Reliability research of hypervapotron under steady-state thermal load

As one of the key components, the divertor target directly facing the plasma and bearing the high thermal load makes a great impact on the operation of tokamak. Reliability research needs to be performed to verify the rationality of this structure. In this paper, optimization and reliability studies were performed for the hypervapotron structure, which referred to the model proposed by Escourbiac et al. Euler-Euler model coupled with the RPI boiling model was used in process of subcooled boiling numerical analysis for hypervapotron. Heat transfer performance with different types of fin was studied and the downstream triangular fin was eventually adopted in the optimized design. Based on this, process of optimizing the gap between the fin and the wall was conducted. The thermal-mechanical analysis results showed that the optimized design can satisfy allowable temperature and structural strength requirements under steady-state thermal load of 10 MW/m2. Subsequently, elastoplastic analysis during cyclic loads was conducted to search local weak spots. Fatigue life was calculated to be 7725 cycles based on numerical analysis and S-N curve. Ratchet assessment result of 10 cycles of thermal stress showed that this design can prevent ratchet failure. This paper proposed one new design of divertor target unit and verified its reliability on fatigue life and ratchet failure, also providing one system analysis process and method for hypervapotron thermal reliability.