Showing papers in "Nuclear Science and Engineering in 1980"
1,242 citations
TL;DR: In this article, general sensitivity theory is presented for treating problems characterized by systems of nonlinear equations with nonlinear responses, and the concept of the Frechet derivative is shown to be fundamen...
Abstract: General sensitivity theory is presented for treating problems characterized by systems of nonlinear equations with nonlinear responses. The concept of the Frechet derivative is shown to be fundamen...
141 citations
TL;DR: A nodal method for the solution of the multidimensional neutron diffusion equation is developed and evaluated in this paper, which is based on the linear form of the nodal balance equation written in terms of terms of nodal coefficients.
Abstract: A nodal method for the solution of the multidimensional neutron diffusion equation is developed and evaluated. The method is based on the linear form of the nodal balance equation written in terms ...
96 citations
TL;DR: In this paper, the Berger empirical formula was used to fit the calculational results for nuclei of low atomic number at energies above 1 MeV and below 0.06 MeV.
Abstract: Buildup factors for photons in infinite homogeneous samples of air, water, and iron have been calculated by a moments method code. The photons were assumed to be emitted from a point source. Comparisons of these results to values obtained earlier, both by experiment and by calculation, show reasonable agreement except in some instances of deep penetration. The parameters in the Berger empirical formula for buildup factors have been evaluated from the present work. The Berger formula is shown to fit the calculational results for nuclei of low atomic number at energies above 1 MeV and below 0.06 MeV. In mid-energy range, differences of as much as 40% are observed. The formula appears to provide excellent fit to the data for nuclei of medium atomic number.
81 citations
TL;DR: In this article, the laminar, transition and turbulent parallel flow pressure drop across wire-wrapped hexagonal rod bundles positioned inside a duct were determined in tests using water, sodium, and air.
Abstract: Laminar, transition, and turbulent parallel flow pressure drop across wire-wrapped hexagonal rod bundles positioned inside a duct were determined in tests using water, sodium, and air A smooth transition region from turbulent to laminar flow that occurred over the Reynolds number range from 5000 to 400 characterized the resulting friction factor behavior The continuous transition region could be explained in terms of the fraction of the flow area in turbulent flowLaminar friction factors calculated from individual subchannel measurements could be correlated by the same expression found for rod-bundle-averaged conditions In the laminar range, the friction factor was correlated by the expression f = 110/Re, in the turbulent range by f = 055/Re025, and in the transition range bywhere is the intermittency factor A general laminar flow friction factor correlation was developed:This correlation agrees satisfactorily with limited laminar flow data from rod bundles having different wire-wrap lead p
74 citations
TL;DR: In this paper, the authors derived the order of convergence for six numerical methods that have been proposed for the slab geometry, multigroup, discrete-ordinates neutron transport equations, and illustrated the results by means of a simple test problem.
Abstract: The order of convergence, as the spatial cell widths tend to zero, is derived for six numerical methods that have been proposed for the slab geometry, multigroup, discrete-ordinates neutron transport equations. Our results, which in two cases differ from earlier experimental results, are illustrated by means of a simple test problem.
73 citations
TL;DR: Fission product decay energy-release rates have been measured for thermal-neutron fission of 235U using scintillation spectrometers for beta and gamma rays separately as discussed by the authors.
Abstract: Fission-product decay energy-release rates have been measured for thermal-neutron fission of 235U. Spectral data were obtained using scintillation spectrometers for beta and gamma rays separately, ...
56 citations
49 citations
TL;DR: In this paper, the prompt neutron multiplicities for photofission of the four isotopes 235U, 236U, 238U, and 232Th have been measured with monoenergetic photons over the energy range from 5.5 to 18 MeV using the...
Abstract: The prompt neutron multiplicities for photofission of the four isotopes 235U, 236U, 238U, and 232Th have been measured with monoenergetic photons over the energy range from 5.5 to 18 MeV using the ...
49 citations
38 citations
Abstract: The fuel spheres in the core of a pebble-bed reactor are mainly distributed statistically. Regular configurations appear only near the walls and on the bottom of the core. A statistical distribution has been studied by means of a proper mock up. For this purpose the coordinates of 3024 sphere centers were defined by measurements so that Monte Carlo games for neutron diffusion could be established. From these results as well as from Monte Carlo calculations for the cubic and tetrahedral sphere configurations, the diffusion constants and the first two mean moments h/sup -/ and h/sup 2 -/ of the passage lengths in the holes were determined. Under the assumption that no correlation exists between the passage lengths in the holes and in the balls, an exact formula for the diffusion lengths was derived using h/sup 2 -//(h)/sup 2 -/.
TL;DR: The 235U(n, 2n) cross section has been measured in the energy range between threshold to 13 MeV using the large gadolinium-loaded liquid scintillator method as mentioned in this paper.
Abstract: The 235U(n, 2n) cross section has been measured in the energy range between threshold to 13 MeV using the large gadolinium-loaded liquid scintillator method. The statistical accuracy of the measurement is on the order of 10%.
TL;DR: In this article, a methodology for the assessment of the uncertainties about the reliability of nuclear reactor systems described by Markov models is developed, and the uncertainties regarding the probability of loss of coolable core geometry (LCG) of the Clinch River Breeder Reactor (CRBR) due to shutdown system failures, are assessed.
Abstract: A methodology for the assessment of the uncertainties about the reliability of nuclear reactor systems described by Markov models is developed, and the uncertainties about the probability of loss of coolable core geometry (LCG) of the Clinch River Breeder Reactor (CRBR) due to shutdown system failures, are assessed. Uncertainties are expressed by assuming the failure rates, the repair rates and all other input variables of reliability analysis as random variables, distributed according to known probability density functions (pdf). The pdf of the reliability is then calculated by the moment matching technique. Two methods have been employed for the determination of the moments of the reliability: the Monte Carlo simulation; and the Taylor-series expansion. These methods are adopted to Markovian problems and compared for accuracy and efficiency.
TL;DR: In this paper, an algorithm is described to detect and locate failed subunits in a nuclear power plant or any other complex network of flow-connected subunits. But the algorithm is not suitable for the detection and location of failed sub-units.
Abstract: Reliable and safe operation of a nuclear power plant or any other complex network of flow-connected subunits requires prompt detection and location of failed subunits. An algorithm is described, wh...
TL;DR: Using an extensive data base of sensitivities and evaluated covariances, this paper incorporated 11 fast-reactor benchmark experiments and 2 neutron-field benchmark experiments into the adjustment of the adjustment algorithm.
Abstract: Using an extensive data base of sensitivities and evaluated covariances, this work incorporates 11 fast-reactor benchmark experiments and 2 neutron-field benchmark experiments into the adjustment o...
TL;DR: In this article, a systematic comparison of the local difference operator approximation in spatial difference schemes for the solution of the transport equation in slab geometry by the method of discrete ordinates is made.
Abstract: A systematic comparison has been made of the local difference operator approximation in spatial difference schemes for the solution of the transport equation in slab geometry by the method of discrete ordinates. The truncation error in different schemes varies according to the nature of the intra-mesh source and flux interpolation, and this explains the good performance of certain recently proposed schemes. The authors have classified the schemes according to the nature of the intra-mesh source interpolation. As a general principle, they find that in each class, the scheme that conserves the spatial moments of source calculated from the previous iteration and avoids flux interpolation is the most accurate.
TL;DR: In this article, a general problem of time-dependent neutron transport in a spatially heterogeneous medium is analyzed by two perturbation methods that have previously been applied to specialized problems.
Abstract: A general problem of time-dependent neutron transport in a spatially heterogeneous medium is analyzed by two perturbation methods that have previously been applied to specialized problems. These ''bucking'' and ''asymptotic'' methods are shown to be equivalent in the sense that the asymptotic method leads to a time-dependent diffusion equation with constant coefficients, whereas the buckling method leads to the corresponding dispersion law. Two applications, the calculation of k /SUB eff/ , and the derivation of a point reactor model are given. Also, the general results obtained here are shown, in several special cases, to reduce to the simpler results obtained previously.
TL;DR: In this article, a method is proposed to derive three kinetic parameters of a zero-power coupled-core system, namely coupling reactivity Δ, mean neutron transit time, and neutron generation time Λ of respective co...
Abstract: A method is proposed to derive three kinetic parameters of a zero-power coupled-core system, namely coupling reactivity Δ, mean neutron transit time , and neutron generation time Λ of respective co...
TL;DR: A generalization of the classical quasi-static method is described in this paper, where amplitude and shape functions are treated on the same footing by applying an iterative Newton method to the integral form of the multigroup diffusion equations.
Abstract: A generalization of the classical quasi-static method is described. ''Amplitude'' and ''shape'' functions are treated on the same footing by applying an iterative Newton method to the integral form of the multigroup diffusion equations. Provision is made for one amplitude function per neutron group. It is shown, further, how this model encompasses Ott and Meneley's improved quasi-static algorithm.
TL;DR: In this article, the results of calculations for a channel in a fast reactor supercell model using different formulas are compared and the limitations of this method, which involves changing only the channel diffusion coefficient, are discussed.
Abstract: Diffusion theory overestimates neutron transport in voided or low-density regions of a reactor when the diffusion coefficient is defined as 1/3..sigma../SUB tr/. Alternative definitions of the diffusion coefficient for such regions have been proposed. The present paper summarizes some definitions of axial diffusion coefficient for cylindrical channels and proposes a modification to an earlier formula. The results of calculations for a channel in a fast reactor supercell model using different formulas are compared and the limitations of this method, which involves changing only the channel diffusion coefficient, are discussed.
TL;DR: In this article, the behavior of contained aerosols following a hypothetical accident of a liquid-metal fast breeder reactor is analyzed, and the effects of turbulent coagulation, thermophoretic deposition, and reduced reduced...
Abstract: The behavior of contained aerosols following a hypothetical accident of a liquid-metal fast breeder reactor is analyzed. The effects of turbulent coagulation, thermophoretic deposition, and reduced...
TL;DR: In this paper, the elastic and inelastic scattering angular distributions of elemental iron were measured from 1.5 to 4.0 MeV with incident neutron resolutions of less than or equal to 50 keV and at incident neutron energy intervals of more than and equal to 1.152 MeV.
Abstract: Neutron elastic and inelastic scattering cross sections of elemental iron were measured from 1.5 to 4.0 MeV with incident neutron resolutions of less than or equal to50 keV and at incident neutron energy intervals of less than or equal to50 keV. Cross sections for the excitation of observed levels at 0.853, 1.389, 2.097, 2.579, 2.677, 2.974, and 3.152 MeV are determined. The observed elastic and inelastic scattering angular distributions fluctuate strongly with incident energy. The experimental results are averaged over broad energy intervals and are compared with the predictions of spherical optical statistical and coupled-channel models, including consideration of direct inelastic excitations. The importance of a comprehensive data base in such energy-averaged interpretations and in the evaluation of data for technological use is stressed.
TL;DR: In this article, the absolute cumulative yields for 49 fission products representing 36 mass chains created during thermal-neutron fission of /sup 239/Pu, including 3 mass chains for which no prior data exist, were determined using Ge(Li) spectroscopy.
Abstract: Absolute cumulative yields have been determined for 49 fission products representing 36 mass chains created during thermal-neutron fission of /sup 239/Pu, including 3 mass chains for which no prior data exist. Using Ge(Li) spectroscopy, spectra were obtained of gamma rays from decay of fission products between 1550 s and 31 days after a 100-s irradiation. Data were obtained for all fission products simultaneously. Gamma rays were assigned to the responsible fission products by matching gamma-ray energies and half-lives. Gamma-ray data associated with decay of /sup 135/I and /sup 140/Ba-/sup 140/La, in particular, were thoroughly studied; uncertainties were obtained for the two largest intensity gamma rays from decay of /sup 135/I that are smaller than previously evaluated uncertainties. Fission product yields were obtained from the data by first determining the appropriate gamma-ray activity as of the end of the irradiation, then correcting for detector efficiency and gamma-ray branching ratio, and, finally, dividing by the number of fissions created in the sample. The number of fissions was determined by direct comparison of gamma rays emanating from fission products created during a careful irradiation of a wellcalibrated /sup 239/Pu-loaded fission chamber. The resulting fission product yields are compared with previous measurements and withmore » recommended yields given in two recent (and independent) evaluations.« less
TL;DR: In this article, it was shown that the phase change takes place by evaporation from a liquid film surface, without vapor bubble generation at the wall, and that even in the presence of artificial cavities, the incipient superheat is statistical in nature.
Abstract: Data on the heat transfer and the pressure drop in sodium under forced convection boiling are presented. It is shown that in annular-dispersed flow, a difference between wall and saturation temperatures is small, being within 1 to 5°C. It is also shown that in two-phase alkali-metal flow with heat input friction losses are smaller than in adiabatic flow. This is associated with a “push aside” effect on the main stream of the vapor flowing from the interface. The heat transfer and friction loss data indicate that the phase change takes place by evaporation from a liquid film surface, without vapor bubble generation at the wall. The experiments showed that, even in the presence of artificial cavities, the incipient super-heat is statistical in nature. The efficiency of the double-reentrant-angle-type cavities and of inert gas injection as a means of stabilizing forced convection boiling of the alkali metal was proven.
TL;DR: In this paper, a one-dimensional gamma-ray transport code BIGGI 4T has been used to calculate attenuation in single layer and multiple layers of lead and water slabs from a plane monodirectional source.
Abstract: A one-dimensional gamma-ray transport code BIGGI 4T has been used to calculate gamma-ray attenuation in single layer and multiple layers of lead and water slabs from a plane monodirectional source....
TL;DR: In this article, an iterative procedure for determining window widths has also been added to the FERDOR method, which optimizes the energy resolution of unfolded spectra, and a plutonium-beryllium neutron spectrum is unfolded as an example of the improvement obtained.
Abstract: Smoothing is an important part of spectrum unfolding by the FERDOR method. This unfolding method is discussed, and changes to the smoothing procedure are presented. An iterative procedure for determining window widths has also been added to the method. This iterative procedure optimizes the energy resolution of unfolded spectra. A plutonium-beryllium neutron spectrum is unfolded as an example of the improvement obtained in unfolded spectra. Response matrices available for use with the FERDOR method are discussed.