Villalpando: sigue al N. ISSN Valladolid: Reno, , v. Barcelona: Labor. ISBN Archivado desde el original el 23 de noviembre de He reports the use of this method for the study of various reactions in non-aqueous medium: reaction of AlCl 3 with pyridine in acetonitrile, of AlCl 3 with HCl in tetrachloroethane and in nitromethane.
Development of on-line uranium enrichment monitor of gaseous UF 6 for uranium enrichment plant. An on-line enrichment monitor was developed to measure the enrichment of UF 6 , flowing through the processing pipes in uranium enrichment plant. A Nal Tl detector was used to measure the count rates of the Uranium enrichment of gaseous uranium hexafluoride in the output end of cascade can be monitored continuously by using the device.
It should be effective for nuclear materials accountability verifications and materials balance verification at uranium enrichment plant. Measurements of uranium enrichment in UF 6 transit cylinders are an important nuclear safeguards verification task, which is performed using a non-destructive assay method, the traditional enrichment meter, which involves measuring the count rate of the keV gamma ray. This provides a direct measure of the U enrichment.
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Measurements are typically performed using either high-resolution detectors Germanium with e-cooling and battery operation, or portable devices equipped with low resolution detectors NaI. Despite good results being achieved when measuring Low Enriched Uranium in 30B type cylinders and natural uranium in 48Y type containers using both detector systems, there are situations, which preclude the use of one or both of these systems. The focus of this work is to address some of the recognized limitations in relation to the current use of the above detector systems by considering the feasibility of an inspection instrument for U enrichment measurements on UF 6 cylinders using the compact and light Cadmium Zinc Telluride CZT detectors.
In the present work, test measurements were carried out, under field conditions and on full-size objects, with different CZT detectors, in particular for situations where existing systems cannot be used e. A Model 48Y cylinder containing UF 6 ruptured upon being heated after it was grossly overfilled. The UF 6 released upon rupture of the cylinder reacted with airborne moisture to produce hydrofluoric acid HF and uranyl fluoride UO 2 F 2.
One individual died from exposure to airborne HF and several others were injured. There were no significant immediate effects from exposure to uranyl fluoride. In developing a response to each of the recommendations, the staff considered actions that should be taken: 1 for the restart of the Sequoyah Fuels Facility; 2 to make near-term improvement; and 3 to improve the regulatory framework. Thermodynamic properties of a high pressure subcritical UF 6 He gas volume irradiated by an external source. A computer simulation study concerning a compressed fissioning UF 6 gas is presented. The compression is to be achieved by a ballistic piston compressor.
Data on UF 6 obtained with this compressor were incorporated in the simulation study. As a neutron source to create the fission events in the compressed gas, a fast burst reactor was considered. As the first line of defense against proliferation, accurate analytical techniques to determine the uranium isotopic distribution in UF 6 are critical for materials verification, accounting, and safeguards at enrichment plants.
As nuclear fuel cycle technology becomes more prevalent around the world, international nuclear safeguards and interest in UF 6 enrichment assay has been growing. At present, laboratory-based mass spectrometry MS , which offers the highest attainable analytical accuracy and precision, is the technique of choice for the analysis of stable and long-lived isotopes. The logistics are cumbersome and new shipping regulations are making it more difficult to transport UF 6. Furthermore, the analysis is costly, and results are not available for some time after sample collection.
Hence, the IAEA is challenged to develop effective safeguards approaches at enrichment plants. In-field isotopic analysis of UF 6 has the potential to substantially reduce the time, logistics and expense of sample handling. However, current laboratory-based MS techniques require too much infrastructure and operator expertise for field deployment and operation. Heat transfer characteristics of UF 6 in a container heated from outer surface.
Thermal hydraulic analysis method taking account of phase change and volume expansion.
Natural UF 6 is transported in a steel container from foreign countries to the enrichment plant in Japan. If the container meets fire accident, it is heated by fire degC and rupture of the container may occur. For the safety point of view, it is necessary to know whether rupture occurs or not.
Because UF 6 has a radiological and chemical hazards, it is difficult to perform a demonstration test with UF 6. So thermal calculation method has to be developed. The rupture is caused by UF 6 gaseous pressure or volume expansion of liquid UF 6. To know time history of internal pressure and temperature distribution in the container, it is important to evaluate thermal phenomena of UF 6. When UF 6 is heated, it changes from solid to liquid or gas at low temperature 64degC and then its volume expands little by little.
