ISSN:0550-3043    

DOI:10.13182/NT69-A28367

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

An absolute determination of uranium reaction rates by means of foil irradiation was carried out in the Fast Zero Power Reactor SNEAK, assembly 3A-2 This requires the measurement of reactionrate traverses as well as their fine structure. These rate distributions were compared with transport and diffusion calculations. The traverse measurements indicate a strong dependence of the axial“buckling”(relative second derivative of the rates) on energy. The calculations with the Karlsruhe SNEAK cross-section set and the Russian ABN set yield these bucklings for238U capture and235U fission in diffusion approximation on the average 5% higher than measured. Only the fast-fission rate distribution of238U is almost correctly calculated using the cross-section sets. The ratio of total plutonium production to235u fission along the z axis was measured and compared with theory. It agrees within the error limits of the experiment. Beyond the error limits are the discrepancies found for the spectral indexσƒ28/σƒ25The fine structure of reaction rates within the fuel platelets is well described by an integral transport code, but again, there are considerable discrepancies between calculated and measured fission-rate ratios.

ISSN:0550-3043    

DOI:10.13182/NT69-A28368

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Experimental data are presented to show the conditions under which a complex fissile system may be conservatively approximated by a simpler system. The complex system consists of an unpoisoned uranium-solution slab in contact, on one face, with a thick region of heavily boronpoisoned uranium solution. The simpler system consists of an unpoisoned uranium-solution slab reflected, on one face, by Plexiglas. A calculated correction to yield a similar result for water is also presented. Use of this approximation will simplify a nuclear-safety engineer's evaluation of complex interacting fissile regions containing heavily poisoned and unpoisoned vessels.Measured critical thicknesses are reported for uranium-solution slabs unreflected, reflected on one face only, and reflected on both faces by Plexiglas. These data and calculations on infinitesolution slabs similarly reflected confirm that the critical height decreases linearly as the percent of the surface area reflected increases.

ISSN:0550-3043    

DOI:10.13182/NT69-A28369

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

A newly developed special two-detector cross-correlation experiment of zero-power reactor-noise analysis is applied to determining characteristic kinetic-reactor parameters. This method–called polarity correlation in the frequency domain–is based on the detailed analysis of the stochastic Coherence Function, in contrast to the analysis of auto and/or cross power spectral density functions. The coherence function is easily obtained by polarity correlation of two filtered random-neutron-noise signals simultaneously sampled in a reactor system using neutronsensitive detectors in the current mode of operation.The advantage and the progress in using this technique is both its simplicity and the automatic elimination of the equipment frequency response, which is of special importance when analyzing fast-reactor-noise spectra.A series of prompt-neutron-decay constant measurements was performed on several configurations of the STARK and SNEAK facilities. Moreover, special attention and effort is dedicated to reactivity shutdown measurements by the polarity correlation method. An on-line reactivity meter is described which is particularly suited to making reactivity measurements in large plutonium fueled reactors. Shutdown reactivity measurements were performed down to -8 dollars.

ISSN:0550-3043    

DOI:10.13182/NT69-A28370

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Most problems of nuclear criticality safety correspond to an array of fissile units arranged in a definite pattern in a surrounding medium of specified composition. For an infinite array, mathematical complications are greatly reduced. A suitable model consists of a purely mathematical portion, bulk material parameters, and boundary parameters.The model can be tied to experimental data at one point by modifying a single material parameter. If the tie-in with integral data is made for systems of nearly the same neutronics, strictly geometric differences may be handled with considerable confidence.Several significant reactivities are discussed including that corresponding to an extremum in the spacing of units.

ISSN:0550-3043    

DOI:10.13182/NT69-A28371

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

A new head-end process step and feasibility study of the process for an operating reprocessing plant, consisting of electrolytic-disassembly cutting and simultaneous lixiviation of metal-clad oxide power-reactor fuels, has been developed and its potential as a fuel head-end reprocessing step for stainless steel and Zircaloy-clad oxide fuels evaluated with unirradiated fuels.The electrolytic cutting and simultaneous lixiviation is realized by the penetration into each of the fuel rods of the assembly, of a layer of hollow, insulated metallic needles by anodic dissolution of a small slit of the fuel cladding by the electrolyte under high pressure, which by its action simultaneously lixiviates the oxide from the fuel rods; the fuel assembly acts as the anode and the needle layer as the cathode.

ISSN:0550-3043    

DOI:10.13182/NT69-A28372

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Mathematical models describing idealized mechanisms of fission-gas release were used as criteria to determine the mode of release from fully enriched UC2-fueled pyrocarbon-coated particles that had slightly235U-contaminated outer coatings.Below 1600°C the release of krypton, and probably iodine and xenon, was due to fissions which occurred in the contaminated outer coating, with the products escaping by solid-state diffusion from the coating.Above 1600°C the krypton release increased more rapidly with temperature. The krypton originated in the fuel core and traversed the outer coating either by solid-state diffusion or Knudsen flow through micropores in the outer coating.The overall increase in release rate with time was probably due to migration of the235U initially in the outer coating, and to the over five-fold increase in235U contamination of the outer coating during irradiation.

ISSN:0550-3043    

DOI:10.13182/NT69-A28373

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Several in-pile experiments in the Halden Boiling Water Reactor with Zircaloy-clad UO2fuel provided a comparison between vibrocompacted and pelleted fuel operating at power densities producing permanent central melting and density effect on oxide thermal conductivity. In addition to the experiments measuring the effect of cold diameter gap on gap heat conductance, fission gas release and the axial expansion of fuel and cladding were measured. The data were obtained from fully instrumented test assemblies using thermocouples, pressure transducers, and elongation differential transformers. Power was measured byγthermometers andβ-current neutron detectors.

ISSN:0550-3043    

DOI:10.13182/NT69-A28374

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

A method has been developed for generating damage functions for the correlation and prediction of neutron-induced property changes. The method affords a procedure for studying and determining the neutron spectral dependence of irradiation-effects data obtained in test reactors withh subsequent application of results to the establishment of more exact engineering design fluence limits for reactor components. The method has been applied to ductile-brittle transition temperature increase data obtained in different test-reactor spectra. Results show that neutrons of all energies must be included for best overall interpretation of the experimental irradiation effects data.

ISSN:0550-3043    

DOI:10.13182/NT69-A28375

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

An analytical model has been developed for using conventional creep data, taken at constant temperature and load, to predict failure times under conditions where stress and temperature vary according to simple, monotonic junctions of time. The validity of this method was examined experimentally for T-111 (Ta-8% W-2% Hƒ) and the experimental data are in good agreement with the predictions.

ISSN:0550-3043    

DOI:10.13182/NT69-A28376

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor