Development of a High Heat Load Test Facility KoHLT-1 for a Testing of Nuclear Fusion Reactor 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. Its major purpose is to carry out a thermal cycle test to verify the integrity of a HIP (hot isostatic pressing) bonded Be mockups which were fabricated for developing HIP joining technology to bond different metals, i.e., Be-to-CuCrZr and CuCrZr-to-SS316L, for the ITER (International Thermonuclear Experimental Reactor) first wall. The KoHLT-1 consists of a graphite heating panel, a box-type test chamber with water-cooling jackets, an electrical DC 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. The graphite heater is placed between two mockups, and the gap distance between the heater and the mockup is adjusted to 2≥3 mm. We designed and fabricated several graphite heating panels to have various heating areas depending on the tested mockups, and to have the electrical resistances of 0.2∼0.5 ohms during high temperature operation. The heat fluxes on the two mockups are deduced from the flow rate and the coolant inlet/outlet temperatures by a calorimetric method. We have carried out the thermal cycle tests of various Be mockups, including two FWQMs (First Wall Qualification Mockups) which have three Be-tiles of 80x80 mm2, six single tile mockups (80x80x1) with an identical cross-section to the FWQM, and six small mockups (35x35x3) with three Be-tiles of 35x35 mm2 bonded to a CuCrZr block. Nominal heat flux was 0.625 MW/m2 or 1.5 MW/m2 depending on the mockup sizes. For the FWQMs, we performed the thermal fatigue tests up to 12,690 and 12,020 cycles at a heat flux higher than 0.625 MW/m2. During the tests, there was no remarkable change in the thermal response of two FWQMs, which demonstrated that the FWQMs had an acceptable bonding quality and an acceptable thermal performance. Some Be tiles of the 80x80x1 mockups and 35x35x3 mockups were detached during a thermal cycle test at the heat-up or cool-down phase. Four of six 35x35x3 mockups passed thermal fatigue testing of 1,100 cycles at a heat flux higher than 1.5 MW/m2 with no change in thermal response. These results indicated no degradation in the Be-CuCrZr joint. Through this study, the reliability of the KoHLT-1 for long time operation at a high heat flux was verified, and its broad applicability is promising