摘要:

AbstractEigenvalue separation, which is used as a criterion to determine the degree of neutronic decoupling of the core, is measured by a static flux-tilt method on Zero-Power Physics Reactor assemblies. Space-dependent nuclear characteristics, such as the radial distributions of the reaction rates and the control rod worths, are also measured for the same assemblies. The calculation/experiment (C/E) values vary with core radius depending on the assemblies. The relationship between decoupling and C/E radial dependence is investigated, and a quantitative relation is found between the eigenvalue separation of the first radial mode and the C/E radial dependence.

ISSN:0029-5639    

DOI:10.13182/NSE113-97

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractA study is conducted to investigate conceptual liquid-metal reactor (LMR) core concepts, employing some unconventional design features for improved economics and safety. The unconventional design elements are used to supplement the conventional measures, which alone have apparently not led to an attractive LMR design for the 21st century. Better economics are obtained through simplicity and compactness of the core design. For simplicity, internal scattered blankets are omitted. Core compactness is achieved by maximum power flattening, resulting from axial and radial enrichment zones along with axial and radial (BeO) reflectors. To further enhance core compactness, the in-core control rods are replaced by reflector controls. For improved safety, the general objective is to reduce both coolant-void and burnup reactivities. However, even with the use of a wide spectrum of unconventional design features, such as burnable poisons, peripheral reflectors, and inner moderating regions, it is not possible to overcome the fact that both coolant-void and burnup reactivities cannot be reduced simultaneously to desirably low levels. The only resolution of this dilemma appears to be to minimize coolant-void reactivity and to“manage”the burnup reactivity losses, such that an accidental insertion of significant amounts of reactivity is mechanically not possible. A conceptual design with these characteristics is described.

ISSN:0029-5639    

DOI:10.13182/NSE93-A24001

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractA simplified model for a liquid-metal-cooled reactor (LMR) transient analysis, in which point kinetics as well as lumped descriptions of the heat transfer equations in all components are applied, is converted from a differential into an integral formulation. All 30 differential balance equations are implicitly solved in terms of convolution integrals. The prompt jump approximation is applied as the strong negative feedback effectively keeps the net reactivity well below prompt critical. After implicit finite differencing of the convolution integrals, the kinetics equation assumes a new form, i.e., the“quadratic dynamics equation.”In this integral formulation, the initial value problem of typical LMR transients can be solved with large time steps (initially I s, later up to 256 s). This then makes transient problems amenable to a treatment on a personal computer. The resulting mathematical model forms the basis for the GW-BASIC program LMR transient calculation (LTC) program. The LTC program has also been converted to QuickBASIC. The running time for a 10-h transient overpower transient is then≍40 to 10 s, depending on the hardware version (286, 386, or 486 with math coprocessors).

ISSN:0029-5639    

DOI:10.13182/NSE93-A24002

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractIt is shown that the SNBoltzmann/Spencer-Lewis equations conserve energy locally if and only if they satisfy particle balance and diamond differencing is used in path length. In contrast, the spatial differencing schemes have no bearing on the energy balance. Energy is conserved globally if it is conserved locally and the multigroup cross sections are energy conserving. Although the coupled electron-photon cross sections generated by CEPXS conserve particles and charge, they do not precisely conserve energy. It is demonstrated that these cross sections can be adjusted such that particles, charge, and energy are conserved. Finally, since a conventional negative flux fixup destroys energy balance when applied to path length, a modified fixup scheme that does not is presented.

ISSN:0029-5639    

DOI:10.13182/NSE93-A24003

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractThe information dimension is one of the simplest quantities that can be used to determine the asymptotic motion of the time evolution of a nonlinear system. The application of this quantity to reactor noise analysis is proposed, and the possibility of its application to power oscillation analysis is examined. The information dimension of this regime is equal to the number of independent oscillating modes, which is an intuitive physical variable. Time series data from computer experiments and experiments with an actual physical system are used for the analysis. The results indicate that the method is useful for a detailed analysis of reactor power oscillation.

ISSN:0029-5639    

DOI:10.13182/NSE93-A24004

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractTwo techniques for measuring the effective delayed neutron fraction have been developed. The techniques are based on a combination of the Rossi-αtechnique and the source-multiplication technique. They require minimal knowledge of the assembly, use variables that can be measured, and are independent of the detector efficiency and the neutron lifetime.

ISSN:0029-5639    

DOI:10.13182/NSE93-2

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractTritium production in a sphere of6LiD with an Oralloy core irradiated by a central source of 14-MeV neutrons has been calculated and compared with experimental measurements. The experimental assembly consisted of an Oralloy sphere surrounded by three solid6LiD concentric shells with ampoules of6LiH and7LiH located in several positions throughout the assembly. The Los Alamos Monte Carlo Neutron Photon Transport Code (MCNP) was used to calculate neutron transport throughout the system and tritium production in the ampoules. The MCNP calculations were three-dimensional and employed ENDF/B-V cross sections. The overall experimentally observed-to-calculated ratios of tritium production were 0.996 (±2.5%) in6LiH ampoules and 0.903 (±5.2%) in7LiH ampoules. Tritium production in a sphere of6LiD without an Oralloy core has been reanalyzed using ENDF/B-V cross sections, and the results are reported. The reanalyzed observed-to-calculated values of tritium production were 1.053 (±2.1%) in6LiH and 0.999 (±2.1%) in7LiH. The foregoing several uncertainties do not include an estimated<6% systematic error in the observed values.

ISSN:0029-5639    

DOI:10.13182/NSE93-A24006

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

AbstractNeutron spectra are measured by the time-of-flight method at laboratory angles from 15 to 120 degfor the reaction Ag(14N,n) at 50 MeV/nucleon. All spectra are fitted with a moving-source model. The cross-section dependences on bombarding energy and on projectile mass are investigated by comparison with published neutron data from the reactions Ag(14N,n) at 35 MeV/nucleon and Ag(36Ar,n) at 35 MeV/nucleon. Application to biological hazard estimation is anticipated.

ISSN:0029-5639    

DOI:10.13182/NSE93-A24007

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor