Thermal-hydraulic study of the Primary Heat Transport System of the DEMO Divertor Cassette Body

The EU-DEMO reactor is supposed to undergo a pulsed duty cycle under normal conditions, which might challenge the qualified lifetime of the main equipment inducing undue thermal and mechanical cycling loads. Moreover, during power operation it is not possible to exclude the occurrence plasma overpower transients that might jeopardize the structural integrity of the plasma-facing components. In this context, the University of Palermo in cooperation with ENEA has launched a research campaign within the framework of the EUROfusion action to investigate the thermal-hydraulic behaviour of the Primary Heat Transport System (PHTS) of the EU-DEMO Divertor (DIV) Cassette Body (CB) during the typical DEMO duty cycle. The study was primarily intended to start the definition of the strategies to be followed to minimize thermal fluctuations due to the pulsed operation. In particular, the attention has been focussed on the assessment of the DIV CB PHTS temperature behaviour during the pulse-dwell transition so to check the potential effectiveness of a direct coolant temperature control by properly tuning the feedwater mass flow rate. The activity has been led following a computational approach based on the adoption of the TRACE thermal-hydraulic system code. Models, assumptions, and outcomes of the analyses are herewith reported and critically discussed.