摘要:

Mass-yield measurements were made for the fission of241Am induced by graphite-moderated reactor neutrons. In most cases gamma-ray spectrometry was used to measure the radioactivity of the isolated fission products. The relative abundance of each nuclide representing a particular fission chain was determined radiochemically with respect to139Ba, whose fission yield was assumed to be 6.22%. The composite results of the three separate experiments are presented.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28135

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

The dynamics of two-phase flow through the coolant channels of a natural-circulation boiling-water nuclear reactor is studied analytically. One-dimensional conservation equations describing the flow through each channel are written in the linearized perturbed form, and Laplace transformation in time is performed. A systematic procedure is developed to approximate the solution.The solution may, in general, be oscillatory both in time and in space. Since the space dependence of the transient steam void fraction is available, it may be multiplied by its reactivity worth to obtain the space-time-dependent void reactivity. The transfer function expressing the relation between the void fraction or velocity of water and the heat flux may be conveniently used to understand the hydrodynamic stability. The analytical techniques developed are applicable to both natural- and forced-circulation systems.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28136

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

In Part I of this series, the authors have developed mathematical techniques to investigate the dynamics of coolant circulation in boiling-water nuclear reactors. This paper is an attempt to apply those techniques to various specific situations. A natural-circulation loop with a single heated channel is considered first. Dependence of the degree of stability upon the steady-state profile of the channel heat flux and the channel length are investigated. The influence of the pressure drops in the downcomer and at the channel inlet upon the transient two-phase flow is studied. The steady-state perturbations in the void fraction and velocity due to a small perturbation in the channel heat flux are predicted. The findings of the present study compare favorably with those obtained by the simplifying assumption made by the earlier investigators that the slip ratio is a constant along the channel length.The more interesting system with two or more channels operating in parallel with a common downcomer is considered next. The strength of the coupling between the dynamics of the flows through the channels increases with the pressure drop in the common downcomer, and this phenomenon is considered quantitatively. Results obtained theoretically are substantiated by comparison with those obtained through elaborate numerical methods and previous observations.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28137

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

The angular distribution of backscattered dose-rate ratio was measured for‘semi-infinite’concrete, aluminum and steel slabs irradiated by plane-parallel beams of Co60and Cs137gamma photons. The photons were incident on the slabs at angles, measured from the normal to the slab, of arccos 1.00, 0.75 and 0.50. For the necessary sensitivity, the backscattered dose rate was measured by a digital dosimetry system using a plastic scintillator as the detector.An empirical formula for differential dose-rate ratio was derived from the experimental data. Comparisons are made with two other experiments and a semi-empirical formula fitted to a Monte Carlo calculation. The experiments generally agree to within 20%. The values based upon the Monte Carlo calculation are generally 20% to 35% lower than the experimental values.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28138

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

Critical experiments were conducted with homogeneous mixtures of PuO2-polystyrene (H:Pu atomic ratio of 15) containing both 2.2 and 8.0% Pu240. Criticality was determined for a series of Plexiglas reflected rectangular prisms ranging from near cubes, to long columns, and to thin slabs; bare arrays of near-cubic geometry were also studied. Critical thicknesses were 16.09±0.41 and 5.99±0.10 cm, respectively, for the bare and reflected infinite slabs of PuO2-polystyrene containing 2.2% Pu240. Corresponding values for the 8.0% Pu240mixtures were 18.48±0.41 and 7.38±0.09 cm. The infinite slab thicknesses for an equivalent Pu239-water mixture (H:Pu = 15,ρ= 1.62 g Pu/cm3) were 11.66±0.30 and 4.38±0.08 cm, respectively, for the bare and water-reflected slabs. Corresponding critical radii for infinitely long cylinders were 10.52±0.16 and 6.54±0.14 cm; radii for critical spheres were 13.81±0.16 and 10.40±0.17 cm.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28139

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

Equilibrium neutron energy spectra inside finite blocks of beryllium at different temperatures have been calculated by solving the energy-dependent Boltzmann equation in the diffusion approximation by numerical iteration. Different sizes of the assembly have been considered. The values of the transport mean free path,λtr(E), (for various temperatures) have been taken from earlier work. Because of the peaks in the transport mean free path, the calculated equilibrium flux differs markedly from the Maxwellian, particularly for small sizes and low temperatures. Calculations also give the values of the decay constant,λfor equilibrium neutrons. Values ofλbased on Placzek kernel agree very well with the experimental values. The reasons why the present calculated values, as also the experimental values ofλ, exceed Corngold's theoretical upper bound have been discussed. The effect onλof‘trapped neutrons’and that of cold neutrons has also been studied by taking different forms forσtr(E).

ISSN:0029-5639    

DOI:10.13182/NSE65-A28140

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

In a semi-infinite block of beryllium at room temperature, the effect of‘trapped’and cold neutrons on the asymptotic equilibrium neutron flux distribution and on diffusion length is investigated by considering various forms for the energy dependence of the transport cross-section. It is found that in static experiments, cold neutrons play a dominant role. The effect of non-l/vabsorbers on the above properties has also been studied.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28141

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

An expression different from the conventional modal expansion about space-dependent linear system kinetics is proposed.The solution is expressed in the form of a Laplace-transformed source transfer function. The Taylor expansion of the function in‘s’(the variable in the transformed domain) is obtained by solving the related stationary equations. The series is approximately continued to the simple form of the transfer function such as the first-order lag or the transport lag expression. In this method, it is not necessary to solve the eigenvalue problem directly. This solution contains the contribution from the higher modes and gives a practical approximation in a simple form, even if the response includes much higher modes.A numerical example is shown. This method is also applicable to general linear distributed constant systems. Some applications to coupled reactor theory and to thermalization kinetics are mentioned.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28142

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

Because of the large physical size of typical boiling-water power-reactor cores, there is a possibility of transients in the spatial power distribution. The vertical coolant flow produces a strong undirectional coupling between the power in the lower and upper parts of the core. This situation is qualitatively analyzed by means of a highly simplified two-node reactor model. The additional assumption that the effective delayed-neutron period and fuel-element thermal time constant are equal makes possible a nonlinear graphical solution of the problem by the parametric trajectory method. In the illustrative numerical examples, the spatial power-distribution transients are mild.

ISSN:0029-5639    

DOI:10.13182/NSE65-A28143

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE65-A28144

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor