摘要:

AbstractExperimental studies have been conducted on scaled hydraulic models of large pressurized water reactors. Measurements were made of the effect of various internal geometries on the flow distribution at the core inlet and on the Euler numbers. Attention was focused on the relationship between the flow distribution and the length of the flow skirt, the length of the lower plenum and the layout of instrumentation tubes. The design of these components was optimized. Flow distributions in the annuli formed by the thermal shield and in the lower plenum were determined analytically and confirmed experimentally.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18661

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA visual and frictional pressure-drop study of low-pressure high-void-fraction two-phase flow has been performed in a boiling-water natural-circulation system with heat addition. Heat was added uniformly by four tubular electrical resistance elements placed parallel to the flow, simulating cylindrical nuclear fuel elements. A 6-ft vertical test channel, 1.25-in. i.d. was used. It contained six opposite pairs of observing windows permitting high-speed motion pictures of the flow to be taken at different operating conditions. Experimental two-phase pressure-drop data at various flow rates were conducted at pressures of 25, 35, and 50 psia, and steam qualities ranging from 0.7 to 7.8% corresponding to void fractions of 63 to 94.5%. Bubbly and transition from bubbly to slug flow regimes were observed. Strong pulsations, inherent in natural-circulation systems with internal heat addition, were also observed. Frictional pressure-drop data were obtained as a function of both quality and mass flow rate. Under the conditions of the investigation, no discontinuities in flow regime or frictional pressure drop were observed and the Martinelli-Nelson correlation for the friction multiplier was found to greatly underestimate the value of the multiplier. A motion-picture film of flow is available as a supplement to this paper.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18662

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe results of efforts to use plasma-spheroidized UO2 particles in the preparation of a UO2-nickel-chromium alloy cermet fuel plate are described. Mechanical property data have been obtained permitting property comparisons between the plate containing plasma-spheroidized fuel and other types of fueled and unfueled plates. The plate containing spherical fuel possesses significantly better ductility and somewhat more consistent properties than other fuel plates tested. The results of an irradiation experiment with the plate containing spheroidized fuel show its performance to be equivalent to the best of those for which data have been published; however, further testing is required to establish whether a definite superiority exists.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18663

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractFuel particles coated with pyrolytic carbon are contemplated for use in several high-temperature gas-cooled reactors. This paper describes the performance of pyrolytic carbon-coated, high-density, uranium oxide particles irradiated at 1300 to 1600°C. The fission-gas release, burnups, and temperatures for five experiments are given. Coated particles with a builtin gap between the fuel and the inner laminar coating began to show evidence of failure by releasing bursts of fission gas after 27.9% uranium burnup, and postirradiation examination revealed delamination of the inner coating. Coated particles made with a porous carbon buffer layer between the fuel and an isotropic coating showed no evidence of failure by fission-gas release, and showed no damage due to irradiation when examined by metallography. Coated particles with neither gap nor buffer, but with a low-density inner coating applied directly to the fuel, retained fission gas successfully but showed enlargement of cracks that had formed at the fuel-coating interface during the coating process. The oxide particles did not flow at high burnup and expand into voids and cracks as the carbide particles did, and the oxide did not diffuse into the carbon coating at high temperatures.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18664

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractZircaloy-clad uranium metal fuel tubes containing dilute (<1000 ppm) Fe, Si, and Al additions that were irradiated under 1200 psi reactor pressure to about 5000 Megawatt days per metric ton of uranium (MWd/tU) swelled less than 3%; in contrast, U-1.5wt%Mo and unalloyed uranium tubes swelled 6 to 10%. External restraints such as provided by thick cladding and reactor pressurization contributed substantially to the volume stability of the tubes by limiting the volume increase that would normally be encountered at exposures beyond the characteristic threshold for swelling.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18665

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA method is presented for predicting the conditions under which graphite will react with cesium at high temperatures and low cesium pressures to form compounds. The method is based on the available thermodynamic data on cesium-graphite compounds and on an understanding of the nature of the bonding forces in these compounds. An expression is given for the threshold pressure, at any temperature, below which no reaction will occur between cesium and graphite. The structural deterioration and swelling of graphite which occurs when cesium-graphite compounds are formed can be avoided by keeping the cesium pressure below the threshold value. The information on the compatibility of cesium and graphite is of potential use in the design of MHD direct-conversion systems, in high-temperature graphite reactors and in systems that require the availability of cesium vapor at controlled pressures, such as thermionic converters.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18666

