On July 1, 2026, the world's first self-developed underwater welding in-situ neutron diffraction research device was put into use on the Engineering Material Spectrometer of the China Spallation Neutron Source (CSNS) in China, and successfully completed the first in-situ observation experiment of the underwater welding process. This marks a significant breakthrough in China's real-time observation of the microstructure of underwater welding and the revelation of its core mechanisms, providing scientific support for the independent control and quality improvement of underwater welding technology for large underwater structures. The device was jointly developed by the team led by Professor Wang Zhenmin from South China University of Technology and the China Spallation Neutron Source Science Center, with manufacturing undertaken by Zhenhai Intelligent Technology (Zhuhai) Co., Ltd.