Duck-Hoi Kim

Manufacturing and Examination for ITER Blanket First Wall Small-Scale Mockups With KoHLT-EB in Korea

The ITER first wall (FW) includes beryllium armor tiles joined to a CuCrZr heat sink. The FWs are one of the critical components in an ITER machine with a surface heat flux of 4.7 MW/m2 or above. The small-scale mockup shall be a part of the qualification tests and used to validate the performance of the dominant manufacturing technologies before the production of larger scale components, and this mockup shall be equipped with a hypervapotron heat sink and manufacturing processes developed for a semiprototype design. The small-scale mockup includes 48 beryllium armor tiles (12 mm × 12 mm) capable of withstanding the specified heat flux values. The tile thickness shall be 6 mm to minimize the beryllium surface temperature and evaporation under high thermal loads. The detailed fabrication process of semiprototype small-scale mockups was developed for a qualification test in Korea. For the CuCrZr and stainless steel, the canned materials are processed into an hot isostatic pressing (HIP) device. In the case of beryllium-to-CuCrZr joining, the HIP was conducted at 580°C and 100 MPa. For nondestructive tests of the fabricated semiprototypes, visual and dimension inspections were performed whenever needed during the fabrication process, and ultrasonic tests were performed using ultrasonic probes. Destructive tests for the qualification semiprototype were performed on a small-scale mockup, which was fabricated together with semiprototypes. The Korea heat load test facility using an electron beam system was constructed with an electron gun (maximum electric power of 800 kW) for a high heat flux application with a 300-kW high-voltage power supply and maximum accelerating voltage of 60 kV. This facility was operated to evaluate the performance test of plasma facing components. A cyclic heat flux test will be performed to evaluate the ITER qualification program.

Commissioning of the Korean High Heat Flux Test Facility by Using Electron Beam System for Plasma Facing Components

Abstract Korean high heat flux test facility for the plasma facing components of nuclear fusion machines will be constructed to evaluate the performance of each component. This facility for plasma facing materials will be equipped with an electron beam gun with a 60 kV acceleration voltage. The system also includes a 300 kW power supply system, a vacuum test chamber, and a beryllium filtration system for the ITER first wall mockups. First, a commissioning test has been scheduled to establish the installation and preliminary performance experiments of the copper hypervapotron mockups and evaluate the thermo-hydraulic specifications. Second, a qualification test will be performed to evaluate the CuCrZr duct liner in the ITER neutral beam injection facility and the ITER first wall small-scale mockups of the semi-prototype, at up to 1.5 and 5 MW/m2 high heat flux, respectively. This electron beam system will be used to qualify the specifications of the plasma facing components in the KSTAR tokamak and other fusion devices.

Thermo-Hydraulic Performance Analysis for Conceptual Design of ITER Blanket Shield Block

Abstract Since the recommendation of blanket redesign by 2007 ITER design review, the blanket system has been developed in the framework of blanket integrated product team composed mainly of ITER organization and procuring parties. As a part of blanket conceptual design tasks, Korea domestic agency has supported the design analyses with respect to the hydraulic and thermal performance of the inboard blanket shield block. Three dimensional thermo-hydraulic and thermo-mechanical analyses of the inboard conceptual model with the poloidal cooling concept were performed. Two kinds of operation scenarios, inductive and non-inductive operations, were considered as representative loading conditions. The pressure drop, heat transfer and coolant uniformity in cooling passages were investigated in detail. The stress evaluation according to relevant code and standard was carried out and thermal bowing at flexible supports was also investigated. This paper presents the detailed analysis results, identifies issues on the conceptual configuration and makes suggestions on design improvements. In addition, this manuscript briefly describes about the complementary study such as the comparison of heat transfer coefficients calculated by empirical formula and CFD, and the effect of surface roughness inside the cooling channels.

ITER blanket engineering challenges and solutions

The ITER blanket design process is very challenging due to demanding design and interface requirements and constraints, including high heat fluxes from the plasma, large electromagnetic loads during off-normal events, sufficient contribution to the shielding of the vacuum vessel and superconducting coils, and tight interfacing space constraints with many key components. This paper highlights some of these challenges and the associated solutions developed as part of the final blanket design effort.

Current status of final design and R&D for ITER blanket shield blocks in Korea

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.

Status of Design and R&D for ITER Blanket in Korea

Abstract Since the decision of blanket redesign by 2007 ITER design review, the blanket system is being developed in the framework of Blanket Integrated Product Team (BIPT) composed mainly of ITER Organization (IO) and procuring parties. Korean Domestic Agency (KODA) is mainly contributing to the design and development of blanket Shield Block (SB). In particular, KODA is supporting the design activities including electromagnetic, thermo-hydraulic and thermo-mechanical analyses to complete the final design of blanket shield block. For the manufacturing of a blanket shield block conventional fabrication techniques based on drilling, milling and welding of stainless steel forged blocks have been adopted. As a consequence of the manufacturing feasibility study, key fabrication techniques to be verified beforehand have been identified and successfully developed in collaboration with related industries. The pre-qualification program of the fabrication and testing of Full Scale Prototype (FSP) is in progress. Until now the material development of 316L(N)-IG stainless steel forging has been successfully completed, and the fabrication of FSP is on-going. Even though the procurement of blanket First Wall (FW) was withdrawn at the 9th meeting of the ITER Management Advisory Committee, the participation of the 2nd pre-qualification program of EHF (Enhanced Heat Flux) FW small scale mock is being valid for securing core engineering technologies. At present the fabricated mock-ups are waiting for high heat flux test with the Electron Beam (EB) gun test facility being newly built in Korea. This paper provides the current status of design and relevant R&D activities of the blanket system to secure key technologies and to fulfill our promise to ITER project.

Results of the qualification test for ITER blanket first wall small-scale mockups in Korea

The ITER first wall (FW) includes beryllium armour tiles joined to a CuCrZr heat sink with stainless steel cooling tubes. The FW panels are one of the critical components in an ITER machine with a surface heat flux of 4.7 MW/m2 or above. The small-scale mockup shall be part of the qualification program and used to validate the performance of the key manufacturing technologies before the production of larger scale components, and this mockup shall utilize the hypervapotron heat sink and manufacturing processes developed for a semi-prototype design. The small-scale mockup includes 48 beryllium armour tiles (12 mm × 12 mm) capable of withstanding the specified heat flux values. The tile thickness shall be 6 mm to minimize the beryllium surface temperature and evaporation under high thermal loads. The detailed fabrication process of semi-prototype small-scale mockups was developed for a qualification test in Korea. For the CuCrZr and stainless steel, the canned materials are processed into an HIP (Hot Isostatic Pressing) device. In the case of beryllium to CuCrZr joining, the HIP was conducted at 580 °C and 100 MPa. For non-destructive tests of the fabricated semi-prototypes, visual and dimension inspections were performed whenever needed during the fabrication process, and ultrasonic tests were performed with ultrasonic probes. Destructive tests for the qualification semi-prototype were performed on a small mockup, which was fabricated together with semi-prototypes. The Korea heat load test facility, KoHLT-EB (Electron Beam) was constructed with an electron gun (Max. 800 kW) for a high heat flux application with a 300 kW high voltage power supply, and maximum accelerating voltage of 60 kV. This test facility was operated to evaluate the performance of these small-scale mockups. A cyclic heat flux test will be performed to evaluate the ITER qualification program.