摘要:

AbstractAn experiment was performed to investigate the transfer of thermal energy by natural convection from molten sodium to a cold plate. A large tank of sodium was used to simulate a semi-infinite mass of sodium. A horizontal circular plate in intimate contact with the sodium surface was cooled by flowing tetralin which caused its temperature to be lower than the sodium bulk temperature. As a result, natural convection occurred in the sodium and thermal energy was transferred from the sodium to the plate. Data were collected at steady-state conditions for values of the Rayleigh number ranging from 4.8×106to 4×107. It was found that the experimental results could be correlated by the expressionwhere Nu is the Nusselt number, and Ra is the Rayleigh number. The calculated probable error in the Nusselt number given by the above equation is 1.08, and the multiple correlation coefficient for the experimental results and the equation is 0.954. The above result is shown to be consistent with the results of other investigators who used different fluids in physical systems somewhat similar to that used in this experiment with sodium.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25816

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractExperimentally determined reactor neutron activation cross sections found by use of the ORNL Graphite Reactor are listed. The general method of measurement is described.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25817

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractA series of fifteen experiments were carried out on an 8×30×32 in. core in the Pressurized Critical Assembly at KAPL. In twelve of these experiments, 0.030-in. boron stainless steel septa bisected the 8-in. dimension. These septa contained various weight per cent B10. In the remaining three experiments, there were no boron-stainless steel septa in the core. The eigenvalues and neutron density distributions were compared with values which were calculated using Deutsch cross sections and“Thin Region Theory.”The eigenvalues which were calculated were within one per cent of the experimental values, with a spread of approximately one per cent. For all the cores, the calculated eigenvalues were lower than the experimental values. Analyses of the neutron density distributions showed the calculated results in fairly good agreement with the experimental results. In all cases, this agreement was as good for the cores which contained the boron septa as for the ones which did not. It therefore appears that the boron has been well represented by“Thin Region Theory,”and that the main discrepancies between calculated and experimental values are due to the inadequacies of adapting the Deutsch scheme to these cores.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25818

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractLarge anomalies have been observed in the Bragg beam produced by Be (101), Be (103), Be (100), and Be (0002) monochromators on the MTR crystal spectrometer. Instead of a smooth spectrum characteristic of a Maxwellian distribution of neutron velocities, many large dips were found. These dips appear to be caused by extinction of the beam due to Bragg reflection by planes in the crystal other than those supplying the Bragg beam to the spectrometer. Calculations of the angles at which such competition can be expected have resulted in the identification of the planes responsible for the principal dips. To establish that these anomalies are due to crystal properties, spectra produced by the (200), (220), and (240) planes of NaCl were also examined. Although a few extinction dips were observed, these were far smaller in number and amplitude than those found in Be, due to the simpler crystal structure and lower reflectivity of NaCl. These effects require careful consideration in high-accuracy experiments with the crystal spectrometer, particularly in the measurement of reactor spectra.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25819

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractThe conventional calculation of power peaking near water gaps assumes an abrupt change in the neutron spectrum at a gap-core interface. The assumption can be seriously in error, and can result in discrepancies of 50% between calculated and experimental peaking values. In this paper, a position-dependent spectrum is obtained by the use of diffusion theory which, when used in peaking calculations, reduces the discrepancy between theory and experiment to the order of 5–10% or less. Recipes based on the position-dependent spectrum are obtained for the specification of position-dependent cross sections which may be used in standard diffusion theory codes. The use of these cross sections in the codes results in an estimate of power peaking factors which represents a considerable improvement over the results given by conventional calculations.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25820

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractMeasurements of Pu239and Pu241fission rates relative to U235have been made in 1.3% enriched uranium metal fueled lattices. Results were obtained in lattices having 0.387-in. diameter rods and water-to-uranium ratios of 2.35:1 or 1:1. The measurements are compared with a calculational model and the agreement is considered good.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25821

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractAn instrument has been developed which can nondestructively determine the U235and boron content of highly enriched, unirradiated fuel assemblies in five to fifteen minutes per element. Two nuclear measurement methods are used: counting of the natural radioactivity of U235and neutron attenuation measurements. For MTR and ETR fuel elements, the instrument appears to be accurate to 0.3% and 4.0% in terms of the respective U235and boron contents.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25822

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractMeasurements of the relative U235fission rates as a function of energy have been made for the TRX facility, a slightly enriched uranium, light water moderated critical assembly. The parameter directly measured is the ratio of the activity of a bare U235foil to that of a similar foil enclosed in a box of absorbing material, which was either cadmium, boron, or gadolinium. The energy dependence associated with these ratios was obtained by the introduction of“effective cutoff energies”for the absorbing shields. A comparison is made with calculated values, based upon a simplified model for the neutron energy spectrum present, and the agreement is considered adequate.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25823

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractThe steady-state space-energy distribution of thermal neutrons in homogeneous media is considered in the diffusion approximation. From the general form of the solution it is shown that the asymptotic (in space) distribution depends upon the source distribution and under different circumstances can be qualitatively different. The relation of the asymptotic flux to the usually found infinite medium spectrum is exhibited. For a heavy gas moderator the asymptotic flux from a source of limited extent is shown to be much softer than an infinite medium spectrum in the same material.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25824

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractA grind-leach method for the recovery of uranium from high-density graphite fuel elements containing greater than 5 weight per cent uranium has been developed on a laboratory scale as a head-end treatment for standard tributyl phosphate solvent extraction processes. With fuel ground to−16 mesh, greater than 99.8% of the uranium can be recovered by leaching twice with boiling 15.8Mnitric acid. Uranium recoveries were lower with less concentrated acid, and with fuel of larger particle size or lower uranium concentration. The grind-leach method is not applicable to fuels containing less than 3% uranium. Leaching−16+30 mesh samples of a fuel containing 1.5% uranium and 7.2% thorium with either boiling 15.8Mnitric acid or 15.8Mnitric acid−0.04Msodium fluoride, resulted in uranium and thorium recoveries of 90 and 86%, respectively.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25825

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor