Failure Modes and Effects Analysis on ITER DFLL-TBM system

As required for licensing process, accident analyses of International Thermonuclear Experimental Reactor (ITER) accounting for site specifications and design changes will be updated. Chinese Dual-Functional Lithium-Lead-Test Blanket Module (DFLL-TBM) system is a key safety-related component of ITER, its detailed safety analysis, which was designated to demonstrate the integrated technologies of both Helium single coolant (SLL) blanket and Helium-LiPb dual coolant (DLL) blanket, was performed. Failure Modes and Effects Analysis (FMEA) was applied to perform the safety analysis of DFLL-TBM. This study described the process of FMEA studies on DFLL-TBM system. All safety-related Postulated Initiating Events (PIEs) was identified. And a set of PIEs recommended to be taken into account in the further deterministic transient analyses were defined for both SLL and DLL blanket concepts separately.     

ITER双功能液态锂铅实验包层系统故障模式影响分析

实验包层模块允许放置在ITER中实验的前提是其对ITER的安全以及对工作人员和环境不构成显著影响。ITER要求各参与方的实验包层模块在实验前必须提交安全分析报告,进而获取安全许可证。在中国双功能锂铅实验包层模块(DFLL-TBM)设计基础上,采用了故障模式影响分析(FMEA)方法对DFLL-TBM进行了安全评估与分析,得到所有可能导致严重后果的假设始发事件,验证了确定论安全分析所选择的三个参考事件可以包络所有的假设始发事件。     

Breaking down the requirements: Reliability in remote handling software

Software requirements have an important role in achieving reliability for operational systems like remote handling: requirements are the basis for architectural design decisions and also the main cause of defects in high quality software. We analyze related recommendations and requirements given in software safety standards, handbooks etc. and apply them to remote handling control systems, which typically have safety-critical functionality, but are not actual safety-systems?for example the safety-systems in ITER will be hardware-based.Based on the analysis, we develop a set of generic recommendations for control system software requirements, including quality attributes, software fault tolerance, and safety and as an example we analyze ITER remote handling system software requirements to identify and present dependability requirements in a useful manner. Based on the analysis, we divide a high-level control system into safety-critical and non-safety-critical subsystems, and give examples of requirements that support building a dependable system.     

A new approach to passive protection against high energy and high current breakdowns in the ITER NBI accelerator

The energy stored in the 1 MV ITER Neutral Beam Injector power supply system will exceed by far the energy stored in the existing largest NB Injectors; as a consequence, the limitation of the grid breakdown effects–grids damage and Electro Magnetic Interference emission–are critical issues. In the present ITER NBI reference design the mitigation system is based on the concept of the concentrated core snubber which, due to the large amount of stored energy, is a huge component. Furthermore, in the NBI a relatively large part of HV capacitance to ground remains downstream the core snubber, so neither the arc peak current nor the high-frequency oscillations can be effectively limited. Moreover, the concentrated core snubber is ineffective in limiting the voltage reversal caused by internal insulation fault, increasing the risk of cascade failures in components like HV bushing and transmission line. The paper proposes an alternative approach to limit the grid breakdown effects, based on the concepts of Damper Resistor- substituting the direct connection to ground of the zero-potential accelerating grid – and of Distributed Core Snubber (DCS) – installed along the whole length of the transmission lines. The DCS concept has been subjected also to experimental validation by a small scale setup supported by electrical modelling.     

The negative ion source test facility ELISE

The ITER neutral beam system is using inductively coupled radio frequency (RF) ion sources, that have demonstrated the required ITER parameters on (small) sources with extraction areas up to 200 cm². As a next step towards the full size ITER source IPP is presently constructing the test facility ELISE (“Extraction from a Large Ion Source Experiment”) operating with a “half-size” source which has approximately the width but only half the height of the ITER source. The modular driver concept is expected to allow a further extrapolation to the full size in one direction to be made. The main aim of this experiment is to demonstrate the production of a large uniform negative ion beam with ITER relevant parameters in stable conditions up to one hour.Plasma operation of the source is foreseen to be performed continuously for 1 h; extraction and acceleration of negative ions up to 60 kV is only possible in pulsed mode (10 s every 180 s) due to limitations of the existing IPP HV system. The design of the source and extraction system implements a high experimental flexibility and a good diagnostic access while still staying as close as possible to the ITER design. The main differences are the source operating in air and the use of a large gate valve between the source and the target chamber.ELISE is expected to start operation at the end of 2011 and is an important step for the development of the ITER NBI system; the experience gained early will support the design as well as the commissioning and operating phases of the PRIMA NBI test facilities and the ITER neutral beam system.     

ITER实验包层吹洗气前处理系统的FMECA研究

实验包层(TBM)输出吹洗气前处理系统将安装在国际热核聚变实验堆(ITER)装卸TBM的通道内(Port Cell),它的功能是将TBM输出的含氚吹洗气进行过滤、除HTO、冷却、调流量等处理,处理后输出到氚提取系统。介绍了该系统的工艺过程和系统组件,以氚释放危险为判据,对该系统进行FMECA(故障模式、影响及危害性分析),并作出分析表。找出了几种故障模式或薄弱环节,进行了尝试性的风险优先数和故障模式危害度计算,提出了设计改进措施和使用补偿措施;最后确定了需要重点关注的4种需导致释非正常过量释放的潜在故障模式。这些故障分析为降低系统氚过量释放危险设计提供了依据,也为TBM其他附属氚系统的安全分析奠定了基础。     

Characterization,test and interpretative simulations of one-dimensional Carbon Fiber Composite prototype for SPIDER experiment

For ITER operations, additional heating systems are required. One of these systems is the neutral beam injector (NBI). The SPIDER experiment, a small-scale NBI, is going to be built with the aim to optimize the beam source. For this reason it is provided with several diagnostics, among which the Short-Time Retractable Instrumented Kalorimeter Experiment (STRIKE). In this contribution, a characterization of the Carbon Fiber Composite (CFC) tiles, which are the main component of the diagnostic, is presented. Such analyses include tests with a power laser, exposure to particle beams and thermal stress tests. The results are discussed, which will drive the definition of the acceptance tests of the final supply of CFC tiles.     

Detailed 3-D nuclear analysis of ITER blanket modules

In ITER, the blanket modules (BM) are arranged around the plasma to provide thermal and nuclear shielding for the vacuum vessel (VV), magnets, and other components. As a part of the BM design process, nuclear analysis is required to determine the level of nuclear heating, helium production, and radiation damage in the BM. Additionally, nuclear heating in the VV is also important for assessing the BM design. We used the CAD based DAG-MCNP5 transport code to analyze detailed models inserted into a 40-degree partially homogenized ITER global model. The regions analyzed include BM01, the neutral beam injection (NB) region, and the upper port region. For BM01, the results show that He production meets the limit necessary for re-welding, and the VV heating behind BM01 is acceptable. For the NBI region, the VV nuclear heating behind the NB region exceeds the design limit by a factor of two. For the upper port region, the nuclear heating of the VV exceeds the design limit by up to 20%. The results presented in this work are being used to modify the BM design in the cases where limits are exceeded.     

Design of Timing Synchronization Software on EAST-NBI

To ensure the uniqueness and recognition of data and make it easy to analyze and process the data of all subsystems of the neutral beam injector （NBI）, it is required that all subsystems have a unified system time. In this paper, the timing synchronization software is presented which is related to many kinds of technologies, such as shared memory, multithreading, TCP protocol and so on. Shared memory helps the server save the information of clients and system time, multithreading can deal with different clients with different threads, the server works under Linux operating system, the client works under Linux operating system and Windows operating system. With the help of this design, synchronization of all subsystems can be achieved in less than one second, and this accuracy is enough for the NBI system and the reliability of data is thus ensured.     

RAMI Analysis of HCCB TBS for ITER

ITER is the first worldwide international experimental nuclear fusion facility, which aims to prove the physics and technological basis for future fusion power plants. As main stages of ITER technical risk control, the reliability, availability, maintainability and inspectability (RAMI) approach should be applied to all ITER components during their design phase to reduce potential technical risks. Test blanket modules play a key role in ITER. Helium cooled ceramic breeder (HCCB) TBM is one of TBM concepts which were proposed by China. HCCB TBM and its ancillary system are called HCCB test blanket system (TBS). The RAMI analysis was performed on the conceptual design of the ITER HCCB TBS in this paper. A functional breakdown was prepared in a bottom-up approach, resulting in the system being divided into 3 main functions, 1 support function, 14 sub-functions and 50 basic functions. These functions were described using the IDEF0 method. Reliability block diagrams were prepared to estimate the reliability and availability of each function under the stipulated operating conditions. The inherent availability of the HCCB TBS expected after implementation of mitigation actions was calculated to be 94.69 % over 2 years. A failure modes, effects and criticality analysis was performed with criticality charts highlighting the risk level of the different failure modes with regard to their probability of occurrence and their effects on the availability.     

Towards the conceptual design of the ITER real-time plasma control system

ITER will be the world's largest magnetic confinement tokamak fusion device and is currently under construction in southern France. The ITER Plasma Control System (PCS) is a fundamental component of the ITER Control, Data Access and Communication system (CODAC). It will control the evolution of all plasma parameters that are necessary to operate ITER throughout all phases of the discharge. The design and implementation of the PCS poses a number of unique challenges. The timescales of phenomena to be controlled spans three orders of magnitude, ranging from a few milliseconds to seconds. Novel control schemes, which have not been implemented at present-day machines need to be developed, and control schemes that are only done as demonstration experiments today will have to become routine. In addition, advances in computing technology and available physics models make the implementation of real-time or faster-than-real-time predictive calculations to forecast and subsequently to avoid disruptions or undesired plasma regimes feasible. This requires the PCS design to be adaptable in real-time to the results of these forecasting algorithms. A further novel feature is a sophisticated event handling system, which provides a means to deal with plasma related events (such as MHD instabilities or L-H transitions) or component failure. Finally, the schedule for design and implementation poses another challenge. The beginning of ITER operation will be in late 2020, but the conceptual design activity of the PCS has already commenced as required by the on-going development of diagnostics and actuators in the domestic agencies and the need for integration and testing. This activity is presently underway as a collaboration of international experts and the results will be published as a subsequent publication. In this paper, an overview about the main areas of intervention of the plasma control system will be given as well as a summary of the interfaces and the integration into ITER CODAC (networks, other applications, etc.). The limited amount of commissioning time foreseen for plasma control will make extensive testing and validation necessary. This should be done in an environment that is as close to the PCS version running the machine as possible. Furthermore, the integration with an Integrated Modeling Framework will lead to a versatile tool that can also be employed for pulse validation, control system development and testing as well as the development and validation of physics models. An overview of the requirements and possible structure of such an environment will also be presented.     

Results of Predictive Fokker?CPlanck Modelling of NBI Deuterons in ITER

First an analytical formalism is presented for calculating the source distribution of ions generated by neutral beam injection (NBI) in tokamak plasmas. A general NBI ion source term, applicable to studies in the phase space up to 6 dimensions, is provided for neutral beams with finite thickness and divergence. Further, using this source term for the envisaged NBI in ITER, we carry out 3D Fokker?CPlanck modelling of the steady-state deuteron distribution function of NBI produced fast deuterons relaxing on bulk plasma components. For two basic ITER scenarios we demonstrate the poloidal profiles of the beam deuteron density, of the NBI generated current as well as of the NBI power deposition to bulk electrons and ions. Further, we evaluate the capability of gamma and NPA diagnostics of NBI ions in ITER and demonstrate the sensitivity of the distributions of NBI generated ions to different ITER operation scenarios.     

The status of the ITER design

In parallel with a rapid build up to almost 300 people within the International Organization at Cadarache, the project team, including many from the member countries represented by their domestic agencies (DA), has concentrated its effort on an overall design review of ITER. An updated technical baseline was presented to council at the end of 2007. Several additional improvements were included during spring 2008 and it is probable that the results of the review will be accepted by council. As a result, the ITER design today provides a robust basis for a technical design that allows operation over a wide range of physical parameters, a design that can operate stably with high gain and can exploit the full scientific potential of the device. In the technical area, design changes have been integrated to improve performance, provide more robust subsystems and to minimize technical or operational risks. All of the adaptations required to support the licensing process as a nuclear facility in France have been made. In parallel major components are already under construction within the DAs. A full overview of the status of ITER design and construction, including the detailed discussion of the 2007 ITER baseline, is given. In addition, the construction status and the overall project review is presented.     

FMEA法评估反应堆控制棒驱动机构可靠性

控制棒驱动机构是反应堆本体中唯一的能动设备,其运行的可靠性对反应堆的反应性控制具有重要的作用。本文在介绍失效模式及影响分析(FMEA)方法的基础上,以我国新设计的反应堆控制棒驱动机构为对象,使用该方法进行可靠性评价。评价结果明确了各设备部件的失效原因和失效模式,确定了各部件的严重性等级和风险等级,为今后控制棒驱动机构的可靠性管理提供支持。     

A model for electrical fast transient analyses of the ITER NBI power supplies and the MAMuG accelerator

The design of ITER Neutral Beam Injector (NBI) is based on a five-stage electrostatic accelerator, known as Multi-Aperture Multi-Grid (MAMuG) and characterised by an overall acceleration voltage of ?1 MV. The MAMuG accelerator requires a five-stage power supply system under strict load protection requirements, being subjected in operation to breakdowns. In this paper a circuit model of ITER Neutral Beam Injector power supplies and MAMuG accelerator is illustrated, for the simulation of fast transients related to accelerator breakdowns in particular. Consideration of the high voltage involved and of the complex inductive and capacitive couplings implied careful assessment of stray parameters by calculations with finite element techniques. The circuit model, developed to address a number of design issues requiring simulations at system level, is now ready for use—the optimisation of passive protections being the most significant application.     

