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.
Human radiation experiments
In the Marshall Island, indigenous residents and crewmembers of the fishing boat "Lucky Dragon No. 5" were exposed to the high yields of radioactive testing during the Castle Bravo explosions conducted at Bikini Atoll. Researchers subsequently exploited this ostensibly "unexpected" turn of events by conducting research on the onset of effects from radiation poisoning as part of Project 4.1, raising ethical questions as to both the specific incident and the broader phenomenon of testing in populated areas.