Helium bubble formation in Pb-16Li within the breeding blanket

Helium is a by-product of the tritium formation reaction by neutron bombardment of lithium. The solubility of helium is estimated to be extremely low, which may result into gas pockets formation. These pockets then cause hot spots within the blanket, reduce its shielding properties and also reduce the tritium breeding ratio by limiting the Pb-16Li volume inside the blanket. To assess the extent of the helium bubble formation, a simplified model of a single sector of the European DEMO breeding blanket had been developed and local production rates of gaseous helium have been estimated. Based on recent development of the blanket geometry, it is possible to estimate the local gas bubble release rate within each module, the gas bubble release profiles along the Pb-16Li conduits and the gas composition.