摘要:

AbstractThe fission-gas release from pyrolytic-carbon-coated fuel particles during irradiation was studied for gas-cooled reactor application. Duplex-and triplex-type coatings on thorium-uranium carbide cores and on uranium carbide cores were tested at temperatures between 2000 and 2500°F (1093 and 1371°C). Both types of coatings retained fission gas quite well up to about 20at.% heavy-metal burnup. Postirradiation examination revealed that the particles with the duplex coating were more susceptible to radiation damage (by the formation of a reaction zone at the core/coating interface) than were the particles with the triplex coating. This damage, however, did not affect the fission-gas release rates.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19554

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractAn investigation has been carried out concerning the transmission of thermal and fast neutrons in air-filled annular ducts. A calculational model to predict the air-gap flux is developed and fitted to the results from foil-activation experiments in a Fe-D2O configuration, the duct length being about half a meter and the annular air gaps varying from 0.5 to 2.0 cm. It is based upon the condition that the flux is theoretically and experimentally divided into uncollided and collided components for both thermal and fast neutrons. The model may be applied to most of the straight annular ducts that occur in reactor shielding, but it is especially designed for the problems met with in short ducts.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19555

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA formal parallelism is shown to exist between two classical variational principles governing the time behavior of mechanical systems and two principles relating to theλ-mode eigenvalue problem of neutron group diffusion theory. By identifying the space variable with the time variable and space derivatives (gradients and divergences) with time derivatives, the‘usual’variational principle of diffusion theory is shown to be analogous to Hamilton's principle and the diffusion equations are analogous to the Lagrange equations. Hamilton's canonical equations are then analogous to the diffusion equations in first-order form, and the analog of the principle involving the canonical integral is a principle closely related to one proposed recently by Selengut and Wachspress.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19556

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe ability to interpret measured (n, 2n) cross sections by the statistical model of nuclear reactions has been tested. Good agreement was observed for 22 nuclei having mass numbers greater than 30. The statistical model was then applied to nuclei in this mass range to estimate both monoenergetic and fission-spectrum-averaged cross sections. The (n, 2n) reaction in structural materials contributes on the order of +0.1% to the reactor multiplication.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19557

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractFor the case of arbitrarily anisotropic scattering in monoenergetic neutron transport theory with no multiplication, the smallest rootκ0of the determinantal equation (which is equal to the inverse of the diffusion length) is considered as given by an infinite series in powers of the absorption parameter,whereΣais the macroscopic absorption cross section andΣis the total macroscopic cross section. It is shown thatαmdepends only on the firstmLegendre moments of the scattering probability.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19558

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe age of fission neutrons to indium resonance energy (1.46 eV) was measured in mixtures of zirconium and water. Three different volume ratios of metal to water were investigated. The experimental technique of a finite plane fission source with essentially infinite plane detectors was used (which was equivalent to using an infinite plane source with axial detectors). Thus, the theoretical corrections to the measured results were only 1.5% or less. This is the same technique used previously at this laboratory to measure the age in pure water, and comparisons were made with those data. The results indicate a linear variation of the age as a function of metal-to-water ratio.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19559

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe Monte Carlo code TYCHE-III has been used to calculate with a high degree of convergence the second, fourth, and sixth spatial moments of the slowing-down density distribution at the indium resonance energy, for neutrons originating from a fission source at a point in infinitely extended water and zirconium-water moderators. The effects of both inelastic scattering and anisotropy of elastic scattering in oxygen and zirconium have been included. For water, the calculations were performed using several widely available sets of data on oxygen cross sections and angular distributions. The effects on the neutron age and higher spatial moments of several fission spectra are also reported. These calculations have been compared with the moments of experimentally measured distributions of neutron flux at the indium resonance energy, after applying a suitable correction to the computed slowing-down moments. The agreement between the calculated and measured values of the neutron ages and higher moments is seen to be satisfactory.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19560

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA method of calculating first-flight collision probabilities in cluster geometry is developed. The method is analytic and approximate and is comparable in speed to codes now available for annular geometry.The proposed scheme is based on a consideration of the properties of the nonescape probability from a nonuniform body in the limits of high and low macroscopic cross sections, together with an interpolation procedure that allows one to determine the probability itself with sufficient accuracy. When calculated for combinations of different rings of fuel pins in a cluster, the resulting set of nonescape probabilities enables one to proceed to a determination of the probability of going from one ring to another. The coolant and the fuel pins are treated separately.Results of the method are compared with exact calculations on two fuel-element types of current interest. In these cases the form factor, defined as the ratio of maximum to mean flux in the cluster, is in error by at most 2%. The hyperfine structure in each ring (i.e. the ratio of the mean flux in the coolant to the mean flux in the fuel) is calculated with comparable accuracy.A one-group calculation on a 37-rod fuel element takes approximately 5 sec on an IBM-7090, so that the method is certainly usable for multigroup applications.

ISSN:0029-5639    

DOI:10.13182/NSE23-03-272

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe application of the variational method in velocity-dependent transport theory is described for the case of a pulsed infinite slab. The extrapolated end point and the buckling as functions of the slab thickness are calculated from a given transcendental equation. The expression for the angular and energy distribution of leakage neutrons has been improved by one iteration of the integral transport equation. The results are discussed for three different scattering models: monatomic gas, Nelkin-Goldman water and the Haywood-Thorson model.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19562

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractEnergy loss by fission fragments in nitrogen gas was studied by means of a pulse technique that measured luminescence excited by a low-intensity Cf252spontaneous fission source. A novel kinetic analysis of competing emission and quenching reactions was developed that gives the power law dependency of energy loss by the fragments in a luminescing gas from the pressure at which maximum luminosity is observed. For nitrogen, the relationshipE = E0(1−f)1.70±0.07is valid for 0.4E0

ISSN:0029-5639    

DOI:10.13182/NSE65-A19563

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor