摘要:

AbstractThe neutron transport equation in toroidal geometry is numerically solved by making use of the discrete-ordinates SNmethod. The computer program developed for this computation is capable of treating a multigroup problem with anisotropic scattering. Numerical examples are given for the first wall and blanket system of a conceptual tokamak reactor design that has an aspect ratio of∼3. To validate the present method, several numerical comparisons have been made with Monte Carlo results as well as with ANISN calculations in the case of an infinite major radius. The toroidal geometry calculation, with a uniform neutron source distribution throughout the plasma region, yields a neutron flux that, at the first wall, is maximum near the top and bottom of the torus. As one moves radially outward from the first wall, the position of the maximum flux rapidly shifts to the outermost point of each poloidal circle, and the flux decreases monotonically along the poloidal circumference until it reaches a minimum at the innermost point of the torus. At∼10 cm from the first wall, for example, the variation becomes>20%. The one-dimensional infinite cylinder calculation shows an overestimate of flux within the first 1 cm of the first wall compared to the present calculation. In the rest of the first wall and blanket system, the one-dimensional model underestimates the fluxes in the outer region of the torus and overestimates the fluxes in the inner region.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27131

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractSeveral properties of vitreous silica relevant to application as an optical element in a reactor were studied, including density, refractive index, optical path, stress relaxation, and optical absorption. The irradiations were in fields characteristic of the fuel regions of several operating reactors and at temperatures up to 370°C. The radiation-induced changes in optical path are significant, but are much smaller than those in the density and refractive index because the last two are of opposite sign. The thermal coefficient of optical path causes changes of comparable magnitude. Optical absorption is not a serious matter in the upper end of the visible region.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27132

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractContemporary algebraic reconstruction methods are utilized in investigating the two-dimensional void distribution in a water analog from neutron transmission measurements. It is sought to ultimately apply these techniques to the determination of time-averaged void distribution in two-phase flow systems as well as for potential usage in neutron radiography. Initially, projection data were obtained from a digitized model of a hypothetical two-phase representation and later from neutron beam traverses across a voided methacrylate plastic model. From 10 to 15 views were incorporated, and decoupling of overlapped measurements was utilized to afford greater resolution. In general, the additive Algebraic Reconstruction Technique yielded the best reconstructions, with others showing promise for noisy data. Results indicate the need for some further development of the method in interpreting real data.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27133

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractExperiments were undertaken to determine the distribution of neutron flux on the core support grid plate of liquid-metal fast breeder reactors by using a semimockup of the grid-plate shield consisting of carbon-steel and aluminum slabs. The experiments were calculated with a conventional calculational procedure containing the TRD-3 two-dimensional removal diffusion code. It was demonstrated that the calculated radial distribution of the fast neutron reaction rates of115In(n,n′)115mIn agreed with the measured values within a factor of 2.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27134

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe measurement of the neutron spectrum from the White Sands Missile Range Fast Burst Reactor (FBR) in the presence of the experimenter's table is reported herein. A reinvestigation of this neutron spectrum was performed as a result of a recently published work, which indicates that the experimenter's table has a considerable softening effect on the neutron spectrum from the FBR. Based on such spectral parameters as average energy, integral fluence, and spectral index, we find the neutron spectrum associated with the experimenter's table to be essentially identical to the free-field leakage spectrum.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27135

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe previously reported work on the spherical harmonics treatment of epithermal-neutron spectra in reactor lattices is further extended and improved. The condensed matrix representation is introduced for the space- and lethargy-dependent vector of the spherical harmonics flux moments. Detailed recurrence relations for the factors resulting from numerical integration of the lethargy transfer integrals, in both the fast and the resonance regions, are provided. For solving systems of interface and boundary condition equations in the space variable, a procedure based on the coefficient matrix partitioning is presented.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27136

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractFast-neutron cross sections of244Cm have been calculated with the combined code ABACUS-NEARREX up to 3.5-MeV neutron energy. These calculations were adjusted with experimental fission cross-section data and provide a consistent theoretical group of cross sections.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27137

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe differential neutron-induced fission cross section of245Cm was measured from 0.01 to 35 eV at the Lawrence Livermore Laboratory 100-MeV electron Linac using∼6µg of245Cm. The energy dependence of the cross section is non-1/v below 1 eV due mainly to a bound level. Normalizing to previous integral data, a thermal (2200 m/s) fission cross section of 2143±58 b is obtained. Resonance parameters were extracted and are compared to previous results. Calculated values of the resonance integrals for fission and capture using these parameters are in good agreement with previous measurements.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27138

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractFission cross-section ratio measurements were made in the 2- to 3-MeV region using235U samples with234U and236U samples containing∼10%235U. Atom ratios were obtained from measured thermal fission ratios and the isotopic analysis and also by alpha counting. Shape measurements were made from threshold to 10 MeV using pure samples and were normalized in the 2- to 3-MeV region. The present values for the234U:235U ratio are up to 5% greater than those previously reported. The results for236U generally agree with those in the literature except for the values reported by Stein et al., which are also lower.

ISSN:0029-5639    

DOI:10.13182/NSE78-2

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractDifferential elastic neutron scattering cross sections of206Pb,207Pb,208Pb, and209Bi are measured at incident neutron energy intervals of∼25 keV from 0.6 to 1.0 MeV. Optical model parameters are obtained from the energy-averaged experimental results for each of the isotopes. The209Bi model was selected for extrapolation to238U by introducing a small (N - Z)/A dependence and the known deformation of238U. Calculated results are descriptive of238U total neutron cross sections from a few hundred keV to>15.0 MeV and of recently measured differential238U elastic and inelastic neutron scattering distributions at energies of3.0 MeV, including new experimental values explicitly obtained for these comparisons. The model and the measurements imply total238U inelastic neutron scattering cross sections considerably larger than in common applied usage.

ISSN:0029-5639    

DOI:10.13182/NSE78-A27140

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor