Lithium hydride
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
Castle Bravo
In terms of TNT equivalence, "Castle Bravo" was about 1,000 times more powerful than each of the atomic bombs that were dropped on Hiroshima and Nagasaki during World War II. "Castle Bravo" is the fifth largest nuclear explosion in history, exceeded by the Soviet tests of "Tsar Bomba" at approximately 50 Mt, "Test 219" at 24.2 Mt, and two other ~20 Mt Soviet tests in 1962 at Novaya Zemlya.