Thermal properties of polycrystalline NdN bulk samples with various porosities

Neodymium mononitride (NdN) pellets with various porosities were prepared by a spark plasma sintering (SPS). The thermal expansion, specific heat capacity and thermal conductivity were measured and compared with those of uranium mononitride (UN), because NdN exists in the irradiated nitride fuels. The thermal expansion and specific heat capacity of NdN were very similar to those of UN. The thermal conductivity of the porosity-free NdN was estimated from the porosity dependence of the thermal conductivity. Unlike the case of the thermal conductivity of UN, that of NdN decreased with increasing temperature.     

Commercial dielectric coated mirrors for ITER diagnostic applications

We report the results obtained for different types of dielectric coated mirrors obtained from two manufacturers. They include standard visible to IR, UV enhanced, and multilayer enhanced narrow range (“cold”) mirrors. Good radiation resistance has been observed for all the mirrors tested, with no marked degradation following gamma irradiation up to doses of 50 and 60 MGy at 170 °C in dry nitrogen atmosphere, but mirrors provided as identical in the same batch have very different reflectivities (as previously reported for other manufacturers). Furthermore specifications given for the overcoating materials are completely unreliable. The preference for SiO₂ overcoating rather than SiO for corrosion protection has been confirmed.     

Columbia University microbeam：development of an experimental system for targeting cells individually with counted particles

Columbia University microbeam was constructed in 1993 and finished by the end of 1995,It is well established and used routinely to irradiate cells in a highly localized spatial region with a defined number of α-particles,By using this probe,it is possible to study a number of radiobiological questions in ways that cannot be simulated by using conventional broad-field exposures.This report describes the development and current capabilities of the Columbia University microbeam,as well as the preliminary researches undertaken.     

Safety assessment for the ultimate heat sink (UHS) system with non-injection concept in nuclear power plants (NPPs)

Following the Fukushima accident, it is proposed to find a better safety system, which has a pool-type cooling system without coolant injections. Since the conventional piping-based injection systems have failed in treating the three major severe accidents, the artificial pool could be constructed to cover the failed reactor core systems in which the pool-like structure is constructed. Regarding this study, there were some previous studies about the ultimate heat sink (UHS). In this study, the system dynamics (SD) modeling is performed in the case of Fukushima Unit 1 accident. The basic events are obtained by the Boolean values as 0 and 1. The quantifications are obtained by the SD algorithm incorporated with the Vensim software. In the simulations work, there is a plateau region between the 25th and 45th years in the interested period. The nonlinear algorithm is applied for the UHS analysis which was not installed for the commercial use yet.     

Structural analyses for equatorial and lower ports of the ITER vacuum vessel

To investigate the structural integrity of the ITER vacuum vessel (VV) and ports, the structural analyses of the regular equatorial and the lower remote handling (RH) ports have been performed. The advanced design of the equatorial regular port adopting a pure friction type flange has been recommended as a reference design by the ITER International Organization. The structural integrity of the equatorial port flange, sealing unit, and connecting duct has been reviewed by conducting nonlinear finite element analyses. The advanced design of the regular equatorial port flange with proper pretension is acceptable in the structural design point of view.From the local analyses for a connecting duct and a sealing unit, it has been found that the stresses are less than the allowable values.The structural analyses of the lower RH port have been also performed to verify the capability for supporting the VV. Since high local stress occurs at the gusset and supporting block, the case study for the lower port has been conducted to mitigate the stress concentration and to modify the component design. The strength of the lower RH port structures can be improved by the design modification of poloidal and toroidal gusset.     

Experimental investigation of the overall residence time of pebbles in a pebble bed reactor (PBR) using radioactive pebble

The granular flow of pebbles in a pebble bed reactor (PBR) under the influence of gravity is a dense granular flow with long-lasting frictional contacts. The basic governing physics is not fully understood and hence the dynamic core of a PBR and non-idealities associated with pebbles flow inside the reactor core are of non-trivial significance from the point of view of safety analyses, licensing, and thermal hydraulics. In the current study, overall and zonal pebbles residence time investigation is carried out by implementing noninvasive radioisotope-based flow visualization measurement techniques such as residence time distribution (RTD) and radioactive particle tracking (RPT). The characteristics of overall pebble residence time/transient number, zonal residence time, and the z-component of average zonal velocities at different initial seeding positions of a tracer particle have been summarized. It is found that the overall pebbles residence time/transient number increases (the z-component of average zonal velocities decreases) from the center towards the reactor wall. Also, pebbles’ zonal residence time results (the whole core is divided into three zones) which provide more insight and understanding about PBR core dynamics have been reported. The benchmark data provided could be used for assessment of commercial/in-house computational methodologies related to granular flow investigations.     

