摘要:

AbstractThe findings of Kalambokas and Henry, about the representation of light water reactor reflectors by boundary conditions, are the basis for the development of a practical scheme for the elimination of the reflector from two-group diffusion calculations of a pressurized water reactor. Boundary conditions are generated once, from a full-sweep diffusion calculation of the core and reflector, then used in short core sweeps to calculate power distributions and criticality for any change in core properties.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17763

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA sufficient condition for the asymptotic stability of nuclear reactors in terms of the equilibrium power level and delayed neutron parameters is presented. The integrodifferential point kinetics equation for an autonomous reactor with an arbitrary nonlinear feedback is written in the quasilinear form. The averaging principle is applied to investigate the stability of the amplitude of the fundamental harmonic of the true nonlinear series solution of this equation. Using a related theorem, a stability criterion is obtained, which is found to be somewhat more general than some previously proposed criteria.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17764

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe USODA (U-tube Steam Generator Controller Design Analysis) code was developed to simulate the transient behavior of a vertical natural circulation U-tube steam generator in pressurized water reactors and to design the optimal level controller. The steam generator was represented by sixth order linear differential equations through matrix reduction. The momentum equation for the recirculation flow models the effects of the separators, U-bend regions, and spatial acceleration. To assure stability, the Lyapunov theorem was adopted. The optimal gains were obtained by minimizing the quadratic performance index and by using both Newton-Raphson and successive overrelaxation methods, which guarantee fast convergence. Sample calculations for Korea Nuclear Unit 2 showed that a control system consisting of standard proportional integral differential controls can be successfully employed for the control of water level. The optimization procedure led to a stable system with good controlled response.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17765

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA method of sampling the Wienke formula for Compton scattering in Monte Carlo calculations has been developed. The Wienke formula differs from the well-known Klein-Nishina formula in that it considers electrons in relativistic Maxwellian motion. The proposed sampling method for the Wienke formula is a rejection technique similar to Kahn's method for the Klein-Nishina formula.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17766

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA new approach for solving electron transport problems by the Monte Carlo method has been developed. The present approach uses pseudo-reduced single elastic and inelastic scattering cross sections instead of the multiple scattering distributions commonly used in conventional Monte Carlo calculations. Transmission and albedo factors for 1- and 0.5-MeV electrons normally incident on materials of low and high atomic number (aluminum and gold) have been obtained and compared with earlier results. The agreement is reasonably good. The present method is simple and considerably reduces data storage in the computer's memory.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17767

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA diffusion theory method is developed for synthetic acceleration of nodal Sn calculations in multidimensional Cartesian geometries. The diffusion model is derived from the spatially continuous diffusion equation by applying spatial approximations that are P1expansions of the corresponding approximations made in solving the transport equation. The equations of the diffusion model are formulated in a way that permits application of existing and highly efficient nodal diffusion theory techniques to their numerical solution. Test calculations for several benchmark problems in X-Y geometry are presented to illustrate the efficiency and stability of the acceleration method when applied to a“constant-linear”nodal transport approximation. The method is shown to yield point-wise flux convergence of 10-4in fewer than ten synthetic iterations for all problems considered and to require substantially less computational effort than unaccelerated solutions.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17768

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured with the high-efficiency rem counter, the multisphere spectrometer, and the NE-213 scintillator in the environment surrounding an intense 14-MeV neutron source facility. The dose distribution and the energy spectra of neutrons around the facility used as a skyshine source have also been measured to enable the absolute evaluation of the skyshine effect.The skyshine effect was analyzed by two multigroup Monte Carlo codes, NIMSAC and MMCR-2, by two discrete ordinates Sncodes, ANISN and DOT3.5, and by the shield structure design code for skyshine, SKYSHINE-II. The calculated results show good agreement with the measured results in absolute values. These experimental results should be useful as benchmark data for shyshine analysis and for shielding design of fusion facilities.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17769

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractIntegral neutron capture and neutron fission cross sections have been measured for the 276-day254gEs. Thermal cross sections and resonance integrals were evaluated using a cadmium filter technique. Capture cross sections were determined from alpha-particle spectrum measurements following neutron irradiations with cobalt flux monitors. Fission cross sections were measured using fission track detection techniques with233U monitors. The fission cross-section values compared favorably with an absorption cross-section determination from a burnout experiment of253Es-254Es. The integral neutron capture and fission cross sections determined for254gEs are:= 28.3±2.5 and Ic= 18.2±1.5 b, and= 1970±200 and IF= 1200±250 b.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17770

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe cross sections of the (n, 2n) reaction of169Tm and of181Ta at 14.61±0.31 MeV were determined relative to the known neutron cross section of the27Al(n,α)24Na reaction. The resulting values are 2014±93 and 1269±46 mb, respectively, when the Ryves et al. decay scheme is followed for the latter. The cross section of the (n, 3n) reaction of169Tm was determined at 18.21±0.24 MeV, relative to the169Tm(n, 2n) cross section, to be 618±25 mb. The shapes of the excitation curves for these three reactions were measured in the 12.3- to 18.3-MeV range. The (n, 2n) reactions were normalized at 14.61 MeV; the (n, 3n) reaction, at 18.21 MeV.

ISSN:0029-5639    

DOI:10.13182/NSE85-3

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractTotal cross sections for the emission of protons and alpha particles have been measured for 9.4- and 11-MeV neutrons incident on a 4.11 mg/cm2thick Type 316 stainless steel target. A newly developed charged-particle time-of-flight spectrometer was used to obtain (n, xp) and (n, xα) cross-section data. The measured gas-production cross sections have been compared with the values predicted on the basis of measured or calculated cross sections of the constituent materials.

ISSN:0029-5639    

DOI:10.13182/NSE85-A17772

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor