Suk-Kwon Kim

DEVELOPMENT OF A HIGH HEAT FLUX TEST FACILITY FOR PLASMA FACING COMPONENTS

A high heat flux test facility using a graphite heating panel was constructed and is presently in operation at Korea Atomic Energy Research Institute, which is called KoHLT-1. One of the major purposes of this facility is to carry out a thermal cycle test of the ITER (International Thermonuclear Experimental Reactor) FWQM (first wall qualification mockup). The facility is equipped with a graphite heating element, a water cooled box-type vacuum chamber, and diagnostic systems. Two mockups are installed in the chamber; two facing mockups are simultaneously heated by a graphite heater installed between two mockups. The graphite heating element has an effective irradiation area of 244 mm × 80 mm and its electrical power is provided by a 40 kW DC power supply. The diagnostic system consists of two independent calorimetric power measuring systems, thermocouples, a vacuum gauge, and a CCD camera. Water cooling, Be treatment, and vacuum pumping systems are also equipped. We performed thermal cycle tests for two Cu mockups, and for Cu and Cu/SS mockups ensure the performance of the KoHLT-1. After that, we carried out thermal cycle tests up to 220 cycles for Cu mockup and FWQM at 0.65 MW/m2, from which the reliability of the KoHLT-1 was verified.

R&D Activities Regarding ITER Blanket First Wall in Korea

Abstract Korea Domestic Agency (KO-DA) was responsible for the procurement of the ITER blanket modules 1, 2, and 6 in the original procurement allocation. According to the procurement reallocation of the blanket system, Korea will procure the blanket shield block in place of the blanket first wall. Nevertheless, several R&D activities in Korea have been performed including optimization of the hot isostatic pressing (HIP) bonding process between Be/CuCrZr and CuCrZr/SS, the nondestructive test method, fabrication feasibility study, high heat flux tests, and design analysis. Especially, KO-DA participated in the qualification program for the mock-up manufacture and high heat flux tests. Several mock-ups were fabricated and tested during the qualification program. The details of the mock-up manufacture and test results are described in this paper. Also, two heat flux facilities were installed based on the graphite heating, and a new electron beam heat flux facility will be built in the near future for the enhanced heat flux mock-up test. As well, some design analysis was performed to investigate the performance of the blanket first wall against thermo-mechanical loading. In this paper, the status of the R&D activities and the results of the qualification tests for KO mock-ups are reviewed.

Joining of Be to Ferritic-Martensitic Steels with Diffusion Barrier Interlayer

Abstract A joining of Be to ferritic-martensitic steels (FMS) is an essential process in the fabrication of ITER test blanket module (TBM). The diffusion barrier layers together with the coated interlayer were applied to the HIP joining of Be and FMS in order to develop the interlayer technology for the fabrication of ITER TBM. Multiple layers formed due to an excessive diffusion of elements in the interface region in the absence of a diffusion barrier layer. Such a complicated interface structure consisting of brittle phases in part would be very prone to fracture even at low stress levels. A Cu foil or a HIPed CuCrZr layer applied as a diffusion barrier was effective to retard the diffusion between Be and FMS. It was revealed that the diffusion barrier layers helped to improve the joining properties by reducing the possibility to form diffusion layers in the interface, which made the Be/FMS joint have an appreciable joining strength.

Long-Term Operation and Basic Corrosion Test in an Experimental Loop for Liquid Breeder in Korea

Korea has developed a liquid breeder blanket and participated in the test blanket module (TBM) program within the international thermonuclear experimental reactor group with a helium-cooled molten lithium (Li) concept. Based on this concept, helium and liquid Li were used as a coolant and breeder, respectively. Additionally, ferritic-martensitic steel (FMS) was considered as a structural material. However, according to our strategy for developing a liquid breeder TBM and its more relevant DEMO concept, not only liquid Li breeders, but also lead-Li (PbLi) breeders were considered. An experimental loop for a liquid breeder (ELLI) was constructed for the purpose of validating the design and fabrication of our electromagnetic (EM) pump; testing the effects of the magneto-hydro-dynamics; and investigating the compatibility of PbLi using structural materials such as FMS. In the ELLI, Pb-15.7Li, where Li is 15.7 at % (called PbLi hereafter), is used as the breeding material, and the EM pump circulates it through the loop. The maximum operating pressure and temperature in the loop are 0.5 MPa and 550 °C, respectively. In this paper, performance tests with the EM pump were carried out. During the three separate experiments, the EM pump was operated for 250 h with a speed of 0.16 m/s for corrosion tests. For a material of corrosion test, tubular-type specimens and cylindrical-type specimens were fabricated and installed in three test pots of the loop. After installing the specimens into the loop, the corrosion test was performed while the EM pump was operating with a 0.16 m/s flow rate at 340 °C for 250 h.

Preliminary Test and Evaluation of Nondestructive Examination for ITER First Wall Development in Korea

ITER first wall (FW) includes a beryllium armour joined to a Cu heat sink with a stainless steel back plate. These FW panels are one of the critical components in the ITER tokamak with a maximum surface heat flux of 5 MW/m2. Therefore, a qualification test needs to be performed with the goal to qualify the joining technologies required for the ITER FW. Various mock-ups were fabricated to develop the manufacturing procedure of FW components. For the nondestructive examination of the fabricated mock-ups, an ultrasonic test (UT) was performed with optimized probes. The UT was performed by using a three-axis digital ultrasonic C-scan system and software. The system comprised an ultrasonic pulser and receiver, model Panametrics 5800PR; a personal computer having an internal analog/digital converter board and four-axis motion control board; and a three-axis scanning tank. Two types of transducers were used for this experiment. One was Panametrics V312-SU, having a center frequency of 10 MHz (nominal) and a piezoelectric element diameter of 0.25 in with a flat protective layer for the Be/Cu. The other was Panametrics V309-SU with a center frequency of 5 MHz and an element diameter of 0.5 in for the Cu/SS interface. Winspect software controlled all aspects of data acquisition, motion control, data archiving, and image display. Based on the acceptance criteria, the average amplitude of the interface signals, which have about 50% of the reference echo amplitude, was recorded and analyzed on each beryllium tile. An image-analysis software analyzed the statistics of amplitude distribution and calculated the unacceptable area. Each mock-up that passed these UTs was concluded to qualify the joining technologies required for an ITER FW by using a high-heat flux test facility. As a result of these qualification tests based on the acceptance criteria of an ITER FW, the fabrication technologies will be utilized to develop the FW of plasma-facing components.

Strength Evaluation of HAZ in Electron Beam Welded ARAA by Small Punch Test for HCCR TBM in ITER

The Korean helium cooled ceramic reflector (HCCR) test blanket module (TBM) has been developed for ITER, and Korean reduced activation ferritic martensitic (RAFM) steel, called advanced reduced activation alloy (ARAA), has also been developed for a structural material of the HCCR TBM. One case of limited optimized electron beam (EB) welding conditions was selected based on previous work, and the weldability of an EB weld was evaluated for TBM fabrication. The micro-hardness was measured from the base to the weld region, and the microstructures were also observed. A small punch (SP) test considering the HAZ was carried out at room and high (550°C) temperatures. The empirical mechanical properties of HAZ in the EB weld were evaluated, and the fracture behavior was investigated after the SP test. The SP results show that the estimated yield and tensile strength of the HAZ were higher than the base metal at both temperatures. A rupture occurred in the base metal region, and an elongated ductile fracture was observed on the fractured surface at both temperatures.

High Heat Flux Test of the KO Standard Mockups for ITER First Wall Semi-Prototype

Abstract The Korean standard mockups with beryllium tile were fabricated to perform the high heat flux test for the qualification test of ITER blanket first wall. These mockups include the 80 mm × 80 mm beryllium armor tiles joined to the CuCrZr heat sink with stainless steel cooling tubes by HIP (Hot Isostatic Pressing) technology. The high heat flux tests were performed in the Korea heat load test facility (KoHLT-1) with the averaged surface heat flux of 1.25 MW/m2 by using a graphite heater. Preliminary thermal and mechanical analyses were carried out to simulate the test conditions and to determine the number of cycles for the fatigue lifetime of the mockups. In our KoHLT-1 facility, the normal heat cycle was based on an expected heat flux of 1.25 MW/m2, and each mockup had to endure the 1,000 normal heat cycles in this heat flux in accordance with the mechanical simulation. In the cyclic heat flux tests, the maximum surface temperature of the beryllium tiles was controlled below 400 °C. As a result of these high heat flux tests with the acceptance criteria of the ITER blanket first wall, the manufacturing technologies of the Korean standard mockups will be utilized to develop the tokamak blanket for the international qualification procedure.

Performance tests of an Experimental Loop for Liquid breeder in Korea

Korea (KO) has developed a Liquid breeder blanket and participated in the Test Blanket Module (TBM) program within the International Thermonuclear Experimental Reactor (ITER) group with a Helium Cooled Molten Lithium (HCML) concept. Based on this concept, helium (He) and liquid lithium (Li) were used as a coolant and breeder, respectively. Additionally, ferritic martensitic (FM) steel was considered as a structural material. However, according to our strategy for developing a liquid breeder TBM and its more relevant DEMO concept, not only liquid lithium breeders, but also lead-lithium (PbLi) breeders were considered. An Experimental Loop for a Liquid breeder (ELLI) was constructed for the purpose of validating the design and fabrication of our electromagnetic (EM) pump; testing the effects of the magneto-hydro-dynamics (MHD); and investigating the compatibility of PbLi using structural materials such as ferritic martensitic steel. In the ELLI, Pb-15.7Li, where Li is 15.7 at % (called PbLi hereafter), is used as the breeding material, and the EM pump circulates it through the loop. The maximum operating pressure and temperature in the loop are 0.5 MPa and 550 °C, respectively. In this study, performance tests with the EM pump were carried out. During the three separate experiments, the EM pump was operated for 250 h with a speed of 0.16 m/s for corrosion tests. For a material of corrosion test, tubular-type specimens and cylindrical-type specimens were fabricated and installed in three test pots of the loop. After installing the specimens into the loop, the corrosion test was performed while the EM pump was operating with a 0.16 m/s flow rate at 340 °C for 250 h.

Preliminary test and evaluation of non-destructive examination for ITER First Wall development in Korea

ITER First Wall (FW) includes beryllium armour joined to a Cu heat sink with a stainless steel back plate. These first wall panels are one of the critical components in the ITER tokamak with a maximum surface heat flux of 5 MW/m2. So, a qualification test needs to be performed with the goal to qualify the joining technologies required for the ITER first wall. Various mockups were fabricated to develop the manufacturing procedure of first wall components. For the non-destructive examination (NDE) of the fabricated mockups, an ultrasonic test (UT) was performed with optimized probes. The UT test was performed by using a three-axis digital ultrasonic C-scan system and software. The system is comprised of an ultrasonic pulser/receiver, model Panametrics 5800PR, a personal computer having an internal analog/digital converter board and four axis motion control board, and a three-axis scanning tank. Two type transducers were used for this experiment. One was Panametrics V312-SU, having a center frequency of 10 MHz (nominal), a piezoelectric element diameter of 0.25 inch with a flat protective layer for the Be/Cu. The other was Panametrics V309-SU with a center frequency of 5 MHz and an element diameter of 0.5 inch for the Cu/SS interface. Winspect software controlled all aspects of data acquisition, motion control, data archiving, and image display. Based on the acceptance criteria, average amplitude of the interface signals, which have about 50% of the reference echo amplitude, was recorded and analyzed on each beryllium tile. Image analysis software analyzed the statistics of amplitude distribution and calculated the unacceptable area. Each mockup that passed these UT tests was concluded to qualify the joining technologies required for an ITER first wall by using high heat flux test facility. As a result of these qualification tests based on the acceptance criteria of an ITER first wall, the fabrication technologies will be utilized to develop the first wall of plasma facing components.

Heat flux test of various Be mockups for ITER FW development at Korea heat load test facility KoHLT-1

We established a heat load test facility using a graphite heating panel in 2008 in order to verify the integrity of a HIP bonded first wall. The facility is called KoHLT-1 and is currently in operation to test the Be mockups. The KoHLT-1 consists of a graphite heating panel, a box-type test chamber with water-cooling jackets, an electrical power supply, a water-cooling system, an evacuation system, an He gas system, and some diagnostics, which are equipped in an authorized laboratory with a special ventilation system for the Be treatment. We designed and fabricated several graphite heating panels to have various heating areas depending on the tested mockups. The heat fluxes on the two mockups are independently measured by a calorimetric method. We have carried out the thermal cycle tests of various Be mockups. The nominal heat flux was 0.625 MW/m2 or 1.5 MW/m2 depending on the mockup sizes