Nuclear characteristic

Boron trifluoride is also employed in nuclear technology by uti1i2ing several nuclear characteristics of the boron atom. Of the two isotopes, B and B, only B has a significant absorption cross section for thermal neutrons. It is used in " BF as a neutron-absorbing medium in proportional neutron counters and for controlling nuclear reactors (qv). Some of the complexes of trifluoroborane have been used for the separation of the boron isotopes and the enrichment of B as (84). 

According to V.M. Goldschmidt and Ya.I. Fersman the spread of chemical elements is determined by their nuclear characteristics. 

Table 23.2 Nuclear Characteristics of XH, 3H (T) and 13C Isotopes Employed Specifically in Life Sciences ...

Curtis, D., Benjamin, T. et al. 1989. The Oklo nuclear reactors cumulative fission yields and nuclear characteristic of reactor 9. Earth and Planetary Science Letters, 89, 193-206. 

Another important nuclear characteristic is the nuclear quadrupole moment which, possessed by nuclei for which 7 1, has given rise to the important field of nuclear quadrupole resonance spectroscopy. A major importance of the quadrupole moment with respect to NMR absorption resides in the effects of quadrupole coupling constants on nuclear relaxation times and, therefore, on the line widths and saturation characteristics of NMR absorption (9). In addition, in favorable situations, quadrupole coupling constants can be derived from the characteristics of nuclear resonance of quadrupolar nuclei 127). Some examples of these effects will be described in Sections III, IV and VI of this chapter. 

The first listing of the elements is generally attributed to Lavoisier in 1789. Of the twenty elements listed, the discovery of five was the result of research conducted by Stheelc of Golltenberg. With the development of nuclear physics and the application of these principles to astronomy and cosmology, in recent years the chemical elements have been viewed from new vantage points with much concentration on physical and nuclear characteristics as well as chemical properties. 

Cosmic portraits of the isotopes are the main burden of this book. For each element there is an historical and chemical introduction, followed by a table of those isotopes of that element that have observed abundance in the natural world. Then a section on each isotope describes its nuclear characteristics, its abundance in the solar system relative to that of silicon, the means of nucleosynthesis of that isotope, astronomical observations ofit, and its participation in isotopic patterns differingfrom those known on Earth, primarily in presolar grains extracted from the meteorites. 

In order to determine the half-life, the decay scheme, and other nuclear characteristics of a radioactive nuclide, it is important to use a sample of very high radiochemical purity. In addition in the measurement of nuclear reaction cross sections, fission yields and in activation analysis, the amounts of the radioactive nuclide produced must be determined. Thus It Is also necessary to determine the yield of... 

The projections are based on a recent forecast (Case B) by the Energy Research and Development Administration (ERDA) of nuclear power growth in the United States (2) and on fuel mass-flow data developed for light water reactors fueled with uranium (LWR-U) or mixed uranium and plutonium oxide (LWR-Pu), a high temperature gas-cooled reactor (HTGR), and two liquid-metal-cooled fast breeder reactors (LMFBRs). Nuclear characteristics of the fuels and wastes were calculated using the computer code ORIGEN (3). 

As indicated in Figure 6, the active portion 10 of the reactor is constructed with excess reactivity, so that changes in the nuclear characteristics of the reactor will... 

No general statement can be made about the elements that can be determined and the samples that can be analyzed, because these depend on the nuclear characteristics of the target nuclide (isotopic abundance), the nuclear reaction (cross-section and related parameters such as threshold energy and Coulomb barrier), and the radionuclide induced (half-life, radiation emitted, energy, and its intensity) for the analyte element, the possible interfering elements and the major components of the sample. CPAA can solve a number of important analytical problems in material science (e.g., determination of boron, carbon, nitrogen, and oxygen impurities in very pure materials such as copper or silicon) and environmental science (e.g., determination of the toxic elements cadmium, thallium, and lead in solid environmental samples). As these problems cannot be solved by NAA, CPAA and NAA are complementary to each other. 

In the core design of large FBRs, it is essential to improve the prediction accuracy of nuclear characteristics from the viewpoint of both reducing construction cost and insuring plant reliability. Extensive work is being performed in this context to accumulate and evaluate many results of reactor physics experiments in FBR field. As a part of the effort to develop a standard data base for large FBR core nuclear design, the physical consistency of JUPITER experiment and analysis was evaluated by full use of sensitivity analysis, effect of different nuclear data Ubraries and q>pUcation of most-detailed analytical tools. 

Fortunately, the resonant frequency of a nucleus depends on its chemical and/or structural environment in addition to its nuclear characteristics (y). 

The reactor core is designed so its nuclear characteristics do not contribute to a divergent power transient. The reactor is designed so there is no tendency for divergent oscillation of any operating characteristics considering the interaction of the reactor with other appropriate plant systems. 

The effect of clustering was also Investigated, in a core arrangement suitable for the proposed heavy y ter operation of EBWR. Into each of thirty-six, 4 x 4 in. clusters positioned to match the central region of the EBWR core were placed 28 fuel pins, spaced in a triangular pattern first at 3/4 in., next at 3/8 in. Several nuclear characteristics of these two core arrangements are compared in the table. 

A multlregton pseudospherlcal assembly (Figure 1) has been designed which uses onty 25 kg of U-233. A Sfdieri-cal U-233 test region is surrounded by a U-235 buffer region of aboutthe same nuclear characteristics. A thorium... 

The program consisted of essentially tlum phases. Nuclear characteristics of the initial PM-1 configuration were determined in the first phase. Based on the data obtained, it was determined that the umfiguratlcm iutd to be modified to satisfy design requirements. The second phase was pursued to establish what conf uration would satisfy these requirements. Analysis of data from the second phase led to the reference design configuration which was studied in the third phase. 

Studies of the nuclear characteristics of DjQHiO- moderated lattices have recently been extended to include measurements of reactivity and flux perturbations. These experiments provided nuclear data on relatively simple configurations for testing theoretical methods. The basic lattices consisted of 1.206-cm-diameter aluminum-clad 2.46%-enrlched UOi fuel rods on a square pitch of 1.511 cm. Moderator compositions varied from 0 to 72% B,0.to provide a wide range of neutron spectrum. Boric acid was added to keep the core radius constant (61.11 cm). 

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