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.
Project 4.1
Project 4.1 was the designation for a medical study conducted by the United States of those residents of the Marshall Islands exposed to radioactive fallout from the March 1, 1954 "Castle Bravo" nuclear test at Bikini Atoll, which had an unexpectedly large yield. Government and mainstream historical sources point to the study being organized on March 6 or March 7, 1954, six days after the "Bravo" shot.