Korea Heat Load Test Facility Research Articles

Plan and progress of the fusion neutron sources development at KAERI for fusion and fission applications

In accordance with the national fusion energy program of Korea, Korea Atomic Energy Research Institute (KAERI) has established a road map for the development of a volumetric fusion neutron source (V-FNS) and begun development of a compact fusion neutron source (C-FNS) for fusion, fission, and industrial applications. Regarding the C-FNS development, KAERI has developed a radio frequency (RF) ion source inclusive of an RF driver and generator, and has designed, fabricated, and tested a target at the “Korea heat load test facility with an electron beam (KoHLT-EB)” prior to assembly with an ion source for investigating the integrity of the target under a high heat flux condition. Test conditions such as heat flux, coolant flow rate, and pressure were prepared using a preliminary analysis and later compared against test results. From the comparison, the design of the target was optimized and its thermal integrity confirmed. Thus far, KAERI has been successful in its development of a C-FNS and has begun preparations for on-site C-FNS and V-FNS designs.

Bonding techniques and performance qualification of plasma facing components for Korean fusion research

KoHLT-EB (Korea Heat Load Test facility with Electron Beam gun) is operated for the performance qualification testing of the plasma facing components (PFC), ITER first wall (FW), ITER TBM (Test Blanket Module) FW, and DEMO PFCs in Korea. A thermal fatigue test shall be performed on the fabricated mockups to validate manufacturing technology, thermo-hydraulic performance and design validation using high heat load testing. The test parameters are defined along with numerically simulated conditions. For the high heat flux testing, various mockups were fabricated by each bonding technique, such as HIP (Hot Isostatic Pressing), vacuum plasma spray (VPS) coating technique. Each fabricated mockup was installed inside the vacuum chamber of KoHLT-EB, and thermo-hydraulic performance tests and thermal fatigue tests were performed to qualify the mockups specification and bonding techniques.

Current Status of Korea Heat Load Test Facility KoHLT-EB for Fusion Reactor Materials

The Korea heat load test facility using electron beam (KoHLT-EB) was constructed and commissioned to perform high heat flux testing on plasma facing components (PFCs), such as ITER blanket first wall, the tungsten divertor, and heat transfer experiments on other cooling devices. Also it will be used for the thermo-hydraulic performance test of ITER helium cooled ceramic reflector test blanket module in Korea. Qualification tests will be performed to evaluate the use of the high heat flux test facility on PFC and fusion reactor materials. For the thermal fatigue test of PFCs, two types of tungsten mockups were fabricated. One is a coated tungsten on the ferritic–martensitic steel (FMS). The other is a hot isostatic pressing bonded tungsten with FMS. Also, the integrity and cooling performance should be tested under the same or similar operation conditions of the ITER PFCs. After the completion of the preliminary mockup test and the facility qualification, the high heat flux test facility, KoHLT-EB, will provide the performance test for the various PFCs in fusion reactor materials and PFCs.

Fabrication and integrity test preparation of HIP-joined W and ferritic-martensitic steel mockups for fusion reactor development

Tungsten (W) and ferritic-martensitic steel (FMS) as armor and structural materials, respectively, are the major candidates for plasma-facing components (PFCs) such as the blanket first wall (BFW) and the divertor, in a fusion reactor. In the present study, three W/FMS mockups were successfully fabricated using a hot isostatic pressing (HIP, 900 °C, 100 MPa, 1.5 hrs) with a following post-HIP heat treatment (PHHT, tempering, 750 °C, 70 MPa, 2 hrs), and the W/FMS joining method was developed based on the ITER BFW and the test blanket module (TBM) development project from 2004 to the present. Using a 10-MHz-frequency flat-type probe to ultrasonically test of the joint, we found no defects in the fabricated mockups. For confirmation of the joint integrity, a high heat flux test will be performed up to the thermal lifetime of the mockup under the proper test conditions. These conditions were determined through a preliminary analysis with conventional codes such as ANSYS-CFX for thermal-hydraulic conditions considering the test facility, the Korea heat load test facility with an electron beam (KoHLT-EB), and its water coolant system at the Korea Atomic Energy Research Institute (KAERI).

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.

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

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.

