Multi-channel retarding field analyzer for EAST

A multi-channel retarding field analyzer (MC-RFA) including two RFA modules and two Langmuir probes to measure the ion and electron temperature profiles within the scrape-off layer was developed for investigations of the interplay between magnetic topology and plasma transport at the plasma boundary. The MC-RFA probe for the stellarator W7-X and first measurements at the tokamak EAST was designed. The probe head allows simultaneous multichannel ion temperature as well as for electron temperature measurements. The usability for radial correlation measurements of the measured ion currents is also given.     

Temporal and spatial study of differently charged ions emitted by ns-laser-produced tungsten plasmas using time-of-flight mass spectroscopy

Tungsten (W) is an important material in tokamak walls and divertors.The W ion charge state distribution and the dynamic behavior of ions play important roles in the investigation of plasma-wall interactions using laser-ablation-based diagnostics such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy.In this work,we investigate the temporal and spatial evolutions of differently charged ions in a nanosecond-laser-produced W plasma in vacuum using time-of-flight mass spectroscopy.Ions with different charge states from 1 to 7 (W+ to W7+) are all observed.The temporal evolutions of the differently charged ions show that ions with higher charge states have higher velocities,indicating that space separation occurs between the differently charged ion groups.Spatially-resolved mass spectroscopy measurements further demonstrate the separation phenomenon.The temporal profile can be accurately fitted by a shifted Maxwell-Boltzmann distribution,and the velocities of the differently charged ions are also obtained from the fittings.It is found that the ion velocities increase continuously from the measured position of 0.75 cm to 2.25 cm away from the target surface,which indicates that the acceleration process lasts through the period of plasma expansion.The acceleration and space separation of the differently charged ions confirm that there is a dynamic plasma sheath in the laser-produced plasma,which provides essential information for the theoretical laser-ablation model with plasma formation and expansion.     

核反应堆物理确定论计算程序系统NECP软件包的研发与应用

NECP软件包是西安交通大学反应堆物理团队开发的确定论核反应堆物理计算程序系统,软件包包括自主化的NECP-Atlas、Bamboo、X和SARAX程序。NECP软件包经过了大量的验证与确认。数值结果表明,NECP软件包精度高,可满足不同反应堆物理计算需求,具有高度的通用性并实现了对压水堆的高保真建模和计算。目前程序已应用于我国大型压水堆项目、示范快堆项目等重点工程。应用结果表明,NECP软件包已达到甚至优于国际先进核设计程序水平,对我国核电软件自主化和核设计能力提升具有重要的意义。     

First experiences with the new W7-X like control system at the WEGA stellarator

The new quality of the superconducting fusion device Wendelstein 7-X (W7-X) is its capability of steady state operation. Additionally the fusion device W7-X is a very complex technical system. The modular and strongly hierarchical control system has been designed to cope with these two requirements unique for fusion devices.To minimize the risks before commissioning the control and data acquisition system at W7-X it will be thoroughly tested in a prototype installation at the WEGA stellarator. WEGA is a classical stellarator which allows steady state plasma pulses at a magnetic field of 0.5 T. Despite its lesser complexity WEGA has the same main components, e.g. magnetic coil systems, ECRH, and diagnostics as W7-X and is therefore considered to be a suitable test-bed for the control system.The installation of the new W7-X like control and data acquisition system has been finished in March this year. Individual components of the control system have already been commissioned during the installation phase. In April final commissioning and testing of the complete system took place. First discharges fully controlled by the prototype control system have been realized.The contribution will focus on first discharges controlled by the new system. Furthermore it presents first experiences that will incorporate into the further development of the control system and the tools for planning, preparation, and realization of plasma discharges.     

Simulation of Targets Feeding Pipe Rupture in Wendelstein 7-X Facility Using RELAP5 and COCOSYS Codes

Wendelstein nuclear fusion device W7-X is a stellarator type experimental device, developed by Max Planck Institute of plasma physics. Rupture of one of the 40?mm inner diameter coolant pipes providing water for the divertor targets during the “baking” regime of the facility operation is considered to be the most severe accident in terms of the plasma vessel pressurization. “Baking” regime is the regime of the facility operation during which plasma vessel structures are heated to the temperature acceptable for the plasma ignition in the vessel. This paper presents the model of W7-X cooling system (pumps, valves, pipes, hydro-accumulators, and heat exchangers), developed using thermal–hydraulic state-of-the-art RELAP5 Mod3.3 code, and model of plasma vessel, developed by employing the lumped-parameter code COCOSYS. Using both models the numerical simulation of processes in W7-X cooling system and plasma vessel has been performed. The results of simulation showed, that the automatic valve closure time 1?s is the most acceptable (no water hammer effect occurs) and selected area of the burst disk is sufficient to prevent pressure in the plasma vessel.     

