Numerical and experimental characterization of heavy liquid metal cooled bundles

The focus of the present research activity was the experimental and numerical investigation of some thermal-hydraulic phenomena peculiar of the heavy liquid metal cooled systems like Lead Fast Reactors. The two activities were carried out in parallel during the three-year research period and performed mainly at the Experimental Thermo-fluid-dynamic Laboratory of ENEA Brasimone R.C., in the framework of a collaboration between ENEA and the Department of Civil and Industrial Engineering of the University of Pisa. The main thermal-hydraulic aspects investigated were the core coolability during normal conditions in wire-wrap and grid spaced bundles and coolability during a specific accident condition called “flow blockage accident”. The experimental activity had two main focuses: the evaluation of heat transfer coefficients in a grid spaced bundle cooled by heavy liquid metal and the evaluation of the thermal-hydraulic field in a grid-spaced bundle affected by different degrees of internal blockage. The numerical activities concerned pre-test and post-test CFD studies, on three different test sections installed in the two HLM cooled facilities at ENEA Brasimone (NACIE-UP and CIRCE). Pre-test CFD simulations were developed for the Blockage Fuel Pin Simulator test section installed in the NACIE-UP facility for the optimization of TCs position near the blockage. Post-test CFD analyses were developed looking for a preliminary assessment of CFD code capabilities and limitations.