An integrated high-performance beam optics-nuclear processes framework with hybrid transfer map-Monte Carlo particle transport and optimization

An integrated beam optics-nuclear processes framework is essential for accurate simulation of fragment separator beam dynamics. The code COSY INFINITY provides powerful differential algebraic methods for modeling and beam dynamics simulations in absence of beam-material interactions. However, these interactions are key for accurately simulating the dynamics of heavy ion fragmentation and fission. We have developed an extended version of the code that includes these interactions, and a set of new tools that allow efficient and accurate particle transport: by transfer map in vacuum and by Monte Carlo methods in materials. The new framework is presented, along with several examples from a preliminary layout of a fragment separator for a facility for rare isotope beams.     

An axial xenon oscillation model

A two-point xenon oscillation model was developed for PWRs. The model employs the nonlinear xenon and iodine balance equations and the one group, one-dimensional neutron diffusion equation having nonlinear power reactivity feedback. A two-term spatial harmonic series solution was assumed for the flux, xenon and iodine distributions. The system was made as close to critical as possible with the assumed distributions using a variational principle. The xenon and iodine concentrations were then obtained from their governing differential equations.The input/output nature of the model makes it ideal for simulation of xenon-induced reactor transients. A comparison of the simulated plant to actual plant data was made. The period of oscillation, stability index and flux amplitude of the simulated plant were all found to match the actual plant data with less than 10% error.     

基于MPS方法的液态铅铋合金内气泡上升流数值模拟

移动粒子半隐式(MPS)方法捕捉多相流体动力学相界面的能力比传统网格方法具有明显优势.本研究采用MPS方法,使用FORTRAN语言自编程序,对单个氩气气泡在液态铅铋合金内从静止到充分发展整个过程中的瞬态动力学行为进行二维数值模拟,得到气泡变形特性与上升速度的关系.结果表明:在气泡上升过程中,气泡由球形先变成酒窝形状,最...     

Nonlinear optical properties of MeV and keV ion beam synthesized Ag nanoclusters

Ag nanoclusters embedded in silica glass matrix have been synthesized by high fluence ion implantation using both keV and MeV ion beams. In keV implantation case, optical absorption shows an intense surface plasmon resonance (SPR) peak corresponding to the Ag clusters formed in the matrix. Transmission electron microscopy (TEM) measurements carried out on identically implanted SiO₂ thin films on a TEM catcher grid shows the presence of Ag nanoclusters of size around 4 nm in the matrix. However, for the MeV implantation case, the SPR peak appears in the optical absorption spectra only after air annealing the sample at 500 °C for one hour. For the annealed samples, TEM measurements show the presence of 6 nm sized Ag nanoclusters. On the other hand the as-implanted sample shows smaller nanoclusters with a lower particle density in the matrix. Interestingly, open aperture z-scan measurements carried out on keV implanted samples did not show any nonlinear absorption, while the MeV as-implanted as well as annealed samples showed nonlinear absorption. The nonlinear absorption coefficient of the MeV annealed sample is extracted from a fit to the z-scan data considering a three photon like absorption process.     

Development of plasma sources for Dipole Research EXperiment (DREX)

Dipole Research EXperiment(DREX) is a new terrella device as part of the Space Plasma Environment Research Facility(SPERF) for laboratory studies of space physics relevant to the inner magnetospheric plasmas. Adequate plasma sources are very important for DREX to achieve its scientific goals. According to different research requirements, there are two density regimes for DREX. The low density regime will be achieved by an electron cyclotron resonance(ECR) system for the ‘whistler/chorus' wave investigation, while the high density regime will be achieved by biased cold cathode discharge for the desired ‘Alfvén' wave study. The parameters of ‘whistler/chorus' waves and ‘Alfvén' waves are determined by the scaling law between space and laboratory plasmas in the current device. In this paper, the initial design of these two plasma sources for DREX is described. Focus is placed on the chosen frequency and operation mode of the ECR system which will produce relatively low density ‘artificial radiation belt' plasmas and the seed electrons, followed by the design of biased cold cathode discharge to generate plasma with high density.     

电离辐射对大鼠脑组织中稀醇化酶、S-100蛋白表达的影响

观察了超大剂量6MeV电子线照射后大鼠脑组织NSE、S-100蛋白的动态变化.对成熟的(Sprague-dawle,SD)大鼠用6MeV电子线进行10Gy、20Gy和30Gy全脑单次照射,应用免疫组织化学法测定大鼠脑损伤后不同时间、不同剂量脑组织中稀醇化酶(Neuro-specific enolase,NSE)、S-100蛋白的相对含量.60只大鼠随机分为对照组和实验组,用6MeV电子线对实验组大鼠进行20Gy全脑单次垂直照射,分别于照射后1d、7 d、14 d和30 d处死大鼠,取其脑组织,用免疫组织化学法测定NSE、S-100蛋白的相对含量,并与对照组进行比较.在上述时间点,脑内海马区S-100和NSE表达有时间规律,照射后7 dS-100蛋白的表达和照射后24h NSE的表达组间存在一定差别.与对照组相比,实验组大鼠脑组织中NSE表达显著下降(p＜0.05),S-100表达显著升高(p＜0.05).在照射后7 d,上述各指标变化的幅度为30Gy组＞20Gy组＞10Gy组.电离辐射可诱导脑组织中S-100蛋白的表达,同时下调NSE在神经元中的表达,脑组织中S-100和NSE表达水平的变化可作为辐射诱导的急性脑损伤的敏感指标.     

Investigation of the compact torus plasma motion in the KTX-CTI device based on circuit analyses

Compact torus (CT) injection is one of the most promising methods for the central fuelling of next-generation reactor-grade fusion devices due to its high density, high velocity, and self-contained magnetised structure. A newly compact torus injector (CTI) device in Keda Torus eXperiment (KTX), named KTX-CTI, was successfully developed and tested at the University of Science and Technology in China. In this study, first, we briefly introduce the basic principles and structure of KTX-CTI, and then, present an accurate circuit model that relies on nonlinear regression analysis (NRA) for studying the current waveform of the formation region. The current waveform, displacement, and velocity of CT plasma in the acceleration region are calculated using this NRA-based one-dimensional point model. The model results were in good agreement with the experiments. The next-step upgrading reference scheme of the KTX-CTI device is preliminarily investigated using this NRA-based point model. This research can provide insights for the development of experiments and future upgrades of the device.     

硫酸铀酰体系中混合萃取剂的研究

试验考察了以7301,TBP,P204和醋酸丁脂 煤油组成的混合萃取体系对硫酸铀酰的萃取情况,同时分别考察了7301,TBP,P204和醋酸丁脂各组分对铀纯化效果的影响。通过小型试验、台架试验和扩大试验,筛选出混合萃取体系的最佳组成,同时确定了以黄饼为原料制备核电级U3O8的工艺流程和工艺参数。试验结果表明:醋酸丁脂虽有助于两相的分离,但溶解损失过大,不宜用作相改良剂;阳离子萃取剂P204可萃取一定量的阳离子杂质,不宜加入;中性分子萃取剂TBP与三脂肪胺一同使用时,其相改良剂的作用优于传统的高碳醇,需要加入;阴离子萃取剂7301可以萃取硫酸铀酰溶液中呈阴离子状态的UO2(SO4)32-。最终确定新混合萃取体系为7301 TBP的煤油溶液。     

X波段2MeV行波电子直线加速管的物理设计

在模拟计算程序LINE-ACC/PC基础上，结合单一搜索方法和非线性最小二乘算法编程，实现一个X波段2MeV行波加速管的物理设计。应用此方法可以有效缩短加速管的优化设计时间。文章给出的优化计算可应用于一类常相速周期结构的加速管设计。文章同时给出了纵向粒子动力学、盘荷波导的几何尺寸及加速管的工作特性等方面的计算结果。     

