Data-Driven Optimization and Validation of Airtightness Test Duration for Hydrogen-Cooled Generators in Nuclear Power Plants

The sealing reliability of hydrogen-cooled generator systems in nuclear power plants is directly related to unit safety and outage critical-path optimization. Conventional airtightness pressure-holding tests usually use the 24 h leakage result as the acceptance criterion, but this occupies a long maintenance window. Early pressure and temperature signals are affected by thermal equilibration, environmental disturbances, and gas–oil coupling, making direct early assessment difficult. Based on historical pressure-holding test data from multiple nuclear power plants, this study develops a short-duration auxiliary assessment method. Test records from different plants are converted into a unified equivalent leakage rate, and a standardized dataset is established. A multi-branch framework is then developed, including leakage-trend prediction, local fluctuation identification, and feature-space validation. A conservative review strategy is introduced to support safety-oriented field decision making. The validation results show that the first 12 h monitoring data can support assessment of the 24 h leakage state. No false negatives were observed within the limited validation set. Samples with inconsistent outputs, near-threshold predictions, or abnormal feature-space locations are recommended for extended pressure holding and further review.