Probabilistic safety assessment (PSA) is a useful tool for evaluating the overall risk of nuclear power plant design. Current research and operational experience indicate that the impact of internal flooding on nuclear safety cannot be ignored. Therefore, in the full-scope PSA analysis of nuclear power plants, internal flooding is an important analysis object. For internal flooding PSA (IFPSA), high energy line breaks (HELBs) need special attention as they can cause additional effects (e.g., pipe whip, jet impingement, steam release, flooding, and blast wave), potentially leading to failure of safety-significant structures, systems, and components. Through investigating domestic and foreign engineering practices, this paper develops a PSA analysis process for HELBs in the Hualong Pressurized Reactor (UK HPR1000). The current analysis results show that the core damage frequency (CDF) of internal flooding PSA considering the high energy line breaks is 4.65E-09/ry, indicating a high safety level of the nuclear power plant design in handling internal flooding and high energy line breaks.