摘要:

A two-dimensional steady-state energy equation, in terms of the fluid enthalpy rise, for a nuclear reactor channel is formulated and solved. To facilitate its usefulness to the reactor designer, the solution is presented in the form of a hot-channel factor. Parametric results are presented so the information may be related to other channel dimensions. Mixing was found to be a function of the nondimensional geometry factor and the Peclet number.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18817

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

During a series of in-pile experiments designed to study irradiation effects on high-performance oxide fuel elements for advanced gas-cooled reactors, heat-transfer data were obtained from four specially instrumented fuel rods. An annular geometry was utilized with rods of 1.9- and 2.18-cm diam being contained in channels of 2.44- and 2.67-cm diam, respectively. The effects of wire-wrapped and machined square-thread surface roughness were measured and compared with the results obtained from a smooth rod. The fuel rods contained UO2pellets of varying enrichment and were clad with type-304 stainless-steel tubing. The test parameters for the data reported are: 1) coolant flow rate from 45 to 150 kg/h of helium at 20 atm which corresponds to Reynolds numbers from 15 000 to 45 000; 2) cladding temperatures to 840°C; and 3) heat fluxes from 30 to 100 W/cm2. The smooth-rod data can be correlated with a standard deviation of±10% by the expressionRoughening the rods increased the heat transfer by approximately a factor of 2 with no significant difference between the wire-wrapped and machined roughnesses. The results are generally found to be in good agreement with the results of previous heat-transfer studies. Some consequences of using heat-transfer promoters in nuclear reactor fuel elements are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18818

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

The influence of axial conduction on thermal entry-region temperature distribution and heat transfer in Hartmann's flow through a magnetohydrodynamic channel is analytically investigated. Viscous dissipation and Joule heating are also considered in the analysis. The temperature solutions, which are found to be Peclet number dependent, reduce to those corresponding to negligible axial conduction as the Peclet number approaches infinity. The appropriate first 12 eigenvalues and the corresponding eigenfunctions have been determined for Hartmann numbers of 1, 4, and 10 and for a wide range of Peclet numbers. The series expansion coefficients, applicable to an arbitrary value of the heat-generation parameter, have been evaluated for a few electric-field magnitude factors of practical importance.By employing the computed constants, the effect of the electric-field magnitude factor and the heat-generation parameter as well as axial conduction on the local temperature profiles and Nusselt numbers are examined and reported.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18819

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

A manganese sulphate bath technique has been used to make an accurate measurement of the9Be (n, 2n) cross section averaged over a pure252Cf spontaneous fission-neutron spectrum. Monte Carlo calculations were performed to correct precisely for spectrum distortion due to elastic scattering in the beryllium. Corrections were also made for all other competing reactions of importance. The result obtained, 144±6 mb, is in good agreement with the value of 150 mb calculated from an excitation curve based on the latest available differential data.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18820

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

The fission cross sections of232Th,233U,234U,235U,236U,237Np,238U,239Pu,240Pu,241Pu, and242Pu from 1 keV to 10 MeV published up to July, 1965, were analyzed previously to select best fission cross sections for fast-reactor analysis. Since the completion of that work, new data have been produced which necessitate reevaluation of the fission cross sections particularly in the region 1 to 5 MeV. The revised data presented here are believed to be of greater consistency and, hence, accuracy than the previous selection.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18821

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

Half-lives of 36 radionuclides have been newly determined, or old data have been reevaluated. In general, the activity of a purified sample was followed for two or more half-lives. The data were analyzed by least squares, using a modern computer program.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18822

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

The kinetic equations for a heavy-water-moderated reactor have terms describing the production of neutrons in the photodisintegration of deuterons. A technique has been developed for the measurement of these short-lived delayed-photoneutron groups. A235U target was placed in the center of a sphere of D2O and a chopped neutron beam from the VPI reactor was allowed to impinge on the target. The time for a revolution of the chopper varied from 86.4 to 0.463 sec in six steps and there are two pulses per revolution. The ratio of“beam-on”target time to“beam-off”target time is 1 to 16.5. During the beam-off time interval, the production rate of delayed neutron and delayed photoneutrons as a function of time was stored in a time base multichannel analyzer. The half-lives of two new delayed-photoneutron groups were determined to be 7.39×10−2and 4.02×10−3sec with relative abundances of 0.0292 and 0.170, respectively. The relative abundances represent the fractions of the delayed-neutron and delayed-photoneutron groups.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18823

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

AbstractThe straightahead approximation, i.e., the approximation that the secondary particles from nucleon-nucleus collisions are emitted in the direction of the incident nucleon, is often used in space-vehicle shielding studies. The validity of this approximation has been tested by comparing calculations made with the angular distribution of secondary particles properly taken into account with calculations using the approximation. Comparisons between the calculations are given for both monoenergetic protons and a typical flare spectrum normally incident on slab shields followed by tissue. The results indicate that the approximation is sufficiently accurate to justify its use in obtaining estimates of the secondary-particle contribution to the dose behind thin shields.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18824

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

A model suitable for the prediction of gamma-ray spectra subsequent to the capture of neutrons into nuclear states of identifiable spin and parity has been developed. The dependence of radiative transition probabilities on the nuclear selection rules is explicitly accounted for. Means are provided for allowing dipole and quadrupole transitions in conjunction with variations in the magnitudes of corresponding transition“matrix elements.”Comparisons are given between experimental capture spectra and corresponding spectra calculated with varying assumptions with respect to pertinent nuclear parameters for two capture states of28Al and one of25Mg. A comparison of calculated spectra using fitted and crudely approximated cascade parameters for the28Al capture states indicates few, if any, differences that would significantly change resultant neutron-capture gamma-ray-production cross sections.

ISSN:0029-5639    

DOI:10.13182/NSE68-A18825

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor

摘要:

The first section of this paper is a mathematical construction of a certain Monte Carlo procedure for sampling from the distributionThe construction begins by defining a particular random variableλ. The distribution function ofλis developed and found to be identical toF(X). The definition ofλdescribes the sampling procedure. Depending on the behavior ofΣ(x), it may be more efficient to sample fromF(X) by obtaining realizations ofλthan by the more conventional procedure described in the paper. Section II is a discussion of applications of the technique to problems in radiation transport whereF(X) is frequently encountered as the distribution function for nuclear collisions. The first application is in charged particle transport whereΣ(x) is essentially a continuous function ofx. An application in complex geometries whereΣ(x) is a step function, and changes values numerous times over a mean path, is also cited. Finally, it is pointed out that the technique has been used to improve the efficiency of estimating certain quantities, such as the number of absorptions in a material.

ISSN:0029-5639    

DOI:10.13182/NSE68-1

出版商:Taylor&Francis    

年代:1968

数据来源: Taylor