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讨论了有外加磁场情况下,强流相对论电子束传输过程中的电荷中和理论,着重讨论了二次电子逃逸时间和外加磁场对空间电荷中和的影响。得知当电子束半径大于2.0 cm 时,在计算空间电荷中和时间时就得考虑二次电子逃逸时间的影响。在一定条件下,外加磁场对空间电荷中和有阻碍作用,对于长漂移室,存在空间电荷中和允许的磁感应强度上限。 相似文献
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《中国原子能科学研究院年报(英文版)》2018,(0)
正电子束3D打印光路仅由1个螺线管和1个偏转磁铁构成,虽然其结构简单,但是要求束斑尺寸达到0.1mm左右,这对于10mA/60kV的强流低能电子束的难度很大,特别是光路还要求大角度偏转。对于无偏转光路,采用Trace3D对光路进行动力学计算的结果如图1所示,螺线管场强为103G。电子束传输过程中的电荷中和率为0.1%,即电流实际流强为10 mA,电荷中和后的流强为0.01mA,所得束斑半径为0.09mm。 相似文献
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本文从等离子体中材料产生的新观点评述了加工等离子体中的尘埃现象,已对SiH,RF等离子体广泛地研究了粒子的气体生长,Si粒子通常通过三个不同的阶段生长,厚约10nm之前的初始生长阶段,其大小是在由等离子体性能及其电子亲合力支配的大小范围内:快速生长阶段和生长饱和阶段,在第一阶段,尽管大部分是中性粒子,但是粒子定域在等离子体/鞘边界附近,在第二阶段,出闰子间极快凝结,这种凝结可用由于高能电子而产生带 相似文献
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在核电站安全壳压力试验过程中,由于涂层油漆及维修化学药品挥发而产生的可燃气体易发生扩散、富集现象,加之于高温高压的试验环境,进一步增加了火灾发生的风险。为提高压力试验的安全性和可靠性,本文基于爆炸极限试验模拟及理论模型计算,对压力试验环境下7种常见的可燃性气体及其混合可燃物的爆炸极限变化规律展开研究。研究结果表明:安全壳内混合可燃物中苯、二甲苯、乙酸乙酯、甲苯等爆炸下限较低的可燃性气体所占的体积分数越大,压力试验过程中发生火灾的风险越高;初始压力的增加增大而造成爆炸的可能性较小;爆炸极限范围随着初始温度的升高而增大,尤其是爆炸下限的降低增加了安全壳内可燃气体爆炸的风险性。 相似文献
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Collective acceleration methods that employ an intense relativistic electron beam (IREB) are discussed. A brief history and a classification of collective acceleration methods are given. Methods examined include IREB injection into neutral gas; IREB injection into vacuum; plasma-filled IREB diodes; and vacuum-filled IREB diodes. Accelerating fields of order 106 V/cm have been observed experimentally. The collective acceleration processes for IREB injection into neutral gas and vacuum are discussed. It is noted that the collective acceleration processes for IREB diodes have not been elucidated yet. A summary of present collective ion acceleration research areas that involve IREB's is given. 相似文献
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The method used to develop sorption-extraction processes in uranium hydrometallurgy over the last 50 years is examined. The first-generation sorption-extraction processes, ionites, and apparatus are described. Data for the second-generation sorption-extraction technology and improvement of apparatus are generalized.The third generation of these processes is characterized by the adoption of porous anionites AM-p and AMP-p in order to make the kinetic characteristics of the sorption and extraction processes closer to one another, by sorption leaching of uranium ores, and by adoption of double synergetic mixtures of extracting agents at the stage of repurification of the commercial reclaim and by the development of fast sorption processes for extracting uranium from productive solutions used in mound and underground leaching. The fourth-generation processes are characterized by the use of high-volume vinyl pyridine ionites, tertiary synergetic mixtures at the extraction stage, combined extraction-desorption processes, solid-phase regeneration of saturated ionites, and conversion of absorbed anions of uranyl-trisulfate into nitrate and chloride complexes. 1 figure. 相似文献
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Abderrafi M. Ougouag Jan Leen Kloosterman Wilfred F.G. van Rooijen Hans D. Gougar William K. Terry 《Nuclear Engineering and Design》2006,236(5-6):669-2004
Models and methods are presented for determining practical limits of the packing density of TRISO particles in fuel pebbles for a pebble-bed reactor (PBR). These models are devised for designing and interpreting fuel testing experiments. Two processes for particle failure are accounted for: failure of touching particles at the pressing stage in the pebble manufacturing process and failure due to inner pressure buildup during irradiation. The second process gains importance with increasing fuel temperature, which limits the particle packing density and the corresponding fuel enrichment. Suggestions for improvements to the models are presented. 相似文献
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《等离子体科学和技术》2020,22(9):94015
The multi-cusped field thruster is a unique electric thruster device, which has many advantages such as long lifetime, large-range thrust throttling ability, high thrust density, and low mass. The thruster employs several alternating polarity permanent magnets to create a periodic magnetic field with several cusps. Previous studies have indicated that the basic ionization and acceleration processes are directly related to the electron motion behavior, which mainly depends on the magnetic field characteristics. The magnet number and magnet stage length are two key magnetic field parameters that have important effects on the thruster performances. In this paper, both the magnet number and magnet stage length parameters are studied for the optimization of a 5 k W multi-cusped field thruster. The results indicate that the three-stage thruster has a better electron confinement than the two-stage thruster. It has lower ion energy loss at the wall, and shows a higher ionization rate. Therefore, the three-stage magnetic field is a superior magnetic field configuration. Besides, the three-stage magnetic field simulation results indicate that an optimal accelerating electric field distribution and ionization region distribution could be obtained when the magnet length ratio is 78:25:20. 相似文献
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Matrix-assisted pulsed laser evaporation of polymeric materials: a molecular dynamics study 总被引:1,自引:0,他引:1
Tatiana E. Itina Leonid V. Zhigilei Barbara J. Garrison 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2001,180(1-4):238-244
Matrix-assisted pulsed laser evaporation (MAPLE) has been recently developed to deposit high-quality thin films for a wide range of polymeric materials. To analyze the evaporation of polymer molecules in MAPLE, we present a molecular dynamics (MD) simulation of laser ablation where the target material is modeled as a solution of polymer molecules in a molecular matrix. The breathing sphere model is used for MD simulations of laser ablation of the molecular matrix. Polymer molecules are described using a bead-spring model, where each bead represents one or several polymer groups. The initial stage of polymer ejection is investigated at different laser fluences and pulse durations. The influence of polymer molecules on the stability of clusters formed in the plume and the processes that can lead to polymer decomposition are discussed. 相似文献
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Pradip Saha Robert E. Gamble Bharat S. Shiralkar James R. Fitch 《Nuclear Engineering and Design》2009,239(5):956-963
This paper discusses the scaling methodology used by GE Hitachi Nuclear Energy (GEH) to show that the data obtained from the small-scale integral test facilities, namely, GIST and GIRAFFE-SIT, are relevant to the postulated loss-of-coolant accident (LOCA) of the 4500 MWt ESBWR. The conservation of mass and energy equations for the steam-water mixture in the reactor pressure vessel (RPV) are transformed to the equations for the rates of pressure change and water mass or inventory change. These equations are non-dimensionalized based on the most dominant physical processes of the individual stages of a LOCA, namely, the late blowdown stage, the GDCS (gravity driven cooling system) transition stage and the full GDCS stage. The magnitudes of the non-dimensional Pi-groups, obtained from these equations, for the 4500 MWt ESBWR are compared with those obtained for the small-scale integral tests mentioned earlier. In addition, simplified analyses were conducted for the first two stages by integrating the non-dimensional RPV depressurization rate and the water inventory change rate equations. The results of the 4500 MWt ESBWR are very similar to the test data obtained from the GIST and the GIRAFFE-SIT test facilities. Therefore, based on both the Pi-group magnitudes and the simplified analyses, it is concluded that the small-scale integral test data mentioned above are applicable to the 4500 MWt ESBWR LOCA applications. 相似文献
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V. V. Seliverstov 《Atomic Energy》2002,93(3):718-726
The basic elements of a method of numerical simulation of processes based on prompt and delayed neutrons in multiplying systems are presented. The method is based on predicting the contribution of the instantaneous state of the system to its state at subsequent definite times and summing the predicted contribution as a systematic transition is made to a new moment in time. The key element of the method is determining the initiation functions – the probabilities that a neutron emitted by a source in a prescribed volume of the system initiates a prompt fission neutron in a definite volume of the system sometime after emission. A procedure is proposed for determining the initiation functions; this procedure is based on the first-collision probability method and uses the standard stationary computer codes. The material presented in this paper comprises the basic results of the first stage in the development of the numerical model for full-scale simulation of the dynamics of the subcritical blanket of an experimental accelerator-driven subcritical system under construction at the Institute of Theoretical and Experimental Physics. It is noted that the model being developed can be used to analyze many important processes in other types of multiplying systems. 相似文献
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《Packaging, Transport, Storage and Security of Radioactive Material》2013,24(4):253-260
AbstractThe role of United Kingdom Nirex Ltd is to provide the UK with safe, environmentally sound and publicly acceptable options for the long-term management of radioactive materials generated by the UK's commercial, medical, research and defence activities. An important part of this role is to set standards and specifications for waste packaging. Waste producers in the UK are currently developing processes for packaging many different types of intermediate-level waste (ILW), and also those forms of low-level waste that will require similar management to ILW. When packaging processes are at the proposal stage, the waste producers consult Nirex about the suitability of the resulting packages for all future aspects of waste management. The response that Nirex provides is based on detailed assessments of the proposed packages, their compliance with Nirex standards and specifications, and their predicted performance through the successive phases of waste management. One of those phases is transport through the public domain. This paper draws on experience gained from more than 200 separate transport safety assessments which have cumulatively covered a wide range of waste types, waste packages and transport packages. 相似文献
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Lucien Bertron 《Nuclear Engineering and Design》1989,114(2)
The good management of the life potential of nuclear plants requires the availability of life indicators which the operators have to keep under control. The best indicators are these prepared and developed for the early stage of the equipments design. Due to the progress accomplished in the 2 or 3 past decades, the design by analysis of the resistance of main components to various mechanical damages supplies several such indicators which can be followed in service by convenient processes. Further progresses are still strongly wished for damages and equipments which are not still covered by such analysis. 相似文献