 fuel matrix while being in good contact with UO2 molecules at the grain boundaries. BeO has desirable thermochemical and neutronic properties, which have resulted in the use of BeO in aerospace, electrical, and nuclear applications. For example, BeO has been used as the moderator and the reflector in some nuclear reactors. However, the major concern with beryllium is its toxicity. But the requirements for safe handling of BeO are similar to those of UO2. Therefore, the toxicity of BeO is not a limiting factor in the use of this material with UO2 (Solomon et al., 2005). 

Neutronic properties Low neutron absorption Minimal induced radioactivity Neghgible moderation... 

Because the neutronics properties are major drawbacks for the use of these metals as cladding materials for Generation IV reactors, use of these materials as thin liners sandwiched with ceramic material composite (CMC), such as SiC/SiC composite, tubes was proposed [55]. In this system responsibilities of creep resistance, thermal stability, corrosion resistance, and gas tightness if necessary, are shared by the triplex layers as designed for CMC/steel composite pipes [56]. 

From the above short review, it appears that most of the present nuclear reactors use a narrow sampling of neutron absorber materials. This, of course, first results from the neutron properties of the elements. This is also a consequence of the materials and elaboration processes availability. For example, AIC has been developed as a surrogate to hafnium and boron is mainly used as boron carbide. This is always a compromise regarding the previous examples, AIC has the lowest melting point of all the core materials and boron carbide is a brittle ceramic enduring premature cracking. 

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