摘要:

AbstractThe results of an experimental study of the behavior of fission products released from metallic uranium and a U-3.5%Mo alloy into helium and air are reported. A thermochromatographic technique for investigating the nature of low-concentration gas species is described and applied to the release of barium, lanthanum, cerium, and molybdenum from irradiated fuels. Barium, lanthanum, and cerium, which deposit at high temperature in helium, are not significantly released into air because of the low volatility of their respective oxides. Molybdenum, which is quite nonvolatile in helium, is released as MoO3in air.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18523

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractExpressions are developed for the rate of production of atomic displacements in iron by neutron spectra found in reactors. Factors considered include anisotropic, elastic high-energy neutron scattering, inelastic high-energy neutron scattering, thermal-neutron capture-gamma recoil-induced displacements, and energy loss by electronic excitation. An evaluation of calculated atomic displacement density as a measure of radiation damage to steel was made by determining if this approach could rationalize the differences in damage rate produced by different reactor spectra. It was found that available data on radiation-induced property changes could be satisfactorily normalized to a common basis by expressing exposure as displacement density when all the above-mentioned factors are given consideration.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18524

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe utilization of the theoretical principle that activities must remain constant at constant temperature and pressure if the number of phases present is equal to the number of elemental constituents present was described. The potential was outlined for use of this principle to achieve compatibility between uranium carbide and certain metals. A sample of UC alloyed with 5 at.% tungsten to control its carbon activity showed no embrittlement of stainless steel after being in positive contact for 3000 h at 800°C (1472°F).

ISSN:0029-5639    

DOI:10.13182/NSE67-A18525

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractEstablished techniques for measuring thermal reactor flux and power which utilize, respectively, arbitrary placement of foils and overall heat balance, have limited accuracy and are difficult to apply. The proposed method is based on135Xe accumulation, as manifested by control-rod positions, plus a set of relative flux factors taken over the entire core instead of only at isolated positions. The technique involves only routine operating data, and required calculations are quite manageable by machine computation. After development of the theory, application is illustrated using a set of data from the Union Carbide Nuclear Company research reactor at Tuxedo, New York. Results are quite reliable when rod positions during the shutdown period are used, but operating period ratios introduce large inaccuracies by magnification of routine imprecision in operating data. It is concluded that the method offers an easily obtainable check on the usual heat-balance information for heterogeneous reactors, particularly if applied to shutdown data or to a xenon equilibrium run.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18526

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA secondary-dose equivalent model for calculating secondary proton and neutron doses in arbitrary geometries is described. The random position of origin of the secondary-nucleon, primary-proton residual kinetic energy and secondary-nucleon kinetic energy, and survival weight at the point of generation of the secondary particles are determined by random sampling techniques. Results from this model are compared with the experiment of Maienschein and Blosser which measured the dose from a 160-MeV proton beam incident on an aluminum slab. The agreement is generally better than the state-of-the-art accuracy for secondary-dose calculations.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18527

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractFrom pulsed-neutron measurements, the most probable slowing down times of 14.1-MeV neutrons to 1.1 and 0.8 eV in water are found to be 1.55±0.15 and 1.85±0.15µsec, using cadmium-shielded6LiI scintillators at distances 10 to 50 cm from the source. No spatial dependence can be found. Subsequent Monte Carlo study of 120 000 neutron cases not only confirms the experimental results, but also yields a more detailed space-energy-time neutron distribution as well as average slowing down times to various epithermal energies.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18528

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractEnergy spectra have been computed for protons, alpha particles, and their secondary electrons slowing down in water irradiated by 14.6-MeV neutrons. Spectra for protons and alpha particles were based on continuous slowing down theory. Anisotropy of the proton-recoil reaction and elastic nuclear collisions of charged particles were found to have negligible influence on energy spectra and the energy-loss distribution. Partitioning of the neutron first-collision dose rate among the three particles was found to be very sensitive to the cutoff energy for production of secondary electrons. An analysis based on treatment of a collisional energy loss of less than 200 eV as localized energy dissipation along a particle track showed that localized electronic energy loss is distributed among protons, alpha particles, and their secondary electrons in the respective fractions 0.530, 0.112, and 0.358.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18529

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractNeutron-capture cross sections of237Np have been measured at eight neutron energies between 0.15 and 1.5 MeV. The experimental method was the activation technique in which the neptunium target was irradiated with a monoenergetic neutron beam and analyzed for the product238Np by gamma-ray spectrometry.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18530

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractIt is shown that variational principles need not be postulated and then correctness proved; they can, in fact, be derived, making their use more a matter of routine than ingenuity. A Lagrange multiplier technique is used to derive a second-order variational principle for estimating an arbitrary functional of the solution to an inhomogeneous equation. The relationship of this principle to a functional Taylor series expansion and to elementary perturbation theory is established. A normalization independent second-order variational principle for an arbitrary functional is derived which reduces to the Schwinger principle if the functional is linear. Two higher order variational principles are derived and shown to be generalizations of the principles of Kostin and Brooks. The Lagrange multiplier technique is applied to the inhomogeneous Sturm-Liouville equation, which leads to a second-order variational principle for estimating an arbitrary functional which allows trial functions that are not continuous and do not satisfy the boundary conditions. This functional is of the type suggested by Buslik plus boundary terms. The differences between a variational principle which can only be used to estimate a functional of interest and one which also acts as a Lagrangian are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18531

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractTwo well-known finite difference approximations to the discrete ordinate equations inx-ygeometry are shown to lead to a singular system of equations for the case of reflecting boundary conditions. These difference schemes are the diamond approximation of Carlson, and the central difference approximation. Despite this singularity it is shown for the diamond scheme that a solution always exists and is, in some sense, unique. For the central difference scheme, however, it is shown that a solution need not, and in most cases will not, exist.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18532

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor