was installed in the Oak ridge gaseous diffusion plant. In 1945, uranium-235, pure enough for use in a.
bomb was produce and sent to Los Alamos, where it was made into a gun-type weapon. One small piece of.
Uranium-235, which was not big enough to hold a chain reaction itself, was fired at another small.
piece. This was done by means of a explosive charge, inside a cylinder shaped tube, which formed a.
supercritical mass that exploded instantly. They were so sure that this would work, that they did not.
even test it. It's first use was made in military action over Hiroshima, Japan, on August 6, 1945. The.
bomb uses a device called an altimeter to measure how far it is from the ground. It sends out radio.
frequencies which are bounced back to it. Microchips in the bomb determine how far it still has to fall,.
and when to detonate. The bombs also have fuses in the front which arm !.
the bomb. They are not inserted until the bomb is ready to be launched.
Before this bomb was developed, another kind was proposed. Uranium-238 could capture a neutron.
and become Uranium-239. All uranium has 92 protons. U-238 has 146 neutrons, and the added neutron raised.
the mass to 239. But U-239 is very unstable and it decays to neptunium-239 (93 protons, 146 neutrons),.
and plutonium-239 (94 protons and 145 neutrons). Plutonium-239 was fissionable, and could be separated.
from uranium by chemical techniques ( much easier than physical process of separating the different.
isotopes of 235 and 238 of the same element).
The first successful reactor was made at the University of Chicago under the Italian physicist.
Enrico Fermi. On December 2, 1942 it made a controlled chain reaction. Five large reactors were built at.
Hanford, Washington, where U-238 was blasted with neutrons to make plutonium. It was then sent to Los.
Alamos. Since another isotope of plutonium was also fissionable, there was a fear that a chain reaction.
could start to soon when the pieces of plutonium where brought together, making it blow apart before it.
