摘要:

AbstractThe Fe54(n,p)Mn54cross section has been measured at eleven points between 3.55 MeV and 17.4 MeV using an activation technique. The excitation function appears to reach a peak at about 5.7 MeV. A fission-neutron cross section based on these and earlier differential data yields a value of 67 mb, in good agreement with some recent integral measurements.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20626

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractHalf-lives have been measured by direct decay for 18 radionuclides. The method of least squares was used to obtain the best straight-line fit to the data. The observed half-lives are 87.9±0.3 d for S35, 52.7±0.5 d for Sr89, 13.6±0.3 y for Nb93m, 35.8±0.5 d for Nb95, 65.5±0.2 d for Zr95, 39.5±0.3 d for Ru103, 368.0±1.8 d for Ru106, 13.6±0.2 y for Cd113, 76.3±6.6 y for Sn121, 2.71±0.02 y for Sb125, 1.99±0.02 y for Cs134, 283.8±0.6 d for Ce144, 2.60±0.02 y for Pm147, 87±9 y for Sm151, 134.2±0.8 d for Tm170, 700±5 d for Tm171, 3.68±0.05 y for Tl204, and 164.4±0.4 d for Cm242. These data are compared with current literature values, and average values of the existing determinations are given.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20627

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA series of experiments to test the Experimental Gas-Cooled Reactor (EGCR) fuel element concept was conducted in the Oak Ridge Research Reactor (ORR) and the Engineering Test Reactor (ETR). The elements tested were sintered UO2fuel pellets contained in stainless steel tubing. Principal test variables were fuel pellet geometry, cladding temperature, and fuel burnup. After irradiation, the elements were examined for dimensional stability, integrity of the cladding, the fractional release of fission gas from the fuel, and any interactions between the fuel and the cladding.Some elements were subjected to unusual and extreme conditions of operation and others were not built to EGCR specifications. Such elements experienced three types of failure: 1) severe cladding fractures, 2) microscopic cladding defects, and 3) failures in associated components. Detailed examination of these experiments showed potential problems which may occur if EGCR fuel elements are operated outside design conditions.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20628

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe electrical resistivity of high purity liquid cesium was determined in a pressurized furnace from 600 to 3000°F (316 to 1649°C) by measurements of the electrical resistance of a Ta-10%W alloy tube, both empty and filled with cesium. The resistivity found for the lower temperatures agrees moderately well with previously published results, the discrepancy decreasing at the highest temperatures.The thermal conductivity of liquid cesium was calculated from its resistivity using a Lorenz number of 2.3×10−8(V/deg K)2.By comparing the cesium data with a reduced resistivity vs reduced temperature curve for mercury, the critical temperature of cesium is found to be 3190°F (1754°C), with a corresponding critical pressure of 130.8 atm from an available vapor-pressure correlation.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20629

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractRecommended values have been experimentally obtained for the angle (defined by its cosineµ0in center-of-mass system) that determines the boundary between‘removal’and‘nonremoval’collisions and regulates the deep penetration of neutrons in the NRN method. Measured attenuations in three different, most common, shield materials: water and magnetite and ordinary concrete, giveµ0= 0.6 (±0.1) for elements withA>1. For hydrogen,µ0= 0.45 is recommended.The results indicate, besides, that the neutron flux predictions are not overly sensitive to the changes in the removal source, caused by varyingµ0. The usual smoothing effect of the diffusion is material dependent, and the strength of the coupling between removal and diffusion parts is seen to decrease when going from water to magnetite and ordinary concrete.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20630

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractStarting from the observation that exponentials of lethargy are just eigenfunctions of the elastic-scattering-energy transfer operator, a Fourier transform with respect to lethargy is applied to the energy-dependent Boltzmann equation. For constant cross sections and isotropic scattering in the center of mass system (but arbitrary anisotropy in the laboratory system) this leads to a‘one-velocity’transport equation with a complex number of secondaries. Hence, if the method of Case is now to be applied it has to be extended to cover this situation. For an infinite medium, however, the solution may readily be obtained by a Fourier transform with respect to the space coordinate. Thus, the exact result is a double Fourier inversion integral, which can be calculated numerically.It is shown that well-known solutions can be obtained by an approximate evaluation of this integral.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20631

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractMonte Carlo calculations have been carried out in great detail on the reflection properties of concrete for fast neutrons. This paper presents the results for the differential angular dose albedo for various incident-beam conditions and touches upon some of the other distributions calculated. The following formula is offered to represent the calculated differential angular dose albedo to better than 10% for about 95% of the values obtained, and which can be used to extend the results to the entire hemispherical range for both incident and reflected neutron velocity vectors:

ISSN:0029-5639    

DOI:10.13182/NSE65-A20632

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractAn analytical model for the prediction of steam-water critical-flow pressure, mass discharge and pressure gradients in the approach region to critical flow is presented. The continuity, momentum and energy equations are applied to successive differential elements along the conduit and are solved numerically on an IBM-7094 digital computer for the maximum discharge flow rate. The proposed model assumes thermal equilibrium conditions and employs the modified Armand correlation to relate the void fraction to steamquality. The frictional losses in the momentum equation are obtained by two methods: a separated flow model and Armand model. A comparison of the analytical predictions with available test results on small diameter pipes shows that: 1) the present model agrees with the published test data; and 2) both frictional loss models are equally valid, and the selection of a particular method depends on the degree of conservatism desired.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20633

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA time optimal criterion for the reactivity-xenon shutdown problem has been formulated and solved by application of the theorems of optimal processes as developed by L. S. Pontryaginet al. We desire the minimum time trajectory between any point of operation in the xenon-iodine phase space to a zero-power shutdown curve subject to the constraint that neither the shutdown curve nor the trajectory to the shutdown curve allow the xenon concentration to exceed an arbitrarily specified maximum. The optimal solution is shown to usually require sequential operation at zero power, variable (decreasing) power, and finally full power. The exact power program is calculated for one example.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20634

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractBy expressing the fluxes associated with a range of experimental period measurements as linear combinations of several trial functions, a generalization of the inhour formula relating measured periods to linear functionals of the perturbation is obtained. The formula is applied to finding the fast periods and values ofkeffassociated with the early stages of super-prompt critical-burst experiments or pulsed die-away experiments. By appropriate choice of trial functions, the formula may be rearranged so that it relates period to a single reactivity-like quantity and other small corrections. Since this quantity is a linear functional, values of it corresponding to different perturbations are additive, even when the over-all flux shapes associated with these perturbations differ. When two trial functions alone are sufficient for a range of experiments, further rearrangement results in a relationship that has the form of the so-called seven-group inhour equation.

ISSN:0029-5639    

DOI:10.13182/NSE65-A20635

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor