Development of End Plug Welding Technique for SFR Fuel Rod Fabrication

Science and Technology of Nuclear Installations, Dec 2016

In Korea, R&D on a sodium-cooled fast reactor (SFR) was begun in 1997, as one of the national long-term nuclear R&D programs. As one fuel option for a prototype SFR, a metallic fuel, U-Zr alloy fuel, was selected and is currently being developed. For the fabrication of SFR metallic fuel rods, the end plug welding is a crucial process. The sealing of the end plug to the cladding tube should be hermetically perfect to prevent a leakage of fission gases and to maintain a good reactor performance. In this study, the welding technique, welding equipment, welding conditions, and parameters were developed for the end plug welding of SFR metallic fuel rods. A gas tungsten arc welding (GTAW) technique was adopted and the welding joint design was developed. In addition, the optimal welding conditions and parameters were established. Based on the establishment of the welding conditions, the GTAW technique was qualified for the end plug welding of SFR metallic fuel rods.

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Development of End Plug Welding Technique for SFR Fuel Rod Fabrication

Development of End Plug Welding Technique for SFR Fuel Rod Fabrication Jung Won Lee, Jong Hwan Kim, Ki Hwan Kim, Jeong Yong Park, and Sung Ho Kim Next Generation Fuel Division, Korea Atomic Energy Research Institute, 111 Daedeok-daero 989 Beon-gil, Yuseong-gu, Daejeon 305-353, Republic of Korea Received 23 May 2016; Accepted 28 August 2016 Academic Editor: Waclaw Gudowski Copyright © 2016 Jung Won Lee et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract In Korea, R&D on a sodium-cooled fast reactor (SFR) was begun in 1997, as one of the national long-term nuclear R&D programs. As one fuel option for a prototype SFR, a metallic fuel, U-Zr alloy fuel, was selected and is currently being developed. For the fabrication of SFR metallic fuel rods, the end plug welding is a crucial process. The sealing of the end plug to the cladding tube should be hermetically perfect to prevent a leakage of fission gases and to maintain a good reactor performance. In this study, the welding technique, welding equipment, welding conditions, and parameters were developed for the end plug welding of SFR metallic fuel rods. A gas tungsten arc welding (GTAW) technique was adopted and the welding joint design was developed. In addition, the optimal welding conditions and parameters were established. Based on the establishment of the welding conditions, the GTAW technique was qualified for the end plug welding of SFR metallic fuel rods. 1. Introduction The generation IV (Gen-IV) program was started by eleven countries in 2000 for the development of an innovative nuclear energy system along with its goals, safety, economics, resource utilization, waste management, proliferation resistance, and physical protection (PR and PP) [1]. Among the six selected systems within the Gen-IV program is a sodium-cooled fast reactor (SFR). It is expected to become available for commercial introduction in around 2030 [2]. In Korea, the R&D on a SFR began in 1997, as one of the national long-term nuclear R&D programs. As the fuel for a prototype SFR, a metallic fuel, U-Zr alloy, was selected and is being developed. In addition, international collaborative research is also under way on U-TRU-Zr fuel developments with the closed fuel cycle of the full actinide recycling, within the Advanced Fuel Project for the international generation IV (Gen-IV) SFR [2, 3]. For the fabrication of SFR metallic fuel rods, the end plug welding is a crucial process [4, 5]. The sealing of the end plug to the cladding tube should be hermetically perfect to prevent the leakage of fission gases and maintain a good reactor performance [6]. In this study, the gas tungsten arc welding (GTAW) technique was chosen for the end plug welding, and the welding joint design, the welding conditions, and parameters were developed. In addition, the optimal welding conditions and parameters were established. To prove the end plug weld integrity, the qualification test of the end plug welding for SFR metallic fuel rods was carried out based on the developed welding technique, welding equipment, welding conditions, and parameters. Through the qualification test, the end plug welding process for SFR metallic fuel rod fabrication was successfully established. 2. Features of SFR Metallic Fuel The specifications and dimensions of the SFR metallic fuel assembly are shown in Figure 1, which is under development at the Korea Atomic Energy Research Institute (KAERI). In the current SFR design development, U-Zr and U-TRU-Zr metallic fuel are used for the early and later stages of reactor operation, respectively. TRU (transuranic elements and transuranium elements) means radioactive elements with atomic numbers higher than that of uranium in the periodic table of elements like neptunium, plutonium, americium, and others. TRU recovered from nuclear fuels irradiated in the commercial nuclear power plant by reprocessing is used for SFR to solve the problem of used nuclear fuel accumulation in the commercial nuclear power plant and increase the utilization of uranium resources. The composition of the fuel is U-20%TRU-10%Zr for the closed fuel cycle and U-10%Zr for the prototype reactor. As shown in this figure, a fuel assembly is composed of a nose piece and a handling socket in the end and a duct in the middle part, which contains 217 fuel rods assembled inside it [7]. Each fuel rod has a lower end plug, a fuel slug, an upper gas plenum, and an upper end plug as shown in Figure 1. The outside of the fuel rod is wrapped with a wire to maintain a gap between neighboring fuel rods. Inside the fuel rod, the gap between the fuel slug and fuel cladding is filled with sodium (Na). The environment of a SFR core is more severe than that of a PWR (Pressurized Water Reactor) core. Thus, high-chromium (9–12% Cr) ferritic/martensitic stee (...truncated)


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Jung Won Lee, Jong Hwan Kim, Ki Hwan Kim, Jeong Yong Park, Sung Ho Kim. Development of End Plug Welding Technique for SFR Fuel Rod Fabrication, Science and Technology of Nuclear Installations, 2016, 2016, DOI: 10.1155/2016/9549805