Jean-Yves Journeaux

ITER CODAC status and implementation plan

CODAC (Control, Data Access and Communication) is the central control system responsible for operating the ITER device. CODAC interfaces to more than 160 plant systems containing actuators, sensors and local control. CODAC is responsible for coordinating and orchestrating the operation of these plant systems including plasma feedback control. CODAC is developed by ITER Organization, while plant systems are developed by the seven ITER parties (China, Europe, India, Japan, Korea, Russia and United States). This procurement model poses enormous challenges, has a big impact on architecture design and requires a strong standardization for better integration and future maintenance. In this paper we briefly describe the CODAC conceptual design, elaborate on the actions taken by the CODAC team to move from conceptual to engineering design during the last year and outline the plans ahead.

Baseline architecture of ITER control system

The control system of ITER consists of thousands of computers processing hundreds of thousands of signals. The control system, being the primary tool for operating the machine, shall integrate, control and coordinate all these computers and signals and allow a limited number of staff to operate the machine from a central location with minimum human intervention. The primary functions of the ITER control system are plant control, supervision and coordination, both during experimental pulses and 24/7 continuous operation. The former can be split in three phases; preparation of the experiment by defining all parameters; executing the experiment including distributed feed-back control and finally collecting, archiving, analyzing and presenting all data produced by the experiment. We define the control system as a set of hardware and software components with well defined characteristics. The architecture addresses the organization of these components and their relationship to each other. We distinguish between physical and functional architecture, where the former defines the physical connections and the latter the data flow between components. In this paper, we identify the ITER control system based on the plant breakdown structure. Then, the control system is partitioned into a workable set of bounded subsystems. This partition considers at the same time the completeness and the integration of the subsystems. The components making up subsystems are identified and defined, a naming convention is introduced and the physical networks defined. Special attention is given to timing and real-time communication for distributed control. Finally we discuss baseline technologies for implementing the proposed architecture based on analysis, market surveys, prototyping and benchmarking carried out during the last year.

Starting Manufacture of the ITER Central Solenoid

The central solenoid (CS) is a key component of the ITER magnet system to provide the magnetic flux swing required to drive induced plasma current up to 15 MA. The manufacture of its different subcomponents has now started, following completion of the design analyses and achievement of the qualification of the manufacturing procedures. A comprehensive set of analyses has been produced to demonstrate that the CS final design meets all requirements. This includes in particular structural analyses carried out with different finite-element models and addressing normal and fault conditions. Following the Final Design Review, held in November 2013, and the subsequent design modifications, the analyses were updated for consistency with the final design details and provide evidence that the Magnet Structural Design Criteria are fully met. Before starting any manufacturing activity of a CS component, a corresponding dedicated qualification program has been carried out. This includes manufacture of mockups using the real manufacturing tools to be tested in relevant conditions. Acceptance criteria have been established for materials and components, winding including joints, cooling inlets and outlets, insulation, precompression, and support structure elements.

Overview of the ITER Toroidal Field Magnet System Integration

The first series components of large D-shaped toroidal field coils (TFC) on the ITER Tokamak project are being fabricated and assembled at European Fusion for Energy (F4E) and Japanese Domestic Agency (JADA) premises since 2013. The TF magnet system consists of 18 individual coils connected in series based on a Nb3Sn cable-in-conduit conductors supplied by a 68-kA rated current with an overall 41-GJ stored energy and a peak magnetic field of 11.8 T. One of the key challenges of the construction of the 18 TFCs and their assembly resides in the control of the integration of the large individually manufactured coil components and in the ultimate management of tolerances on the final assembly into the Tokamak pit. This paper presents the integration aspects related to main TFCs subcomponents under fabrication starting from the TF conductor production, the winding of individual double pancakes, and their heat treatment and impregnation. This includes the fabrication of key prototypes for qualification purpose such as helium supply inlets, the electrical joints, and the design of the winding pack insertion into the structural TFC case during the final welding enclosure. Each preassembled 40° sector of a TFCs pair is then integrated into the torus according to tight tolerance requirements to provide both the so-called TF magnetic center line data and to guarantee the final operating wedged design into the inner leg region. The assembly of the coils terminal is then completed by connecting services through the power feeder busbars, the quench detection high voltage cables and the cryogenics interfaces pipe system.

Cryogenic instrumentation for ITER magnets

Accurate measurements of the helium flowrate and of the temperature of the ITER magnets is of fundamental importance to make sure that the magnets operate under well controlled and reliable conditions, and to allow suitable helium flow distribution in the magnets through the helium piping. Therefore, the temperature and flow rate measurements shall be reliable and accurate. In this paper, we present the thermometric chains as well as the venturi flow meters installed in the ITER magnets and their helium piping. The presented thermometric block design is based on the design developed by CERN for the LHC, which has been further optimized via thermal simulations carried out by CEA. The electronic part of the thermometric chain was entirely developed by the CEA and will be presented in detail: it is based on a lock-in measurement and small signal amplification, and also provides a web interface and software to an industrial PLC. This measuring device provides a reliable, accurate, electromagnetically immune, and fast (up to 100 Hz bandwidth) system for resistive temperature sensors between a few ohms to 100 kΩ. The flowmeters (venturi type) which make up part of the helium mass flow measurement chain have been completely designed, and manufacturing is on-going. The behaviour of the helium gas has been studied in detailed thanks to ANSYS CFX software in order to obtain the same differential pressure for all types of flowmeters. Measurement uncertainties have been estimated and the influence of input parameters has been studied. Mechanical calculations have been performed to guarantee the mechanical strength of the venturis required for pressure equipment operating in nuclear environment. In order to complete the helium mass flow measurement chain, different technologies of absolute and differential pressure sensors have been tested in an applied magnetic field to identify equipment compatible with the ITER environment.

Design, Test, and Validation of Thermometric Chains for ITER Magnets

The accurate measurement of the temperature of ITER magnets is of fundamental importance, to make sure that the magnets operate under well-controlled and reliable conditions, and allows suitable flow distribution in the magnets through the helium piping. Therefore, the temperature measurements shall be reliable and accurate. In this paper, we present the full thermometric chain of ITER magnets, from the sensor and its attachment, to the electronic conditioning of the signals. The thermoblock is based on a CERN design, which has been further optimized due to thermal simulations carried out by CEA. The electronic system is based on a lock-in measurement and amplification of small signals and provides a web interface and a software to monitor and record temperatures. This device allows the reliable, accurate, electromagnetically immune, and fast (100-Hz bandwidth) measurement of resistive temperature sensors between a few ohms to 100 k Ω. Measurements are also available through Profinet and Modbus TCP fieldbus for process automation. The cryogenic test bench for validation of the full thermometric chain is described, with a particular attention to the accuracy of the measurement. First results of this qualification are presented, which give good confidence in the reliability and accuracy of the thermometric system for ITER magnets.