Impact of Pressure Equalization Slot in Flow Channel Insert on Tritium Transport in a DCLL-Type Poloidal Duct

A SiC-based flow channel insert (FCI) is used as an electrical and thermal insulator in the Dual Coolant Lead Lithium (DCLL) blanket. To reduce the stress of the FCI structural material, the pressure equalization slot (PES) is implemented in the FCI wall. However, the PES affects the tritium transfer behavior and loss rate. Therefore it is important to examine the tritium loss rate and ensure it remains below an allowable limit. In the present study, we analyze tritium transport and quantify the tritium loss rate in a front duct of the DCLL-type outboard blanket where PbLi moves poloidally. Three types of poloidal ducts have been considered: one without the PES, one with the PES in the wall parallel to the magnetic field and one with the PES in the wall perpendicular to the magnetic field. Tritium concentration fields are obtained by solving a fully 3-D problem with appropriate boundary conditions at various interfaces. Results show a high tritium concentration at the location of reversed flow when a PES was located in the wall parallel to the field. Furthermore, when any PES was introduced, the PES changed the velocity profiles and thus changed the tritium concentrations in the core and gaps, which increases the tritium losses from 1.244% to 1.413% under the calculation conditions.