Hydraulic analysis of the DTT divertor module

Understanding coolant flow behaviour in the divertor module is critical for managing the high thermal loads encountered in Tokamak plasma scenarios. Effective cooling ensures system integrity, optimal performance, and prolonged component lifetime, especially in high-heat flux environments. This study investigates the hydraulic performance of the DTT (Divertor Tokamak Test) divertor module, focusing on achieving uniform flow distribution.

The DTT facility, under construction at ENEA C.R. Frascati, is designed to explore power exhaust solutions for DEMO. The initial DTT divertor comprises 54 water-cooled modules, each handling a total mass flow rate of 577 kg/s with water temperatures ranging here considered from 30 °C to 74 °C. Each module includes an Outer Target (OT), Inner Target (IT), and Central Target (CT), with coolant entering through an outboard manifold and flowing through nine OT tubes. Two of the external pipes return directly to the outlet manifold, while the remaining pipes continue through additional components, necessitating calibrated orifices to achieve balanced flow distribution.

A Computational Fluid Dynamics (CFD) model was developed to optimize orifice sizing in OT pipes and evaluate flow uniformity. Sensitivity analyses assessed the effects of bulk water temperature variations and manufacturing tolerances on orifice dimensions. The model also examined total pressure drops and localized losses caused by twisted tapes in the tubes promoting flow swirling. Finally, the impact of flow rate fluctuations on critical heat flux was analysed, offering insights into the hydraulic system robustness under variable conditions. Simulations were performed using ANSYS software, providing an evaluation of the divertor module cooling performance.