The fuel for the large majority of the fusion energy in a thermonuclear weapon is lithium deuteride, a solid. But here's some theories now how this works, one o

The fuel for the large majority of the fusion energy in a thermonuclear weapon is lithium deuteride, a solid. But here's some theories now how this works, one of which is changing the amount of tritium gas in the primary; but note that the primary (no pun intended) purpose of the tritium in the primary is to boost fission output through neutron release https://en.wikipedia.org/wiki/Variable_yield https://en.wikipedia.org/wiki/Variable_yield