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Assessment of residual heat removal and containment spray pump performance under air and debris ingesting conditions. [PWR]

This report presents an assessment of the performance of Residual Heat Removal (RHR) and Containment Spray (CS) pumps during the recirculation phase of reactor core and containment cooldown following a Loss-of-Coolant Accident (LOCA). The pumped fluid is expected to contain debris such as insulation and may ingest air depending on sump conditions. Findings are based on information collected from the literature and from interviews with pump and seal manufacturers. These findings show that for pumps at normal flow rates operating with sufficient Net Positive Suction Head (NPSH), pump performance degradation is negligible if air ingestion quantities are less than 2% by volume. For air ingestion between 3% and 15% by volume, head degradation depends on individual pump design and operating conditions and for air quantities greater than 15% performance of most pumps will be fully degraded. Also, small quantities of air will increase NPSH requirements for these pumps. For the types and quantities of debris likely to be present in the recirculating fluid, pump performance degradation is expected to be negligible.