Reliability Analysis of External Power Grid Based on LOOP Initiating Event in Nuclear Power Plants: A Case Study of a Nuclear Power Plant in Southern China

The loss of offsite power (LOOP) in nuclear power plants (NPP) represents a critical initiating event that is closely associated with the design characteristics of both the site and the plant itself. Given the severe consequences that can arise from such an incident, precise modeling of LOOP events is essential for conducting effective probabilistic safety assessments (PSA) of nuclear facilities. Unlike other internal initiating events, LOOP analysis primarily emphasizes the fault characteristics inherent to the external power grid connected to the plant. However, constrained by cross-industry data barriers and divergent analytical frameworks, current domestic analyses of LOOPinitiating events predominantly rely on generic databases or international operational experience data. This approach fails to characterize the reliability level of the local external grid specific to the nuclear power plant's location and cannot provide targeted recommendations for enhancing the plant's power supply reliability. Consequently, this limitation has garnered significant attention within the nuclear industry. This paper establishes a systematic analytical framework based on failure mode classification and proposes an evaluation method that incorporating critical factors such as the power network system, connection lines between nuclear power plants, and environmental coupling. A quantitative analysis and risk assessment are performed using a case study involving a nuclear power plant located in southern China, providing valuable technical support for assessing site suitability risks.