Animation of the production of tritium from a lithium blanket in a fusion reactor. The lithium blanket is a design feature in a deuterium-tritium fusion reactor, in which the neutrons (yellow) produced by the fusion reaction are absorbed by a lithium-6 nucleus, which then splits into a helium-4 nucleus and a tritium (hydrogen-3) nucleus. This is an advantageous way of producing tritium, which is scarce and difficult to transport. It is also advantageous as it removes an energetic neutron. Although the lithium blanket is enriched in the lithium-6 isotope, it will also contain some lithium-7, which generates another neutron. See clip K003 6962 for that reaction.