Analysis of Steady State and Operational Transients of the Versatile Loop Facility in support to Lead Fast Reactor development

Among the Generation IV technologies currently under development, Lead Fast Reactors (LFRs) are one of the most promising. They adopt lead or lead-bismuth eutectic (LBE) as the primary coolant. In recent years, a significant effort has been carried out by Westinghouse Electric Company (Westinghouse) to design a pool type, 450 MWe Net, passively safe, liquid lead-cooled fast neutron reactor. The Reactor Vessel (RV) has an integral configuration, with all primary system components located within. The primary pool is provided with compact, hybrid microchannel heat exchangers to extract heat from lead and deliver it to the secondary fluid (supercritical water). To test the components to be installed in the Westinghouse LFR and demonstrate the feasibility as well as the operability of the overall system, Ansaldo Nucleare has designed the Versatile Loop Facility (VLF) in partnership with Westinghouse and is currently installing it at their Wolverhampton site in the United Kingdom. The experimental infrastructure includes a fuel pin bundle simulator (FPBS--representing a fuel assembly) and primary heat exchanger (PHE) utilizing the innovative microchannel heat exchanger design. The Department of Astronautical, Electrical and Energy Engineering (DIAEE) of Sapienza University of Rome, in collaboration with ENEA, is supporting the VLF by performing best-estimate thermal-hydraulic transient analysis focused on the secondary loop. The selected numerical tool is RELAP5 system code. This paper presents the main calculation outcomes, demonstrating the appropriateness of the system, as well as the effectiveness of the control strategies adopted in both operational and off-design conditions.