 
Nuclear Fission: Discovery and Technological Development |
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| Nuclear Fission Resources |
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Concerning the basics of nuclear fission --
this is a short list of some of the best links, selected by the education
committee of the Canadian Nuclear Society.
The Virtual Nuclear Tourist !
has some fission basics (including more links) at
The US Nuclear Energy Institute has
a web site called Science Club - Nuclear World at
http://www.nei.org/scienceclub/nuclearworld/nw_splittingatom.html
and a similar one at the World
Nuclear Association : The ABCs of Nuclear Science (educational site from Lawrence Livermore National Laboratory) is at http://www.lbl.gov/abc/index.html ....the part about fission is at http://www.lbl.gov/abc/Basic.html#Fission Our own AECL has a nice fission
animation at The Particle Adventure (another, more general, educational site from Lawrence Livermore National Laboratory) is at http://particleadventure.org/ Natural Radioactive Decay animation is at http://www.mines.utah.edu/~ggapps/radiation/radiation.html Virtual Radiation Museum is at http://www.medphysics.wisc.edu/~vrm/VRMHOME.HTM |
In the 1890s Henri Becquerel
(pictured at left) was investigating phosphorescent minerals, those which after
exposure to light would glow in the dark. He
wrapped
photographic plates in black paper and tried placing various materials against
the wrapped plates. Nothing happened until one day in 1896 when he tested
uranium minerals and their salts. These caused strong darkening of the wrapped
photographic plate, the first indication of the existence of a new form of
radiation that could pass through paper and darken the photographic plate.
Becquerel had
discovered
radioactivity.
Radioactivity
can occur naturally, or, as learned through many investigations during the first
half of the 20th Century, radioactive isotopes can be produced
artificially by bombarding a target nucleus with a sub-atomic-size
particle,
a process called transmutation. Whether it’s the parent or the target nucleus
which changes into a daughter, the change is relatively small; the daughter has
a mass only a small amount different from the parent or target. Then suddenly,
late in 1938, Otto Hahn (pictured at right with Lisa Meitner) and Fritz
Strassmann (pictured at left) discovered a fundamentally new and unexpected
exception. After irradiating uranium with neutrons, they were surprised to
detect barium, an element only about half of the mass of uranium. The conclusion
was inescapable; they had split the uranium atom into two parts. They had
discovered nuclear fission -- the splitting of the atom.
Two physical properties of nuclear fission are
particularly exciting and important; splitting the uranium nucleus with a
neutron
releases energy and a few additional neutrons. Almost immediately, Siegfried
Flügge and Leo Szilard,
independently, realized that those two properties meant the possibility of a
nuclear chain reaction. A nuclear
chain reaction, if it could be made to occur very quickly, meant the possibility
of a new weapon of war, the atom bomb. A slow, controlled chain reaction might
be used to generate electric power or to produce fissionable material for atom
bombs. As the clouds of World War II darkened over Europe and the rest of the
world, scientists focused attention on learning what was need to design and
manufacture atom bombs. Enrico Fermi (pictured at right) built the first
man-made nuclear fission reactor under the stands of Stagg Field at the
University of Chicago, which became operational on December 2, 1942. At the
time, Fermi and everyone else thought that was the first self-sustaining nuclear
chain reaction, but they were wrong; Mother Nature had beat them to the punch.
Interestingly, just months after the discovery of nuclear fission, Siegfried
Flügge speculated on the possibility of nuclear explosions in
uranium deposits. But, as you will see by perusing this website, there is much
more to the story of natural nuclear fission.