C.H. Choi

ITER vacuum vessel design and construction

Abstract According to recent design review results, the original reference vacuum vessel (VV) design was selected with a number of modifications including 3D shaping of the outboard inner shell. The VV load conditions were updated based on reviews of the plasma disruption and vertical displacement event (VDE) database. The lower port gussets have been reinforced based on structural analysis results, including non-linear buckling. Design of in-vessel coils for the mitigation of edge localized modes (ELM) and plasma vertical stabilization (VS) has progressed. Design of the in-wall-shielding (IWS) has progressed in details. The detailed layout of ferritic steel plates and borated steel plates is optimized based on the toroidal field ripple analysis. The procurement arrangements (PAs) for the VV including ports and IWS have been prepared or signed. Final design reviews were carried out to check readiness for the PA signature. The procedure for licensing the ITER VV according to the French Order on Nuclear Pressure Equipment (ESPN) has started and conformity assessment is being performed by an Agreed Notified Body (ANB). A VV design description document, VV load specification document, hazard and stress analysis reports and particular material appraisal were submitted according to the guideline and RCC-MR requirements.

Final design of the beam source for the MITICA injector

The megavolt ITER injector and concept advancement experiment is the prototype and the test bed of the ITER heating and current drive neutral beam injectors, currently in the final design phase, in view of the installation in Padova Research on Injector Megavolt Accelerated facility in Padova, Italy. The beam source is the key component of the system, as its goal is the generation of the 1 MeV accelerated beam of deuterium or hydrogen negative ions. This paper presents the highlights of the latest developments for the finalization of the MITICA beam source design, together with a description of the most recent analyses and R&D activities carried out in support of the design.

Status of the KSTAR Tokamak Construction

The KSTAR is a superconducting tokamak under construction at the Korea Basic Science Institute (KBSI) in Daejeon, Korea. The project mission aims at a steady-state operation and advanced tokamak physics. At present, the project is in the peak of fabrication and assembly phase. The fabrication of the major tokamak structures such as vacuum vessel, cryostat, port system, thermal shields, and gravity support, is completed. The manufacture and testing of the 30 superconducting magnets are rigorously being progressed. As of Sep. 2005, 16 toroidal field coils and 4 large poloidal field coils are completed. To verify the operational feasibility of the KSTAR coils, cool-down and current charging tests of a real sized prototype TF coil and a pair of CS model coil have been carried out. The assembly of the device has begun from beginning of 2004. Now, the vacuum vessel body, thermal shields and 8 toroidal field magnets are assembled on the tokamak position. Assembly finish is scheduled for August 2007. This paper describes the manufacture and assembly progress of the KSTAR tokamak

Overview of the negative ion based neutral beam injectors for ITER

The ITER baseline foresees 2 Heating Neutral Beams (HNBs) based on 1 MeV 40 A D(-) negative ion accelerators, each capable of delivering 16.7 MW of deuterium atoms to the DT plasma, with an optional 3rd HNB injector foreseen as a possible upgrade. In addition, a dedicated diagnostic neutral beam will be injecting ≈22 A of H(0) at 100 keV as the probe beam for charge exchange recombination spectroscopy. The integration of the injectors into the ITER plant is nearly finished necessitating only refinements. A large number of components have passed the final design stage, manufacturing has started, and the essential test beds-for the prototype route chosen-will soon be ready to start.

In-service inspection and instrumentation for ITER vacuum vessel

In-service inspection (ISI) is required according to the French Order for Nuclear Pressure Equipment and also to protect plant investment and to ensure machine availability. The ITER VV maintenance and monitoring program includes Inservice Monitoring, Periodic Test and Periodic Inspection. Inservice Monitoring includes commissioning tests, continuous vacuum and water leakage monitoring and load follow-on monitoring. Periodic Test includes regular pressure tests and leak tests. For the outer shell welds of the main vessel, the equatorial region of “port #7” and lower penetrations are selected for Periodic Inspection. R&D for ISI is underway and tools and maintenance systems are being developed. Mock-ups were constructed to demonstrate its feasibility. In addition, a study of acoustic emission monitoring has started using a mock-up. The VV instrumentation is a system to monitor the VV status in normal and off-normal conditions. The VV instrumentation system includes approximately 1600 sensors, mounting devices, cables, cable holders, vacuum feed-throughs for the vessel and the cryostat, control cubicles and interrogating systems. Approximately 850 thermocouples are installed to monitor temperatures on plasma-side and cryostat-side surfaces of the vessel. Resistive and FBG strain gauges are also mounted on the vessel surfaces. Displacement sensors and accelerometers are installed to obtain data of VV movements during plasma disruptions or VDEs. These data are utilized to calculate forces on the VV. This calculation is essential to categorize plasma disruption or VDE events during the ITER operational phase.

Status of ITER neutral beam cell remote handling system

Abstract The ITER neutral beam cell will contain up to three heating neutral beams and one diagnostic neutral beam, and four upper ports. Though manual maintenance work is envisaged within the cell, when containment is breached, or the radiological protection is removed the maintenance must be conducted remotely. This maintenance constitutes the removal and replacement of line replaceable units, and their transport to and from a cask docked to the cell. A design of the remote handling system has been prepared to concept level which this paper describes including the development of a beam line transporter, beam source remote handling equipment, upper port remote handling equipment and equipment for the maintenance of the neutral shield. This equipment has been developed complete the planned maintenance tasks for the components of the neutral beam cell and to have inherent flexibility to enable as yet unforeseen tasks and recovery operations to be performed.

Structural analysis of the KSTAR toroidal field magnet system

The toroidal field (TF) magnet system of Korea superconducting tokamak advanced research (KSTAR) device consists of 16 superconducting coils enclosed in the steel cases. The TF magnet structure protects the winding pack from mechanical, electrical, and thermal loads, and also supports three pairs of poloidal field (PF) coils as well as four pairs of central solenoid (CS) coils. A three-dimensional finite element (FE) model including the winding pack, insulation and filler material has been developed using solid brick elements, and a hybrid model with beam-shell elements has been also built for the verification purposes. The structural reliability of the TF magnet system is investigated by performing various analyzes such as a global/local analysis, a detailed analysis, and a fatigue evaluation. The results reveal that the maximum stress intensities of the TF magnet structure are below the allowable stress limit and its fatigue life complies with the requirements of the design criteria, so it can safely withstand the reference scenario operations. In addition, the design loads obtained from analysis results can be used for the detailed structural design of other supplementary components.

Structural analysis work on ITER Vacuum Vessel

The structural integrity of the ITER Vacuum Vessel is verified by elastic and/or non-linear analyses. The typical loads for the Vacuum Vessel are also explained. Electromagnetic load by vertical displacement event of plasma is most serious load. Major design modifications from basic design requirement are verified.

Final design and start of manufacture of the ITER Vacuum Vessel ports

The ITER Vacuum Vessel (VV) features upper, equatorial and lower ports. Although the port design has been overall completed in the past, the design of some remaining interfaces was still in progress and has been finalized now. As the ITER construction phase has started, the procurement of the VV ports has been launched. The VV upper ports will be procured by the Russian Federation DA, while the equatorial and lower ports will be procured by the Korean DA. The main industrial suppliers were selected and development of the manufacturing design is in progress now. Since the VV is classified at nuclear level N2, design and manufacture of its components are to be compliant with the French code RCC-MR and regulations of nuclear pressure equipment in France. These regulations make a strong impact to the port design and manufacturing process, which is in progress now.

Fabrication Design and Code Requirements for the ITER Vacuum Vessel

The ITER vacuum vessel (VV) is a double walled torus structure and one of the most critical components in the fusion reactor. The design and fabrication of the VV as nuclear equipment shall be consisted with the RCC-MR code based on French fast breeder reactor. The VV is a heavy welded structure with 60 mm thick shells, 40 mm ribs and flexible housing of 275 mm diameter. The welding distortion should be controlled since the total welding length is over 1500 m. To satisfy the design requirement, the electron beam welding (EBW) and narrow gap gas tungsten arc welding (GTAW) techniques are to be applied and developed through the fabrication of mock-ups. The fabrication design has been developed to manufacture the main vessel and port structures in accordance with the RCC-MR code. All fabrication sequences including welding methods are also established to meet the demanding tolerance and inspection requirement by HHI as a supplier.Copyright