摘要:

AbstractThe analysis of the three-dimensional continuous refueling is approximated by the variational method. The axial flux distribution is treated by the trial function and expressed by the analytic expression, using the elliptic function. Introducing the perturbation technique in the flux expansion, the higher order cross-section expansion correction of the axial flux distribution is achieved by using the elliptic function as the base function in the flux expansion. It is shown that the group constants, averaged by the flux and its square, can be expressed by the simple rational function. As a special example, the nature of the eigenvalue under continuous unidirectional refueling is shown, and it is pointed out that some caution is required if the fuel burnup is evaluated by the reactivity-area method.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21110

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractA new analytical method is presented for computing the thermal utilization of a noncylindrical unit cell containing a cylindrical fuel rod. No cylindrization of the cell is required. The boundary condition at the outer edge of the cell is formulated in terms of a procedure that minimizes the square of the neutron current at a number of unspecified points along the edge. This leads to rapid convergence in computations of the thermal utilization, even with tightly packed lattices for which previous methods may not converge. The method is used to derive specific formulas for the thermal utilization using diffusion theory; the method of Amouyal, Benoist, and Horowitz; and, finally, thePNmethod with anisotropic scattering. Sample computations using these models are also presented.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21111

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractA series of static critical experiments has been performed on an accurate mockup of the SORA Reactor. SORA is a proposed NaK cooled, repetitively pulsed fast reactor which would be used as a high-intensity neutron source for time-of-flight experiments. The reactivity of this reactor is varied by a movable reflector. Those parameters which are related to the kinetics of the reactor have been investigated thoroughly in the critical experiments. They have been measured for both beryllium and iron reflectors of several sizes and for various core and fixed reflector configurations.The total reactivity of the movable reflectors varied from $3.7 for a 11.0-cm-wide iron reflector to $12 for a 26.2-cm-wide beryllium reflector. The reactivity of the movable reflector as a function of its position has been shown to have a parabolic dependence on position characterized by the parameterαx, which varied from 4 to 9.9¢/cm2. The prompt-neutron time decay is described by a fast decay constant which varied between 0.30 and 0.55/µsec and a slow decay constant which varied between 0.05 and 0.10/µsec. The critical mass for the various experiments was between 50.3 and 57.3 kg of uranium enriched to 93.2 wt%235U. Using space-independent neutron kinetics with one delayed-neutron group, it has been shown that with a 24-cm-high×7-cm-thick×21-cm-wide beryllium reflector the assembly will produce 100 pulses/sec∼50-µsec wide at half-maximum power with a peak-to-average power ratio of∼180.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21112

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractPulsed reactors are being investigated for the purpose of producing high-intensity pulsed-neutron beams for research. Leakage-emission-time-distribution measurements as a function of neutron energy have been carried out using the Resselaer Polytechnic Institute (RPI) electron linear accelerator in conjunction with a disk chopper and neutron diffraction spectrometer. Data were obtained simultaneously with the chopper and crystal spectrometer by looking at opposite sides of the moderator. This experiment was designed to investigate the importance of different variables in determining the pulse characteristics of moderators. The eventual objective is to optimize the maximum thermal-neutron intensity and minimum pulse width from pulsed-fission-neutron sources. Neutron time and energy distributions were measured for light water, polyethylene, Lucite (a metacrylate plastic), powdered zirconium hydride, and ammonia. The water, polyethylene, and zirconium-hydride samples were measured at room temperature and all the materials except water were also measured at liquid-nitrogen temperature. The effects on pulse characteristics of homogeneously poisoning light water samples were studied, as well as the effects of heterogeneously poisoning polyethylene. The effect of varying the thickness of the moderator was also investigated. Pulse widths at half-maximum of 11µsec at 0.05096 eV and 24µsec at 0.01274 eV were observed for solid ammonia and heterogeneously poisoned polyethylene samples. For neutron energies between 0.08 and 0.01274 eV, solid ammonia gave the best observed figure of merit, peak intensity/(FWHM)2. The data show that neutron pulse characteristics from a moderator can be altered significantly by varying the material and its temperature, as well as by adding poison and optimizing the geometry. Time distributions were observed in the energy region of 0.012 to 0.63 eV. The time resolution, in this energy region, for the diffraction spectrometer ranged from 2.8 to 10.8µsec compared with 7.6µsec for the chopper.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21113

