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In April 2020, manufacturing of the ITER vacuum vessel (VV) first sector has been completed by the Korean domestic agency, manufacturing having started in February 2012. The ITER VV sector is the largest fusion VV structure in the world. Each step of the manufacturing was a challenge as a first-of-a-kind, and a French nuclear pressure vessel. The paper provides an overview of the major challenges which were overcome over the last 10 years.

Manufacturing design of Korean sectors and ports for the ITER Vacuum Vessel (VV) has been developed to comply with the tight tolerance and severe inspection requirements. The first VV sector and lower ports are being fabricated slowly under strict regulations after verification using several real scale mock-ups and qualifications for welding, forming and NDE. During three years after start of fabrication, manufacturing progress on four poloidal segments of the first sector is that (1) all inner shells were welded, (2) forgings for complicate components have been machined, (3) port stubs and poloidal T-ribs were assembled, and (4) machined components are welded on the inner shells by narrow-gap TIG welding and electron beam welding. The progress of lower ports is that (1) inner shells of stub extensions were bent and treated with heat, (2) T-ribs were fabricated and examined by qualified phased array UT, (3) supporting pads and gussets have been machined, and (4) inner shells are assembled with T-ribs and machined forgings. The progress rate of manufacturing is around 40% up to the end of 2015 for the first sector and lower port stub extensions.

As a participant of ITER project, ITER Korea has to supply two ITER vacuum vessel sectors (Sector #6, #1) of total nine ITER VV sectors. After the procurement arrangement with ITER Organization, ITER Korea made the contract with Hyundai Heavy Industries (HHI) for fabrication of two sectors. Then the start of the manufacturing design was initiated from January 2010. HHI made three real scale R&D mock-ups to verify the critical fabrication feasibility issues on electron beam welding, 3D forming, welding distortion and achievable tolerances. The documentation according to IO and the French nuclear safety regulation requirement, the qualification of welding and nondestructive examination procedures conform to RCC-MR 2007 were proceed in parallel. The mass production of raw material was done after receiving ANB (agreed notified body) verification of product/parts and shop qualification. The manufacturing drawing, manufacturing and inspection plan of VV sector with supporting fabrication procedures are also verified by ANB, accordingly the first cutting and forming of plates for VV sector fabrication started from February 2012. This paper reports the latest fabrication progress of ITER vacuum vessel Sector #6 that will be assembled as the first sector in the ITER pit. The overall fabrication route, R&D mock-up fabrication results with forming and welding distortion analysis, qualification status of welding and nondestructive examination (NDE) are also presented.

The detailed design of ITER thermal shield (TS), which is planned to be procured completely by Korea, has been implemented since 2007. In this paper, the design and the supporting analysis are described for the critical components of the TS, the vacuum vessel TS (VVTS) outboard panel, labyrinths and VVTS supports. The wall type of VVTS outboard panel was changed from double wall to single wall, and the verification analyses were carried out for this design change. The dimensions of the labyrinths were determined and the heat load through the labyrinth was analyzed to check the design requirement. The preliminary result of the VVTS inboard and outboard supports were obtained considering the structural rigidity.

ITER thermal shield, which is to be fully made by Korea, is very large system and its tolerance requirement is so tight that the precise design and manufacture are indispensable. Therefore, it is very important that the critical components of the thermal shield are tested before the manufacture of full-scale thermal shield to avoid possible risks. In this paper, mock-ups of the thermal shield components are described and the test results are reported. The weld test and the reliability test were performed for the cooling tubes. The silver coating was also tested for small specimens to investigate the quality and the process of coating. Effect of chromate treatment to prevent the discoloration on the silver coating surface was also investigated experimentally.

The thermal shield system of ITER plays the role of reducing heat loads transferred by thermal radiation and conduction from warm components to the components and structures that operate at 4.5 K. In the design of thermal shields, it is of importance to ensure that they maintain thermal loads within the specified design criteria. In the present work, a study is conducted on thermal analyses in order to confirm that the thermal shield design can accommodate the thermal loads during the plasma operation state and the baking state of the ITER vacuum vessel. Design of the cooling tube layout of a vacuum vessel thermal shield is followed based on the results of thermal analyses. It is demonstrated that the present results can be applied to the detailed design of the ITER thermal shield system.

Based on the design done by the ITER international organization (ITER-O) and other participant teams, the more detail engineering design of the ITER vacuum vessel port and support is progressed by the Korea ITER project team. In this work, the recent design elaboration and manufacturing feasibility study from 2006 mainly focused on the equatorial and lower port are reported. The fabrication status and test plan of vacuum vessel support mock-up are also introduced.

A study is conducted on the conceptual design of the structure and cooling channels of the upper port plug of International Thermonuclear Experimental Reactor (ITER). Modification of the earlier port plug design is made and a simple fabrication method is proposed. It is shown that the newly designed port plug can accommodate the installation of both diagnostic and electron cyclotron heating (ECH) devices. Design assessment is carried out through structural and thermo-hydraulic analyses. Results of the analyses show that the port plug structure is stable against one of the most severe plasma events and the total pressure drop of the coolant is within the allowable level.

Sodium in most biological systems relaxes biexponentially and generates a multiple-quantum signal. In a multiple-quantum filtering sequence, the sodium contributing to the multiple-quantum signal is in single-quantum coherences during the preparation and acquisition times, while it is in multiple-quantum coherences during the evolution time. In contrast to the biexponential relaxation of single-quantum coherences, double- and triple-quantum coherences relax monoexponentially during the evolution time with fast and slow transverse relaxation rates, respectively. This unique feature of multiple-quantum filtering is exploited to measure the transverse relaxation rates of phantoms simulating intracellular and extracellular sodium by analyzing the double- and triple-quantum signals acquired at various evolution times. As a byproduct, the relative ratio of multiple-quantum signals derived from intracellular and extracellular sodium can also be simultaneously determined. This technique may enable the distinction between intracellular and extracellular sodium content in biological systems without using potentially toxic shift reagents.

Breakthrough of single-quantum coherence is shown to occur after application of a double-quantum filter with the conventional four-step phase-cycling scheme. This single-quantum breakthrough is due to the intersequence stimulated echo which has been generated by the radiofrequency pulses in the preceding pulse sequence and appears at the same time as the double-quantum coherence signal in the current pulse sequence. Moreover, the phase of the intersequence stimulated echo is the same as the phase of the double-quantum coherence signal; i.e., the phase of the intersequence stimulated echo is twice the phase change of the radiofrequency pulses in the creation period when their phase is rotated in accordance with the conventional four-step phase-cycling scheme. Consequently, the intersequence stimulated echo passes through the double-quantum filtration in the conventional four-step phase-cycling scheme and gradient pulses. A new phase-cycling scheme which can filter out the single-quantum breakthrough signal is proposed here and its effectiveness is verified experimentally and by computer simulations.

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 © 2011 by ASME

The main function of the ITER blanket shield block (SB) is to provide nuclear shielding and support the first wall (FW) panel. It needs to accommodate all the components located on the vacuum vessel (in particular the in-vessel coils, blanket manifolds and the diagnostics). The conceptual, preliminary and final design reviews have been completed in the framework of the Blanket Integrated Product Team. The Korean Domestic Agency has successfully completed not only the final design activities, including thermo-hydraulic and thermo-mechanical analyses for SBs #2, #6, #8 and #16, but also the SB full scale prototype (FSP) pre-qualification program prior to issuing of the procurement agreement. SBs #2 and #6 are located at the in-board region of the tokamak. The pressure drop was less than 0.3 MPa and fully satisfied the design criteria. The thermo-mechanical stresses were also allowable even though the peak stresses occurred at nearby radial slit end holes, and their fatigue lives were evaluated over many more than 30 000 cycles. SB #8 is one of the most difficult modules to design, since this module will endure severe thermal loading not only from nuclear heating but also from plasma heat flux at uncovered regions by the FW. In order to resolve this design issue, the neutral beam shine-through module concept was applied to the FW uncovered region and it has been successfully verified as a possible design solution. SB #16 is located at the out-board central region of the tokamak. This module is under much higher nuclear loading than other modules and is covered by an enhanced heat flux FW panel. In the early design stage, many cooling headers on the front region were inserted to mitigate peak stresses near the access hole and radial slit end hole. However, the cooling headers on the front region needed to be removed in order to reduce the risk from cover welding during manufacturing. A few cooling headers now remain after efforts through several iterations to remove them and to optimize the cooling channels. The SB #8 FSP was manufactured and tested in accordance with the pre-qualification program based on the preliminary design, and related R&D activities were implemented to resolve the fabrication issues. This paper provides the current status of the final design and relevant R&D activities of the blanket SB.

Equations describing the multiple-quantum (MQ) signal produced by an MQ pulse sequence are systematically derived in both absence and presence of refocusing RF pulses. When the RF pulses in an MQ pulse sequence satisfy certain conditions, these equations may be arranged in a factorized form. The off-resonance effects on the MQ signal due to chemical shift can then be analyzed separately during the preparation and evolution times. Using the reformulated equations, the dependence of the amplitude of an MQ signal on the phase shift induced by the resonance offset during the preparation and evolution times is demonstrated. By use of the new equations, it is shown that the off-resonance effects, occurring during both the preparation and evolution times, may be described in terms of the same physical process, i.e., interference between echo and antiecho. In applying the off-resonance effects for the elimination of the MQ signal in the presence of chemical shift, it is possible to suppress the MQ signal over a wider off-resonance bandwidth by use of the nonrefocused preparation and evolution times than by use of a single time. Furthermore, by taking an alternative approach in deriving the equations, the interference between echo and antiecho due to the resonance offset is shown to be insensitive to the flip angle of the creation RF pulse (usually the second π/2 RF pulse). The theoretical findings were experimentally verified by use of a phantom containing sodium in agarose.

New double-quantum filtering (DQF) schemes are theoretically developed by reformulating the equations describing the double-quantum (DQ) signal. The equations describing the second- and third-rank DQ signals are simplified by restricting the RF phases as required for DQF. The equations are then factorized into two terms representing the separate contribution to the DQ signal from the RF pulses involved in the preparation and evolution times. This allows analysis of the DQ signal of a particular DQF scheme separately for each of these times in a concise manner. By use of the reformulated equations, the conventional DQF scheme is shown to be only one of four possible DQF schemes. The three new DQF schemes offer some desirable properties over the conventional DQF scheme. In the conventional DQF scheme, the third-rank DQ signal declines rapidly to null as the flip angles of the creation and readout RF pulses deviate from 90 degrees to 54.7 degrees or 125.3 degrees. In addition, the second- and third-rank DQ signals in the conventional DQF scheme are opposite in their polarities, resulting in attenuation of the total DQ signal due to destructive interference between them. In one of three new DQF schemes, the DQ signal does not vanish at 54.7 degrees and 125.3 degrees, but varies smoothly with the same functional dependence on the RF flip angles as the second-rank DQ and triple-quantum signals. Furthermore, in two of the three new DQF schemes, the second- and third-rank DQ signals have the same polarity so that the total DQ signal may be enhanced through constructive interference between them. These features of new DQF schemes have been confirmed experimentally.

The rate of furfural decarbonylation was investigated in the presence of a charcoal supported palladium catalyst using potassium carbonate as accelerator in the liquid phase between 150 and 160°C. Reaction speed varied with the quantity of catalyst and increased exponentially with temperature. Activation energy under these experimental conditions was 310 kJ/mol. Reaction by-products were mainly of high molecular weight, resulting from various dimerization reactions involving furan and/or 2-methyl furan. These products covered the surface of the catalyst and blocked active sites, resulting in deactivation.

During continuous furfural decarbonylation, using a carbon supported palladium catalyst, a high catalytic activity (36 000 g of furan per g of palladium) was observed. Furan productivity remained almost constant for 45 h and then decreased gradually to reach a new low level after 90 h. Analysis of residues indicated that by-products are partly responsible for the decrease in furan productivity.