Verification of the qualified nodalization of the Table Top facility

MYRRHA (Multi-purpose hYbrid Research Reactor for High-Tech Applications) is a 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 transmutating 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 Primary Heat eXchangers (PHX) of the pool-type reactor are the most important interface between the primary and the secondary systems, by removing power under normal operation and decay heat in accidental conditions. In order to characterize the thermal resistance of a single tube of the PHX at a scale 1/10, a 2.5 kW water/steam open loop facility named Table Top has been developed. More than 29 experiments (runs) have been carried out in the range 8-16 bar of pressure and a qualified nodalization of the plant has been developed. The verification of the nodalization will determine if the latter can accurately represent the loop behavior, necessary to the project progress. The procedure contains 17 steps, but only the last three remain undone, regarding the transient, the steady state and the heat losses. All three will be assessed for five selected runs. For this purpose, each input deck must be beforehand adjusted in order to fit experimental data in terms of initial and boundary conditions. After computation by RELAP5 3.3, each output data is compared to thermal-hydraulic parameters acceptance criteria already defined. Each computed parameter (pressure, temperature…) must meet the acceptance range for the nodalization to be validated. In a second time, acceptance criteria will be defined for the draining phase of the installation by dry-out. One run will be assessed in the same way as previously explained.