Application of MDSplus on EAST Tokamak

EAST is a fully superconducting Tokamak in China used for controlled fusion research. MDSplus, a special software package for fusion research, has been used successfully as a central repository for analysed data and PCS （Plasma Control System） data since the debugging experiment in the spring of 2006 [1]. In this paper, the reasons for choosing MDSplus as the analysis database and the way to use it are presented in detail, along with the solution to the problem that part of the MDSplus library does not work in the multithread mode. The experiment showed that the data system based on MDSplus operated stably and it could provide a better performance especially for remote users.     

MDSplus automated build and distribution system

Support of the MDSplus data handling system has been enhanced by the addition of an automated build system which does nightly builds of MDSplus for many computer platforms producing software packages which can now be downloaded using a web browser or via package repositories suitable for automatic updating. The build system was implemented using an extensible continuous integration server product called Hudson which schedules software builds on a collection of VMware based virtual machines. New releases are created based on updates via the MDSplus cvs code repository and versioning are managed using cvs tags and branches. Currently stable, beta and alpha releases of MDSplus are maintained for eleven different platforms including Windows, MacOSX, RedHat Enterprise Linux, Fedora, Ubuntu and Solaris. For some of these platforms, MDSplus packaging has been broken into functional modules so users can pick and choose which MDSplus features they want to install. An added feature to the latest Linux based platforms is the use of package dependencies. When installing MDSplus from the package repositories, any additional required packages used by MDSplus will be installed automatically greatly simplifying the installation of MDSplus. This paper will describe the MDSplus package automated build and distribution system.     

MDSplus与EAST数据服务系统之间的中间件设计

介绍了聚变实验数据采集与管理软件包MDSplus与基于LZO压缩算法的数据服务系统之间的中间件的设计思路与实现方法.该中间件解决了数据双份不同格式存贮的难题,已成功地应用于中科院等离子体物理研究所的EAST装置,使得熟悉MDSplus接口的用户不需知道任何LZO和文件系统的知识就可以透明地访问EAST实验数据,为建立虚拟合作实验室奠定了的基础.     

A web based MDSplus data analysis and visualization system for EAST

In an EAST (Experimental Advanced Superconducting Tokamak) experiment, the convenient data analysis and visualization tools are very important for physicists and engineering experts to view the operational status of the device. Along with the increasing data sampling rate and pulse length, it will be increasingly challenging for the end user to view the data conveniently under limited Internet bandwidth. We propose a software based on jScope [1] called WebScope for data visualization. By applying java applet techniques, this software can be accessed directly over the Internet via a variety of web browsers without installing client software. Using this data viewer the frequency will be effectively adjusted according to the computer displaying resolution, which saves the total amount of data to be transferred across the Internet and enables the user to view the data quickly. When the signals are zoomed or unzoomed, the data frequency will be re-adjusted to the displaying resolution. With WebScope, data of various experiments in different servers can be viewed in either a single panel or multiple frames, which makes it easier for cross comparison among different data sources. The system was successfully applied to EAST experiment and achieved excellent performance. Its design, function and implementation details will be introduced in this paper.     

Tokamak TCABR: Acquisition system,data analysis,and remote participation using MDSplus

Each plasma physics laboratory has a proprietary scheme to control and data acquisition system. Usually, it is different from one laboratory to another. It means that each laboratory has its own way to control the experiment and retrieving data from the database. Fusion research relies to a great extent on international collaboration and this private system makes it difficult to follow the work remotely. The TCABR data analysis and acquisition system has been upgraded to support a joint research programme using remote participation technologies. The choice of MDSplus (Model Driven System plus) is proved by the fact that it is widely utilized, and the scientists from different institutions may use the same system in different experiments in different tokamaks without the need to know how each system treats its acquisition system and data analysis. Another important point is the fact that the MDSplus has a library system that allows communication between different types of language (JAVA, Fortran, C, C++, Python) and programs such as MATLAB, IDL, OCTAVE. In the case of tokamak TCABR interfaces (object of this paper) between the system already in use and MDSplus were developed, instead of using the MDSplus at all stages, from the control, and data acquisition to the data analysis. This was done in the way to preserve a complex system already in operation and otherwise it would take a long time to migrate. This implementation also allows add new components using the MDSplus fully at all stages.     