In this study, thermal calculation method has been developed taking phase change and thermal expansion of UF 6 into account. In the calculation, a two-dimensional model is adopted and natural convection of liquid UF 6 is analyzed. As a result of this study, numerical solutions have been obtained taking phase change and volume expansion into account. From the Lab to the real world : sources of error in UF 6 gas enrichment monitoring. Safeguards methods have changed over the years, most recently switching to an improved safeguards model that calls for new technologies to help keep up with the increasing size and complexity of today's gas centrifuge enrichment plants GCEPs.
One of the primary goals of the IAEA is to detect the production of uranium at levels greater than those an enrichment facility may have declared. In order to accomplish this goal, new enrichment monitors need to be as accurate as possible. Specifically explored are various factors that could potentially contribute to errors in a final enrichment determination delivered by the AEM.
There are many factors that can cause errors in the determination of uranium hexafluoride UF 6 gas enrichment, especially during the period when the enrichment is being measured in an operating GCEP.
To measure enrichment using the AEM, a passive keV kiloelectronvolt measurement is used to determine the U content in the gas, and a transmission measurement or a gas pressure reading is used to determine the total uranium content. A transmission spectrum is generated using an x-ray tube and a 'notch' filter. In this dissertation, changes that could occur in the detection efficiency and the transmission errors that could result from variations in pipe-wall thickness will be explored. Additional factors that could contribute to errors in enrichment measurement will also be examined, including changes in the gas pressure, ambient and UF 6 temperature, instrumental errors, and the effects of uranium deposits on the inside of the pipe walls will be considered.
The sensitivity of the enrichment calculation to these various parameters will then be evaluated. Previously, UF 6 gas enrichment. We report a convenient method for the generation of volatile uranium hexafluoride UF 6 from solid uranium oxides and other U compounds, followed by uniform deposition of low levels of UF 6 onto sampling coupons.
Under laminar flow conditions, UF 6 is shown to interact with surfaces within a fixed reactor geometry to a highly predictable degree. We demonstrate the preparation of U deposits that range between approximately 0.
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The data suggest the method can be extended to creating depositions at the sub-picogramcm -2 level. The isotopic composition of the deposits can be customized by selection of the U source materials and we demonstrate a layering technique whereby two U solids, each with a different isotopic composition, are employed to form successive layers of UF 6 on a surface. The result is an ultra-thin deposit that bears an isotopic signature that is a composite of the two U sources.
Further, the method allows access to very low atomic or molecular coverages of surfaces. All rights reserved. Neutron methods for measuring U content in UF 6 gas. In the United States and Russia, UF 6 gas streams of highly enriched uranium and lower enrichment uranium am being blended to reduce the stockpile of the highly enriched material. The resultant uranium is no longer useful for weapons, but is suitable as fuel for nuclear reactors.
In the United States, blending occurs at the U. In Russia, the blending takes place at Novouralsk.
The United States is purchasing the blended product produced in Russia in a program to reduce the availability of enriched uranium that can be used for weapons production. Monitoring the U mass flux of the input stream having the highly enriched uranium will provide confidence that high-enrichment uranium is being consumed in the blending process, and monitoring the output stream will provide an on-line measure of the U in the mixed product. The Portsmouth plant is a potential test facility for non-destructive technology to monitor blending.
In addition, monitoring the blending at Portsmouth can support International Atomic Energy Agency activities on controlling and reducing enriched uranium stockpiles. Investing in UF 6 long-term security of supply. The front-end nuclear fuel supply chain for LWRs encompasses four major industrial stages that are mining and concentration, conversion, enrichment, and eventually fuel fabrication. The different stages involve uranium in different chemical and physical forms. Enrichment of the U fissile isotope requires gaseous UF 6.
As the standard output of mine is U3O8, referred to as ''yellow cake'', a purely chemical stage is therefore needed to fluorinate U3O8 and turn it into UFe: this is the conversion stage. U3O8 inventories management is thus performed at the conversion sites. Purification of the mining concentrates is also needed prior to actual conversion into UFe. This step is important because the front-end supply chain facilities have strict specifications concerning impurities. With the Comurhex 2 project, AREVA is not only shaping the future of conversion market and contributing to the security of supply of its customers, but it is also developing innovative techniques and reorganizing the conversion process steps.
Providing such guaranteed and valuable conversion supply with a brand new plant is our strong commitment to a sustainable nuclear fuel cycle. The three main axes of sustainable development, economical, social, and environmental, are truly taken into account in the development of the new project. Measurement of U enrichment in UF 6 by passive gamma spectrometry. For the assay of UF 6 , a single-channel analyzer SCA system of a passive gamma spectrometer has been developed.
Basic measuring conditions were studied: such as the effects of sample density and heterogeneity and the effects of cylinder material and wall thickness.