摘要:

AbstractMany detailed multigroup transport calculations require group-to-group Legendre transfer coefficients to represent scattering processes in various nuclides. These (fine group) constants must first be generated from the basic data. This paper outlines an alternative technique for generating such data, given the total scattering cross section of a particular nuclide on a point-wise energy basis,σ(E’), and some information regarding the angular scattering distribution for each initial energy point.The evaluation of generalized multigroup transfer matrices for transport calculations requires a double integration extending over the primary and secondary energy groups where, for a given initial energy, the integration over the secondary energy group may be replaced by an integral over the possible scattering angles. In the present work, analytic expressions for these angular integrals are derived that are free of truncation error. Differences between the present method (as implemented in ROLAIDS) and other methods (as implemented in MINX and XLACS-2) will be explored. Of particular interest is the fact that, for hydrogen, the angular integration is shown to simplify to the point that, for many weight functions, the integration over the primary energy group might also be performed analytically. This completely analytic treatment for hydrogen has recently been implemented in NEWXLACS.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20115

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractA method of cross-section adjustment and evaluation is presented. Based on a finite element representation, the method is especially appropriate for cross sections that are well represented by continuous functions. It is also suitable for many problems outside the area of cross-section evaluation where one desires to fit curves that have complicated shapes not easily described by low-order polynomials. The algorithm is based on least-squares techniques that use complete covariance information and prior values. Nuclear model calculations, microscopic and integral data, and the results of prior multigroup adjustments can be combined in a single consistent evaluation. Results are presented for an illustrative example and for the evaluation of the54Fe(n, p) dosimeter cross section.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20116

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractThe Fokker-Planck equation for the transport of energetic charged particles in hot plasmas and for one-dimensional plane geometries is solved by a new multigroup approach. The numerical scheme proposed here takes into account the strong anisotropy of the Coulomb scattering operator, as well as the possible large values of the removal cross section. Numerical results are given for two particular examples: the transport of protons in a boron hydride plasma and of 3.5-MeV alpha particles in a deuterium-tritium plasma. A good agreement is achieved with corresponding results from a less general“moment method”developed in previous works.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20117

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractPerturbation theory for the coupled set of nonlinear equations of hydrodynamics describing inertially confined pellet fusion systems is developed based on a physical model similar to that embodied in the laser fusion code MEDUSA. Toward this end, a set of hydrodynamic adjoint equations and importance functions are defined. The perturbation theory presented can be an efficient tool for estimating the effects of many different alterations in the data field and design variables on a system performance parameter. Applications of this perturbation theory to sensitivity and uncertainty analysis of pellet fusion systems are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20118

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractGeneralized trajectories that characterize the fuel inventories of fusion-fission symbionts are derived and analyzed. The resultant formulations are based on physically relevant processes and lead to mathematically tractable expressions. By analytical/numerical test and a specific comparison, it is concluded that this formulation leads to more exact fissile and fusile fuel characterizations than are possible with conventional procedures.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20119

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractA procedure for determining the expected number of failures of systems undergoing phased missions is described. Approximations to this procedure are also presented. The emergency core cooling system of a boiling water reactor is analyzed to demonstrate this methodology. The results of this analysis show that these procedures have practical application and the approximations provide a close estimate to the exact expected number of failures.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20120

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractIn the frame of the transport theory, the importance of an extraneous neutron source is calculated by using several methods. One of them, which was developed in a previous paper, requires only standard calculations, while the adjoint fluxes must be supplemented in the conventional approach. The spherical plutonium-metal assembly JEZEBEL is chosen as a benchmark problem for numerical comparisons. All calculations are performed with the ANISN code by using several options and various degrees of approximation.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20121

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractA simple revision of a computational process is proposed for a point-detector problem in Monte Carlo transport calculation using the score point selection technique. The effectiveness of the modification is demonstrated by a test calculation. By this revision, the computation time required has been considerably reduced, without a significant increase of the statistical error.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20122

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractThe adjustment of differential data can improve the agreement between calculation and experiment of integral quantities, but the adjustment process also introducesa posterioricorrelations among the data that were not part of thea prioriassumptions. In a forward calculation of integral parameters using adjusted differential data, thea posterioricorrelations in general reduce the estimated uncertainty since the linear independence among differential data is reduced but the correlations inhibit the use of integral data to improve individual pieces of differential data. The adjusted data are validated for the calculation of integral parameters similar to those used in the adjustment. The physical interpretation of data adjustments is illustrated using a simple model to analyze bare homogeneous critical assemblies.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20123

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractEmploying a 95-cm3Ge(Li) detector, positioned 20 m from the Oak Ridge Electron Linear Accelerator white neutron source, the cross section for 478-keV gamma-ray production from 0.48- to 5.0-MeV incident neutrons on7Li was determined. The incident neutron flux was measured with a solid-state, recoil-proton detector and polyethylene radiator. These results, which are an unambiguous measurement of neutron inelastic scattering to the 478-keV7Li state, are listed and compared with recent measurements from other workers and the ENDF/B-V evaluation.

ISSN:0029-5639    

DOI:10.13182/NSE80-A20124

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor