摘要:

AbstractA direct measurement of the graphite absorption cross section has been made in the Physical Constants Testing Reactor (PCTR). The sample tested was reactor grade (GBF) graphite, and had a 2200 m/sec absorption cross section of 3.80±0.04 mb including all impurities. This measurement also provides a normalization for the Hanford Test Reactor relative measurement which have been in progress for over fifteen years.Samples of American, French, and British graphite were also tested in the HTR to provide a basis for comparing the results of American, British, and French graphite absorption cross-section measurements. The graphite bars involved have also been tested at Harwell and Saclay.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25736

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractSome of the differential equations of thin fin theory have been rewritten to include an internal heat generation term, and solutions have been obtained for fins of rectangular, triangular, and“optimum”profiles. Fin temperature distributions and heat removal rates are exhibited as functions of the other variables involved by means of dimensionless parameters. In addition, criteria are discussed for determining whether the use of fins is worthwhile in a given application where internal heat generation is present in the fins.The analysis presented here should find wide application, not only to actual fins, but to many other problems where thin fin theory applies, such as determination of the heat transfer characteristics of thin structural members used in reactors.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25737

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractNatural uranium dioxide specimens of Shippingport PWR-l blanket-rod geometry are exposed in the Materials Testing Reactor (flux 2×1014n/cm2−sec) and discharged periodically (every three weeks) for measurements in the Reactivity Measurement Facility (RMF). The time-integrated thermal and epithermal fluxes are measured during each exposure cycle, and together with the MTR Daily Power Logs, give the complete exposure history. Measurements in the RMF are used to determine an experimental value forη/η0(η0is the preirradiation value) which may be compared with the theoreticalη/η0calculated for the measured exposure history using appropriate neutron-interaction parameters. In the theoretical calculations, the thermal absorption cross section of stable fission products is taken to be 50 barns per fission. Although the experimental and theoretical results are derived completely independently, agreement within 1% inη/η0is found for the behavior following all cycles of irradiation comprising exposures from zero to 15,600 Mwd/ton.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25738

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractThe second fundamental theorem of reactor theory states that a good estimate of the non-leakage probability from a bare reactor is given by the Fourier transform of the infinite medium kernel evaluated at the asymptotic buckling of the reactor. Inönühas investigated the validity of this theorem for the one-velocity slab reactor with isotropic scattering by means of a variational technique. He finds its use gives very good results even for quite small reactors with dimensions of the order of a few mean free paths. In the present paper the effect of anisotropy in the scattering on the validity of the theorem is investigated by a variation-iteration technique. It is concluded that the theorem is, in general, less reliable the more anisotropic the scattering.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25739

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractThe elastic-plastic deformation of a tube subjected to radially uniform heat generation is considered using Tresca's yield function, its associated flow rule, and a linear work-hardening law. The tube is assumed to be in the state of plane strain and all the elastic and thermal parameters are taken to be temperature independent. For a uniform heat sourceQ, which increases monotonically with time and which has an insulated inner surface, yielding commences at the inner boundary and propagates outward upon further thermal loading. Immediately after initiation of yield, a plastic region (inner) and an elastic region (outer) are formed with the tangential stress as the intermediate principal stress in both regions. The maximum strength of a heat source,QM, to which a tube may be subjected is taken to correspond to that value ofQwhich makes the tube almost entirely plastic. This value ofQis computed for several graphite tubes of different thicknesses and then compared with an experimentally obtainedQFwhich corresponds to total failure (fracture) of these tubes. A value of approximately 2.5 is obtained forQF/QMfor tubes of moderate thicknesses. Furthermore, the ratioQF/QMremains practically constant as tube thickness increases. Agreement between theory and experiment especially in depicting the dependence of failure load on tube thickness and temperature gradient is considered excellent in light of the many assumptions made. The application of this theory to the design of nuclear reactor fuel elements is also pointed out.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25740

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractInformation about effective neutron temperatures has been inferred from measurements of the ratio of the thermal-fission activity of a Pu239foil to that of a U235foil. A discussion of the ratios obtained in various assemblies which were placed in the center of a graphite thermal column is presented. The assemblies were made of natural uranium, lead, or graphite. In some cases the assemblies were surrounded by a layer of water. The experiments were conducted at thermal-column temperatures which ranged from 18 to 640°C. The data obtained in the case of the graphite assembly are used as a calibration of the neutron temperature. To within the accuracy of the experiment, the shape of this calibration curve is the same as the shape obtained from the data of C. H. Westcott. The results, for all other cases, indicate for the range of temperatures investigated that the ratio of the thermal-column temperature to the effective neutron temperature in an assembly varies linearly with the temperature of the thermal column.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25741

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractThe densities of liquid lead and of liquid nickel-lead solutions containing up to about 3.5 atomic per cent nickel were measured as a function of temperature using a modified Archimedean method. It was found that the densities of the nickel-lead solutions were greater than that of pure liquid lead and increased with increase in nickel content. Partial molal volumes for nickel and lead were then determined by the method of intercepts. The results indicate that for the composition region investigated the partial molal volume of lead does not differ significantly from the molal volume of lead and the partial molal volume of nickel approaches a value of zero at high dilution.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25742

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractA redetermination of the agefor neutrons of indium-resonance energy (1.46 ev) from a point U235fission source is reported. Foils were irradiated in a geometrically simple arrangement in the Penn State Reactor pool, and counted in a standard manner. The value obtained,τ= 27.3±0.9 cm2, is in better agreement with current theory than those from previous measurements. The spatial distribution found here differs most markedly from those observed in previous experiments by having a larger slope in the region within a few centimeters of the source.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25743

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractIn many instances resonance capture of neutrons can be calculated by one of two basic approximations. The narrow resonance approximation is valid if the practical width is small compared with the maximum energy loss of a neutron in an elastic collision. If the reverse is the case, the absorber atoms may be regarded as infinitely heavy. There are cases of wide, weakly absorbing, resonances however in which neither of these methods is reliable. Examples of these are given. An alternative method for calculating resonance capture for such resonances is presented and compared with Monte Carlo calculations of the capture fraction in bismuth-graphite lattices.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25744

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor

摘要:

AbstractOne possible nuclear reactor fuel element design consists of plate-type subassemblies cut transversely into a number of sections in the direction of flow. The use of such interrupted-plate elements should result in lower surface temperatures than full-length plate-type subassemblies by taking advantage of both a continuous entrance effect on the film coefficient of heat transfer (1) and reduced engineering hot channel factors.The purpose of this paper is to report the results of experimental investigations of the pressure drop through such interrupted-plate-type fuel elements. In particular, the joint losses between adjacent sections of a plate-type subassembly, and the entrance-pIus-exit losses on entering the initial section and leaving the final section of subassembly, have been measured as a function of Reynolds Number and, in the case of the joint losses, as a function of the spacing between the sections. Measurements have been made on six configurations; one subassembly with the plates in adjacent sections of the subassembly parallel and one with them perpendicular to each other (in-line and crossed), each subassembly being tested for the square-edged, rounded leading edge, and both ends rounded cases. Most of the measurements were made on 2 in. long sections of 2.1-in. sq. subassembly containing ten 0.087×1.82 in. plates and eleven 0.087×1.82 in. channels. The effect of longer sections was also investigated.Experimental values of dimensionless joint loss and entrance-pIus-exit loss coefficients were calculated from experimental over-all pressure drops using values for the friction factor from the literature. These experimental loss coefficients are presented graphically as a function of Reynolds Number for each configuration tested. All of the loss coefficients showed slight decreases with increasing Reynolds Number in the range tested (Reynolds Numbers from 10,000 to 100,000). Values of the joint loss coefficients are also presented graphically as a function of spacing between the sections for each configuration at a Reynolds Number of 50,000. This graph shows that the joint loss coefficients are higher than the entrance-plus-exit loss coefficients if the adjacent plate sections are square-edged and crossed, approximately the same if the adjacent sections are crossed but have rounded ends, and lower if the adjacent sections are in-line. The joint loss coefficients approach the experimental entrance-plus-exit coefficients (which agreed well with values in the literature) at large spacings, and the two were essentially equal when the spacing reached 0.05 to 0.50 in. depending on the configuration.

ISSN:0029-5639    

DOI:10.13182/NSE60-A25745

出版商:Taylor&Francis    

年代:1960

数据来源: Taylor