摘要:

AbstractThe space-independent reactor kinetics equations with two reactivity feedbacks are analyzed for stability and nonlinear oscillations. Expressions are derived using Fourier series methods for determining the frequency and fundamental amplitudes of the oscillations in reactivity and power. These results are compared with exact solutions of the system equations and agree in all cases for equilibrium power levels near the critical power level. The system of equations is examined for the effect of delayed neutrons on oscillatory solutions. When delayed neutrons are included, unstable limit cycles are found as well as stable limit cycles.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19320

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractIn a reactor with feedback linearly proportional to the power level, the delayed neutrons permit the existence of unstable limit cycles. This means that, for linearly stable systems, the delayed neutrons can cause the system to become unstable for large enough disturbances. We demonstrate this analytically when the frequency of the limit cycle is near to the linear critical frequency. General criteria, based on the feedback transfer function, are given for the necessary existence of periodic solutions. Techniques for determining the stability of these periodic solutions are then shown. Examples are given for several reactor models.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19321

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe stationary interaction parameter between the plane surfaces of two identical, cylindrical, polyethylene disks has been measured with the pulsed neutron method. It was shown that it is possible to overcome the delay effect caused by the flight of the neutrons in the gap between the moderators through the insertion was varied between 0.06 and 0.77; the resulting values of the interaction was varied between 0.06 and 0.77; the resulting values of the interaction parameter varied from 0.93 to 0.24. Two different thicknesses of the disks were employed; one assembly gave decay constants from 10 000 to 17 000 sec−1and the other assembly yielded values in the range 17 000 to 40 000 sec−1. Although full equilibrium of the neutron distribution was not reached in all cases for the last series, the two series show a general agreement. A calculation based on a zero’th-order Bessel function as radial distribution and (cosθ)/πas angular distribution of the neutrons leaving the interacting surfaces gives a too-large interaction parameter for all separation distances. However, the overestimate is small when the surfaces are close together.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19322

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractAn improved collision probability method for thermal-neutron-flux calculation in a cylindrical reactor cell has been developed. Expanding the neutron flux and source into a series of even powers of the radius, one gets a convenient method for integration of the one-energy group integral transport equation. It is shown that it is possible to perform an analytical integration in thex-yplane in one variable and to use the effective Gaussian integration over another one. Choosing a convenient distribution of space points in fuel and moderator the transport matrix calculation and cell reaction rate integration were condensed. On the basis of the proposed method, the computer program DISKRET for the ZUSE-Z 23 K computer has been written. The suitability of the proposed method for the calculation of the thermal-neutron-flux distribution in a reactor cell can be seen from the test results obtained. Compared with the other collision probability methods, the proposed treatment excels with a mathematical simplicity and a faster convergence.

ISSN:0029-5639    

DOI:10.13182/NSE42-01-23

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe total neutron cross sections of nitrogen and iron have been measured with high resolution (0.035 nsec/m) in the neutron energy range from 0.5 to 9.0 MeV. The nitrogen measurements have provided evidence that a recently reported discrepancy in the total nonelastic cross section is not a result of errors in the total neutron cross section. The iron cross section obtained was found to be in best agreement with the recent Karlsruhe data with respect to the positions and presence of structure; however, the present measurements have revealed cross sections in the valleys which are lower. Comparisons are made of the present measurements on nitrogen and iron with previous measurements.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19324

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractCalculations have been carried out to estimate the absorbed-dose and dose-equivalent rates at various depths in the atmosphere produced by an energetic solar flare—the flare of February 23, 1956. The dose rates are determined both by computing flux spectra using air only and applying flux-to-dose conversion factors and by computing the dose rates in tissue using an air-tissue-air arrangement. The two methods of calculation are in reasonable agreement when the flux-to-dose factors are applied to the forward-flux spectra, but the calculations indicate that previous results obtained using omnidirectional-flux spectra overestimate the dose rates. Also, the effect of the fuel carried by a supersonic aircraft on the dose received by the passengers in the event of a solar flare has been considered and found not to be substantial.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19325

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractRadioactive particles escaping a surface carry a portion of the disintegration energy. The fluxes of particles, power, and energy are referred to as residual fluxes. In this paper a method is formulated for predicting residual fluxes emanating from a composite surface consisting of an active substrate layer protected by a clad layer. Application of this method requires only knowledge of the particle ranges in the layer materials. Using existing range-energy equations, generalized plots are presented for estimating residual quantities for heavy particles. Calculations show that fractional residual power and particle fluxes vary from 0.5 for thin (monoatomic) layers to zero for very thick layer or heavily cladded systems. Typical values of the residual power are 0.1 W/cm2for alpha particles and 10 W/cm2for fissioning surfaces.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19326

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe relative importance of Brownian and gravitational coagulation on the transient behavior of an aerosol undergoing coagulation and gravitational settling is discussed. A comparison is given of the particle size distribution and settling rates calculated for a typical high-mass density aerosol using a gravitational coagulation capture efficiency,э, of unity, anэcalculated as a function of particle radius, and anэof zero. It is concluded that the use ofэ= 1.0 predicts a non-log-normal size distribution and seriously overestimates the aerosol deposition rate, particularly at short times after the onset of settling.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19327

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractA unique geometry is found for a heat generating cylindrical rod cooled on both sides within a coolant channel, which leads to the same coolant temperature and the same surface temperature on both sides of the rod. The“optimum”rod i.d./o.d. is close to one-half and the corresponding overall void fraction close to 57% for cylindrical, hexagonal, or square channel configurations.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19328

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe results of an analytical study are presented for the case of fully developed heat transfer to fluids in laminar, longitudinal flow through unbaffled rod bundles. The rods represent reactor fuel pins, which consist of ceramic cores encased in a metallic or alloy cladding. The study was based on the thermal boundary condition of uniform heat flux on the inner surface of the cladding. The three prime independent variables are rod spacing (P/D), relative cladding thickness [(r2−r1)/r2], and relative cladding conductivity (kw/kf). These have been varied over the ranges of 1.05 to 1.30, 0.025 to 0.300, and 0.10 to 4.00, respectively; and the following quantities have been determined as functions of the above variables: rod-average heat transfer coefficients, circumferential variation of outer-surface cladding temperature, same for the inner surface of the cladding, circumferential variation of local heat flux, and finally, circumferential variation of local heat transfer coefficients. It is shown that the assumption of circumferentially uniform heat flux on the inner surface of the cladding is valid for any practical fuel subassembly designs of a sodium-cooled reactor for a central-station power plant. Of the three prime independent variables, theP/Dratio has by far the greatest influence on the heat transfer behavior of the system; and of the remaining two variables, the influence of thekw/kfratio is about the same as that of the (r2−r1)/r2ratio at the lower values of (r2−r1)/r2, but appreciably greater at the higher values of (r2−r1)/r2. The greater theP/Dratio and the lower the other two ratios, the more the system behaves like the standard uniform-wall-heat-flux case. The results are all expressed in the form of convenient dimensionless groups and are correlated by simple mathematical expressions, for ready use by the design engineer.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19329

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor