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
A Japanese fishing boat, "Daigo Fukuryū Maru" (Lucky Dragon No.5), came in direct contact with the fallout, which caused many of the crew to grow ill; one died of a secondary infection. This resulted in an international incident and reignited Japanese concerns about radiation, especially as Japanese citizens were once more adversely affected by US nuclear weapons. The official US position had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radioactivity released. Japanese scientists who had collected data from the fishing vessel disagreed with this.