摘要:

AbstractThe possibility of constructing an intense hard-spectrum neutrino source≈13 MeV based on theβ–decay of8Li (T1/2= 0.8 s) is studied. Applications of such a source are considered in neutrino investigations. The source can be developed on the basis of a neutron-to-antineutrino lithium converter through (n,γ) activation of7Li isotopes irradiated by neutrons from the active zone of a reactor. The physical parameters of the lithium converter are compared with those of other neutrino sources. Different geometries for a converter using heavy water are considered. The converter efficiency is calculated as a function of the purity of the7Li isotope and the expected tritium activity values. The cross section of the neutrino-deuteron reaction increases rapidly in both the neutral (ṽe+ d→n + p + ṽe) and the charged (ṽe+ d→n + n + e+) channels as the converter efficiency is improved. The real efficiency is 9%, and the cross sections are enhanced by factors of 2.5 and 5 in the respective channels.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20074

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractSince the anisotropic behavior of nucleon-nucleon scattering becomes strong with increasing incident energy, the isotropic picture used in previous theories should be generalized and examined. A discussion of a nucleon double-differential cross-section calculation based on anisotropic intranuclear scattering is presented. The calculated results indicate that the anisotropic effect slightly improves the agreement with the experimental data.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20075

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractDouble-differential cross-section formulations are presented of a light composite particle projectile considering pickup-type reactions with one and two particles above the Fermi sea by using energy-averaged and energy-angle correlated kernels, respectively. The calculated results of cross sections, spectra, and double-differential cross sections indicate that generally the contributions of the pickup-type reactions with two particles above the Fermi sea are∼15 to 25% when the incident energies are50 MeV in some region of the outgoing energies and angles, whereas the forward tendency of the calculated angular distributions by the pickup configuration with two particles above the Fermi sea is weaker than that by the pickup configuration with one particle above the Fermi sea. The energy-angle correlation must be considered for the reactions of the outgoing composite particle with a higher incident energy.

ISSN:0029-5639    

DOI:10.13182/NSE93-66

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractBuildup factors for various shielding materials exhibit large variations in magnitude and in curve shapes as a function of penetration depth as a result of the stochastic nature of the scattering processes for different incident photon energies.In a quest for adequate functional representation of point isotropic gamma-ray buildup factor data, a family of functions based on an expanded polynomial orthogonal set is introduced.The approximation function has the form.In the foregoing formula, a andβare generally constants that differ for each material, and in that respect, this formula presents a family of functions, while Aiare independent parameters of the function. This is not always valid, and for some materials, modifications are introduced where besides Ai, an additional independent parameter is (βwhileαremains constant throughout the whole energy domain.A polynomial-based function approach is validated as a possible choice [besides the well-known geometrical-progression (G-P) function] for point-kernel calculations. Results of approximations to exposure point isotropic buildup factors for water, concrete, and iron with four and for lead and beryllium with five independent parameters of presented function are in good agreement with the basic data within 4%, over the standard data domain. The results are compared with five-parameter G-P function fitting on the maximum-percentage-relative-error basis. The validity of using the independent parameters of the function to interpolate buildup factors for intermediate source energies is ascertained.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20077

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe exact solution of the depletion chain equations for arbitrary values of depletion constants is obtained. New nonsingular coefficients are introduced, and recurrence formulas that provide an efficient and accurate method of calculation are derived. Generality and simplicity of the method are found to be useful in evaluating depletion chains with one hundred or more nuclides in the chain, such as the s-process chain in studies of nucleosynthesis by neutron capture. The method can also be used to check the validity of approximate solutions.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20078

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe objective of this analysis is to obtain an algebraic correlation for flooding and unflooding in a pressurized water reactor (PWR) hot leg during reflux core cooling. This correlation may be used in loss-of-coolant accident analysis codes such as RELAP5.The one-dimensional two-fluid model equations are solved to obtain a void fraction profile along the pipe. A jump condition is included in the model to account for the possibility of a hydraulic jump. The flooding correlation by Mishima and Ishii is used to determine the flooding point.The model is validated against the scaled-down data of Krolewski and the full-scale data of Ohnuki, Adachi, and Murao. Reducing the coefficient of the flooding correlation to match the full-scale data is necessary to account for the effect of diameter size.Based on the validated model, a flooding correlation is obtained along the lines of the Wallis flooding criterion. It is further shown that under the conditions prevalent during PWR refluxing, the hysteresis between flooding and unflooding is not relevant, so the same correlation is valid for both.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20079

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe recent use is reported of neutron activation analysis to determine the elemental content of silicon-germanium layers that were epitaxially grown on antimony-doped single crystal silicon substrates. The substrates formed part of gold-contact Schottky diode circuits. Gamma rays from the activation products75Ge and77Ge were used, and the usefulness was demonstrated of the gallium KαX ray, emitted in the electron capture decay of71Ge, to identify and quantify the germanium in our samples. Minor components of the silicon matrix and their bulk atomic concentrations for specimens having masses of∼56 mg were germanium (4 ppm), gold (2 ppm), and antimony (32 ppm). Estimates for the germanium atom fraction x, in the layers, in the range of 6 to 8%, were obtained for the samples studied.

ISSN:0029-5639    

DOI:10.13182/NSE94-A20080

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor