摘要:

Safety analysis of sodium-cooled plutonium-fueled fast reactor plants must be concerned with the possibility of fires involving these materials. Design of an air cleaning system for such a facility requires basic data defining the aerosol characteristics of sodium and plutonium released during a fire. Size characteristics of the aersol produced during sodium and plutonium fires were determined for different atmospheres ranging from 20.8% oxygen, 79.2% nitrogen to 100% nitrogen. The aerosol produced by burning gram quantities of sodium was compared with that produced by a fire involving 600 lb of sodium. Sodium aerosol count median diameter ranged from 0.07 to 1.09µand was independent of oxygen concentration. Small and large scale fires produced an aerosol with comparable size characteristics. Plutonium aerosol count median diameter ranged from 0.02 to 0.09µand was also independent of oxygen concentration. When plutonium alloy was burned under reduced oxygen conditions, the fraction airborne ranged from 2.×10-7to 4.×10-6. Fires involving plutonium alloy and sodium together produced airborne plutonium-sodium ratios ranging from 0.34 to 0.008%.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17237

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

The hydrogenated terphenyl mixture HB-40 which is in use as a reactor organic coolant, has been irradiated at 350°C with 1.5-MeV electrons. Changes in composition and properties are reported. Decomposition proceeded at half the rate per unit dose observed previously during reactor irradiations where 62% of the absorbed energy was due to fast neutrons. This indicates a dependence of hydroterphenyl radiolysis on Linear Energy Transfer, whereby recoil protons produce 3.2±0.6 times as much decomposition as electrons. Some differences between the physical properties of electron-irradiated material and the properties of reactor-irradiated material were noted.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17238

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

The dissolving rate of sol-gel thorium oxide is increased three- to sixfold when approximately 1 wt% MgO is incorporated into the thoria. The MgO is introduced by adding an Mg(NO3)2solution to the thoria sol. Thoria containing MgO is suitable for use in reactor targets. Dissolving rates were increased under all preparative conditions investigated; density and physical properties were also satisfactory. The oxide retained its improved dissolving characteristics following irradiation in a reactor. The preparation of the ThO2-MgO was demonstrated by the production of 500-lb batches in commercial equipment.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17239

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

This paper describes a comparative study of analytical models for calculating the hydrodynamic stability of natural-circulation boiling systems and experimental data. The models were evaluated by comparing their physical assumptions, the mathematical simplifications, the methods of solving the equations, and, in some cases, their predicting abilities. The predicting abilities of the models were determined by programming them for a digital computer and using the program to predict experimental loop stability. The models all have many common features. Each is a statement and solution of the conservation equations for the two-phase and single-phase fluids, derived and applied using essentially the same physical assumptions. In all of the models studied, the dynamics of the instability can be described as linear feedback between flow rate and vapor volume. Although some of the models include nonlinearities in the flow-void interaction, the non-linearities are not important in determining the instability threshold, but merely affect the limit cycle oscillation. All the models contain empirical correlations for slip ratio, friction, and heat transfer derived from steady-state data.There are three major differences between the models: 1) the different slip ratio and friction assumptions or correlations, 2) the extent to which distributed parameters are spatially lumped, and 3) the use of linearized small perturbations and computation in the frequency domain, or integration of the differential equations in time with retention of nonlinear effects. The first two differences have important effects on the accuracy of the models' predictions, whereas the third difference is a matter of convenience.The STABLE-3 program by Jones is the most reliable, and predicts the threshold of instability for loop experiments within 20% for about 70% of the tests. The model of Jahnberg is a distant second in predicting loop stability.The application of Jones' FABLE program, which includes the STABLE-3 hydrodynamics in addition to feedback from the reactor kinetics equations, to the EBWR produces a calculated instability threshold in agreement with the reported 120 MW. The important destabilizing mechanism in the EBWR arises from differences between the plate-type and the rod-bundle-type fuel assemblies in the core in their steam void response to power disturbances. These dissimilarities allow the excitation of a hydrodynamic resonance interaction between the regions with the different fuel assemblies that lowers the instability threshold.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17240

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

Eight activation detectors,235U(n,f), Np(n,f),238U(n,f), P(n,p), Al(n,p),56Fe(n,p), Al(n,α), and63Cu(n, 2n) are placed on a firm experimental foundation to prepare for the investigation of fission-neutron spectra in Part II. Gross beta-gamma counting with methane-flow counters is employed to achieve the exceptional stability of detector response required for spectrum determinations. Calibration and specification of detector excitations are based on relative cross-section measurements performed at the Los Alamos Van de Graaff. The latter have been tailored to supplement existing cross-section information and to aid in its evaluation. Deduced detector excitations are specified in fifty energy groups with uncertainties assigned in a separate seven-group excitation structure appropriate for the investigation of distributed neutron spectra.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17241

