MYRRHA primary heat exchanger experimental simulations on CIRCE-HERO

In the frame of the MYRRHA ADS technological development, an intense research effort has been undertaken by European Commission, in particular for the Heavy Liquid Metal technology assessment. In this scenario, EURATOM HORIZON2020 funded the SESAME & MYRTE projects, coordinating a series of thermal hydraulics experiments and simulations for the safety assessment of liquid metal fast reactors. In particular, in the MYRTE project, a dedicated activity has been defined, consisting of a low pressure experimental campaign realized at the ENEA Brasimone Research Centre and concerning a double wall Steam Generator Bayonet Tube (SGBT), aiming at supporting the development of the Primary Heat Exchanger (PHX) of MYRRHA. The CIRCE (CIRColazione Eutettico) pool facility hosts a devoted Test Section (TS) named HERO (Heavy liquid mEtal pRessurized water cOoled tubes). HERO consists of seven double wall bayonet tubes, with an active length of 6 m, arranged in a hexagonal geometry. This solution aims at improving the plant safety reducing the possibility of water-lead/leadalloy interaction thanks to a double physical separation between them and allowing an easier control of potential leakages of the coolant by pressurizing the separation region with inert gas. The experimental campaign in CIRCE-HERO has been supported by a pre-test analysis using system thermal-hydraulic codes (i.e. RELAP5). A sensitivity analysis has been performed considering the mass flow rate and HERO inlet temperature for both the water and LBE, fixing the operating pressure at 16 bar. A test matrix, as produced as output of the sensitivity analysis and aimed at reproducing as faithfully as possible the thermal-hydraulic behaviour of the MYRRHA PHX under different operating conditions, is here presented. The experimental results collected from the low pressure tests on HERO test section are reported and discussed.