Radiation damage evolution in ceramics

A review is presented of recent results on radiation damage production, defect accumulation and dynamic annealing in a number of ceramics, such as silicon carbide, zircon and zirconia. Under energetic particle irradiation, ceramics can undergo amorphization by the accumulation of point defects and defect clusters (silicon carbide) or direct impact amorphization (zircon). Ceramics that resist radiation-induced amorphization have mechanisms to dissipate the primary knock-on atom energy, such as replacement collision sequences that leave the lattice undisturbed and low-energy cation site exchange. The presence of engineered mobile defects, such as structural vacancies in stabilized zirconia, can dynamically anneal radiation damage. Thus, defect engineering is a promising strategy to design radiation tolerance for applications such as nuclear waste disposal.     

Engineering evolution of the FAST machine

FAST (Fusion Advanced Studies Torus) is a proposal for a Satellite Facility which can contribute the rapid exploitation of ITER and prepare ITER and DEMO regimes of operation, as well as exploit innovative plasma facing component systems for DEMO. FAST is a compact (Ro = 1.82 m, a = 0.64 m, triangularity δ = 0.4) and cost effective machine able to investigate, with integration capability, non linear dynamics effects of alpha particle behaviour in burning plasmas. FAST operates in high performance H-mode (B_T up to 8.5 T; I_P up to 8 MA), as well as in advanced tokamak mode (I_P = 3 MA), and in full non inductive current mode (I_P = 2 MA). Helium gas at 30 K is used for cooling the resistive copper magnets. This allows for a pulse duration up to 170 s at 3 MA/3.5 T. The vacuum vessel (VV), segmented into 20-degree modules, is capable to accommodate a 40 MW RF power system. The machine has been designed to house a 10 MW Negative Neutral Beam Injection (NNBI) system. Tungsten (W) or liquid lithium (L-Li) have been chosen as the divertor plate materials, and argon or neon as the impurities to be injected for mitigating the thermal loads.     

Defect evolution in MeV ion-implanted silicon

Lightly doped silicon samples of both n- and p-type have been implanted with low doses of H, B and Si ions using energies between 1 and 6 MeV. The resulting electrically active point defects were characterized by deep level transient spectroscopy (DLTS) and several of these defects involve oxygen and/or carbon, two major impurities in as-grown crystalline silicon. Both interstitial- and vacancy-type defects are observed; in particular, interstitial carbon is found to migrate at room temperature with a diffusion constant of 1 × 10⁻¹⁵ cm² s⁻¹ and is effectively trapped by interstitial oxygen atoms. The concentration of implantation-induced defects increases linearly with dose but the defect production decreases at high enough dose rates. This dose rate effect depends on the ion mass and is qualitatively predicted by computer simulations of the defect reaction kinetics.     

吐哈盆地形成及其演化

在分析吐哈地区区域应力场性质的基础上,把盆地的形成与发展分为3个阶段。重点阐述各阶段的受力性质、盆地类型、沉积环境及沉积厚度。     

The evolution of gas from uranium dioxide

Conclusions We have examined the basic laws governing the character of gas evolution and the behavior of uranium dioxide during the operation of a fuel element prior to thorough burn-up. The behavior of the uranium dioxide and the evolution of gases depend directly on the distributions of energy evolution and temperature with respect to radius in the fuel element, and on the process of structure formation and burn-up in the different zones of the fuel. The evolution of gases from uranium dioxide during irradiation can be estimated on the assumption that all the gaseous fission products evolve from the columnar crystal zone and that evolution of gases from the equiaxial grain zone takes place by a mechanism of thermally activated diffusion.Sorption of gaseous fission products at the surface of the fuel can lead to errors in determining the quantity of gaseous fission products evolved from the uranium dioxide during postreactor determination by the fuel-can puncture method.Translated from Atomnaya Énergiya, Vol. 40, No. 5, pp. 390–395, May, 1976.     