Twodant solutions for the 2-D C5G7 MOX benchmark

The C5G7 MOX benchmark was proposed to test the ability of commercial transport codes to treat reactor core problems without spatial homogenization. The benchmark requires solutions in the form of normalized pin powers as well as the eigenvalue. In the work, the two-dimensional benchmark calculation using the TWODANT code within the DANTSYS code package has been performed with proper spatial and angular approximations. The TWODANT code solves the multigroup discrete ordinates form of the Boltzmann transport equation in two-dimensional geometry. The calculation results show a good agreement in comparison with the reference solution obtained from a seven-group MCNP calculation. In addition, sensitivity studies on mesh and angular refinements have been performed to produce a higher quality solution. In the results, it is found that in the TWODANT calculation the spatial approximation in a staircase form of the circular fuel pin with relatively high quadrature order of S_N is a viable method for solving the2-D C5G7 benchmark.     

Hydraulic analysis of the Wendelstein 7-X cooling loops

Actively water cooled in vessel components (IVC) are required for the long pulse operation of the stellarator Wendelstein 7-X (W7-X). In total, the cooling pipes have a length of about 4.5 km, supplying the coolant via 304 cooling circuits for the IVC. Within each cooling loop, the IVC are organized mostly in parallel. A homogeneous flow through all branches or at least the minimum specified flow in all of the branches of a circuit is crucial for the IVC to withstand the loading conditions. A detailed hydraulic simulation model of the W7-X cooling loops was built with the commercial code Flowmaster, which is a 1-D computational fluid dynamics software. In order to handle the huge amount of pipe-work data that had to be modelled, a pre- and post-processing macro was developed to transfer the 3D Catia V5 CAD model to the 1-D piping model. Within this model, the hydraulic characteristics of different types of first wall components were simulated, and compared with their pressure drop measurements. As a result of this work, the need for optimization of some cooling loops has been identified and feasible modified solutions were selected.     

Service oriented architecture for scientific analysis at W7-X. An example of a field line tracer

Service oriented architecture based on web-services is a universal method of combining software components. SOAP web-services chosen for W7-X are characterized by strong standards and readily available tools. In this paper the SOAP technology is explained and is illustrated with a new service for field line tracing.The field line tracing package consists of a C++ library and a web-service interface. It features a flexible structure and can handle a realistic machine geometry. The following problems can be solved: getting a field line; making Poincaré maps; calculating flux surface characteristics; calculating heat fluxes to the wall; constructing magnetic coordinates, etc. The service is applied to estimate W7-X divertor loads with an 1/1 error field.     

Characterization of an energy source for modeling hypothetical core disruptive accidents in nuclear reactors

The experimental methods for and results of determining the expansion characteristics of the detonation products of an energy source that simulates the pressure-volume change relationships for sodium vapor expansions during hypothetical core disruptive accidents in a fast test reactor are presented. Rigid cylinder-piston experiments performed at two scales (ratio 1:3) to determine a pressure-volume relationship as a function of source mass and expansion environment are described. Some of these measurements are compared with code calculations for the source. The results show: (1) that the pressure-volume relationship depends significantly on the presence of water in the cylinder and comparatively little on the timescale of the expansion, the presence of steel balls in the water, or a Mylar sheet on the water surface; and (2) the experiment's scale. A relationship between the measured work energy from the source and the charge mass is presented, and pressure-volume change measurements are compared with previous experimental measurements and with theoretical calculations for a 150 MWsec hypothetical core disruptive accident. The measurements and code calculations of the pressure-volume relationship for the source agree reasonably well.     

核电厂SCIENCE程序包反射层功能扩展研究

文章根据实际工作需要,阐述了基于来自法国的SCIENCE V1程序包进行反射层计算的功能扩展开发;深入研究部分功能的实现细节,按需增加部分代码,扩展开发出反射层计算功能。应用扩展后的SCIENCE程序包研究秦山二期堆型反射层参数,并与1、2号机组共19个循环堆芯的实测值进行比较,结果符合良好,满足工程精度要求。通过对SCIENCE V1程序包的功能扩展研究,扩大了SCIENCE V1程序包的适用范围,同时积累了大型程序的研发经验。     

Reduction in spatial discretization error in the method of characteristics by using the mobile-chord ray tracing method

The mobile-chord method is applied to the method of characteristics (MOC) to reduce the spatial discretization error in ray traces. In the mobile-chord method, the offset of a ray trace in a strip depends on the azimuthal angle and this variation cancels the spatial discretization error of each ray trace. Although the mobile-chord method has been employed in the evaluation of the collision probability, it has not yet been applied to the MOC. The mobile-chord method is implemented in the AEGIS code, which is a lattice physics code based on the MOC. Verification calculations are carried out for the pin-cell and whole core geometries of the C5G7 benchmark problem by using UO₂ and mixed oxide (MOX) fuels. The calculation results indicate that the spatial discretization error in the mobile-chord method is smaller than that in the equidistant ray tracing method, which is commonly used in conventional MOC codes. Since the mobile-chord method can be used along with the cyclic ray tracing method, it is expected to be an attractive candidate for conventional MOC codes.     

Experiment planning using high-level component models at W7-X

The superconducting stellarator Wendelstein 7-X (W7-X) is a fusion device, which is capable of steady state operation. Furthermore W7-X is a very complex technical system. To cope with these requirements a modular and strongly hierarchical component-based control and data acquisition system has been designed.The behavior of W7-X is characterized by thousands of technical parameters of the participating components. The intended sequential change of those parameters during an experiment is defined in an experiment program. Planning such an experiment program is a crucial and complex task. To reduce the complexity an abstract, more physics-oriented high-level layer has been introduced earlier. The so-called high-level (physics) parameters are used to encapsulate technical details.This contribution will focus on the extension of this layer to a high-level component model. It completely describes the behavior of a component for a certain period of time. It allows not only defining simple value ranges but also complex dependencies between physics parameters. This can be: dependencies within components, dependencies between components or temporal dependencies.Component models can now be analyzed to generate various views of an experiment. A first implementation of such an analyze process is already finished. A graphical preview of a planned discharge can be generated from a chronological sequence of component models. This allows physicists to survey complex planned experiment programs at a glance.     

Charge state distribution and its equilibration of 2 MeV/u sulfur ions passing through carbon foils

Charge state distributions of 2.0 MeV/u sulfur ions of various initial charge states (6, 10, 11, 13+) after passing through 0.9, 1.5, 2.0, 3.0, 4.7, 6.9 and 10 μg/cm² carbon foils have been studied. It is observed that the processes involving the L-shell electrons are equilibrated within the target thickness of 5 μg/cm² and the charge equilibration over this thickness is ruled by the K-shell processes. Measured charge state distributions do not flat off to establish equilibrium within the measured thicknesses, but the mean charge states almost saturate to 12.4 for all initial charge states examined. Calculation with ETACHA code, developed by Rozet et al. [Nucl. Instr. and Meth. B 107 (1996) 67], is employed, although the present impact energy is lower than the assumed region for the code.     

基于CMS程序包的环形燃料堆芯物理计算分析

为研究在大型商用压水堆中采用环形燃料元件的可能性,需分析环形燃料的堆芯物理性能。本文研究了CASMO5程序计算环形燃料组件物理参数出现偏差的原因及其处理方法,分析了4组环形燃料先导组件加入秦山二期核电站平衡循环堆芯之后的堆芯物理参数。计算结果表明,装载的环形燃料先导组件对堆芯物理性能影响较小,基于CMS程序包开展环形燃料堆芯物理性能分析计算是可行的。     

Simulation of start-up measurements with the KIKO3D code and its application for determining the scram rod worth uncertainty in the VVER-440 reactor

