Neutron bombardment with

Numerous nuclear transformations have been induced by processes in which atoms have been bombarded with neutrons, protons, deuterium, carbon atoms and ions. 

Neutron-rich lanthanide isotopes occur in the fission of uranium or plutonium and ate separated during the reprocessing of nuclear fuel wastes (see Nuclearreactors). Lanthanide isotopes can be produced by neutron bombardment, by radioactive decay of neighboring atoms, and by nuclear reactions in accelerators where the rate earths ate bombarded with charged particles. The rare-earth content of solid samples can be determined by neutron... 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

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... 

Activation Process of inducing radioactivity in a material by bombardment with other types of radiation, such as neutrons. 

In the early years of this century the periodic table ended with element 92 but, with J. Chadwick s discovery of the neutron in 1932 and the realization that neutron-capture by a heavy atom is frequently followed by j6 emission yielding the next higher element, the synthesis of new elements became an exciting possibility. E. Fermi and others were quick to attempt the synthesis of element 93 by neutron bombardment of but it gradually became evident that the main result of the process was not the production of element 93 but nuclear fission, which produces lighter elements. However, in 1940, E. M. McMillan and P. H. Abelson in Berkeley, California, were able to identify, along with the fission products, a short-lived isotope of... 

Apart from g Pu, which is a nuclear fuel and explosive, the transuranium elements have in the past been produced mainly for research purposes. A number of specialized applications, however, have led to more widespread uses. I Pu (produced by neutron bombardment of I Np to form 93 Np which decays by jS-emission to 94Pu) is a compact heat source (0.56 Wg as it decays by a-emission) which, in conjunction with PbTe thermoelectric elements, for instance, provides a stable and totally reliable source of electricity with no moving parts. It has been... 

The nucleus of an atom consists of protons and neutrons that are bound together by a nuclear force. Neutrons and protons are rearranged in a nuclear reaction in a manner somewhat akin to rearrang ing atoms in a chemical reaction. The nuclear reaction liberating energy in a nuclear power plant is called nuclear fission. The word fission is derived from fissure, which means a crack or a separation. A nucleus is separated (fissioned) into two major parts by bombardment with a neutron. 

In 1938 Niels Bohr had brought the astounding news from Europe that the radiochemists Otto Hahn and Fritz Strassmann in Berlin had conclusively demonstrated that one of the products of the bom-bardmeiit of uranium by neutrons was barium, with atomic number 56, in the middle of the periodic table of elements. He also announced that in Stockholm Lise Meitner and her nephew Otto Frisch had proposed a theory to explain what they called nuclear fission, the splitting of a uranium nucleus under neutron bombardment into two pieces, each with a mass roughly equal to half the mass of the uranium nucleus. The products of Fermi s neutron bombardment of uranium back in Rome had therefore not been transuranic elements, but radioactive isotopes of known elements from the middle of the periodic table. 

Tn their years together Hahn and Meitner did significant research on beta- and gamma-ray spectra. They discovered the new element protoactinium-91 and, at Meitner s suggestion, took up, and made great progress with, work on neutron bombardment of nuclei that Enrico Fermi had commenced in Rome. In 1938, this research was suspended when Adolph Hitler annexed Austria and Meitner had to flee Germany. 

When bismuth-209 is bombarded with nickel-64, one neutron and a new isotope, X, is formed. The isotope then goes through a series of alpha particle emissions. 

Actually, then, by our symbol jjU we are representing not an atom, but a nucleus. Our equation is written in terms of nuclei and particles associated with them. This nuclear equation tells us nothing about what compound ol uranium was bombarded with neutrons or what compound of barium is formed. We are summarizing only the nuclear changes. During the nuclear change there is much disruption of other atoms because of the tremendous amounts of energy liberated. We do not know in detail what happens but eventually we return to electrically neutral substances (chemical compounds) and the neutrons are consumed by other nuclei. 

Several kinds of cancer therapy use radiation to destroy malignant cells. Boron neutron capture therapy is unusual in that boron-10, the isotope injected, is not radioactive. However, when boron-10 is bombarded with neutrons, it gives off highly destructive a particles. In boron neutron capture therapy, the boron-10 is incorporated into a compound that is preferentially absorbed by tumors. The patient is then exposed to brief periods of neutron bombardment. As soon as the bombardment ceases, the boron-10 stops generating a particles. 

When uranium-235 nuclei are bombarded with neutrons, they can split apart in a variety of ways, like glass balls that shatter into pieces of different sizes. In one process, uranium-235 forms barium-142 and krypton-92 ... 

Technetium-99m is produced by a sequence of reactions in which molybdenum-98 is bombarded with neutrons to form molybdenum-99, which undergoes p decay to technetium-99m. 

Since this change in distribution of the radioactive iron occurs most strongly in samples which have suffered a heavy fast neutron bombardment, one surmises that there must be a reaction with the products of bulk radiation damage. The products have not been identified. 

Beyond Z = 100, synthesis by neutron bombardment of uranium is no longer effective. Instead, nuclides in the Z = 95 to 99 range are bombarded with beams of light nuclei. For example, mendelevium (Z = 101) was first... 

University of Chicago in 1942, was designed and used for this purpose. Significant amounts of plutonium form when natural uranium is placed in a reactor and bombarded with neutrons. The resulting mixture can be treated by appropriate chemical methods to recover the plutonium in pure form. 

C22-0054. Identify the compound nucleus and final product resulting from each of the following nuclear reactions (a) carbon-12 captures a neutron and then emits a proton (b) the nuclide with eight protons and eight neutrons captures an a particle and emits a y ray and (c) curium-247 is bombarded with boron-11, and the product loses three neutrons. 

C22-0095. Neutron bombardment is an elegant way of doping silicon with phosphoms to convert it into an... 

Activation—The process of making a material radioactive by bombardment with neutrons or protons. 

Radioactivity, Induced—Radioactivity produced in a substance after bombardment with neutrons or other particles. The resulting activity is "natural radioactivity" if formed by nuclear reactions occurring in nature and "artificial radioactivity" if the reactions are caused by man. 

Like einsteinium, this unstable element was discovered in the fallout from the first hydrogen bomb. To date, only fragments in microgram amounts can be isolated. 258Fm ends the series of transuranium elements that can be produced in a reactor by neutron bombardment. The longest-lived isotope decays with a half-life of 100 days... 

The artificial actinides are created when atoms of smaller elements are bombarded with fast-moving particles, usually neutrons. 

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