Sabena: Subassembly boiling evolution numerical analysis

This paper describes the computer code SABENA that has been used in subassembly sodium boiling evolution numerical analysis as a contribution to fast breeder reactor safety analysis. SABENA is a two-fluid model subchannel code system to calculate coolant boiling and two-phase flow in a rod bundle together with external loop characteristics which affects the overall boiling behavior in the bundle section. With the use of relatively simple but reasonable constitutive models, the SABENA code has been applied to and validated against many multi-pin sodium boiling problems. The results have shown excellent agreement with the experiments. The numerical methods and models employed in the code have proven to be robust and efficient in light of the extreme severity of the conditions characterizing low-pressure sodium boiling.     

An evolution of molten core cooling strategies

Fundamental mechanisms behind the molten core cooling strategies are revisited to provide an insight for a proper implementation of severe accident management guideline (SAMG) and a development of an engineered safety feature. From the results of a qualitative evaluation and a quantitative plant analysis, weak points of the current severe accident management guideline for an operating plant are identified and a revision of the molten core cooling strategies is proposed. In addition, technical issues for various kinds of core catcher concepts are discussed.     

Actinide evolution and equilibrium in fast thorium reactors

The development of accelerator-driven sub-critical reactors operating with pure and enriched thorium fuel mixtures has been heralded as delivering a new era in sustainable nuclear power production. Many benefits have been claimed for these systems, particularly with respect to their ability to consume existing plutonium stockpiles and their inability to breed additional plutonium. This paper examines the operation of fast thorium reactors using a lumped model that can demonstrate to first-order accuracy the principles of actinide evolution and equilibrium and allow the identification of trends within the nuclide transformations. The fundamental mechanisms that affect nuclide evolution are demonstrated and the freedoms and constraints bounding this process are shown. Fast reactors operating with a 100% thorium fuel source are shown to generate plutonium and to offer no advantage over enriched thorium fuel in terms of actinide generation in longer-term operation.     

Modeling texture evolution during uni-axial deformation of Zircaloy-2

Texture development in zirconium reactor components greatly affects their in-service performance, in particular influencing dimensional stability, hydride induced cracking and fracture. Understanding texture evolution in terms of micromechanical deformation mechanisms contributes to improved engineering design of the components. The texture evolution during uni-axial deformation of Zircaloy-2 obtained using neutron diffraction was interpreted with a visco-plastic self-consistent model, based on an extensive data set achieved through in situ and ex situ neutron diffraction measurements. In the model, the influences of prism, basal, pyramidal〈a〉, pyramidal〈c + a〉 slip, tensile twinning, and hardening due to dislocation interactions were considered. Model parameters were adjusted to obtain a simultaneous ‘best-fit’ to the stress-strain curves, Lankford coefficients, development of peak intensities in three dimensions and post-deformation textures, for specimens compressed or pulled in three principal directions relative to the slab texture. The texture formation was found to be directly related to the activation of different deformation mechanisms. Pyramidal〈a〉 slip was unnecessary in the modeling. Accounting for interactions between deformation modes was critical to correctly predicting texture development and stress-strain curves. This study provides further understanding on the plastic deformation of Zircaloy-2.     

Bubble formation and evolution behavior from vertical wall orifice

Bubble formation is an integral part of the twophase flow science.Through numerical simulation and experiments using different air flow rates and orifice diameters,the present study aims at investigating the behavior of bubble formation and evolution from vertical wall orifice in quiescent pure water.For the experiments,the images of the bubble formation process under different working conditions were recorded using a high-speed camera and analyzed the entire process.The bubble formation process can be divided into three stages,namely nucleation,stable growth,and necking.According to the obtained results,bubble forms only when the air-phase pressure exceeds the threshold pressure at wall orifice.Due to the influence of the threshold pressure and buoyancy,the bubble volume decreases with an increase in the wall orifice diameter for the same flow rate.Moreover,the volume of fluid method is applied to simulate bubble formation in a three-dimensional model and the"buffer volume"is considered in the simulation model.The simulation resultsmatched well with the experimental data,which proves the existence of threshold pressure and the periodic pressure fluctuation at the wall orifice.