Yuanzineng kexue jishu (Nov 2024)
Study on Application Characteristic of Hot-pressing B4C Block in ITER Diagnostic Equatorial Port 12
Abstract
The diagnostic equatorial port 12 (EQ#12) of the International Thermonuclear Experimental Reactor (ITER) integrates plasma diagnostic systems for observing and providing feedback on plasma operating conditions. Therefore, the integrated design of In-VV (vacuum vessel) area needs to consider important factors such as material out-gassing performance and port cooling capacity under the premise of port weight limitation and nuclear shielding requirements. Based on the standardized integration concept of EQ#12 In-VV area, the boron carbide (B4C) shielding block was prepared by hot-pressing process, and its basic properties (such as microscopic morphology, physical and chemical properties), vacuum out-gassing characteristics and heat transfer characteristics under actual conditions were studied by SEM, mass spectrometry, symmetrical structure constant conductance method, steady-state heat flow method and finite element analysis. The results indicated that the density of B4C shielding block under this hot-pressing process is (2.50±0.01) g/cm3, with few internal micro-pores. The total boron content reaches 77.20% and the content of impurity elements such as Fe and Co are not more than 0.03%. After baking treatment under vacuum conditions, the main gas composition released by the block is hydrogen and the out-gassing rate per unit area of hydrogen is as low as 6.94×10−9 Pa·m3·s−1·m−2. The thermal contact conductance of B4C and stainless steel under vacuum condition (approximately 10−3 Pa) was tested at 100-500 ℃ and 1 MPa interfacial pressure. According to the test results, the thermal simulation analysis of B4C under the application condition shows that it can effectively take away nuclear heat under the operating conditions of ITER device and the local maximum temperature will not exceed 221.6 ℃, also it can be heated to 209.1 ℃ for effective degassing after 48 hours of baking. The study on the application characteristics of this hot-pressing B4C block material provides an important reference for the selection of shielding materials in the vacuum chamber of nuclear fusion devices.
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