Answer: atombomb

AnswerCrossword Clue
ATOMBOMB

Manhattan Project project

ATOMBOMB

Mushroom-making weapon

ATOMBOMB

1940s Los Alamos development

ATOMBOMB
It was used to discover fermium
ATOMBOMB
Little Boy, e.g.
ATOMBOMB14-year-old invention.
ATOMBOMBModern weapon.
ATOMBOMBPhenomenon of our time.
ATOMBOMBEnola Gay's load
ATOMBOMBMushroom cloud producer
ATOMBOMBFat Man or Little Boy