Experimental analysis of stationary and transient scenarios of ALFRED steam generator bayonet tube in CIRCE-HERO facility

In the framework of the HORIZON2020 SESAME European project (SESAME Project, EURATOM H2020, 2015), an experimental campaign has been carried out on the large LBE pool integral effect CIRCE facility at CR ENEA Brasimone (Tarantino et al., 2011). The experiments are based on the HERO Test Section installed into CIRCE (Rozzia et al., 2017), aiming at supporting the development of the ALFRED design (Frignani et al., 2017). The secondary loop for the HERO SGBT unit has been designed and realized for the SESAME experimental campaign, and both the primary and secondary systems have been instrumented. Three transient tests have been designed and carried out, consisting of a protected loss of flow accident occurring with the facility operated in nominal full power conditions for both primary side (LBE) and secondary side (high pressure water). The three transient tests start from the same steady state conditions, characterized by ∼0.33 kg/s of subcooled water entering into the 7 tubes of SGBT mock-up at about 180 bar and 335 °C, and exiting in superheated steam condition at about 400 °C. The Lead Bismuth Eutectic alloy (LBE), flowing in the shell side of the SGBT with a mass flow rate of about 40 kg/s, is cooled from about 480–400 °C. The transient tests investigated PLOFA scenarios, discerned on the basis of different transient reduction of power supplied by FPS, liquid metal gas lift (enhanced circulation) and feedwater mass flow rate. More specifically, in the first TT power decreased following the decay heat curve, gas lift was set to 0 kg/s and feedwater to 30% mass flow rate (simulating Decay Heat Removal, DHR, system) in 2 s. The second TT differs from the first one only for the feedwater reduction to 0% in about 2 s (without DHR). The third TT simulated the power decay curve, DHR (feedwater to 30% in 2 s) and reactor pump flywheel by a gas lift reduction based on a defined table. This work aims to present the experimental data achieved, in terms of mass flow rates and temperature for both primary and secondary system, providing relevant information about the system behaviour when subjected to accidental scenarios