Beryllium isotope, half-life

Beryllium has a high x-ray permeabiUty approximately seventeen times greater than that of aluminum. Natural beryUium contains 100% of the Be isotope. The principal isotopes and respective half-life are Be, 0.4 s Be, 53 d Be, 10 5 Be, stable Be, 2.5 x 10 yr. Beryllium can serve as a neutron source through either the (Oi,n) or (n,2n) reactions. Beryllium has alow (9 x 10 ° m°) absorption cross-section and a high (6 x 10 ° m°) scatter cross-section for thermal neutrons making it useful as a moderator and reflector in nuclear reactors (qv). Such appHcation has been limited, however, because of gas-producing reactions and the reactivity of beryUium toward high temperature water. 

Soft, silver white metal that is isolated in the tiniest of amounts. All isotopes are radioactive, the longest-lived has a half-life of 22 years. The element is an intermediate in the decay series of 235U. Strong alpha emitter that is used in radioactivation analysis and forms an effective neutron source with beryllium. 

Another short-lived isotope of beryllium, 7Be, decays to 7Li by electron capture with a half-life of —53 days. This half-life is so short that any atoms present in chondrite components must have been produced in the solar system essentially immediately before the host object formed. A hint of the presence of 7Be in the form of large excesses of 7Li in an Allende CAI was presented by Chaussidon et al. (2006). However, these authors were not able to demonstrate a tight correlation with the 9Bc/ Li ratio. 

Tritium is also one of the products obtained by bombardment of fluorine, beryllium, antimony, copper, or silver with deuterons, or the bombardment of boron and nitrogen with neutrons. Tritium is the simplest known radioactive isotope. It decays by emission of beta particles to form an isotope of helium and has a half-life of about 12 years. 

This chapter focuses on subduction zone processes and their implications for mantle composition. It examines subduction contributions to the shallow mantle that may be left behind in the wedge following arc magma genesis, as well as the changing composition of the slab as it is processed beneath the fore-arc, volcanic front and rear arc on its way to the deep mantle. Much of this chapter uses boron and the beryllium isotopes as index tracers boron, because it appears to be completely recycled in volcanic arcs with little to none subducted into the deep mantle, and cosmogenic e, with a 1.5 Ma half-life, because it uniquely tracks the contribution from the subducted sediments. 

A very unstable isotope of beryllium, Be, undergoes a emission with a half-life of 0.07 fs. How long does it take for 99.99% of a 1.0-/u,g sample of Be to undergo decay ... 

The trace alkali and alkaline earth cations are present in the following amounts lithium, 10-300 mg kg-1 rubidium, 20-500 mg kg-1 beryllium, 0.5-10 mg kg-1 strontium, 600-1000 mg kg-1 barium, 100-3000 mg kg-1 and radium, perhaps 10-7 mg kg-1. Some varieties of fmit trees are sensitive to as little as l mg L-1 Li+ in irrigation water, but Li+ toxicity is rare. Rubidium, cesium, strontium, and barium have all been studied in the laboratory, but have received little attention in the field. Strontium has been studied because its radioactive isotope 90Sr (half-life = 28 years) is produced by nuclear fission and could cause long-term soil contamination after nuclear explosions or accidents. In soils the toxic Be2+ ion behaves more like AI3 1 than like the other alkaline earth cations. 

CaS04 2 H2O) in plasters to decorate their tombs. These two alkaline earths are among the most abundant elements in the Earth s crust (calcium is fifth and magnesium sixth, by mass), and they occur in a wide variety of minerals. Strontium and barium are less abundant but like magnesium and calcium, they commonly occur as sulfates and carbonates in their mineral deposits. Beryllium is fifth in abundance of the alkaline earths and is obtained primarily from the mineral beryl, 863 2(8103)6. All radium isotopes are radioactive (the longest lived isotope is Ra, with a half-life of 1600 years). Pierre and Marie Curie first isolated radium from the uranium ore pitchblende in 1898. Physical properties of the alkaline earths are given in Table 8.4. 

One of the most common photoneutron sources, which produces neutrons of relatively low energy (26 keV) is a combination of antimony-124 and beryllium (Sb-Be source). In contrast to the (a, n) source, where the short range of the a particles necessitates intimate mixing of the reactants, the antimony can be separate from the beryllium, and the source can be switched off by separating the two. The half-life of Sb " is rather short (61 d), but the source can be reactivated by exposure to the high neutron flux in a reactor, when neutron capture in Sb leads to the formation of the active isotope. 

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