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

Statistical aspects of neutron transport in low-power reactors are studied from the viewpoint of branching processes. The probability generating function of a neutron population originating from an ancestor neutron is expressed in the form of the factorial moment expansion, and it is shown how a factorial moment is constructed out of the lower-order moments. The formalism is based on a physical statement that neutrons occupying a certain set of the prescribed space-time points are composed of subgroups which are chain related to the closest common branching point. The statement is found to be a natural extension of Feynman’s derivation of the well-known formula for Variance-to-Mean Ratio Method of measuring reactor noise.The form of the factorial moment expansion of the one-ancestor problem is applied to counting statistics in reactors with random sources. The result turns out to be the factorial cumulant expansion of the probability generating function of count number. It is shown that all the higher factorial cumulants are successively constructed out of the lower orders. New adjoint fields are introduced. It is pointed out that analysis of reactor noise depends on two models of introducing extraneous neutrons into the system, i.e., the random source model and the burst-of-neutrons model.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17242

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

Differential energy and angle spectra from a point isotropic137Cs source in an effectively infinite medium of water have been determined forγ-ray penetrations of 1, 2, 3, and 4 mean-free-paths at 15°intervals. The spectra were unfolded from scintillation spectrometer measurements by an analytic method based on the Scofield iteration scheme. An integration of the results over all angles yielded differential energy spectra which were consistent with multigroup transport calculations. The measurements were also carried out in a condensed, air-like medium. A comparison of the results with those obtained in water showed that the differences in attenuation coefficients between the two materials caused spectral differences only at very low energies for small separations between source and detector, which were consistent with theoretical calculations.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17243

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

Position-dependent thermal spectra have been measured in a paraffin-moderated235U multiplying assembly using two independent methods. Steady-state spectra were obtained with the time-of-flight technique employing a 24.40-m flight in conjunction with the Rensselaer Polytechnic Institute linear accelerator; asymptotic (in time) spectra were obtained with the pulsed-LINAC chopper technique. A new technique was developed to monitor the source intensity with a tracking reliability of±1.5%. The measured spectra are compared to a series of DTF-IV transport calculations using aP1kernel andP1source; the spatial source was obtained from a transport calculation. The spectrum calculations were performed with a polyethylene kernel utilizing either the Goldman model or the Koppel-Young four-oscillator model. The experimental spectra are generally in closer (better than 5%) agreement with calculations using the Goldman kernel than with those using the Koppel-Young kernel. This result is consistent with the total cross section of polyethylene measured by Armstrong.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17244

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

A general expression allowing the calculation of the influence on cell factors of an anisotropic component of the scattering law in a given medium is established in the framework of the integral transport theory. This expression is applied to the calculations of the thermal utilization, fast fission factor, and diffusion coefficients. In the case of the thermal utilization, the effect of the anisotropic scattering in the moderator can be taken into account by a rigorous correction whatever the cell; this correction coincides with the classical transport correction only for widely spaced lattices, and still with some restrictions; for closely packed lattices the transport correction has no theoretical justification, and seriously underestimates the effect. In the fuel, the transport correction is no more theoretically justified, although it leads to good results for rather large rods; a very simple formula is established from the general expression, allowing the calculation of the correction tof, without using the transport cross section. This formula leads, for all the rod diameters considered, to results in very good agreement with referenced values obtained by theS8method. An analogous formula for the fast-fission factor is established.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17245

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

Neutron-wave propagation in moderating media is investigated within the framework of the diffusion approximation to the Boltzmann equation, using a realistic scattering model and the eigenfunction expansion method. The eigenfunctions are obtained from the thermalization theory solution to the exponential experiment with their corresponding eigenvalues being the fundamental and higher diffusion lengths of the medium. Expanding the energy dependence of the neutron-wave problem in these eigenfunctions leads to a simpler and more accurate secular determinant than that obtained from a Laguerre polynomial expansion. Solving the secular determinant yields the squared complex inverse relaxation lengths for the asymptotic energy mode and for the continuum energy modes. A discrete energy formulation, Simpson's rule integration scheme, and the Jacobi method of matrix diagonalization are used in the numerical solution to the eigen-value problem. The dispersion law for graphite, obtained by direct solution of the complex secular determinant, is compared with experimental results. This investigation indicates that high-energy-mode contamination will not seriously affect neutron-wave experiments in graphite in the frequency range where diffusion and thermalization parameters can be obtained.

ISSN:0029-5639    

DOI:10.13182/NSE67-A17246

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor