One way that scientists on the Manhattan project would refer to fissile elements indirectly was by using the last digit of their atomic number and of their atom

One way that scientists on the Manhattan project would refer to fissile elements indirectly was by using the last digit of their atomic number and of their atomic mass. So Pu-239 would be called 49 and U-235 would be called 25. Some examples: http://www.atomicarchive.com/Docs/ManhattanProject/LosAlamos.shtml http://www.atomicarchive.com/Docs/ManhattanProject/LosAlamos...