摘要:

The stability requirements of in-core thermionic reactor concepts are examined analytically, utilizing an approximate two-region description of the fueled diode. General stability requirements for the model are derived and then evaluated for possible ranges of design considerations with regard to operating power-density levels, diode dimensions and materials, and fuel materials. The stability of this type of reactor is shown to be only weakly dependent on design considerations provided the static power coefficient is negative. The reactor is sluggish in its response to reactivity or load perturbations, the response time to reattain equilibrium being of the order of minutes. A comparison between the approximate stability criterion and the corresponding criterion obtained from a detailed analog-computer simulation of a specific reactor concept indicates the approximate criterion is conservative, as postulated.

ISSN:0550-3043    

DOI:10.13182/NT69-A28355

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

In the design of irradiation experiments, prediction of the perturbation of the thermal-neutron flux by the experiment test specimens is frequently a problem. In order to obtain a model for calculating these perturbation effects, an experimental study was performed. A cylindrical shape was selected as being most typical of irradiation test specimens, and measurements of perturbation effects were made for several cylinders having different dimensions and made from different materials.Regression analysis was used to obtain polynomials from these measurements. These polynomials can be used to predict the flux perturbation, depression, and self-shielding factors as functions of cylinder materials and dimensions and control-rod position. The polynomials include a wide range of sizes and materials so that almost any cylindrical specimen that might be found in a typical irradiation capsule can be evaluated. In general, the error at the fitted points was only a few percent over the range of variables corresponding to most common materials and dimensions.In many cases, the polynomials have several distinct advantages over numerical models or mockup measurements. They are general (insofar as a cylinder is a typical shape for reactor test specimens), and they are simple to use since they require no computer calculations or reactor time. Also, their uncertainty can be established quantitatively (excluding the uncertainty due to reactor differences).These measurements were made in the Plum Brook test reactor. Because this is a typical reactor configuration (light-water moderated, MTR-type fuel elements with metal-to-water ratio of 0.75) much like many other reactors that can be found in industry and government today, these results should be generally useful. For reactors differing from this typical configuration, the results can be used to estimate flux perturbation effects after consideration is given to basic reactor differences. Also, we feel that the success we have experienced with this approach to the perturbation problem will be of interest to others confronted with this problem and having the facilities to repeat these measurements for their reactor.

ISSN:0550-3043    

DOI:10.13182/NT69-A28356

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

The utility of238Pu produced from237Np irradiation depends on the amount of236Pu present. Calculations of236Pu produced by the (n,2n) reaction on237Np indicate that light-water power reactors produce238Pu containing 10 to 20 times as much236Pu as that produced in the USAEC D2O-or graphite-moderated plutonium production reactors, and the liquid-metal fast breeders produce 300 to 400 times as much236Pu as the production reactors.

ISSN:0550-3043    

DOI:10.13182/NT69-A28357

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Vandium alloys have been identified as one of the leading alternate cladding materials for liquid-metal-cooled fast breeder reactors for circumventing the possible limitations of austenitic stainless steels. Two of the more important aspects of this usage on which little information is available are sodium corrosion and compatibility with ceramic fuels. In this study, a series of experimental vanadium alloy compositions were found to increase in weight and in hardness after 500-h exposure to flowing sodium containing<10 ppm oxygen at∼790°C; these changes are due to the absorption of oxygen, carbon, and nitrogen. In 1000-h tests at 800°C, some incompatibility was observed only between vanadium alloys containing iron and uranium-carbide fuel. However, these screening tests have identified three vanadium alloy compositions as worthy of further study.

ISSN:0550-3043    

DOI:10.13182/NT69-A28358

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

During the study of the stress-rupture properties of austenitic stainless steels in high-purity static liquid sodium, zirconium foil was placed in the sodium to getter oxygen and maintain a high-purity sodium environment throughout the test. Results of the biaxial stress-rupture tests on thin-walled Type-304 and Type-316 stainless-steel tubing in the range 1200°F (649°C) to 1400°F (760°C) showed that the rupture strength of the tubing was significantly lower in the zirconium-gettered static sodium than in non-gettered static sodium or helium. This reduction in rupture strength was greater with higher test temperature and longer exposure time. In the presence of sodium, the zirconium foil decarburized the stainless steel; the decarburization process also resulted in an extensive sigma-phase formation on the region of the tubing exposed to sodium. The decarburization increased with test temperature and time of exposure. It was concluded that the decreased stress-rupture strength of specimens tested in zirconium-gettered sodium was caused by decarburization of the stainless steel.

ISSN:0550-3043    

DOI:10.13182/NT69-A28359

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

The response of several large area (2 cm2), totally depleted surface-barrier and partially depleted, diffused-junction silicon detectors to beta particles has been investigated in the temperature interval of 300 to 20.2°K. The surface-barrier detectors jailed at liquid nitrogen temperature due to cracking of the epoxy in the lavite ring which is an integral part of the detector.The variation in pulse height, due to mono-energetic betas with temperature in partially depleted detectors, conforms to theory, being mainly due to the change of the energy necessary to create an electron-hole pair. The pulse-height change was∼4 to 5% over the temperature range 300 to 20.2°K. However, some anomalies in the pulse height are observed in the temperature range 30 to 20.2°K during the cooling process.

ISSN:0550-3043    

DOI:10.13182/NT69-A28360

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

Formation of fission-fragment etch pits in glass was investigated with emphasis on the application of the method to the measurement of uranium distributions in solids and low-flux neutron dosimetry. The application of the method to the determination of uranium distributions, in both small and large specimens, was illustrated with specimens∼450µm in diameter and with large, uranium-doped cesium iodide crystals. Upper and lower detection limits for uranium and neutron fluence were established for the glass slides employed. The purpose of the research was to illustrate the applicability of etch-pit techniques to a range of problems in nuclear technology.

ISSN:0550-3043    

DOI:10.13182/NT69-A28361

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

摘要:

This note describes some refinements of the cadmium-difference method of determining epithermal-neutron spectra through the use of ultra-thin detector layers, typical energy groups, and a combination of resonance probes an one support in a“plural foil.”

ISSN:0550-3043    

DOI:10.13182/NT69-A28362

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

ISSN:0550-3043    

DOI:10.13182/NT69-A28364

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor

ISSN:0550-3043    

DOI:10.13182/NT69-A28365

出版商:Taylor&Francis    

年代:1969

数据来源: Taylor