Safety Analysis of Heat Treatment System and TF Nb₃Sn Coil Joint Annealing Experiment

Superconducting magnets for China fusion engineering test reactor (CFETR) are inseparable from Nb3Sn coils. The process of "wind-and-react" is used in Nb3Sn coil manufacturing. The quality of annealing treatment directly determines the superconductivity of future magnets. In order to complete the heat treatment of TF Nb3Sn coil joint, a controlled atmosphere heat treatment system was upgraded by the Institute of Plasma Physics. Heat treatment has the characteristics of complex system structure, long operation cycle, high risk, etc. Therefore, it is necessary to conduct safety analysis and failure prevention of heat treatment. In this paper, the failure mode and effects analysis (FMEA) method will be used for the safety analysis of upgraded system. Through this method, the potential faults of the system can be found, and the faults can be classified into different levels. According to the analysis results, preventive measures for the first-level failure of heat treatment were put forward and the feasibility of preventive measures was verified. The heat treatment of the experimental internal joint of the CFETR TF coil was completed by using the upgraded system, and all the heat treatment technical indexes met the requirements.