ECCS
Emergency Core Cooling System
Emergency Core Cooling System (ECCS) automatically injects borated water into the reactor core to remove decay heat and prevent cladding failure during loss-of-coolant accidents.
ECCS in pressurized water reactors (PWRs) includes high-pressure injection (HPI), low-pressure injection (LPI), and accumulators that activate on low pressure or high containment pressure signals. In boiling water reactors (BWRs), it features core spray and low-pressure coolant injection systems. Post-Three Mile Island upgrades ensured ECCS reliability with redundant pumps and diverse injection paths, targeting peak cladding temperature below 1200°C and hydrogen generation under 1%.
Why it matters now
ECCS performance is central to NRC licensing for SMRs like NuScale, amid 2025-2026 deployments for data center PPAs requiring proven safety margins. Enhanced ECCS mitigates LOCA risks highlighted in post-Fukushima reviews.