Modeling of Primary Heat eXchanger (PHX) at HEXACOM installation: MSc thesis

MYRRHA (Multi-purpose hYbrid Research Reactor for High-Tech Applications) is a pool type fourth generation, lead-bismuth cooled fast nuclear reactor under development at SCK CEN. It is the first reactor to be driven by a particle accelerator, therefore intrinsically safe. Its purposes are to reduce nuclear waste volume and radiotoxicity by transmuting minor actinides, produce important volumes of high purity radioisotopes for nuclear medicine and cancer treatment, and contribute to nuclear fusion and fundamental physics research. The PHX (Primary Heat eXchanger) component constitutes the core of the HEXACOM loop, a representation of the MYRRHA secondary system, to remove power under normal operation and decay heat in accidental conditions. It consists of a single double wall bayonet tube of which the external walls are coextruded excepts for helical cavities which are filled by Helium. A campaign of experiments on the PHX has been organized from 18/11/2024 to 21/11/2024, in order to assess its performances. The post-analysis of this campaign has been divided in two phases. The first phase has been accomplished and consisted in providing a first estimation of its global heat transfer coefficient. This report is part of the second phase of the analysis that concentrates on the development of a qualified nodalization of the PHX experimental campaign according to a predefined procedure for experimental installations. This procedure contains 17 steps. However, in order to limit the lengh of this document, only the last (and most important) three steps will be completely addressed in this report, regarding the transient, the steady state and the heat losses. The objectives of this activity are to evaluate the capabilities of the TH system code RELAP version 5 MOD 3.3 in simulating one experimental case (operation at reduced fedwater inlet mass flow) of the PHX campaign. The final goal is to provide a reliable assessment of the convective heat transfer coefficients at both water/steam and LBE sides. These data will be used by SCK CEN to finally assess the thermal resistance of the PHX double wall.