Numerical study on the purge gas flow and heat transfer characteristics in helium cooled solid breeder blanket of CFETR

The helium cooled solid breeder blanket module was proposed and designed to achieve the goal of self-sustainable tritium breeding in China Fusion Engineering Test Reactor (CFETR), which was regarded as the transition from ITER to DEMO fusion reactors. A series of preliminary analyses, including thermal hydraulics, neutronics, structural mechanics and materials, have been performed for the blanket module design. However, most literatures focus on the thermal hydraulic behaviors of high pressure helium coolant flowing in cooling channels, while the thermal hydraulic characteristics of low pressure purge gas flowing slowly in pebble beds of tritium breeding zones has not been investigated in detail. In this work, the three dimensional model of typical helium cooled solid breeder blanket module was established employing Computational Fluid Dynamics (CFD) method. The corrected Ergun equation was adopted to simulate the coolant flow features in the porous medium. The temperature and flow field distributions in the First Wall (FW), neutron multiplier zones and tritium breeding zones were achieved. The most critical parts in the blanket module during normal operation condition were illustrated. Besides, the influences of purge gas inlet velocity and tritium breeding pebble-bed ball diameter on the whole blanket module thermal hydraulic features were revealed. This work could contribute to the design and optimization of helium cooled solid breeder blanket in CFETR.