The reasons for large discrepancies between the computed and measured values of the efficiency of control rods observed during start-up experiments on the Russian pressurized water type VVER reactors are discussed. The numerical simulation of the measurements including the prediction of the ex-core detector signals was used to resolve the discrepancies. The time and space dependent neutron flux in the core during these measurements have been calculated by the KIKO3D nodal kinetic code. For calculating the ionization chamber signals the Green function technique has been applied. The Green functions of ionization chambers have been evaluated via solving the neutron transport equation in the reflector regions with the MCNP Monte Carlo code. The detector signals have been calculated and compared with measured ones using the inverse point kinetics transformation. Large number of asymmetric rod drop measurements (with one rod stuck) and some differential rod worth measurements from the Zero Power Physics Tests were provided by the Paks NPP for validation. The experiments cover different fuels (without and with enrichment zoning) and loading patterns. The intermediate range ionization chambers have been used during the scram measurements. The newly developed method provides fairly sufficient match of measured and calculated results. The time behavior of the detector readings observed in the measurements are described by the code in a consistent manner.As a further application the uncertainty of scram rod worth of the KARATE-440 code system was determined by static calculations and subsequent simulation of rod drop with the KIKO3D code. The calculated results were compared to measurements carried out by the Paks NPP. The uncertainty of scram rod worth is established by statistical analysis.     

Development of Z_(eff) diagnostic system on the Globus-M(M2) tokamak and the first experimental results

Studying the behavior of effective ion charge Zeff,which indicates the degree of pollution of plasma and can provide valuable information about many processes taking place in plasma,mechanisms of the releasing impurities,transport,etc is of great interest.This paper describes the development of the Zeffdiagnostic system for the Globus-M2 tokamak.The effective ion charge is determined on the basis of measurements of the bremsstrahlung intensity and Thomson scattering data—Teand neprofiles.The results of the first Zeffmeasurements obtained for several discharges on the Globus-M tokamak are presented in this paper.The results have been validated by simulation using the ASTRA transport code for the same discharges,and it has demonstrated a good agreement with the experimental results.     

核电工程环境保护类微机程序包开发设计综述

核工程环境保护类微机程序包集成了核电软件中心截至１９９３年所搜集到的共３２个核电工程辐射环境影响评价程序,实现了所有这些程序向微机的移植,完成了使用频率较高的程序之间的连接,增添了原有程序的报表输出和图形化处理功能,并且,结合我国辐射环境影响评价的规范,评价了这些程序在辐影响评价中的适用性。     

Overview of results from Wendelstein7-X HTS current lead testing

The High Temperature Superconductor (HTS) current leads (CL) for the Wendelstein 7-X stellarator (W7-X) with a maximum current of 18.2 kA are designed and manufactured by the Karlsruhe Institute of Technology (KIT). In addition the acceptance tests of the W7-X HTS CLs are performed at KIT. Therefore the existing TOSKA facility has been extended by a test cryostat connected to the main vacuum vessel. After the extensive prototype CL test campaigns in 2010 the final acceptance tests of 14 series CLs started in 2011. The estimated completion of the routine test campaign is in December 2012. The main parts of each acceptance test are the determination of the heat load at the 4.5 K level, of the necessary 50 K He mass flow rate through the heat exchanger as well as the simulation of a loss of flow accident of the 50 K He mass flow at full current (18.2 kA). The tests also include a long-time operation at the maximum current of 18.2 kA to demonstrate the steady state operation capability of the HTS CLs. In the present paper an overview of all conducted HTS CL acceptance tests is given. The results for the different CLs are summarized and compared to the specifications.     

Improvement of Neutron Source Introduction Method for Absolute Measurements of Low Reactor Power

The neutron source introduction method was applied to absolute measurements of low reactor power at the Static Experiment Critical Facility STACY. To obtain the effective neutron source intensity more accurately, which is a key parameter for the source introduction method, the neutron source is newly defined as fission neutrons from the first fission reaction caused by neutrons emitted from the external neutron source. To obtain the newly defined effective neutron source intensity, the probability that a neutron from the external neutron source causes a fission reaction is calculated using the Monte Carlo code MCNP. This calculation took into consideration the three-dimensional complicated core structures. Furthermore, the fission reaction distribution, fundamental mode forward and adjoint flux distribution in a critical state were calculated using the three-dimensional transport code THREEDANT. Following the principle of the neutron source introduction method, an external neutron source was inserted near the STACY core tank and the reactor power was measured. The reactor powers by the neutron source introduction method were in good agreement with the ones from the analyses of the FP activity generated by high power operation.