Noto Earthquake Impact on Nuclear Plants: Safety Measures
Following the Noto Peninsula Earthquake on January 1, 2024, the Atomic Energy Association (ATENA) led a collaborative study with operators and manufacturers to assess impacts on nuclear power plants, focusing on the Shika Nuclear Power Plant. The Knowledge Organization SWG on Noto Peninsula Earthquake Power Plant Equipment investigated equipment failures and malfunctions, including transformer damage, diesel generator automatic stops, spent fuel pool incidents, and CRD housing support bracket failures. For transformers, insulation oil leakage from pipe damage occurred due to response accelerations exceeding design values, but external power redundancy proved effective. Seismic reinforcement is not mandatory; instead, procedures for stopping transformers during oil leaks and early recovery measures for pressure relief plate operation are recommended. Diesel generator automatic stops during parallel operation were analyzed, leading to initiatives for more reliable operational actions, such as preventing power factor decrease. Spent fuel pool items falling prompted on-site inspections to prevent foreign material intrusion. CRD housing support bracket components falling off led to measures for preventing component detachment through installation management and structural review. For other equipment like on-site roads, seawalls, and pure water tanks, no new knowledge was extracted as failures were within expected ranges. The study emphasizes voluntary safety improvements based on lessons learned.