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractAn analysis is performed which indicates that beta particle backscattering measurements are highly sensitive to source-scatterer separation distances. It is shown that the primary betas emitted by the source strike the scatterer according to a Cauchy statistical distribution. Then, making the assumption that the primary betas are adsorbed on the scatterer and isotropically reemitted, an effective counting geometry can be obtained. A comparison of this effective geometry with the source geometry will then give an indication of the expected backscatter signal sensitivity. It is shown that a 50-mil separation distance can result in a backscatter measurement error of 25%. Zumwalt’s empirical relationship for saturation backscattering is used to analytically predict the expected normalized (source signal equal to one) signal as a function of source-scatterer separation distance and scatterer atomic number. Finally, aluminum, nickel, niobium, palladium, and tantalum scatterers are employed using thallium-204 (204Tl) and phosphorus-32 (32P) beta sources in conjunction with a thin-window halogen-quenched G-M tube to compare experimental and analytical results. This experiment shows that Zumwalt’s equation provides an excellent fit to the experimental results in all instances except when employing the low atomic number scatterer, aluminum.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18667

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThis experiment was conducted to obtain data to be used in calculating the number of fissions produced by neutrons in bulk239Pu as a function of neutron energy. The data provide a consistent set of group-averaged cross sections and self-shielding factors. Although self-shielding factors have beencalculatedfrom cross-section data, no previous experiments to measure the energy dependence of239Pu self shielding exist. A consistent set of cross sections is possible because of the wide neutron energy range over which this experiment was done. No attempt was made to determine resonance parameters, since in this experiment poor energy resolution was used to improve statistics. (Resonance parameters are, in fact, unnecessary to determine group-averaged cross sections and room-temperature self-shielding factors.) Good-geometry self-shielding factors were measured by a plutonium fission counter shielded by various thicknesses of plutonium. Average fission cross sections, total cross sections, and self-shielding factors have been determined in 11 energy groups whose end points are in the ratio of 2.15-to-1. The energy range was 2.15 eV to 10 keV. The LRL Linac neutron time-of-flight facility was used, with a neutron resolution of 0.18μsec/m. The detector consisted of a spark chamber that was sensitive to fission fragments, facing a 0.4 mg/cm2plutonium-239 foil. Seven Pu absorber foils ranging from 0.06 to 3 g/cm2were used in the self-shielding measurements. This range of absorber thickness yields an adequate description of the resonance-produced surface-absorption effect throughout the above energy region.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18668

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe bounded periodic behavior of the reactor power is studied for those instances when the equilibrium power is greater than the critical power level. Simple formulas are derived, for reactors witharbitrarylinear feedback and no delayed neutrons, for the amplitude and frequency of the limit cycles. These quantities are shown to be related to the ratio of the equilibrium-to-critical power level and to the Laplace transform of the feedback kernel. Since the techniques used apply for arbitrary values of the fundamental component of the power oscillation, they are used to derive a describing function which is valid for large amplitude disturbances. Conditions for the existence of critical power levels and, hence, limit cycles are discussed. Formulae for investigating the stability of these limit cycles are also derived. Applications are made to the circulating fuel reactor and to the two-temperature reactor. It is also suggested that the results can be used in two practical situations: 1) When the oscillation amplitude is indistinguishable from the reactor noise, the power level can exceed critical; and 2) When the oscillation amplitude is large, the reactor can be used as a self-sustained pulse-modulated neutron source.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18669

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe use of a hybrid computer results in an efficient method of analyzing the transience in high-performance nuclear reactor cores using ceramic fuels such as UO2. The nature of the space dependence of the variables is such that a great deal of multiplexing of computer components is possible. As a consequence of multiplexing, an iterative procedure is necessary to obtain the closed-loop system response for a finite (but arbitrary) interval of time. A mathematical proof of the uniform convergence of the iterative process has been obtained. This proof is based on the principle of contraction mapping. The economy which may be realized in computer equipment and programming effort for this area of system analysis is discussed with illustrative examples. The computing techniques developed are applicable to the analysis of any nonlinear feedback control system.

ISSN:0029-5639    

DOI:10.13182/NSE67-A18670

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor