摘要:

AbstractThe results of an extensive series of total helium production cross-section measurements for incident neutrons in the 14- to 15-MeV energy region are presented, and an experimental data base for the prediction of helium generation in candidate fusion reactor materials is provided. The measurements were made by isotope-dilution gas mass spectrometry. They include the pure elements Be, B, C, O, F, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ag, Sn, Ta, Pt, Au, and Pb; the separated isotopes of B, Fe, Ni, Cu, and Mo; and the alloy steels Type 316 stainless steel, HT-9, and 9 Cr-1 Mo. The results are in generally good agreement with other total helium production measurements in the literature, but comparisons with the ENDF/B-V nuclear data file indicate that the helium gas production files require revision for the structural elements vanadium, chromium, manganese, cobalt, and nickel. Comparisons with published cross sections for individual reaction channels indicate that reactions other than (n,α) contribute significantly to helium production in several materials.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18608

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractNeutron transmission through a zirconium oxide sample containing the radioactive93Zr isotope was measured by pulsed neutron time of flight. R matrix parameters for some of the resonances up to 6-keV neutron energy were determined. The first resonance, for example, was found at (110.43±0.01) eV with partial widthsГn= (348±9) meV andГγ= (141±21) meV and quantum numbers Jπ= 2+.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18609

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA multilevel method is applied to the load-following control of a boiling water reactor using a nodal reactor model with practical operational constraints and thermal limits. Due to the very large size of the problem, a decomposition is made using hierarchical control techniques. The optimization of the resulting subproblems is performed using the feasible direction method.An objective functional, of quadratic form, is defined to reflect the control objective, namely, to achieve the desired thermal power (tracking) with minimum effort, returning to the initial xenon and iodine concentration as closely as possible. Nodal source equation and discretized Xe-I dynamic equations are formulated as equality constraints, while the linear heat generation rate and the rate of power increase are formulated as inequality constraints. Core flow and control rod position are the control variables. A simplified model of the core is used, with 4×4 fuel assemblies that have one control rod at the center.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18610

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe Monte Carlo scheme for deep-penetration problems, where both transport and collision kernels are biased synergistically, leads to minimum variance. Obtaining a proper biasing parameter is still a problem. For certain values of biasing parameter, the variance could be infinite even in a very simple problem. Using moment equations of statistical error prediction, a critical biasing parameter is obtained. A biasing parameter greater than the critical parameter may lead to an unbounded second moment in a simple one-dimensional homogeneous shield problem. A prescription is provided that may help to avoid a poor selection of the biasing parameter.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18611

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractMapping of source-hydrogenous medium systems within the framework of three-group diffusion theory is discussed. Each system is presented by the point of the map with coordinates: X ratio of first- and second-group diffusion lengths, andГratio of slowing down and thermal diffusion lengths. This mapping leads to the method of source-medium systems classification, which reduces the phase space of the problem. In accordance with this method, source-medium systems can be characterized by only two parameters, scale and shape. Thermal flux in the systems with the same shape parameter can be described with the same“generalized flux function (GFF).”The approach of GFFs is investigated for direct and inverse problems. The first one is presentation of thermal flux for certain source-medium systems with the help of these functions, and the second one is estimation of medium neutron transport parameters from the measured thermal flux through GFFs.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18612

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractRadiation transfer is relevant to a number of key technical issues related to nuclear reactor safety studies. To gain understanding of thermal radiation transfer under hypothetical reactor accident conditions, analysis of radiation transfer in a finite length cylindrical vessel containing high-temperature aerosols that absorb, emit, and scatter thermal radiation has been performed. The fine particles are assumed to be produced by the dispersion of the reactor core debris under high pressure. The model parameters used in the calculations correspond to those proposed in the High-Pressure Melt Streaming experimental program. Results of calculations show that the extinction coefficient and the single scattering albedo of the aerosol and the emissivity of the vessel are important model parameters. The sensitivity studies have identified the radiative property data base needed to make realistic radiative transfer calculations relevant to hypothetical reactor accidents in which fine aerosol particles are generated from the core debris.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18613

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractMeasured and calculated neutron and gamma-ray energy spectra from∼14-MeV neutrons streaming through a stainless steel duct having a length-to-diameter ratio of 4.6 are compared. The 1.45-m-long duct is imbedded in a concrete block. The spectra were measured with an NE-213 liquid scintillator as a function of detector location relative to the mouth of the duct. The calculated data were obtained using the Monte Carlo code MCNP and the discrete ordinates code DOT 4.3. The calculations were performed using a two-dimensional cylindrical model of the experiment with symmetry about the duct axis. The measured and calculated neutron and gamma-ray spectra are compared at two distances from the mouth of the duct and at detector locations on and off the duct axis. The neutron spectra calculated with MCNP agree with the measured data within∼5 to 50% at all detector locations. The data calculated using the discrete ordinates method are in good agreement with the experiment for the cases where the detector is on axis but are in poor agreement at the off-axis detector locations. The gamma-ray spectra calculated with both radiation transport methods are in good agreement (∼5 to 25%, depending on photon energy) with the measured spectra.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18614

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractGamma-ray energy deposition measurements were made in a simulated fast reactor blanket of the Purdue University Fast Breeder Blanket Facility (FBBF) using CaF2:Dy thermoluminescent dosimeters (TLDs). The TLDs were encased in either stainless steel or lead sleeves, and cavity ionization theory corrections known as f factors were used to relate the TLD dose to the sleeve dose. Corrections for the neutron response of the TLDs were made by determining the relative contributions of the TLDs neutron and gamma-ray responses.Radial experimental heating rates are presented and compared to calculations. The calculations significantly underestimate the experimental gamma-ray energy deposition rates in both stainless steel and lead. The underestimation is ~30% in stainless steel and ~15% in lead at the transformer/blanket interface and increases with increasing radius, reaching -50% in stainless steel and ~40% in lead at the outside of the 0.51-m-thick blanket. This underestimation trend is attributed to a general underprediction of the“bulk”neutron population by the neutron flux calculations.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18615

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE86-A18616

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE86-A18617

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor