LI Sha, YUAN Ye, ZHONG Duojun.Study on Brazing Process and Defects Control of CF3 Fuel Assembly Bottom Nozzle[J].Electric Welding Machine, 2022, 52(12): 77-84. DOI： 10.7512/j.issn.1001-2303.2022.12.09.
Study on Brazing Process and Defects Control of CF3 Fuel Assembly Bottom Nozzle
The bottom nozzle of CF3 advanced PWR fuel assembly is a creative space curved structure, which needs to be assembled and brazed by the vacuum brazing technology. According to the characteristics of 304L stainless steel base metal and BNi-7 filler metal, the brazing process curve was determined. Then the effect of brazing cycles on the impact properties, room temperature and high temperature tensile strength of the base metal, as well as the shear strength and microstructure of the brazed joints were tested and analyzed. The results show that even after four-stage brazing cycles, the mechanical properties and microstructure of the base metal and brazed joints are not significantly adversely affected. In order to improve production efficiency and reduce energy consumption, it is recommended to use two-stage brazing cycles assembly, plus the optional third brazing cycle repair brazing process. And also, through adjusting the joint clearance, improving the structure of the bottom nozzle, the machining process of the guiding tube hole, and the structure of the double blade, the defects such as flow channel blockage, lack of filler metal, and so on, are avoided. Eventually, the product yield is increased and production efficiency are raised.
CF3 PWRfuel assemblymechanical propertymicrostructurebrazing cycledefects control
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