摘要:

AbstractThe ability of one-dimensional momentum balances to predict behavior during two-phase oscillatory flow has been examined. Flow oscillations in a Freon-Freon vapor system were induced by cycling a three-way valve so as to divert a varying portion of the total flow from the test section.The data taken included the phase shift between the pressure and flow curves and the head fluctuation to flow fluctuation ratio. These data were compared with theoretical predictions obtained via the impedance method. Although some discrepancies between predictions and measurements were observed, the discrepancies were generally within the range of error associated with the measurement and analysis techniques used.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26916

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe extent of penetration of flowing molten ceramic fuel in steel channels before solidification is a problem that arises in the analysis of hypothetical core disruptive accidents. Considerations of fuel crust behavior indicate that fuel freezing in steel channels can occur in two distinct ways that can be identified as conduction-limited freezing (fuel crust growth) and bulk freezing (fuel crust removal). Fuel crust removal can arise from two sources: (a) mechanical breakup and (b) melting heat transfer. Explicit formulas providing rough estimates of critical fuel crust removal conditions are presented. If the conditions in the fuel flow are such to prevent fuel crust growth then the steel wall melting can become severe. It is proposed here that steel ablation rapidly leads to fuel freezing in a bulk manner via turbulent mixing between the relatively“cold”molten steel and hot molten fuel. This steel ablation-induced freezing concept is used to obtain a simple expression for molten fuel penetration into steel channels.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26917

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractIt is well known that a strong need exists for design criteria to limit liquid cross-flow-induced vibration in heat exchanger tube bundles. This need has become even more critical with the advent of the nuclear power industry and the large heat exchange systems that it employs.An extensive series of experimental vibration tests has been conducted on tube bundles of contemporary interest in a large water tunnel. The main objective of these tests has been to develop a design criterion to limit vibration amplitudes. It has been found that the main excitation mechanisms are turbulence, some vortex shedding, and hydroelastic instability. The results of these tests are correlated and presented in an orderly fashion.It is found that the most serious excitation mechanism is hydroelastic instability. Criteria are advanced for establishing upper velocity limits based on the experimental findings. The vortex shedding mechanism is found to only be a problem for tubes in the inlet region of some bundles. Strouhal numbers associated with observed resonances are tabulated and discussed. Tube response to random turbulence has been studied for numerous bundles but is found to be of secondary significance.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26918

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractDifferential cross sections for the production of secondary neutrons and photons from aluminum have been measured at 127 deg (lab) for incident neutron energies in the range 1 to 20 MeV. An electron Linac was used as a neutron source with a white spectrum. Incident neutron energies were determined using time-of-flight techniques for a source-to-sample distance of 48 m. Secondary spectra were determined by unfolding the pulse-height distributions observed in an NE-213 scintillation counter. The results are compared to the current evaluated data file (ENDF/B-IV, MAT 1193).

ISSN:0029-5639    

DOI:10.13182/NSE76-A26919

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractTime-of-flight measurements of the neutron capture cross section of59Co were carried out in the energy region 2.5 to 1000 keV using the Oak Ridge Electron Linear Accelerator and a pair of nonhydrogenous liquid-scintillator gamma-ray detectors. Resonance energies and capture areas were determined for a large number of resolved resonances up to 85-keV neutron energy, and radiation widths for 35 known s-wave resonances were derived. Positive correlation coefficients (ρ≃0.3) between the radiative widths and neutron reduced widths of these s-wave resonances for both possible spin states were calculated. The significance of the correlations is discussed.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26920

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe241Am neutron absorption cross section, which is predominantly capture, has been measured from 0.01-eV to 370-keV neutron energy. The Oak Ridge Electron Linear Accelerator was used as the source of pulsed neutrons. Resonance parameters have been derived for the data up to 50 eV. The capture gamma-ray detector used was the“total energy detector,”which is a modification of the Moxon-Rae detector. This detector required that the events be weighted by their pulse height in the detector and that the net efficiency of the detector be low. The cross section was normalized at thermal-neutron energies (0.02 to 0.03 eV), and the shape of the neutron flux was measured relative to the10B(n,α) cross section up to 2 keV and relative to the6Li(n,α) cross section at higher neutron energies. The results of the measurement indicate a lower cross section (∼25%) between 0.3 and 100 eV than has been previously indicated and an appreciably higher cross section (by 100% at 100 keV) from 20 to 370 keV.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26921

