Liquid-Metal Thermal-Hydraulic Numerical Analyses in Support of the Upcoming CIRCE-THETIS Experimental Campaign

Liquid metal cooled reactors are among the design proposals accepted by the Generation IV International Forum for the fourth generation of nuclear power plants. During the last decade, many European Union (EU) projects started with the goal to pave the way for the development of this type of reactor. The present research work is performed in the framework of the EU Partitioning And Transmuter Research Initiative in a Collaborative Innovation Action (PATRICIA) project, supporting the development of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA). Among the cornerstones of the project are experimental and numerical analyses involving the CIRColazione Eutettico (CIRCE) facility set at the ENEA Brasimone Research Centre. The upcoming experimental campaign will address the new CIRCE-THETIS configuration, including a new kind of heat exchanger named THETIS: a helical coil steam generator (SG) whose heat transfer capabilities and impact on pool thermal hydraulics are to be investigated. The main goal of the present work is to provide numerical support to experimentalists to help them set up the CIRCE-THETIS experimental facility, the operating conditions test matrix, and postulated transients, providing information about potential needed updates or dangerous conditions. This paper reports on pretest computational fluid dynamics and system thermal-hydraulic analyses performed at the University of Pisa in the frame of the PATRICIA project. The new SG was first addressed assessing its heat transfer capabilities. Sensitivity analyses were performed; among the outcomes, the excellent heat transfer capabilities of the SG were highlighted. The pool and the reactor vessel auxiliary cooling system component were later investigated reporting valuable information concerning both postulated steady-state and transient conditions. The performed analyses had a relevant impact on the design of the facility, suggesting updates based on numerical calculations. After the experimental campaign, posttest analyses will be performed to draw lessons from the observed phenomena. This will also provide room for improvement of the adopted numerical tools.