Beryllium nuclear properties

At low temperatures (15 million K), reactions between helium nuclei are inhibited by electrical repulsion. On the other hand, the nuclear properties of lithium, beryllium and boron nuclei (Z = 3,4, 5), and in particular their stability, are such that they are extremely fragile, decaying at temperatures of only 1 million K. For this reason, they are not formed in appreciable quantities in stars and cannot serve to bridge the gap between helium and carbon, species noted for their nuclear stability but which, it should be recalled, occur only in minute amounts in nature. 

The nuclear properties of fuel cladding material must also be satisfactory. For thermal reactors, it is important that the material have a reasonably small absorption cross section for neutrons. Only four elements and their alloys have low thermal-neutron absorption cross sections and reasonably high melting points aluminum, beryllium, magnesium, and zirconium. Of these, aluminum, magnesium, and zirconium are or have been utilized in fuel-element cladding. 

No fewer than 14 pure metals have densities se4.5 Mg (see Table 10.1). Of these, titanium, aluminium and magnesium are in common use as structural materials. Beryllium is difficult to work and is toxic, but it is used in moderate quantities for heat shields and structural members in rockets. Lithium is used as an alloying element in aluminium to lower its density and save weight on airframes. Yttrium has an excellent set of properties and, although scarce, may eventually find applications in the nuclear-powered aircraft project. But the majority are unsuitable for structural use because they are chemically reactive or have low melting points." ... 

Beryllium i s a strong and light metal with useful nuclear character-istics (its atomic number is 4). It oxidizes readily and the oxide is toxic. Its properties are li sted in Tabl e 6.2. It i s produced by C VD on an experimental basis. 

Beryllium oxide shows excellent thermal conductivity, resistance to thermal shock, and high electrical resistance. Also, it is unreactive to most chemicals. Because of these properties the compound has several applications. It is used to make refractory crucible materials and precision resistor cores as a reflector in nuclear power reactors in microwave energy windows and as an additive to glass, ceramics and plastics. 

One attractive property of beryllium is its nonsparking quality, which makes it useful in such diverse applications as the manufacture of dental appliances and of nuclear weapons. Beryllium-copper alloys find use as components of computers, in the encasement of the first stage of nuclear weapons, in devices that require hardening such as missile ceramic nose cones, and in the space shuttle heat shield tiles. Because of the use of beryllium in dental appliances, dentists and dental appliance makers are often exposed to beryllium dust in toxic concentrations. 

This is what they thought at first. I m giving you a bit of history here. The reaction of beryllium-8 and helium-4 seemed too slow. There was one chance that the reaction speed could be boosted—if carbon-12 had a very special property an energy almost exactly equal to the combined energy of beryllium-8 and helium-4 at temperatures in a red giant. Chemists called this kind of facilitated nuclear reaction resonant. If by some miracle this were true, then the triple-alpha process could work. ... 

Beryllium oxide is used as a reflector and moderator in nuclear reactors. In addition to its low neutron-capture cross section, BeO has physical, mechanical, and chemical properties that allow its use at elevated temperatures, but its high cost and propensity to damage under irradation have limited its applications " ... 

Beryllium has become a strategically important metal in the nuclear and weapons industries. Magnesium and beryllium are valued for their individual properties, but they are especially important when alloyed with other metals. 

Other metals such as beryllium, hafnium, niobium, vanadium, and zirconium are known to have nuclear and other properties which make them desirable materials of construction in various designs of nuclear reactor, but also they have, or may have in the future, important uses outside that field. All these metals except hafnium have been used or proposed for canning materials to clad and protect the nuclear fuel metals from corrosion by the reactor coolants or moderators, air, carbon dioxide, water, heavy water, graphite or molten sodium, etc. In some cases the specifications for neutron-absorbing impurities are of the same order as for the fuel metals uranium and thorium. Hafnium, however, with a high neutron-capture cross-section, is a useful material for reactor control rods and exhibits favourable metallurgical properties under irradiation. 

Beryllium is used commercially in three major forms as a pure metal, as an alloy with other metals, and as a ceramic. The favorable mechanical properties of beryllium, e.g., its specific stiffness, have made it a major component for certain aerospace applications in satellites and spacecraft. As a modulator and reflector of neutrons, beryllium is of interest in fusion reactions and for nuclear devices that have defense applications. When a small amount of beryllium is added to copper, the desirable properties of copper (i.e., thermal and electrical conductivity) are kept but the material is considerably stronger. The superior thermal conductivity of beryllium oxide ceramics has made the product useful for circuit boards and laser tubes. A more complete discussion of the applications of beryllium was recently reviewed [2]. 

Topics under the practical importance of the alkaline-earth metals include their significance in living systems, the incidence of beryllium disease, radiochemical applications as components and residues of nuclear power, metallurgical uses in preparing pure metals and alloys, use in fireworks and X-ray technology, the definition and properties of hard water, and the role of calcium phosphate in bone and teeth structure. 

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). 

Owing to its material properties - very light and very strong - beryllium is an important industrial metal. Generally alloyed with other metals such as copper, it is a key component of materials used in the aerospace and electronics industries. In addition, beryllium has a small neutron cross-section, which makes it useful in the production of nuclear weapons and in sealed neutron sources (Taylor et al. 2003). Unfortunately, beryllium is responsible for a severe lung disease, chronic beryllium disease (CBD) or berylliosis and, in addition, was listed in 1993 as a Class A human carcinogen by the International Agency for Research on Cancer (1993). 

In summary, a heavy-water-moderated nuclear fission reactor fueled with UO3 or U3O8 can be operated with natural uranium that is produced by means of a standard uranium wet chemistry solvent extraction purification process. Additionally, given the neutronic properties of other elements, it is expected that similar reactors can be operated with uranium carbide, uranium tetrafluoride, and uranium-beryllium alloys. 

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