Abstract: The steam generator tube rupture (SGTR) accident in a lead-cooled fast reactor (LFR) may lead to the leakage of high-pressure water or steam from the secondary loop into the primary loop containing lead-bismuth eutectic (LBE). This process involves intense pressure release, two-phase flow interactions, and dynamic load impacts, raising serious safety concerns and attracting widespread attention. However, the submerged jet behavior of steam in the LBE pool is complicated by the non-condensable nature of steam when it exists as superheated steam or in the wet steam region. Direct experimental investigation using steam and LBE is challenging due to the high temperature and opacity of LBE. Therefore, this study adopted air and water as transparent alternative working fluids to simulate gas submerged jet phenomena under conditions analogous to liquid metal environments. The objective of this study is to experimentally characterize the hydrodynamic and pressure oscillation behaviors of high-speed submerged jets of non-condensable gas, providing fundamental data for the safety analysis of SGTR accidents in LFRs. A high-speed submerged jet experimental facility was constructed. Compressed air was injected through sparger of different diameters (3, 5, 8, 10, 13, and 18 mm) into a still water tank. The inlet pressure was varied from 0.15 MPa to 0.9 MPa. High-speed photography was employed to capture the jet evolution and phase interface morphology. High-frequency pressure sensors were installed near the sparger exit to record dynamic pressure oscillations. The experimental results show that the flow field of the high-speed air jet in water can be divided into two distinct regions: an inertial jet region near the sparger and a buoyant plume region farther downstream. In the inertial jet region, complex phase interface behaviors such as necking, bulging, back-attack, and interfacial vortex evolution are observed, all of which significantly affect the jet morphology and mixing characteristics. The penetration length of the inertial jet increases linearly with increasing inlet pressure. Pressure oscillation signals generated near the nozzle hole exhibit different intensities and frequencies. When the hole diameter is 8 mm or smaller, the maximum pressure oscillation intensity increases with increasing inlet pressure. When the hole diameter is 10 mm or larger, the maximum pressure oscillation intensity first rises and then falls as the inlet pressure increases. The overall pressure oscillation intensity remains within 120 kPa, and the dominant frequency ranges from 10 Hz to 300 Hz. These findings provide quantitative insights into the jet behavior that would occur in an LFR SGTR accident. From the perspective of the design and analysis of LFR steam generators, it is necessary to consider the vibration and fatigue crack propagation of heat transfer tubes and their supporting structures under pressure loads over a wide frequency range. Therefore, the heat transfer tube bundle should be rationally arranged, and additional damping or flow-guiding structures should be incorporated to prevent flow-induced vibration of the tube bundle after the occurrence of a rupture accident.