Tritium breeders are key functional materials for achieving tritium self-sufficiency in the breeding blanket of nuclear fusion reactors. Conventional pebble bed tritium breeders are limited due to an upper bound of packing factor, stress concentration-induced fragmentation, and high gas flow resistance, making them difficult to simultaneously achieve efficient heat and mass transfer, thus restricting the enhancement of tritium production performance. In this study, a design concept employing porous tritium breeders based on triply periodic minimal surfaces (TPMS) was proposed as an alternative to the conventional pebble bed configuration. Typical Gyroid and I-WP structures were selected as research objects, and a flow-solid coupled numerical model under reactor-relevant operating conditions was proposed to systematically compare the sweep gas flow behavior and heat transfer characteristics of the two TPMS structures with those of the conventional pebble bed.

The geometric model of the pebble bed was constructed by discrete element method (DEM), while the Gyroid and I-WP structures were generated based on implicit trigonometric parametric representations. Numerical simulations were performed by a software named Ansys Fluent with the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) model to investigate the flow and heat transfer characteristics of helium within porous microchannels. Gyroid-type porous tritium breeder samples were fabricated by a stereolithography system, and their internal three-dimensional architectures were reconstructed via micro-computed tomography (micro-CT). The pressure drop and effective thermal conductivity of the samples were measured using a helium flow resistance pressure-drop measurement setup and a Hot Disk TPS 2500S thermal conductivity analyzer, respectively.

Compared with the conventional pebble bed configuration, TPMS-based tritium breeders exhibit significant advantages in thermo-hydraulic performance. The Gyroid and I-WP structures both effectively reduce flow resistance and improve flow field uniformity, which is beneficial for sweep gas transport and heat removal. Among the two TPMS configurations, the Gyroid structure demonstrates superior performance. Within the inlet velocity range of 0.1-0.2 m/s, the average flow velocity is increased by approximately 56%, the pressure drop is reduced by 50%, and the effective thermal conductivity is enhanced by 13.7%, compared with the pebble bed. These improvements are mainly attributed to the continuous integrated solid skeleton and the highly interconnected pore network of the TPMS structures. In addition, the Gyroid porous tritium breeder samples are fabricated via additive manufacturing, and the thermo-hydraulic experiments are conducted under representative operating conditions. The experimental results show good agreement with the numerical data, confirming the reliability of the numerical model.

This study targeted breeding blanket applications in nuclear fusion reactors and proposed a TPMS-based porous ceramic tritium breeder design. The thermo-hydraulic characteristics of Gyroid and I-WP tritium breeder structures were systematically evaluated and compared with those of a conventional pebble bed via combining numerical simulations with experimental investigations. The results demonstrated that both TPMS configurations could exhibit significantly lower flow resistance and superior thermo-hydraulic performance relative to the pebble bed, with the Gyroid structure showing the best overall performance. The numerical predictions were in reasonable agreement with the experimental results, confirming the reliability of the developed model and preliminarily demonstrating the engineering feasibility of the Gyroid porous ceramic tritium breeder.