RAMI Analysis Program Design and Research for CFETR (Chinese Fusion Engineering Testing Reactor) Tokamak Machine

Chinese Fusion Engineering Testing Reactor (CFETR) is a test reactor which shall be constructed by National Integration Design Group for Magnetic Confinement Fusion Reactor of China with an ambitious scientific and technological goal. The reactor has the equivalent scale compared with ITER, but has the complementary function to ITER. CFETR is a demonstration of long pulse or steady-state operation with duty cycle time not less than 0.3–0.5 and the full cycle of tritium self-sustained with TBR not less than 1.2. At the same time it will be exploring options for DEMO blanket and divertor with an easy changeable core by remote handling way. To be able to reach its scientific and technological objectives, as one of technical risks control methods, RAMI analysis need to be done during the hold lifetime of CFETR, from conception design to decommissioning. Base on stating of CFETR lifetime and preliminary operational programme, the RAMI analysis program and process are designed and discussed, it consists of five major steps: (1) functional analysis are performed, (2) calculating reliability block diagrams, (3) analyzing failure mode, effects and criticality analysis, (4) risk mitigation actions are taken to ensure every system is compatibility with RAMI objectives, (5) All the RAMI analysis are integrated as the final RAMI analysis reports to be reviewed in the system final design review. Along with the elements of the analysis the vacuum vessel (VV) system was performed to provide as examples, detailed showing how the CFETR RAMI analysis is carried out. CFETR RAMI analysis guidelines were designed and established, after constantly revised and improved these analysis criteria and programs will become the basis standards for CFETR RAMI analysis. Preliminary RAMI analysis of CFETR VV system was obtained, which will be updated with the VV system design progresses.     

Development of a RF-driven ion source for the ITER NBI system

Extensive R&D work on RF-driven negative hydrogen ion sources carried out at IPP Garching led to the decision of ITER to select this type of source as the new reference source for the ITER NBI system. The principle suitability of the RF source has been demonstrated in a small scale, short pulse length experiment: accelerated current densities, co-extracted electron currents at a source operation pressure, all well inside the range of the ITER requirements have been achieved simultaneously. In subsequent experiments, pulse lengths up to 1 h and the possibility of modularly extending the source to ITER source dimensions were demonstrated. The results achieved at the various IPP test beds, the lessons learnt during optimising the source for negative ion production and extraction as well as the problems still to be solved are summarized. As the next step in support of the NBI development for ITER, IPP plans to build a new test facility for beam extraction from a source of half the size for ITER.     

Design of Waveform Generator for NBI in EAST

The control system of neutral beam injector (NBI) monitors the status of NBI equipments, controls all of the power supply, realizes data acquisition and network, and provides a unified clock for all subsystems of NBI system. As an important part of NBI control system, waveform generator (WG) monitors the parameters of the experiment and displays these parameters in the waveform terminal. The WG software also can send simple experiment commands and make it easy for experiment test. The WG software develops under Windows operating system, using labview language. The design is related to many kinds of technologies, such as client/server communication, multithreading and cyclic redundancy check technology, TCP protocol and so on.     

RAMI analysis of the ITER CIS

ITER is the first worldwide international project aiming to design a device that proves the physics and technological basis for fusion power plants to produce nuclear fusion energy. In the project, the RAMI approach (reliability, availability, maintainability and inspectability) has been adopted for technical risk control to guide the design of components in preparation for operation and maintenance. RAMI analysis of the ITER central interlock system (CIS), which shall provide investment protection for the ITER systems was performed on the conceptual design. A functional breakdown was prepared in a bottom-up approach, resulting in the system being divided into 5 main functions and 7 sub-functions which are described using the IDEFØ method. Reliability block diagrams (RBDs) were prepared to estimate the reliability and availability of each function under stipulated operating conditions. Initial and expected scenarios were analyzed to define risk-mitigation actions. The inherent availability of the ITER CIS expected after implementation of mitigating actions was calculated to be 99.86% over 2 years, which is the typical interval of the scheduled maintenance cycles. A failure modes, effects and criticality analysis (FMECA) was performed to initiate risk mitigation action. Criticality matrices highlight the risks of the different failure modes with regard to the probability of their occurrence and impact on operations. It was assessed that the availability of the ITER CIS, with appropriate mitigating actions applied, meets the project availability requirement for the system.     

Design of Timing System Software on EAST–NBI

Neutral Beam Injector (NBI) is one of the main plasma heating and plasma current driving methods for Experimental Advanced Superconducting Tokomaks. In order to monitor the NBI experiment, control all the power supply, realize data acquisition and network, the control system is designed. As an important part of NBI control system, timing system (TS) provides a unified clock for all subsystems of NBI. TS controls the input/output services of digital signals and analog signals. It sends feedback message to the control server which is the function of alarm and interlock protection. The TS software runs on a Windows system and uses Labview language code while using client/server mode, multithreading and cyclic redundancy check technology. The experimental results have proved that TS provides a stability and reliability clock to the subsystems of NBI and contributed to the safety of the whole NBI system.