Small Mock-Up Fabrication and High Heat Flux Test for Preparing the 2nd Qualification of the ITER Blanket First Wall

For the second qualification of the blanket First Wall (FW) procurement of the International Thermonuclear Experimental Reactor (ITER), a semi-prototype of the FW has been designed with increased local surface heat flux up to 5 MW/m2. In order to investigate the fabrication procedure and methods, two types of mock-up were fabricated; one was with twelve Be tiles for high heat flux test to check the joining integrity between Be tiles and the bending Cu block and the other was for testing the thermal-hydraulic prediction by commercial code, ANSYS-CFX when it has a complex geometry such as hypervapotron, which was used for designing the semi-prototype. The former was successfully fabricated and the test conditions were obtained through the preliminary analysis with ANSYS-CFX. The later was successfully fabricated and the test with KoHLT-2 (Korea Heat Load Test facility) was performed; mass flow rate of inlet coolant was the same as the ITER condition and heat flux was loaded up to 0.65 MW/m2. The results show that the temperature of the mock-up can be predicted using the ANSYS-CFX even with the complex geometry.

Fabrication and high heat flux test of large mockups for ITER first wall semi-prototype

The main topic of an ITER blanket first wall procurement is to qualify whether each party has the key technology needed for the fabrication and joining of first wall components. A semi-prototype qualification project will be released requiring that the single components of a full-scale first wall must be fabricated and successfully pass high heat flux tests using a hypervapotron cooling channel. In this work, various mockup types have been modeled and fabricated to develop the joining technology for a semi-prototype. The semi-prototype, which has three double-fingered panels, is a scaled-down component of a full-size first wall. The standard or slit mockups with a 80 mm × 80 mm single beryllium tile joined to a CuCrZr heat sink were fabricated to qualify our HIP (Hot Isostatic Pressing) technology for the joining of semi-prototype. These standard mockups were installed to perform a high heat flux test in the Korea heat load test facility (KoHLT). For a preliminary test of a semi-prototype, thermo-hydraulic mockups of 710 mm × 100 mm were designed and fabricated to verify the Cu/SS cooling performance, such as hypervapotron. For the high heat flux test in our KoHLT facility, the normal cycle is based on an expected heat flux of 300 s in accordance with the ITER qualification specifications. These tests will be performed to qualify the joining technologies, which is required for an ITER blanket first wall and a semi-prototype.

HIGH HEAT FLUX TEST WITH HIP BONDED 35X35X3 BE/CU MOCKUPS FOR THE ITER BLANKET FIRST WALL

To develop the manufacturing methods for the blanket first wall (FW) of the International Thermonuclear Experimental Reactor (ITER) and to verify the integrity of the joint, Be/Cu mockups were fabricated and tested at the KoHLT-1 (Korea Heat Load Test facility), a graphite heater facility located at the Korea Atomic Energy Research Institute (KAERI). Since Be and Cu joining is the focus of the present study, the fabricated mockups had a CuCrZr heat sink joined with three Be tiles as an armor material, unlike the original ITER blanket FW, which has a stainless steel structure and coolant tubes. Hot isostatic pressing (HIP) was carried out at 580℃ and 100 MPa for 2 hours as the method for Be/Cu joining. Three interlayers, namely, 1㎛Cr/10㎛ Cu, 1㎛Ti/0.5 Cr/10㎛Cu, and 5㎛Ti/10㎛ Cu were applied as a coating to the Be tiles by a physical vapor deposition (PVD) method. A shear test was performed with the specimens, which were fabricated by the same methods as those used to fabricate the mockups. The average values were 125 MPa to 180 MPa, and the samples with the 1㎛Cr/10㎛Cu interlayer showed the lowest value. No defect or delamination was found in the joints of the mockups by the developed ultrasonic test using a flat-type probe with a 10 MHz frequency and a 0.25 inch diameter. High heat flux (HHF) tests were performed at 1.0 MW/m² heat flux for each mockup using the given conditions, and the results were analyzed by ANSYS-CFX code. For the test criteria, an expected fatigue lifetime about 1,000 cycles was obtained by analysis with ANSYS-mechanical code. Mockups using the interlayers of 1㎛Ti/0.5㎛Cr/10㎛Cu and 5㎛Ti/10㎛Cu survived up to 1,100 cycles over the required number of cycles. However, one of the Be tiles in the other two mockups using the 1㎛Cr/10㎛Cu interlayer was detached during the screening test, and others were detached by discharge after 862 cycles. The integrity of the joints using the proposed interlayers was proven by the HHF test, but the other interlayer requires more study before it can be used for the joining of Be to Cu. Moreover, it was confirmed that the measured temperatures agreed well with the analysis temperatures, which were used to estimate the lifetime and that the developed facility showed its capability of the long time operation.