Nuclear reactions, prompt

Molnar, G. L., and R. M. Lindstrom. 1998. Nuclear reaction prompt gamma-ray analysis. In Nuclear methods in mineralogy and geology Techniques and applications. Ed. A. Vertes, S. Nagy, and K. Stivegh. 145-164. New York Plenum. 

Nuclide—A species of atom characterized by the constitution of its nucleus. The nuclear constitution is specified by the number of protons (Z), number of neutrons (N), and energy content or, alternatively, by the atomic number (Z), mass number A (N+Z), and atomic mass. To be regarded as a distinct nuclide, the atom must be capable of existing for a measurable time. Thus, nuclear isomers are separate nuclides, whereas promptly decaying excited nuclear states and unstable intermediates in nuclear reactions are not so considered. 

Glascock, M.D. (1994). Nuclear reaction chemical analysis prompt and delayed measurements. In Chemical Analysis by Nuclear Methods, ed. Alfassi, Z.B., John Wiley, Chichester, pp. 75-99. 

R.B. Bouiton, G.T. Ewan, Simultaneous analysis of light elements using prompt nuclear reaction gamma rays, Anal. Chem. 49 (1977) 1297-1303. 

Objections against these findings were soon raised. The strongest peak attributed to element 126 could experimentally be accounted for [55] by a prompt y-ray from the (p,n) nuclear reaction with natural 140Ce, a major component of the monazite crystals. The weaker peaks were shown to stem from to K x-rays from traces of ordinary elements such as antimony and tellurium [56]. When a more specific technique for the excitation of x-ray spectra was applied to the inclusions, namely by monochromatic synchrotron radiation tuned to the x-ray absorption edges, the evidence for superheavy elements vanished [57,58]. Furthermore, attempts failed [59] to detect them in bulk monazites through isolation of an A>294 fraction with a mass... 

In general, the activity of the radionuclide produced by the nuclear reaction is measured after irradiation, either directly or after chemical separation. However, the prompt y-ray photons emitted in (n,y) reactions may also be counted on the site of their production. For that purpose, the samples must be irradiated outside the nuclear reactor or by another neutron source, and the y-ray photons are recorded by means of a y-ray spectrometer. The intensity I of the y rays produced by the nuclear... 

In this Chapter we briefly consider the production and prompt isolation of the nuclear reaction products. The thermalization of recoils and the synthesis of compounds are discussed in more detail, as is the transportation of thermalized recoils by aerosol particulates to remote equipment for chemical experiments. The separations on chromatographic principles are discussed in Chapter 4. Some basic information about detection and measurement was given in Chapter 1 when describing concrete experiments. 

Prompt activation analysis (Erdtmann and Petri, 1986 Alfassi, 1990) uses the prompt radiation accompanying a nuclear reaction for determining elemental or isotopic concentrations. The variety of prompt methods is large because a sample can be irradiated with various particles - neutrons, charged particles or gamma-rays. Prompt activation analysis permits the determination of several elements - about 17 elements in environmental matrices (Germani et al., 1980) - but most analysis are used for the determination of light elements (H, He, Li, B, C, N, Si, S, Cl) as well of Cd and Gd. 

The beta-current neutron detector is a solid state ion chamber which is used in nuclear reactor technology. It consists of an emitter in which a nuclear reaction occurs, leading to the emission of primary /3 particles (e.g. through the reaction ( Rh(n,7) Rh(/8 , 4.2 s) Pd) or secondary electrons (e.g. through absorption of the prompt y s emitted in the neutron capture). These electrons represent a current and are collected by a collector. The radioactive decay type detectors have a response time depending on the product half-life, which the capture-y detectors lack. These detectors have a limited lifetime for the Co(n,y) Co it amounts to 0.1 % per month at 10 n cm s . The lifetime depends on... 

NDP is a prompt nuclear analysis technique, which employs a nuclear reaction that results in emission of charged particles with a specific kinetic energy. It is one of the most powerful non-destructive techniques for depth profiling of some light elements especially for and Li, which have very high thermal neutron capture cross-sections of 3837 and 940 barn respectively. 

The nuclear reactions are described as taking place in two steps (1) the formation of a compound nucleus in a highly excited virtual level, and (2) the dissociation of this compound nucleus leading to a state of high excitation of the product nucleus. The product nucleus, which decays promptly by electromagnetic transitions, ends up in the ground state or in some low-lying metastable level called an isomer. 

These experiments gave direct evidence of an explosive chain reaction. They gave an energy production of up to twenty million watts, with a temperature rise in the hydride up to 2 C per millisecond. The strongest burst obtained produced 10 neutrons. The dragon is of historical importance. It was the first controlled nuclear reaction which was supercritical with prompt neutrons alone. 

Therefore, summing up the activities of Minatom in 1997, we had an ambivalent feeling. On one hand, the unbiased results which would suit us at any other time. However, two spontaneous chain reactions prompted us to draw the most important conclusion the problems of nuclear safety, the observance of regulations and standards should be the focus of attention, since the origin of all incidents was the infringement of general safety rules. 

In prompt gamma-ray activation analysis the measurement is done simultaneously with the bombardment, and excited intermediates of the nuclear reactions emitting the so-called prompt gamma-rays are determined. The characteristic wavelength (gamma-energy) of this emission can be used for qualitative analysis and their intensity for quantitative analysis of the target material. 

PROMPT Of neutrons or gamma-rays which are emitted immediately during a nuclear reaction such as fission and neutron capture. 

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