Investigation of the packing structure of pebble beds by DEM for CFETR WCCB
Li2TiO3/Be12Ti mixed pebble beds with multi-sized particles are one of the potential candidates for the WCCB (water-cooled ceramic breeder blanket) of the CFETR (China Fusion Engineering Test Reactor). To meet the neutronics requirements of a WCCB, a study of the packing structure of the concerned pebble bed is necessary. In this paper, the discrete element method (DEM) is applied to produce a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. According to the current simulation, the packing factor of a mono-sized pebble bed is 0.62–0.64, while the value will become more than 0.75 for Li2TiO3/Be12Ti mixed breeding pebble bed with a diameter ratio of not less than 5 as well as an appropriate mixed volume ratio, and thus can meet the neutronics requirements.
Keywords: WCCB, pebble bed, packing structure, discrete element method, fusion blanket