摘要:

AbstractThe slowing-down distribution of Po-Be neutrons has been measured in aluminum-water, zirconium-water, and iron-water mixtures up to metal water ratios of 2:1 by volume. The second moment of the distribution has been obtained from these measurements and compared with theoretical calculations based on a solution of the transport equation. The effect of varying the source spectrum and cross sections in the calculations is discussed.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25515

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe neutron age for fission neutrons and Po-Be neutrons was measured in mixtures of D2O and H2O. The age was evaluated from the second moment of the slowing-down distribution at the 1.4-ev resonance of indium. The ages of fission neutrons at concentrations of 99.8, 99.0, 98.4, 95.3, 94.0, 91.8, 48.6% D2O, and in pure H2O were 109, 107, 106, 93, 86, 78, 38.6, and 31 cm2, respectively. In the range from 100 to 90% D2O, the rate of decrease of the age was approximately 4 cm2for each additional per cent of H2O. The ages of Po-Be neutrons in 99.4, 48.6% D2O, and in H2O were 148, 72.5, and 55.7 cm2, respectively.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25516

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractA general formulation of the critical reactor equations is made to include space and velocity variation; the noncritical reactor is treated by using the effective multiplication factor. Two methods are developed for solving the general equation by splitting it into a pair of simultaneous equations: the space-energy split and the fission source split. By using unit sources one equation can be inverted to obtain a pair of integral equations for iterative solution of the general equation.The meaning of neutron importance and the physical picture associated with the concept are given. By using its physical meaning the importance balance equation, which is adjoint to the neutron flux equation, is derived by several methods. Neutron importance is used to formulate the change in reactor power produced by a change in reactor parameters. The effective multiplication factor and reactivity are introduced; the perturbation equation for reactor power change is developed in terms of reactivity.The necessary assumptions to derive the diffusion approximation are given, and the general diffusion equation with continuous energy dependence is obtained. From this the multigroup diffusion equations can be obtained, including the multigroup diffusion perturbation equations. The same methods used for the general critical reactor equation are applied to the diffusion equation to obtain its solution by splitting it into a pair of coupled integral equations. The integral equation for the effective multiplication factor is developed in terms of the fission source variable, and a stationary variational formula obtained for estimating the effective multiplication factor.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25517

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractSimple, analytic expressions for temperatures and axial fuel expansions in an exponentially heated, heterogeneous reactor are derived. Constant thermal resistances, equal to the steady-state values, are assumed, and the effects of using this assumption are discussed. Multiregion fuel elements are treated, both with and without coolant flow. The effect of mechanical inertia upon axial expansion of fuel rods with one fixed end is taken into account. Numerical examples which pertain to EBR-II are presented.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25518

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractA technique is described for determining control rod shutdown reactivity for tall reactors (small relative axial leakage) which may also be applicable to other reactor geometries. This method assumes that the rod bank region is an exponential assembly with the critical portion of the reactor as the driving source for the exponential. Comparison is made with the results obtained from the rod drop technique.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25519

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractSome new techniques have been applied in the determination of relative neutron fluxes in water moderated critical assemblies. Alloy wires of Mn-Fe, In-Al, Au-Al, and U-Zr have been prepared with a high degree of uniformity between individual samples of a given material. Beta activation of these wires is measured by thin scintillation crystals in conjunction with specially stabilized electronics. This procedure results in good“plateaus”of counting ratevsphotomultiplier voltage, discriminator setting, and amplifier gain. The counting time of a wire is controlled by a decaying sample of the activated material. Thus, as the counting continues, the counting interval becomes progressively longer, providing automatic decay correction of the data. Several benefits obtain from this method. The statistics of counting for a wire of a given activation level are independent of the time of counting; nonuniform decay (e.g., mixed fission product decay) is handled with the same facility as simple exponential decay.Automatic sample changers are used which make possible the counting of larger numbers of samples (approximately 1500 per day) with a minimum of personnel. These changers have been so adjusted that good precision in positioning is maintained. The automatic features of the counting system permit a rapid qualitative evaluation of the data.An error analysis has been made which indicates an experimental counting error (exclusive of statistical error due to decay) of approximately 0.8%. This error, when combined with the appropriate statistical error, has been applied to improve the use of computer codes in obtaining accurate least square fits of theoretical curves to the experimental data.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25520

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractA study is made of the transient motion of a suddenly released column of liquid poison, such as mercury or borated water, as it moves through the control tubes of a reactor. Two basic systems are described. The first system consists of a tank of liquid poison, situated above the reactor, connecting directly to control tubes extending down into the core. The second system is a U-tube arrangement in which the liquid poison enters through tubes that extend upward from the base of the core. By making the tank or standpipe diameter larger than the control tube diameter it is possible to obtain initial fluid column accelerations greater than gravitational acceleration. When solid control rods are used in reactors, it is necessary to employ auxiliary springs to give an initial acceleration greater than gravitational. High initial accelerations are inherent features of liquid poison scram systems. It is found that the initial acceleration is gravitational acceleration multiplied by the ratio of standpipe area to control tube area. An exploitable feature of the U-tube system is that the liquid column undergoes a natural rapid deceleration. It may therefore be possible to do away with damping devices that are often required at the base of a solid control rod channel. The equations of motions of the system are derived and integrated. The general solution in both cases gives the displacement time explicitly in terms of elliptic functions; in the U-tube system the unconfined fluid column is found to execute uniform elliptic oscillations.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25521

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractTwo methods are evaluated for the suppression of neutron-induced activation outside hydrogenous shields: the addition of a 1/υabsorber to the hydrogenous shielding material, and the addition of a layer of 1/υabsorbing material to the outside of the shield. When the material being activated has a 1/υcross section, a closed-form solution is obtained. The results should prove valuable in determining to what extent activation outside a shield can be reduced by any combination of these two methods.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25522

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractAs the result of an attempt to prepare unordered compounds of graphite containing more than 1.5×10-3acceptor per carbon atom by the introduction of both chemical acceptors and radiation damge centers, evidence has been found for mutual destruction of chemical acceptors and damage centers. An analysis of the kinetic behavior of the mutual destruction indicates that the extent of destruction is independent of the order in which the radiation damaging and chemical treatments are carried out. From some auxiliary experiments made necessary by the discovery of the above interaction it is concluded that the graphite bisulfate residue compounds are stable at room temperature, and that the bisulfate ion is not appreciably decomposed by the gamma flux in the reactor during short irradiations.The dependence of some electrical properties of graphite on the concentrations of both chemical acceptors and radiation damage centers has been analyzed on the basis of the two-band theory of a semiconductor above its degeneracy temperature. It is concluded that whereas the Hall effect may be reasonably well understood the behaviors of the electrical resistance and magneto-resistance cannot be understood in terms of this theory, so that the introduction of additional hypotheses appears necessary.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25523

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE58-A25524

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor