Transient thermal-hydraulics considerations of tandem mirror LiPb cooled blankets during start-up/shutdown operations

Abstract The operational aspects of fusion reactors are being recognized as important ingredients of the design process. In this paper, we present analyses and modeling relevant to the understanding of blanket performance during transients. The use of LiPb as a blanket coolant is considered in this paper from the viewpoint of transient operation during initial start-up. When LiPb is first introduced into the blanket tubes in the form of a molten metal, freezing/blockage and thermal shock to the tubes may occur. We first model the transient thermal behavior of the coolant (LiPb)-tube system. We then proceed to analyze the thermal shock to the blanket tubes upon contact with the hot LiPb. It is shown that freezing/blockage due to excessive heat losses from the LiPb coolant is not a major design consideration. However, thermal stresses caused by differential expansion during transients should be mitigated by appropriate pre-heating of blanket modules.