Feasibility Study on the Analysis of MOX Particle Behavior

A plenty of plutonium is dealt in Plutonium Fuel Fabrication Facility and the facility is required to confine plutonium within a limited space such as glove box (GB) because plutonium is a-emitter and causes an internal exposure. The MOX particles entrainment occurs and some of them are transiting to the outlet of GB without deposition to floor and wall. The entraining rate and the transiting rate are reported as Airborne Release Fraction (ARF) and Respirable Fraction (RF) in the literatures. However, no activities of model development and analytical approach have been found for ARF and RF. Thus, a feasibility study is done in this paper on the behavior of MOX particles in GB such as entraining and transiting. A modeling code has been developed by improving AQUA-SF code and the RF values for abnormal occurrences, such as free-fall spill, outflow and fire, have been analyzed and compared with those reported. This paper also shows the analytical results of the improved code together with the simulated experimental results. It is found that the calculated values are almost corresponded to those reported and that the improved code can estimate MOX particle behavior in GB well.     

3D Simulation of Solid-Melt Mixture Flow with Melt Solidification Using a Finite Volume Particle Method

Relocation and freezing of molten core materials mixed with solid phases are among the important thermal-hydraulic phenomena in core disruptive accidents of a liquid-metal-cooled reactor (LMR). To simulate such behavior of molten metal mixed with solid particles flowing onto cold structures, a computational framework was investigated using two moving particle methods, namely, the finite volume particle (FVP) method and the distinct element method (DEM). In FVP, the fluid movement and phase changes are modeled through neighboring fluid particle interactions. For mixed-flow calculations, FVP was coupled with DEM to represent interactions between solid particles and between solid particles and the wall. A 3D computer code developed for solid-liquid mixture flows was validated by a series of pure-and mixed-melt freezing experiments using a low-melting-point alloy. A comparison between the results of experiments and simulations demonstrates that the present computational framework based on FVP and DEM is applicable to numerical simulations of solid-liquid mixture flows with freezing process under solid particle influences.     

Differential cross sections on fragment (2 ≤ Z ≤ 9) production for carbon,aluminum and silicon induced by tens-of-MeV protons

The double-differential cross sections (DDXs) for the inclusive reactions producing heavy nuclei with Z = 2–9 (fragments) from carbon, aluminum, and silicon targets induced by 50 and 70 MeV protons are systematically measured at several angles (30°, 60°, 90°, and 135°) using a specially developed Bragg curve counter and the energy-time-of-flight method. The DDXs of a silicon target for the proton-induced reaction producing fragments heavier than lithium were measured for the first time. The present results are compared with past experimental data, the LA150 evaluated data by the Los Alamos group and several intranuclear cascade models (Bertini and ISOBAR), and the JAEA-version quantum molecular dynamics model (JQMD) coupled with the Generalized Evaporation Model (GEM), which are implemented in the Particle and Heavy Ion Transport code System (PHITS). The present results agree well with the past experimental data and LA150 data for α -particle production. For the fragments heavier than lithium, the present results show forward-peak angular distributions rather than isotropic ones stored in LA150. Calculations with the ISOBAR and GEM models well reproduced our experimental results except for light fragments especially in the high-energy region.     

四极磁场中粒子束输运的非线性分析及模拟

为了提高粒子在四极磁场中输运轨迹计算的精度,基于李代数方法,分析和计算粒子束在四极磁场中空间电荷的非线性效应,得到二级近似下粒子坐标的映射公式,编写了粒子束在四极磁场中传输的模拟程序QML。用模拟程序对四极磁场中的传输进行了模拟计算,并对模拟结果进行了分析。模拟结果表明,在空间电荷的非线性效应的影响下相图产生了明显的扭曲,对粒子束包络曲线横向发散作用明显。     

γ辐射对小鼠脾脏及红细胞的氧化损伤

报道２Ｇｙ６０Ｃｏγ射线照射小鼠后２４ｈ，对其脾脏ＳＯＤ活力及ＬＰＯ含量的影响，以及对小鼠外周红细胞的ＳＯＤ活力及其释放Ｏ_２~－能力的影响。