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split except by bombardment by particle accelerators. For all practical
purposes, the one true element whose atoms can be split comparatively easily
is the metal Uranium. Uranium's atoms are unusually large, henceforth, it is
hard for them to hold together firmly. This makes Uranium-235 an exceptional
candidate for nuclear fission.

Uranium is a heavy metal, heavier than gold, and not only does it have
the largest atoms of any natural element, the atoms that comprise Uranium have
far more neutrons than protons. This does not enhance their capacity to
split, but it does have an important bearing on their capacity to facilitate
an explosion.

There are two isotopes of Uranium. Natural Uranium consists mostly of
isotope U-238, which has 92 protons and 146 neutrons (92+146=238). Mixed with
this isotope, one will find a 0.6% accumulation of U-235, which has only 143
neutrons. This isotope, unlike U-238, has atoms that can be split, thus it is
termed "fissionable" and useful in making atomic bombs. Being that U-238 is
neutron-heavy, it reflects neutrons, rather than absorbing them like its
brother isotope, U-235. (U-238 serves no function in an atomic reaction, but
its properties provide an excellent shield for the U-235 in a constructed bomb
as a neutron reflector. This helps prevent an accidental chain reaction
between the larger U-235 mass and its `bullet' counterpart within the bomb.
Also note that while U-238 cannot facilitate a chain-reaction, it can be
neutron-saturated to produce Plutonium (Pu-239). Plutonium is fissionable and
can be used in place of Uranium-235 {albeit, with a different model of
detonator} in an atomic bomb. [See Sections 3 & 4 of this file.])

Both isotopes of Uranium are naturally radioactive. Their bulky atoms
disintegrate over a period of time. Given enough time, (over 100,000 years or
more) Uranium will eventually lose so many particles that it will turn into
the metal lead. However, this process can be accelerated. This process is
known as the chain reaction. Instead of disintegrating slowly, the atoms are
forcibly split by neutrons forcing their way into the nucleus. A U-235 atom
is so unstable that a blow from a single neutron is enough to split it and
henceforth bring on a chain reaction. This can happen even when a critical
mass is present. When this chain reaction occurs, the Uranium atom splits
into two smaller atoms of different elements, such as Barium and Krypton.

When a U-235 atom splits, it gives off energy in the form of heat and
Gamma radiation, which is the most powerful form of radioactivity and the most
lethal. When this reaction occurs, the split atom will also give off two or
three of its `spare' neutrons, which are not needed to make either Barium or
Krypton. These spare neutrons fly out with sufficient force to split other
atoms they come in contact with. [See chart below] In theory, it is
necessary to split only one U-235 atom, and the neutrons from this will split
other atoms, which will split more...so on and so forth. This progression
does not take place arithmetically, but geometrically. All of this will
happen within a millionth of a second.

The minimum amount to start a chain reaction as described above is known