Conceptual design of solid-type Pb (x) Li (y) eutectic alloy breeding blanket for CFETR

As a key component of the Chinese Fusion Engineering and Test Reactor (CFETR), the blanket is responsible for tritium breeding, neutron shielding and energy conversion. Blankets can be classified into solid and liquidaccording to the form of tritium breeder. Among them, the solid blanket utilizes the pebble beds as both the tritium breeder and neutron multiplier, and it has been a popular scheme due to its advantages, such as good material compatibility and non-magnetohydrodynamic effects. However, it usually adopts beryllium or an alloy (i.e. Be and Be12Ti) for multiplying neutrons, causing a very high cost of the solid blanket due to the scarcity of natural resources of beryllium, and this hinders its development. In this paper, a novel solid blanket utilizing a PbLi eutectic alloy was proposed to make up the above deficiency. Pb83Li17 is usually applied in a liquid blanket due to its lowmelting point. However, this kind of alloy can have a higher melting point by adjusting the atomic ratio of Pb/Li, and thus it can be used in the solid blanket both for the tritium breeder and neutron multiplier. Based on the blanket modular design of CFETR, the optimization of the radial layouts, the atomic ratio of Pb/Li and the packed structure of the pebble beds are studied through neutronic and thermal hydraulic analysis. The results indicate that the solid-type Pb (x) Li (y) can satisfy the requirement of tritium self-sufficiency, and the global tritium breeding ratio is larger than 1.0. In addition, the cooling system design can retain the maximum temperature of Pb (x) Li (y) at a lower level without melting. Overall, this kind of solid-type Pb (x) Li (y) blanket is feasible from the perspective of neutronic and thermal hydraulics, and it avoids using beryllium; thus, the cost is highly reduced.