transmutation, nuclear fission and fusion
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Transmutation, Nuclear Fission and Fusion. Nuclear Transformations. Nuclear Transformations : Changing one element into another by particle bombardment. α. O. N. H. Nuclear Transformations. Rutherford: 1919 First to discover nuclear transformation. - PowerPoint PPT PresentationTRANSCRIPT
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Transmutation, Nuclear Fission and Fusion
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Nuclear Transformations
• Nuclear Transformations: Changing one element into another by particle bombardment
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Nuclear Transformations
• Rutherford: 1919 First to discover nuclear transformation
H O He N 11
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How is this different from radioactivity?•Not a natural occurrence•Can be controlled – stopped or started•Two reactants instead of one•Uses bombardment by a lighter particle
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Nuclear Transformation
• Irene Curie and Frederick Joliot– Were the 1st to create an artificial radioactive
isotope– 14 years after Rutherford
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Nuclear Transformation
• How was it done?– Both sets of scientists used alpha particles
• They bombarded a larger nucleus with a smaller particle.
– Both the nucleus and alpha particle were positive so they repelled each other. • Very high energies needed to accomplish
transformation. – A particle accelerator was used to accelerate the
particles to the required speeds.
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Accomplishing Nuclear Transformation• Neutrons also used. Why would they
be easier? – They are neutral and not repelled so they
are absorbed easier.– This is the method used to extend the
periodic table.
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Creating Synthetic Isotopes
• Synthetic isotopes are made by using particle accelerators – Prior to 1940, the heaviest known element
was Uranium• Since 1940, many transuranium elements have
been produced from nuclear transformations.
– Get to name them after anything you want • Countries or scientists are common
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Writing Equations
• Write equations showing the neutron formation of Americium
• Bombard (react) Pu-240 with a neutron.• Take the product from ‘a’ and have it
undergo beta decay.
• Show the gamma decay of Am-243.• Show the alpha decay of Am-243.
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NUCLEAR FISSION AND FUSION
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Nuclear Energy
• Two types of nuclear processes that release energy:– Fusion: combining two light nuclei to form
a heavier nucleus– Fission: splitting a heavy nucleus into two
nuclei with smaller mass numbers
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Nuclear Fission
•Was discovered in the late 1930s–A Uranium-235 nucleus was spilt into two lighter elements during neutron bombardment:
•The fission of 1 mole of U-235 releases 26 million times as much energy as the combustion as 1 mol of methane
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Nuclear Fission
• Besides the product nuclides, neutrons are also produced
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Nuclear Fission
– Each fission event will produce neutrons that can collide with even more U-235 nuclei
– Because each fission event produces neutrons, we call it a chain reaction
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Nuclear Fission
• For the fission to be self-sustaining at least ONE neutron from each fission event must go on to split another nucleus– If less than one neutron causes a fission event,
– If exactly one neutron from each fission event causes ANOTHER fission event, the process sustains itself and is said to be
– If more than one neutron from each fission event causes another fission event, the process escalates and the heat build-up causes an explosion
(AKA: Ka-Boom)
critical
the process dies out
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Nuclear Fission• During WWII, the US carried out a research
effort called the Manhattan Project– The goal was to build a bomb based on the
principles of nuclear fission– This project produced the first fission bomb
• Used on Hiroshima and Nagasaki in 1945
– The bomb operates by rapidly escalating fission events that produce an explosion!
Oak Ridge, Tennessee. 60,000 workers worked for three years to separate 2 kilograms of uranium-235 from uranium-238 for the Manhattan Project
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The other Energy Source: Nuclear Fusion• Combining two light nuclei to create
one heavier nucleus– Produces even more energy than fission
• Occurs in stars - including our sun– Fusion of protons to form helium
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Fusion
•Efforts are underway to develop a feasible fusion process
–There is a ready availability of light nuclides•Deuterium( ) is in seawater
–Can serve as fuel for fusion reactions
•Initiating fusion is much more intensive than initiating fission
H21
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Fusion
• Forces binding nucleons together only work at very small distances– Getting protons close requires lots of
energy
• Must be shot at each other– This is because the protons repel each
other, so the repelling forces must be overcome with spee
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Fusion• Need temperatures of 40 million Kelvin
– Product of fusion is plasma, which is hard to contain
– Scientists are studying two types of systems to produce the extremely high temperatures required:• High powered lasers• Heating by electric currents (magnets)