4 were built during WW2
By the end of Operation Crossroads in the summer of 1946, the US had built a total of 9 atomic bombs and detonated 5 of them, leaving only 4 in the stockpile. Records obtained by the Bulletin of the Atomic Scientists suggest that by the end of 1946 the US had built 5 more atomic bombs, ending the year with 9 in the stockpile.While the Hanford reactors had a design capacity of 3 atomic bomb cores every month, its very obvious that they were being operated far below capacity through 1945 and 1946 to minimize neutron irradiation damage to the graphite moderator and/or shutdown for repairs frequently.
The Manhattan Project began in 1942 and ended in August 1947, with the establishment of the Atomic Energy Commission. A rough estimate is that in this time 15 to 20 atomic bombs had been built, with 5 of those detonated, leaving a stockpile by the time the Manhattan Project ended of 10 to 15 atomic bombs.
2
7 :)
As both atomic bombs and supernovas vary in yield, this question has no single answer.
They only built 2 and used them in the bombing of Nagasaki and Hiroshima.
Atomic bombs- Zero.
2
100
Many atomic bombs were detonated for "test" purposes. Fortunately none were used in war.
Well, to my research there hasn't been any nuclear bombs, Aussie has built.
2 atomic bombs and 2 million HE bombs and 5 million incendiary fire bombs