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractThe diffusion parameters of light water have been measured by the pulsed-source method. The neutron bursts were produced from a Texas Neutron Generator by pulsing the ion source and using the3H (d, n)4He reaction. Neutrons were injected into spherical volumes of H2O and the decay constants of the neutrons were determined by means of an enriched BF3miniature proportional counter. Neutron lifetime measurements were performed on small and large water samples with values of the geometric buckling from 0.035 to 0.655 cm−2. A harmonic analysis was conducted for the large geometries, while the waiting time method was used for the smaller ones. In the harmonic analysis, it appeared that a detector in a sphere is more sensitive to neutron fluctuation with time than it would be in a rectangular or cylindrical system. The diffusion parameters,D0andC, were determined by fitting the decay constants to the equationsand, whereandare the geometric and the corresponding transport buckling, respectively. The second fit gave a lower standard deviation of C than did the first fit.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21114

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractA scattering kernel for liquid diphenyl has been determined from a model for the diphenyl molecule in which the carbon and hydrogen atoms make harmonic oscillations about their equilibrium position. The hindered translations and rotations of the molecule as a whole, which are characteristic of the liquid state, were considred as free translations of the molecule to which an effective mass was associated.A set of interatomic force constants which describes the vibrational motions of the molecule was found and then used for a complete normal-mode calculation. These force constants were calculated, using a modified least-squares technique which gives the best fit for the vibrational frequencies of the molecule measured by optical techniques.The amplitude vectors calculated from the computed set of force constants were used, together with the measured vibrational frequencies, to construct the weighted frequency spectrum used in the slow-neutron calculations.The scattering law was computed, in the harmonic approximation, by means of the code GASKET. The code FLANGE was used to interpolate the scattering law and to produce the scattering kernel. The total scattering cross section, the single differential cross section, and other neutron parameters were calculated and compared with experimental data with gratifying results.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21115

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractThe thermal-neutron capture cross sections for the reactions128Te (n,γ)129gTe and128Te (n,γ)129mTe have been measured by a neutron activation method, using gold as a standard. Samples of powdered tellurium enriched to 96.5% in128Te were measured by gamma spectrometry. The found values are 199.7±8 and 16.1±0.7 mb, respectively. The resonance integrals have been calculated by irradiating tellurium and gold, or cobalt, with and without cadmium covers; their values are 1.48±0.13 b and 77.4±5.2 mb, respectively.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21116

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractTime-of-flight measurements of the neutron angular flux spectrum in graphite have been made to provide a standard of comparison for neutron penetration calculations. The spectrum from 0.002 eV to 15 MeV was measured with an accuracy of±13 to 32% and a resolution of±2 to 10%, at angles from 0 to 60°and penetrations to 66 cm. Comparisons with Monte Carlo and discrete ordinates calculations using ENDF/B cross sections indicate fairly good agreement except in resonances and near zero degrees for discrete ordinates. Scalar fluxes have also been calculated with the moments method.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21117

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractThe neutron decay spectrometer depends on the spectral analysis of the proton-electron pairs that originate from neutron decay. A spectrometer has been constructed which, compared to the prototype instrument, provides for increased collection efficiency, improved energy analysis, and reduced background. The resolving power,ΔE/E, was measured over the neutron energy range 13

ISSN:0029-5639    

DOI:10.13182/NSE69-A21118

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

AbstractExperiments have been carried out to determine the difference between gammaray absorption in an inhomogeneous layer of material, composed of spherical heavy metal particles (tungsten) in a nonabsorbing matrix, and absorption in a uniform heavy metal sheet of the same average thickness. The results can be used to evaluate a function describing the distribution of absorber thickness at different points on the layer. The gamma rays used ranged in energy from 35 to 122 keV.

ISSN:0029-5639    

DOI:10.13182/NSE69-A21119

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor