Neutral and ionized alkaline metal bombardment type heavy negative-ion source (NIABNIS)

A new type of high current, heavy negative-ion source has been developed in which simultaneous bombardment of both neutral and ionized alkaline metal particles on a sputter cone is utilized for overcoming the disadvantages of the universal negative ion source and the Aarhus negative ion source. To supply a sufficient amount of neutral and ionized cesium particles onto the sputtering target surface, a plasma cesium ion source is used for the primary cesium ion source, and the distance between the extraction aperture of the cesium ion beam and the sputtering target is minimized. This results in a compact body and high yields of negative ion currents. Two experimental apparatus are used: a prototype source for mainly investigating the operating principle and a high current negative ion production source with a target cooling system. The neutral cesium particle bombardment was found to be effective in increasing the negative ion production efficiency. The target surface temperature also had a great influence on this efficiency. Negative ion production experiments of group III, IV and V elements were mainly made. 320 μA of the C^? ion current and 3 μA of the ¹¹B^? ion current were obtained. Negative ion currents obtained to-date are also given for various targets.     

Modification of an Ion Source for the Production of Microampere 4He- Beams

Several modifications of the ion source of a model EN Tandem Van de Graaff Accelerator have increased the production of 4He- beams by a factor of 100 over that first obtained with the source (~10 nA). While using H2 gas for charge exchange, the replacement of the source drift tube by a screen and the installation of a system for precise adjustment of the button alignment with respect to the extractor electrode increased the output to 150 nA at the ion source. Recently potassium vapor has been used for charge exchange. Since the introduction of this technique, 4He- beam currents of 1. 2 ?A have been regularly produced. The 4He+ ions from a duoplasmatron ion source are accelerated to 20 keV and passed through the standard exchange canal which is modified by the addition of a potassium vapor chamber. Analyzed 4He++ beams of 0.3 to 0.8 ?A have been obtained with terminal voltage between 1.8 and 6 MV. The modified source has been used with K-vapor exchange for continuous periods of up to 120 hours without deterioration of source performance. Normal operation with H2 gas exchange for other beams is possible without the interruption of the source operation.     

用于溅射负离子源的透射表面电离器的研制

介绍了１种应用于表面电离型溅负离子源的球面形透射表面的电离器，并阐述了原理。这种电离器可使铯蒸气直接通过，避免了铯蒸气绕射造成电离表面铯原子通量低的缺点，增大了铯离子的产额也使离子源的流强较采用非透射型电离器时提高了５０－８７％。‘     

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.     

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.     

A Granular Inorganic Cation-Exchanger Selective to Cesium

The investigation results on the structure, sorptive-selective properties and exchange reversibility of the adsorbent selective to cesium cations are presented in this paper. A trade mark of this adsorbent is Termoxid-35. The composition of Termoxid-35 is the “mixed” nickel ferrocyanide distributed over zirconium hydroxide as an inorganic carrier. The structure of the cation-exchanger was studied by the infrared spectroscopy and the X-ray diffraction, differential-thermal and thermo-gravimetric analyses. The adsorbent is the double-phase system consisting of a highly-dispersed amorphous phase of zirconium hydroxide and a micro-crystalline phase of mixed nickel ferrocyanide. The isotherms of cesium cation adsorption in the pH region of 6.2 to 9.6 in the presence of 1 mol/l NaCl are presented. The distribution coefficient for cesium in the Henry region increases with the pH of the solution and reaches 6.5 x 10⁵ cm³/g at pH = 9:6. The distribution coefficient for cesium is more than 1.0 x 10⁴ cm³/g with the concentration of the cation in the solid phase of 0.1 mmol/g. The cesium cation sorption on the ion-exchanger is irreversible.     

