Behaviors of passive safety systems under a Feed Water Line Break LOCA on a Generation III+ Boiling Water Reactor

• A large break LOCA experiment is performed at a BWR integral testing facility.
• A large break LOCA is mitigated by the design function of passive safety systems.
• Passive containment cooling system is demonstrated to be able to provide long term cooling.
• Emergency core cooling system supplies makeup coolant to ensure the core cover and fuel intact.

A postulated Large Break Loss-Of-Coolant-Accident (LB LOCA) on a generic Generation III+ Boiling Water Reactor (BWR) equipped with passive safety systems has been analyzed by conducting integral tests at a scale-down test facility, named Purdue University Multi-Dimensional Integral Test Assembly (PUMA). The integral tests simulate the hypothetical Feed Water Line Break (FWLB) accident caused by a guillotine rupture of the Feed Water Line (FWL) attached to the reactor vessel. This research is motivated to evaluate the behaviors of passive safety systems and to provide experimental data for the Validation and Verification (V&V) of related system codes. The experiment simulates the LOCA transient after the reactor vessel depressurizes to 1 MPa (150 psi) from normal operating pressure. The early high-pressure blowdown process of LOCA transient is simulated by the system code. The plant system conditions at 1.0 MPa calculated by the system code are interpreted as the initial conditions for the integral test with appropriate scaling. The normal FWLB integral test is also repeated with the partial failure of the PCCS to evaluate the safety margin. Experimental data indicates that this LB LOCA is successfully mitigated by the functioning of Emergency Core Cooling System (ECCS) and Passive Containment Cooling system (PCCS), with no occurrence of core uncover or containment overpressure.