Thermo-mechanical Analysis Of Helium Cooled Solid Breeder Blanket For CFETR

According to the Roadmap of Chinese Magnetic Confinement Fusion Energy, the first phase of Chinese Fusion Engineering Test Reactor (CFETR) will obtain about 200 MW fusion power, achieve steady state or long pulse plasma operation and attain tritium self-sustainability. Breeding blanket of fusion reactor is the key component of attaining tritium self-sustainability. Besides tritium breeding, breeding blanket also has the following two main functions:energy exhaust and conversion and radiation-shielding. Therefore, the blanket for fusion reactor has to meet the requirements of neutronics, thermal hydraulics, structural mechanics and safety, which makes the design of blanket rather challenging. To support the development of CFETR, the thermo-mechanical assessment of a helium cooled solid breeder (HCSB) blanket for CFETR has been conducted. The results provide reference for future design of CFETR HCSB blanket.In this PhD dissertation, steady state thermal analysis and transient thermal analysis of the blanket module following CFETR plasma pulse are conducted. Furthermore, sensitivity analysis of several factors impacting the blanket temperature field (i.e., thermal conductivity of pebble bed, the thermal hydraulic parameters and thermal contact conductance of pebble bed-wall) is performed. Steady state results show that the temperatures of the blanket sub-components are within limits. The temperature fields are also used as inputs to structural analysis under monotonic type loading (M-type). The temperature evolution of blanket sub-components is obtained through transient thermal analysis. The temperature on blanket increases with respect to the thermal loading during ramp-up. The temperature of first wall increases quicker than that of breeding zone during ramp-up. The temperature of first wall decreases faster than that of breeding zone during ramp-down. The large inversion of temperature gradient between first wall and breeding zone during plasma ramp-up and ramp-down will be the cause of large cyclic thermal stress. The results of transient thermal analysis are used as inputs to structural analysis under cyclic type loading (C-type). It is obtained that pebble bed packing factor and pebble size have very little impact on blanket temperature. It is found that the variation of thermal conductivity of pebble bed has large influence on the temperature of pebble bed. Reducing the thermal conductivity will largely increase the temperature of pebble bed. The temperature will not change after the thermal conductivity is increased to a certain value. As the inlet mass flow rate increases (decreases), the temperature on blanket decreases (increases). The temperatures will not change after the inlet mass flow rate is increased to a certain value. The maximum temperatures on blanket vary linearly with the inlet temperature, but not significantly. The roughness of cooling channels at breeding zone has limited impact on temperature of breeding zone and will largely increase pressure loss; adding roughness to cooling channels at breeding zone is not worthwhile. The change of thermal contact conductance between pebble bed and wall has a limited impact on the temperature of the blanket. The current blanket design can easily tackle the influence of TCC variation. Even the pebble bed totally loses the contact with wall, the temperatures on the blanket still stay within design limits. It can be concluded that the current blanket design has a good thermal stability.Based on thermal analysis, thermo-mechanical analysis has been performed. The structural strength assessment criteria and methods for fusion blanket have been explained following the Structural Design Criteria for ITER In-vessel Components (SDC-IC). The analysis and assessment of M-type damage modes of the blanket (without taking into account the electromagnetic loading) has been performed with respect to the SDC-IC rules. The current blanket has a robust behaviour in preventing M-type damage modes. Thereafter, the analysis and assessment of C-type damage modes of the blanket has been conducted under SDC-IC rules. The blanket shows a robust performance against C-type damage modes. Preliminary FFMEA analysis of the blanket system has conducted, obtaining a list of blanket reference accidents. Following SDC-IC level D criteria, the thermo-mechanical analysis of the blanket under typical accidental condition (In-box LOCA) is performed. Results show that the blanket has good mechanical performance even under In-box LOCA condition.The research carried out in this PhD dissertation will provide good reference for design of future CFETR blanket.