Properties of a thermionic diode placed in an autonomous-discharge plasma

The physical properties of a thermionic diode intr.oduced into an autonomous-discharge plasma in cesium and mercury vapors are considered. In this way, it is possible to obtain increased values of emf and output voltage of the diode, depending mainly on the temperature of the plasma electrons. The distribution of the parameters of the mercury plasma in the interelectrode space of such a diode are measured. Certain conclusions are drawn from the results.Translated from Atomnaya Énergiya, Vol. 18, No. 5, pp. 447–451, May, 1965     

Cesium vapor source based on gas-regulated heat pipe for an autonomous thermionic egc

The results of work on the development of a source of cesium vapor for a thermionic EGC based on a gasregulated heat pipe and investigations of its basic technical characteristics in the cesium vapor range 30–700 Pa are presented. It is shown that the evacuation capacity and zero response time of a gas-regulated heat pipe based vapor source and the possibility of continuously monitoring the cesium vapor pressure via the temperature in the adiabatic zone and the pressure in the gas reservoir are all effective.     

TOPAZ-2型空间核反应堆电源转换器除气研究

结合热离子发电元件工作环境,分析了TOPAZ-2型空间核反应堆电源热离子发电元件除气的必要性。根据电源结构特点,确定氦气腔体、热离子发电元件发射极和接收极、铯集气腔体和冷却剂内套管为主要除气部件。利用CFD程序和专用程序分别计算得到堆芯容器和热离子发电元件额定工况下的工作温度,结合部件除气要求最终确定了各部件除气工况。编制了用于热离子发电元件发射极和接收极除气计算的二维传热程序,通过对比程序计算结果与单根热离子发电元件除气试验结果验证了程序编制的正确性。利用该程序计算得到热离子发电元件发射极和接收极的除气功率。综合电源除气部件除气工况、除气环境要求和除气计算结果,确定了转换器除气方案。     

热离子转换器中添加氧的研究

添加并控制电极间隙内氧的含量对提高热离子转换器（TIC）的能量转换效率和功率密度具有关键作用,因此本文针对TIC中氧的不同添加途径及其对转换性能的影响进行系统研究。吸附氧后的电极在吸附Cs后的功函数较单吸附Cs更低,从而提高了TIC的输出功率密度和转换效率。TIC中氧的添加途径主要有两种：一是利用蒸气源添加,即直接将氧或氧化物以气态的形式添加至电极间隙内;二是利用接收极添加,即通过释放接收极上氧化物的氧或活性过渡金属材料内溶解的氧为电极间隙内供氧。对比分析认为,采用活性金属作为接收极能得到性能更优异、可靠性更高、寿命更长的TIC,因此选择或设计一种新型的接收极材料可作为含氧TIC的一个发展方向。     

Thermionic Analysis by Use of a Digital Computer

As accurate and rapid techniques for analytical performance prediction of thermionic plasma diodes are presently lacking, an IBM digital computer program has been developed to semiempirically predict diode performance. Experimental curves of voltage versus current are presented for tantalum, molybdenum, and rhenium for a wide range of emitter and cesium temperatures. These are processed by the program to determine the optimum efficiency characteristics for various emitter temperatures. Graphical presentations of the processed data indicate the maximum obtainable efficiencies using any of the three emitter materials. The corresponding values of cesium temperature and diode voltage necessary to obtain this efficiency and the corresponding power densities are also presented.     

Thermionic Analysis by Use of a Digital Computer

As accurate and rapid techniques for analytical performance prediction of thermionic plasma diodes are presently lacking, an IBM digital computer program has been developed to semi-empirically predict diode performance. Experimental curves of voltage versus current are presented for tantalum, molybdenum, and rhenium for a wide range of emitter and cesium temperatures. These are processed by the program to determine the optimum efficiency characteristics for various emitter temperatures. Graphical presentations of the processed data indicate the maximum obtainable efficiencies using any of the three emitter materials. The corresponding values of cesium temperature and diode voltage necessary to obtain this efficiency and the corresponding power densities are also presented.     

Current drive operation in a tokamak

Three modes of current drive operation in a tokamak — continuous, cyclic, and rfinitiated-are studied for air core and iron core transformer. It is found that the air core transformer is in general more flexible than the iron core transformer for current drive operation. For continuous operation, the shutoff time of the Ohmic heating circuit of the air core transformer can be reduced to zero by using a bias current. On the other hand, the shutoff time of the iron core transformer remains finite even if the bias current is used, because of hysteresis. For cyclic operation, methods of shortening the recharging time are investigated for both types of transformer. The effects of the transformer on rf-initiated operation are investigated. A model design of a saturable iron core tokamak for current drive experiments is also presented.     

Early construction and operation of the highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (III) – a unique simulation code to evaluate time-dependent Cs adsorption/desorption behavior in column system

A simulation code was developed to evaluate the performance of the cesium adsorption instrument operating in Fukushima Daiichi Nuclear Power Station. Since contaminated water contains seawater whose salinity is not constant, a new model was introduced to the conventional zeolite column simulation code to deal with the variable salinity of the seawater. Another feature of the cesium adsorption instrument is that it consists of several columns arranged in both series and parallel. The spent columns are replaced in a unique manner using a merry-go-round system. The code is designed by taking those factors into account. Consequently, it enables the evaluation of the performance characteristics of the cesium adsorption instrument, such as the time history of the decontamination factor, the cesium adsorption amount in each column, and the axial distribution of the adsorbed cesium in the spent columns. The simulation is conducted for different operation patterns and its results are given to Tokyo Electric Power Company (TEPCO) to support the optimization of the operation schedule. The code is also used to investigate the cause of some events that actually occurred in the operation of the cesium adsorption instrument.     

Study of thermionic energy converter with electromagnetic regulation of working substance pressure

Conclusion A method is proposed for electromagnetic regulation of the size and composition of the working substance vapor fed into the interelectrode gap of a TEC. It is been demonstrated that this method can be used to increase the output electrical parameters and operating efficiency of thermionic converters. Experimental studies were conducted on TECs with cesium and cesium-oxygen vapor source with electromagnetic regulation of the size and stoichiometric composition of the mixture fed into the TEC interelectrode gap. The studies showed that in cesium-oxygen TECs magnetic regulation allows the maximum electrical power of the converter to be raised further, probably because of the more optimal stoichiometric composition of the mixture. A cesium-barium vapor source with magnetic regulation of the stoichiometric composition of the mixture is proposed. Russian Research Center “Kurchatov Institute,” and Sukhumi Physicotechnical Institute, Republic of Georgia. Translated from Atomnaya énergiya, Vol. 85, No. 2, pp. 107–111, August, 1998.     

热离子能量转换器铯电弧工况下电子势能的分布特性

为阐明热离子能量转换器铯电弧工况下电子势能分布的特征,基于动理学方法建立了电极间隙低温弱电离等离子体的输运方程,将等离子体鞘层处理为输运的边界条件。采用牛顿迭代法编制了计算程序,实现了等离子体输运方程与边界条件的自适应解耦求解。研究发现,采用输运理论获得的伏安特性与实验符合较好,随着输出电流密度的增大,发射极鞘层的电子势能跃变产生了由非单调到单调的变化,同时接收极鞘层的电子势能发生跃变方向的改变。     

Volatility of fission products during reactor accidents

This paper summarizes some current generic work on the behaviour of iodine, cesium, and tellurium under conditions expected to occur during postulated reactor accidents. We discuss Knudsen cell experiments to elucidate the high-temperature properties of fission-product mixtures, steam-flashing experiments to measure iodine transfer to the gas phase, and the formation and volatility of organic iodides in aqueous solutions.     

Procedure for extrareactor heating of the electrodes and measurement of the current-voltage characteristics of thermionic multielement power-generating fuel channels

Conclusions A method has been developed for performing extrareactor preloop tests of multielement PGCs by the reverse-current method. An experimental stand equipped with electronic apparatus was developed. Extra reactor tests of single- and multi-element thermionic converters and PGCs with a thermal power of 1–3 kW and cesium vapor pressure of 3–5 hPa were performed. The preloop tests of multielement PGCs by the reverse-current method on thermal stands make it possible to diagnose the quality of a part efficiently at minimum cost. I. N. Vekua Sukhumi Physicotechnical Institute. Translated from Atomnaya énergiya, Vol. 78, No. 2, pp. 88–93, February, 1995.     

Cesium solubility,diffusion and permeation in zirconium carbide

To compare the relative effectiveness of ZrC vis-a-vis SiC as a fission product barrier in fuel structures for high temperature gas cooled reactor (HTGR) applications, a series of cesium infusion experiments on various ZrC powders, and ZrC coated graphite structures was performed to study the cesium solubility, diffusivity, and permeability of this coating material. The ZrC powder results yield a solubility of Cs in ZrC, S(ppm wt) = (1.7 × 10^?6) exp[229 kJ/RT], over the temperature range 1485–1896 K. The diffusion coefficient of Cs in ZrC is 10^?18–10^?16 m²/s over a similar temperature interval. The activation energy of diffusion is estimated to be ≈ 50 kJ/mole.The results of experiments in which both SiC and ZrC coated graphite samples were exposed to cesium are more difficult to interpret. The results support the conclusions of the ZrC powder experiments that ZrC is comparable to SiC as a diffusion barrier to cesium.     

Modeling cesium behavior in nuclear reactor fuels at high temperatures

Cesium has important influences on the steady state and transient behavior of nuclear reactor fuel because of its large fission yield and high volatility. Recent experiments show that the release of cesium coincides with the disruptive behavior of rapidly heated fuel. This report investigates the pressure buildup of cesium in fuel pores during fast power transients. A model was developed which estimates the pressure of cesium in the pores as a function of temperature and oxygen/metal ratio of the fuel. The results of the calculation with this model show that cesium has a higher potential for pressure buildup, at temperatures near the fuel melting point, than xenon. There are, however, open questions which concern the kinetics of the cesium release to the pores, the chemical stability of the cesium compounds, and the microscopic distribution of the cesium.     

Studies on the synthesis and characterization of cesium-containing iron phosphate glasses

Isotopes of cesium and strontium can be utilized as radiation source for various industrial and medical applications after their separation from high level nuclear waste. However, these elements need to be immobilized in a suitable matrix. In the present work, a systematic approach has been made to immobilize inactive cesium into iron phosphate glass. Up to 36 mol% of Cs₂O has been loaded successfully without crystallization. The glass transition temperature of the cesium loaded glass was found to increase initially and then decrease as a function of Cs₂O content. Mössbauer studies show that the concentration of Fe³⁺ ions in the cesium loaded glasses is >95%. Volatilization experiments at 1263 K show that the weight loss is >0.5% for a period of 4 h. The 36 mol% of Cs₂O loaded iron phosphate glass with high Fe³⁺ content described in this paper is reported for the first time.     

从高放废液中萃取铯的杯冠化合物的研究进展

文章概要综述了与从高放废液中去除铯离子有关的杯冠化合物的合成方法和对金属离子的配位识别能力及分子模拟等方面的研究进展情况。 1 ,3 杯 [4]冠 6化合物对铯离子呈现出很强的络合能力 ,是分离铯离子的性能优异的新型萃取剂。     

New Inorganic Sorbent for Ion-Selective Purification of Liquid Radioactive Wastes

The basic physical-chemical properties of a new inorganic sorbent, with the trademark Termoksid-35, and investigations of the sorption-selective properties of this material with respect to cesium isotopes are presented. The results presented demonstrate that the inorganic ion exchanger Termoksid-35 is highly selective in neutral and alkali media to cesium isotopes, despite the presence of a high concentration of salts; this makes it possible to use this ion exchanger for ion-selective purification of liquid radioactive wastes. 5 figures, 1 table, 9 references.     

New-generation space thermionic nuclear power systems with out-of-core electricity generating systems

The basic problems of the development of long service life thermionic nuclear power systems for space applications for supplying power to transport power modules, intended for placing spacecraft in a geostationary orbit using electrorocket motors and for providing prolonged operation of onboard systems for up to 10–15 years, are examined. Concepts for power systems with multi- and single-element thermionic low-temperature energy-conversion systems, which are placed outside the reactor core and in which heat is delivered to the emitters using molybdenum-lithium heat pipes at 1600–1670 K, are discussed as an example. Computational results are presented for the electro- and thermophysical characteristics of electricity generating systems and power systems with different variants of the design-technological solutions, including the possibility of increasing the service life by reserving a part of the thermionic electrical power. The mass/size characteristics of the power systems with basic variants of the systems are obtained and recommendations based on research and development work are made, 8 figures, 8 references. Translated from Atomnaya énergiya, Vol. 89, No. 1, pp. 22–34, July, 2000.     

On the NBI system for substantial current drive in a fusion power plant: Status and R&D needs for ion source and laser neutralizer

The requirements for the heating and current drive systems of a fusion power plant will strongly depend on the DEMO scenario. The paper discusses the R&D needs for a neutral beam injection system — being a candidate due to the highest current drive efficiency — for the most demanding scenario, a steady state tokamak DEMO. Most important issues are the improvement of the wall-plug efficiency from the present ∼25% to the required 50–60% by improving the neutralization efficiency with a laser neutralizer system and the improvement of the reliability of the ion source operation. The demands on and the potential of decreasing the ion source operation pressure, as well as decreasing the amount of co-extracted electrons and backstreaming ions are discussed using the ITER requirements and solutions as basis. A further concern is the necessity of cesium for which either the cesium management must be improved or alternatives to cesium for the production of negative ions have to be identified.     

磷酸锆-磷钼酸铵复合离子交换剂提取铯

研究了浸泡法合成磷酸锆-磷钼酸铵(ZrP-AMP)复合离子交换剂及其在酸性条件下吸附解吸铯,并对硝酸铀酰溶液吸附进行了研究.研究结果表明,提高反应物中盐酸量可以合成能进行柱分离操作的磷酸锆颗粒,ZrP-AMP对铯的交换容量可以达到59mg/g,回收率可以达到80%.