摘要:

AbstractTransport of neutral particles in a toroidal plasma is treated in the same manner as that of neutrons by the Monte Carlo method. A new sampling technique of flight-path length is proposed for the torus geometry. Several routines relating to the toroidal geometry have been developed and incorporated into the neutron and gamma-ray transport Monte Carlo code“MORSE.”Results obtained from sample calculations to check the cylindrical approximation show that hot neutrals escape more easily from the torus than from the cylinder, while cold neutrals are retained better in the cylinder. Furthermore, the spectrum of the leakage neutrals is compared with the neutral and ion spectra inside the torus.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18692

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractThe variational formulation of the even-parity form of the within-group neutron transport equation is generalized to include complex trial functions. The introduction of transverse leakage effects through the buckling term exp(iB·r) leads, in general, to a coupled set of Euler equations for the real and imaginary even-parity flux components. The coupling between real and imaginary flux components is retained in both discrete-ordinates and finite element angular approximations. Employment of the spherical harmonics approximations in angle, however, leads to an uncoupled set of Euler equations if an appropriate choice of axes is made. Hence, a rigorous buckling treatment of third-dimensional leakage can be incorporated into two-dimensional transport computations without solving for the imaginary flux component.The foregoing spherical harmonic formulation is combined with finite element discretization in space in the multigroup criticality code FESH. One- and multigroup results are presented to demonstrate the elimination of ray effects and to examine the errors introduced by the DB2leakage correction used in conventional transport calculations.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18693

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractTime-optimal control of axial xenon oscillations in pressurized water reactors is investigated in the present study, properly accounting for operating constraints on the allowable axial offset (AO) band. The system equation describing the spatial xenon oscillations has been reformulated using a lambda mode expansion in a form that readily allows a physical interpretation of the state vector and the system equation. In particular, AO measurements can be used to define the entire system parameters completely. Previous optimal control studies have been limited to the case of controls to the origin in the xenon-iodine phase plane. Our present investigation indicates that time-optimal controls should, in general, involve bang-bang controls to a line segment in this phase plane, subject to a band constraint on allowable AO or available control strength. A suboptimal control strategy, which can be applied directly in actual operating conditions without the aid of on-line computers, is also proposed. Verification of the proposed time-optimal control strategies is performed through computer simulations of xenon-induced transients.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18694

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractThe prompt neutron multiplicities for photofission of the four isotopes235U,236U,238U, and232Th have been measured with monoenergetic photons over the energy range from 5.5 to 18 MeV using the annihilation in flight of fast positrons. The delayed neutron yield has been measured for all four isotopes at 10.9- and 16.8-MeV photon energies. The ratio of first- to second-chance fission has been measured as a function of energy up to 17-MeV excitation energy for236U and238U photofission.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18695

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractA simplified method based on the intermediate resonance approximation is proposed to deal with the double heterogeneity encountered in design calculations of high-temperature gas-cooled reactors. First, a fuel rod with grain structure is homogenized by introducing an equivalent homogeneous material, in the form of an intermediate resonance approximation, that contains a fictitious moderator substituted for both the grain heterogeneity and the scattering in moderator region. Second, the cluster configuration of the homogenized rods is treated by use of the fictitious moderator. This method is shown to offer a convenient and simple means with good accuracy and short computing time when combined with the“table look-up”method of resonance shielding factors.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18696

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractNeutron capture by the heavier stable ruthenium isotopes and by natural rhodium has been measured at the Oak Ridge Electron Linear Accelerator time-of-flight facility up to 500 to 700 keV. Most of these isotopes are important as fission products. Strength functions S0, S1, S2, and Sγwere fitted to the average cross sections derived for the pure isotopes up to 113 keV. Resonance parameters were fitted for∼100 cross-section peaks for each isotope.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18697

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractNeutron elastic and inelastic scattering cross sections of elemental iron were measured from 1.5 to 4.0 MeV with incident neutron resolutions of≲50 keV and at incident neutron energy intervals of≲50 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.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18698

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractPressure suppression pools used in nuclear reactors are subject to hydrodynamic processes involving complicated free surface configurations. A new numerical method, SOLA-VOF, developed to handle such problems is described and evaluated through comparisons with laboratory test data. Results from numerous computations provide a detailed understanding of the hydrodynamic phenomena associated with boiling water reactor vent-clearing processes. In addition, calculations show the sensitivity of the results to variations in the water vapor content, vent submergence depth, vent orifice size, and to the influence of fluid-structure interactions.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18699

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

摘要:

AbstractA generalized time-dependent nonlinear perturbation theory for coupled fields of neutrons, nuclides, and delayed neutron precursors is presented in a unified, yet detailed, formulation for diverse areas of applications, including depletion analysis, xenon poisoning, reactor kinetics, and pulsed neutron problems. Several applications of this formulation are discussed including cross-section sensitivity analysis and reactor design and operation sensitivity analysis.

ISSN:0029-5639    

DOI:10.13182/NSE80-A18700

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE80-A18701

出版商:Taylor&Francis    

年代:1980

数据来源: Taylor