Theoretical modeling of the effective thermal conductivity of the binary pebble beds for the CFETR-WCCB blanket

• A modified SZB (M-SZB) model is proposed for estimation of effective thermal conductivity of binary pebble beds with different materials.
• The M-SZB model considers the influence of packing factor, particle size, pressure, temperature, contact area.
• The M-SZB model agrees well with experimental data within a deviation of 20%.
• Calculate the effective thermal conductivity of binary mixed pebble beds by M-SZB model for WCCB.

The effective thermal conductivity (keff) is an important characteristic parameter for the thermo-hydraulics analysis of the ceramic breeder blanket. However, for the binary pebble beds composed of different particle materials, the experimental data of keff were very rare in the literature and limited theoretical models were found to be suitable for the accurate prediction. In this study, we have proposed an improved SZB (M-SZB) model to obtain the keff for the binary pebble beds composed of different particle materials. For the Li2TiO3/Be12Ti mixed pebble bed which used in the design of water-cooling ceramic breeder blanket(WCCB) for the China Fusion Engineering Test Reactor (CFETR), the keff values were calculated by the proposed SZB model and they ranges between 2.0 and 4.0 W/(m·K).