Cesium/xenon co-sputtering at different energies during ToF-SIMS depth profiling

In this paper, ToF-SIMS dual beam depth profiles of H-terminated silicon wafers were performed with cesium primary ions and for different beam energies. The aim of this study was to investigate the influence of the cesium beam energy on the secondary ion yields during ToF-SIMS dual beam depth profiling. For this purpose, both the cesium beam energy and the cesium surface concentration were varied but the analysis conditions were kept identical for all depth profiles (i.e. Ga⁺ at 25 keV, 45°). For each sputter beam energy (i.e. 250 eV, 750 eV and 2000 eV), the cesium surface concentration was varied by diluting the cesium sputtering beam by xenon ions. This technique allows performing ToF-SIMS depth profiles with cesium surface concentration varying from zero (for pure xenon beam) to a maximum value (for pure Cs beam), depending on the bombardment conditions. For all the beam energies, the Si⁺ signals were found to decrease with the increasing cesium coverage and the lower the energy, the faster the decrease. The Cs⁺, the SiCs⁺ and the signals were found to exhibit a maximum for well defined Cs/Xe mixtures, which were found to depend on the secondary ion species and on the beam energy. Moreover, the maxima were found to shift to higher Cs beam content with the increasing energy. This effect is due to the variation of the cesium surface concentration with the varying beam energy. XPS analysis of the Cs/Xe craters and DYNTRIM computer simulations allowed us to convert the cesium beam scale to a cesium surface concentration scale and to interpret our results.     

Design of the Prototype Negative Ion Source for Neutral Beam Injector at ASIPP

In order to support the design,manufacture and commissioning of the negativeion-based neutral beam injection(NBI) system for the Chinese Fusion Engineering Test Reactor(CFETR),the Hefei utility negative ion test equipment with RF source(HUNTER) was proposed at ASIPP.A prototype negative ion source will be developed at first.The main bodies of plasma source and accelerator of the prototype negative ion source are similar to that of the ion source for EAST-NBI.But instead of the filament-arc driver,an RF driver is adopted for the prototype negative ion source to fulfill the requirement of long pulse operation.A cesium seeding system and a magnetic filter are added for enhancing the negative ion density near the plasma grid and minimizing co-extracted electrons.Besides,an ITER-like extraction system is applied inside the accelerator,where the negative ion beam is extracted and accelerated up to 50 kV.     

Theoretical study of the adsorption of Cs,Cs+, I,I−, and CsI on C60 fullerene

Theoretical investigation for the adsorption of the cesium atom (Cs), the cesium iodide molecule (CsI), the iodine atom (I), the cesium cation (Cs⁺), and the iodide anion (I^?) onto the surface of a single fullerene molecule (C₆₀) are reported. A hybrid exchange–correlation functional using the Coulomb-attenuating method (CAM-B3LYP) is employed. The adsorption energies, i.e., the opposite of enthalpy change through adsorption, are calculated to be 143, 12, 9, 46, and 49 kJ mol^?1 for Cs, CsI, I, Cs⁺, and I^?, respectively. The equilibrium constant for Cs is calculated to be 7×10³ atm^?1 at the temperature of 1000 K and is seven orders of magnitude higher than that for CsI, indicating that the C₆₀ molecule adsorb the Cs atom highly selectively against the CsI molecule.     

Sorption and Desorption Behavior of 60Co, 85Sr,and 137Cs in a Porous Tuff

Sorption experiments of ⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs were carried out to study sorption characteristics onto a porous tuff. Sorption kinetics and rate controlling step were examined. The effects of particle size on sorption and distribution ratio were also investigated. Desorption experiments were carried out by using extracting reagents to distinguish sorption mechanisms such as reversible sorption in groundwater condition, ion exchange, association with ferro-manganese oxides or oxyhydroxides, and irreversible fixation. Strontium sorbed onto the tuff surface mainly by the ion exchange reaction which was fast and reversible. Cobalt and cesium do not sorb by simple step. The main sorptive binding of cobalt was the association with ferro-manganese oxides and the secondary one was the irreversible fixation. Diffusion into the lattice of rock minerals controlled the sorption rate of cobalt. The main sorption of cesium was the irreversible fixation, secondary one was the ion exchange.     

Some Experiments and a Practical Method on Dosimeter Glass Washing Process

With the object of gaining an insight into cesium behavior in its relation to oxygen concentration in sodium-stainless steel systems, a deposition experiment was carried out with use made of stainless steel capsules containing 20 g of sodium and a trace amount of radioactive cesium.

The capsule was vertically set to establish a steep axial temperature gradient, descending forward the bottom, and maintained during a period considered ample for the sodium oxide contained in excess of saturation to settle on the capsule bottom. The oxygen concentration in the sodium was varied by adjusting the temperature of the capsule bottom. The radial distribution of cesium across samples sectioned from different parts along the length of the capsule tube were determined on annular samples extruded from sections of the capsule after chilling for rapid solidification of the sodium.

The activation energy for cesium deposition was obtained from partition coefficients—defined as the ratio of cesium concentration on the stainless steel surface and that in the bulk sodium. The resulting data on activation energy indicate that cesium radioisotope deposits in the temperature region below 440°C presumably by physical adsorption on the stainless steel surface when it has previously been exposed to high temperature sodium, and that this surface adsorption appears to be insensitive to differences in oxygen concentration in the sodium.     

Distribution Coefficient of Cesium and Cation Exchange Capacity of Minerals and Rocks

The sorption behavior of cesium on a variety of minerals and rocks has been investigated by batch equilibration using ¹³⁷Cs. The distribution coefficient (K_d) of cesium increased with decreasing concentration of cesium and approached a constant value in dilute regions. The distribution coefficients determined at a trace level (K_dt,tr) differed more than four orders of magnitude strongly depending on the kinds of samples, for example, about 30 on quartz and 10⁵ on tuffs. The values of K_d,tr are related to the cation exchange capacity (CEC; meq/g) determined from the saturated sorption of cesium for individual samples as : log K_{d, tr} =log CEC + constant. Most K_{d, tr} values were found to approximately follow this linear relationship.     

Molten Salt Oxidation of Ion-exchange Resins Doped with Toxic Metals and Radioactive Metal Surrogates

Ion-exchange resins doped with toxic metals and radioactive metal surrogates were test-burned in a bench-scale molten salt oxidation (MSO) reactor system. The purposes of this study are to confirm the destruction performance of the two-stage MSO reactor system for the organic ion-exchange resin and to obtain an understanding of the behavior of the fixed toxic metals and the sulfur in the cationic exchange resins. The destruction of the organics is very efficient in the primary reactor. The primarily destroyed products such as carbon monoxide are completely oxidized in the secondary MSO reactor. The overall collection of the sulfur and metals in the two-stage MSO reactor system appeared to be very efficient. Over 99.5% of all the fixed toxic metals (lead and cadmium) and radioactive metal surrogates (cesium, cobalt, strontium) remained in the MSO reactor bottom. Thermodynamic equilibrium calculations and the XRD patterns of the spent salt samples revealed that the collected metals existed in the form of each of their carbonates or oxides, which are non-volatile species at the MSO system operating conditions.     

铯在钨(110)表面吸附行为的第一性原理研究

通过基于密度泛函理论的第一性原理计算方法,研究了铯原子在钨(110)表面上的吸附行为。计算结果表明,通过原子数之比定义的最大单层铯原子吸附率为0.4,铯原子的吸附位置随吸附率的增加而变化。铯原子吸附率为0.25时,最可能的吸附位置是长桥,而铯原子吸附率达0.4时,铯原子在钨(110)表面形成完整的单原子层,并呈现-ABA′B′-结构形式。随铯原子吸附率的增加,表面功函数先减小后增大,最终稳定在2.134 eV,其中最小值1.524 eV出现在吸附率为0.25时,该最小值低于纯铯(110)表面的功函数。偶极子模型和分态密度计算结果表明,铯原子向钨基体表面的电子转移机制和铯原子电子能量分布的变化是造成表面功函数降低的原因。     

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.     

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.     

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.     

相转移法制备137Cs 3D打印用光敏树脂的可行性研究

为弥补目前国内外精密异形放射源制备工艺的不足,将3D打印技术引入放射源制备领域。本研究采用相转移方法制备¹³³Cs 3D打印用光敏树脂,使用高分辨电感耦合等离子体质谱(ICP-MS)进行检测,探索制备条件。并通过溴化镧探测器对制备的¹³⁷Cs 3D打印用光敏树脂材料进行检测。结果表明,通过相转移方法制备的三种¹³³Cs 3D打印用光敏树脂和¹³⁷Cs 3D打印用光敏树脂中铯元素分布不均匀度<5%。相转移法作为一种操作简便、反应条件温和的方法可用于制备含有铯元素的3D打印用光敏树脂,且具有一定普适性。     

亚铁氰化钾钛吸附Cs^＋的机理研究

研究了亚铁氰化钾钛在模拟酸性高放废液中吸附Ｃｓ＋的行为。实验研究了温度、粒度、振荡频率、Ｃｓ＋浓度等因素对Ｃｓ＋吸附速度的影响，测定了吸附过程中亚铁氰化钾钛组分随所吸附的Ｃｓ＋量的变化。与亚铁氰化钾钛在ＣｓＮＯ３溶液中吸附Ｃｓ＋的行为相比较可知，亚铁氰化钾钛对Ｃｓ＋的吸附主要是粒扩散和膜扩散混合控制，是亚铁氰化钾钛中的Ｋ＋与溶液中的Ｃｓ＋进行了交换。