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractLight charged particles (LCP) and fission elements formed in ternary fission of252Cf have been investigated. The energy spectra of light particles, alphas, and protons were studied using aΔE×(E +ΔE) particle-identifying telescope apparatus. A coincidence circuit was used in such a way that the K x rays from the ternary fission fragments were electronically gated by a designated LCP and then stored in a multichannel analyzer. The K x rays were analyzed using a high-resolution lithium-drifted silicon spectrometer, permitting accurate identification of the elements in the charge distribution of fission fragments. Experimental results indicate the influence of the odd-even effect and also of shape deformation of alpha-accompanied ternary fission.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26922

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe results from a series of criticality experiments with three different mixtures of oxides of plutonium and uranium are presented. The fuel mixtures consisted of235U-depleted uranium homogenized with∼8, 15, and 30 wt% plutonium and blended, homogeneously, with polystyrene to achieve H:(Pu + U) atomic ratios of∼7, 3, and 3, respectively. Critical sizes are given for rectangular parallelepipeds of each of the fuels fully reflected with a methacrylate plastic (Plexiglas). Critical sizes are also given for unreflected parallelepipeds of the 30-wt% plutonium-enriched fuel mixture. For the 30-wt% plutonium-enriched mixture, sufficient fuel was available to permit determining that the critical thickness of a fully reflected slab of this material, infinite in two dimensions, was 12.93 + 0.14 cm.Comparisons were made between the critical assemblies and calculational results using ENDF/B-III cross sections and the KENO and DTF-IV computer codes. Wherever comparisons could be made, the DTF-IV and KENO results were within 1% of each other; however, some of the comparisons between calculations and experiments differed by 2 to 3% in keff.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26923

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractTo estimate analytically the effects of discrete model and evaporation model inelastic scattering on the fast neutron spectrum, the original Greuling-Goertzel (GG) approximation was developed with the help of the generalized function theory.In place of the collision density functionψ(u), the two-term Taylor's expansion of a test function of a functionalψwas proposed to obtain analytic expressions of lethargy moments of inelastic scattering kernels. By using these moments, the author derived the standard GG approximation including all inelastic events.By introducing an approximate separable kernel of the evaporation model inelastic scattering, another conventional treatment of inelastic scatterings was proposed, i.e., the external source approximation of inelastic scattering. In this approximate method, elastic scattering was treated by the ordinary GG approximation.The present standard GG theory was useful for the preliminary description of fast neutron spectrum in a mixture in which a large amount of fuel elements is not included, while the external source approximation was shown to estimate reasonably the effects of inelastic scattering on fast neutron spectrum in any medium.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26924

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractAn elementary function for the collision density of neutrons slowing down from a plane source in hydrogen is synthesized through a set of schemes incorporating several known explicit features of the exact solution. First, the Marshak distribution is assigned a distorted lethargy variable that makes its zeroth and second spatial moments exact at all lethargies while automatically preserving its detailed accuracy at large lethargies. The same exact moments are also required of a specific functional form able to assume the correct spatial dependence at small lethargies. Then, a linear combination of these functions is constructed with coefficients making the two moments and the first spatial derivative at the source plane exact at all lethargies. The resulting distribution automatically becomes correct at both lethargy extremes. In addition, a remaining lethargy-dependent parameter makes the fourth spatial moment exact at all lethargies except within a finite interval of intermediate values, where its error must reach a maximum of 2.7%. Extraneous roots from multiple bifurcations of the parameter are identified by their unphysical implications. For computational simplicity, both this parameter and the incorporated function for the exact spatial derivative at the source plane are replaced by fitted elementary functions. The resulting expression for the collision density agrees very closely with McInerney's Monte Carlo calculations. Some extensions are described in a separate Note.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26925

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor