MYRRHA Primary Heat Exchanger design

The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) facility, prototype of an Accelerator Driven System (ADS) reactor planned to be built in the SCK•CEN domain, in Mol, Belgium, in the next decade, presents several innovative and challenging objectives to be fulfilled. No electric power generation is foreseen for MYRRHA, with the 100 MWth evacuated via a two-phase water secondary system and, ultimately, through an aero-condenser system. A most important component of the reactor is the primary heat exchanger (PHX), which thermally and hydraulically connects the primary LBE pool with the secondary water loop. The secondary system conditions (temperature, pressure, mass flow rate) are supposed to stay constant at all power levels, with the primary system "following" the power variations by modifying its T/H parameters. A preliminary mechanical assessment has shown how the mechanical stresses induced by temperature gradients in the PHX tube thickness is below the allowable limits in nominal operation and accidental conditions as well. A preliminary analysis about the boiling channel instability has demonstrated how the MYRRHA PHX design does not suffer any problem coming from two-phase flow stability, and the flow behaviour remains stable under all power level and operating conditions.