[en] Highlights: • The results of the experiment and the numerical analysis are compared. • The numerical analysis results are lower than the experimental results. • The margin of the pressure drop is suggested. - Abstract: The blanket shield block (SB) is located inside the ITER vacuum chamber, and the main function is to provide the thermal and nuclear shielding to the vacuum vessel and external components. The SB is foreseen to undergo a significant heat load which is a body load throughout the whole thickness of the SB under normal operation conditions. Therefore, the cooling configuration in SB should be designed very carefully based on the various experiences. The pressure drop in the cooling design is one of the most important factors to balance a water distribution of overall blanket cooling system. In order to verify the pressure drop characteristic and validate the design methodology of SB, experiment and numerical analysis are performed and compared their results. These results would be a benchmarking of the numerical results with experimental results to assess the gap between calculations and experiments.

[en] Highlights: • The SB#08 FSP were manufactured by using conventional manufacturing processes such as cutting, milling, drilling and welding. • Especially, a strong back system was adopted in order to prevent welding deformation during cover plate welding process. • Post-Welding Heat Treatment (PWHT) for stress relieving and Hot He Leak Test (HHLT) were waived from the lake of huge test facility in the pre-qualification program. • The PWHT combined with the HHLT, however, were implemented to remove the residual stress and to confirm the soundness of welded parts as an internal R&D activities after the pre-qualification program. • Three dimensional inspection also carried out after the PWHT to check the dimensional stabilization. - Abstract: The tight tolerance requirement is one of key issue to manufacture the ITER blanket shield blocks (SBs) which have many interfaces with the First Wall (FW) and Vacuum Vessel (VV). Manufactured SB shall be satisfied with general tolerances (Class “C” of ISO 2768-1 and “L” of ISO 2768-2) and specific tolerance in 2D general assembly drawings. In order to fulfill the tight tolerance requirements in the final stage of SB, stress relieving after welding operations in the manufacturing process shall be performed. Hot helium leak test, Post Welding Heat Treatment (PWHT) and three-dimensional inspection before and after heat treatment were implemented by using the Full Scale Prototype (FSP) of SB in the framework of domestic R&D activities. The hot He leak test was performed at 250 °C for 30 min, and the result was satisfied the requirements. PWHT was carried out at 400 °C for 24 h by brazing furnace with test chamber. The deformation value before and after was measured by contact type coordinate measuring machine. The objective of this study is to verify dimensional stability of SB after stress relieving. The results will support to determine the machining allowance prior to welding process.

[en] The new joining method of SiC components with channel was developed in this study by using hot-press. The SiC ceramics was joined by using mixed Al₂O₃, Y₂O₃, SiO₂ and SiC powders. Joining was carried out at from 1500 deg. C to 1900 deg. C for 1 h, under an applied pressure, range from 5 MPa to 20 MPa. Microstructural characterization was carried out for the joined materials by optical and scanning electron microscopy. The mechanical property of the joint was evaluated through a tensile test. The joint strength was increased with increasing joining temperature and pressure. In joining of complex shape SiC components, the serious deformation of substrate occurred because of high joining temperature and pressure. The low joining condition, In case of 1800 deg. C and 20 MPa, deformation of substrate not occurred. It is possible that the deformation of substrate was controlled by joining temperature. The joint layer of SiC component by using new joining method was cleaned and uniformed.

[en] ITER project is progressing and the structural material of the blanket will be conventional stainless steels. In the future, the SiC/SiC composites will be employed as the important part of the reactor. Main construction of the reactor will be keep stainless steels such as SUS316L and RAFM steels, the interface technology of SiC and steels will be essential. There are many situation of to connect the SiC component and steel structures, the development of technology for the connecting is not enough. Mismatch of coefficients of thermal expansion (CTE) prevent the simple diffusion bonding of plates, normally insert materials are used to absorb the mismatch of the CTE. There is a possibility to use the CTE mismatch for the connecting, and in present research, some fundamental researches of potential techniques to connect SiC/SiC composites and steels using the metallurgical method have been developed and investigated.

[en] As an advanced liquid phase sintering method of SiC/SiC composites production, Nano-Infiltration and Transient Eutectic-phase (NITE) process has been intensively studied, where large volumetric shrinkage during sintering process is an issue to be solved. The objective of this work is to investigate the effects of preform densification on microstructure and mechanical properties of SiC/SiC composites fabricated by hot-press of preforms. The significant improvement seen in preform is the suppression of macro-pores at inter-/intra- fiber-bundles. Finally, this is contributing the reduction of volumetric shrinkage to suppress fiber damage and micro pore formation and eliminate macro pore formation after sintering. And, the composites fabricated presents microstructure homogeneity. The improvement in structure is reflected in high flexural strength. However, pseudo-ductility was worth than anticipated. The brittle behavior of the composites is interpreted to be caused by the damage of PyC interphase. (author)

[en] In this study, the evaluation of shear strength for joined SiC ceramics was conducted by using a torsion test. Two specimen types based on F734-95 ASTM Standard and one proposed for miniature test specimen in this study were prepared. The effects of specimen size and geometry were investigated by using finite-element stress method (FEM) analysis. The specimens were joined by the NITE process with mixed powder of Al₂O₃, Y₂O₃, SiO₂ and SiC as joining adhesive. Joining was carried out at 1800 deg. C for 1 h, under an applied pressure of 20 MPa by hot pressing. The fracture surfaces after torsion test were observed by using optical microscopy.

[en] In order to establish the industrialization basis of advanced SiC fibers and SiC/SiC composites to be used in nuclear fusion reactors, R and D of Tyranno-SA grade fibers (Cef-NITE^TM) and NITE-SiC/SiC with sufficient quality control has been carried out. The important elements in this effort are fiber structure control and matrix density and homogeneity control. From the continuous heat treatments of pre-crystallized SiC fibers, the improved uniformity of grain size for radial position in 7-10 μm diameter SiC fibers has been confirmed with the fiber strength over 2.0 GPa. In order to establish stable mass production of NITE-SiC/SiC (Cera-NITE^TM), with sufficient quality control, efforts on production of mid-products, such as green sheets, prepreg sheets and preforms, have been extensively carried out. The important elements were to improve the homogeneity and density of preform so that the following sintering process has been modified for improving structure control.

No abstract available

[en] For fusion energy realization, attractive energy conversion system and fuel supply system are essentially required. The current ITER test blanket module study has dual coolant lithium lead (DCLL) system as the attractive blanket option. The concept of making ceramic thermal insulation panels for DCLL blanket has been presented, however, realistic material systems have not been proven so far. This work is trying to present the porous SiC/SiC thermal insulation panel based on the current NITE-method technology. Typical panels with through thickness and in-plane channels and porosities tailored were designed, fabricated and evaluated, successfully. Thermal conductivity of those panels were controlled, as designed, and the tailoring capability of thermal conductivity by NITE-method was presented. This concept and technology can satisfy the basic material requirements as well as economical requirements and large scale production requirements.

[en] Highlights: • The procedure of structural integrity and fatigue assessment was described. • Case studies were performed according to both SDC-IC and ASME Sec. • III codes The conservatism of the ASME code was demonstrated. • The study only covers the specifically comparable case about fatigue usage factor. - Abstract: The ITER blanket Shield Block is a bulk structure to absorb radiation and to provide thermal shielding to vacuum vessel and external vessel components, therefore the most significant load for Shield Block is the thermal load. In the previous study, the thermo-mechanical analysis has been performed under the inductive operation as representative loading condition. And the fatigue evaluations were conducted to assure structural integrity for Shield Block according to Structural Design Criteria for In-vessel Components (SDC-IC) which provided by ITER Organization (IO) based on the code of RCC-MR. Generally, ASME code (especially, B&PV Sec. III) is widely applied for design of nuclear components, and is usually well known as more conservative than other specific codes. For the view point of the fatigue assessment, ASME code is very conservative compared with SDC-IC in terms of the reflected K_e factor, design fatigue curve and other factors. Therefore, an accurate fatigue assessment comparison is needed to measure of conservatism. The purpose of this study is to provide the fatigue usage comparison resulting from the specified operating conditions shall be evaluated for Shield Block based on both SDC-IC and ASME code, and to discuss the conservatism of the results.