Asymmetric decay heat removal in MYRRHA: experiments in the E-SCAPE facility

MYRRHA is an accelerator-driven system, coupling a proton accelerator to a subcritical reactor cooled by lead-bismuth eutectic (LBE), under development by SCK CEN in Belgium. The reactor design is based on a pool configuration, all components of the primary system housed within the main vessel. In this context, the thermal-hydraulic experimental program considers separately the performance of individual reactor components, and the integral pool dynamics in steady-state and in anticipated transients. The E-SCAPE (European SCAled Pool Experiment) facility is a thermal hydraulic 1/6-scale model of the primary system of the MYRRHA reactor. Replicas of the main components are placed in the main vessel, while pumps and heat exchangers are located in two external circuits. Operating conditions in LBE are representative of (scaled) decay heat removal in terms of mass flow rate (up to 120 kg/s), core power (up to 100 kW) and temperature (200 – 340 °C). This arrangement allows the study of different scenarios, including forced circulation, natural circulation, flow transitions and asymmetric operation. Two specific asymmetric scenarios, corresponding to possible initiating events for design-basis accidents, are studied in the present experimental campaign, framed within the European collaborative project PASCAL (2020-2024). First, a single pump failure is investigated. Second, partial loss of heat sink is simulated by stopping the flow of secondary coolant in only one circuit. These scenarios are compared to a reference symmetric case. Their evolution depends on the fluid mixing in the cold and hot plena.