摘要:

AbstractThis new, dry process employs fluidization and particle-coating techniques and involves direct conversion of uranium hexafluoride to a solid, (uranyl fluoride), by hydrolysis with steam followed by reduction of the uranyl fluoride to the dioxide by reaction with steam-hydrogen mixtures. Process studies were carried out in 3-in.-diameter Monel reactors. The uranium-hexafluoride/steam reaction was conducted continuously at relatively low temperatures, about 200 C, at a uranium hexafluoride rate equivalent to 174 lb uranium h-1ft-2of reactor cross section and a steam rate of about 3.25 times the stoichiometric requirement. Seed addition was required to offset particle-growth effects. Uranium losses to the off-gas were less than 0.01% of the hexafluoride fed. Reduction of the uranyl fluoride to the oxide was demonstrated in batch tests. Low-fluoride (<250 parts/106residual) material was consistently produced in four hours at 650 C and in seven hours at 600 C using a 50:50 mixture of steam and hydrogen. Pellet-fabrication tests on dioxide powders ground to -325 mesh gave sintered densities of about 94% of theoretical.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19567

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractExponential experiments with light-water moderator were conducted to determine criticality standards for the handling of uranium metal enriched to 3 wt % U235. These measurements, made with massive rods 2 and 3 in. in diameter, were combined with Hanford measurements with smaller rods to provide critical bucklings and masses for H20-moderated lattices over a range of rod diameters from less than 0.15 in. to more than 3 in. Subcritical buckling measurements are compared with the more conventional approach-to-critical method.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19568

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractA negative Doppler effect has been observed in measurements on a metallic uranium sample (enriched to 93% in U235) placed in a typical fast-reactor spectrum which has a median fission energy of 195 keV. The plausibility of the negative sign is supported on theoretical grounds, although with the use of standard analytical techniques and the limited number of resonance parameters at present available, it cannot be calculated for this spectrum. The value forwas found to be -5.65×10-6/°C. New measurements on U238have been made, and the data on Th232, previously published, have been extended to 930 C. The agreement between analytical and experimental values for the latter two materials is good.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19569

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe fast-neutron spectrum has been measured at several positions in the IRR-1 pool-type reactor using seven activation detectors. The spectrum was calculated by the simultaneous analysis of the data from the seven detectors. Adjacent to the core the spectrum was found to be close to the fission spectrum, with a slight dip between 3 and 4.5 MeV. At increasing distances from the core, the spectrum becomes harder, with a pronounced dip between 3 and 4.5 MeV.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19570

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractA rod drive using a stepping motor has been developed for the Argonne Advanced Research Reactor critical experiment. The control rod is suspended from a roller chain which meshes with a sprocket driven by the motor. Rod position is indicated by counting the number of steps. Scram is produced by interrupting the power to the motor windings, thus removing the motor's holding torque. This design offers significant reductions in size and cost compared to existing types.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19571

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe cross section for the reaction 35-h Rh105(n,γ)30-sec Rh106has been measured using a TRIGA reactor in the pulsed mode of operation as a neutron source. The effective thermal-neutron (0 to 0.5 eV) cross section was found to be 13 300±1 500 b, relative to a 36-b cross section for Co59. The cadmium ratio was observed to be≥20 in a neutron flux for which a cadmium ratio of 7 was measured for cobalt.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19572

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe thermal-neutron capture cross section of Ce140and its resonance capture integral, measured by an activation method, have been found to be 0.59±.06 barns and 0.48±.05 barns, respectively.The effective capture cross section of Ce141in the Materials Testing Reactor was found to be 29±3 barns. This value was determined by mass analysis for the neutron-induced Ce142.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19573

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractCalculations of the critical sizes of cubic arrays of interacting fissionable units are compared with critical experiments. The units are of two types: vessels containing 5 liters of an aqueous solution of highly enriched uranium, and cylinders of highly enriched uranium metal. The arrays are surrounded by various thicknesses of hydrogenous reflectors. Agreement between calculation and experiment is reasonably good. The similarity of the results obtained with the widely differing types of units invites confidence in general applications of the method of calculation. Tables are presented for computing critical and safe sizes of cubic arrays of 8, 27, 64, or 125 identical units as a function of the albedo of the reflector surrounding the array and of the reactivity of an individual unit.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19574

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe transmission of thermal neutrons through cadmium covers as a function of cadmium thickness was measured in a graphite stack at various heights above the thermal column of the AE-6 water-boiler reactor. Both dysprosium-alloy and indium-alloy foils were used as detectors and were beta-counted. Because the thermal flux incident on a cadmium cover is depressed relative to the flux incident on a bare foil, a foil with a thick cadmium cover on one side only was used for the zero-thickness measurement and its activity was doubled. The resultant thermal activities for a thin detector were consistent with the exponential integral 0.9302(dΣα) a cadmium thickness greater than 0.025 cm, whereand a value of 2450 barns was used for the absorption cross section of cadmium.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19575

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe buildup of xenon poisoning is a prime factor in restarting a high-flux thermal reactor after shutdown. To restart the reactor at any time, sufficient excess reactivity must be present to override the xenon poisoning. The amount of excess reactivity required can be minimized by determining an optimum reactor shutdown program. Based on Pontryagins Maximum Principle, optimum shutdown programs are determined for various flux levels ranging from 1014n/cm2sec. to 1016n/cm2sec. Results show that a considerable reduction in the peak value of xenon concentration can be realized by relatively simple shutdown programs.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19576

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor