Chapter 25 Nuclear Chemistry
25.3 fission and Fusion of Atomic Nuclei
Chemistry
Today we are learning to:1. Describe what happens in a nuclear chain reaction
2. Explain the use of water in the storage of spent fuel rods
3. Distinguish fission reactions from fusion reactions
Fission and Fusion of Atomic Nuclei
Nuclear Fission
When the nuclei of uranium-235 or plutonim-239 are bombarded with
neutrons, they undergo fission, the splitting of a nucleus into smaller
fragments.
The steps are as follows:
i.
A slow moving neutron strikes a uranium-235 nucleus
ii.
The nucleus splits into two roughly equal halves
iii. 3 more neutrons are released
iv. These neutrons start a chain reaction with other uranium-235
nuclei
Fission and Fusion of Atomic Nuclei
Nuclear Fission
Fission and Fusion of Atomic Nuclei
Nuclear Fission
Chain Reaction Video
Fission and Fusion of Atomic Nuclei
Nuclear Power
Indian Point Energy Center is a three-unit nuclear power plant station
located in Buchanan, New York just south of Peekskill NY.
Half-Life
Fission and Fusion of Atomic Nuclei
Nuclear Power
Neutron moderation is a process that slows down neutrons so the reactor
fuel (uranium-235 or plutonium-239) captures them to continue the chain
reaction. Water and graphite are good moderators
Neutron absorption is a process that decreases the number of slowmoving neutrons. Control rods, made of a material such a cadmium, are
used to absorb neutrons.
Fission and Fusion of Atomic Nuclei
Nuclear Waste
• Why are spent fuel rods from a nuclear reaction stored in water?
• They are highly radioactive and dangerous to the environment
• Water keeps spent fuel rods cool
• Water acts as a radiation shield, absorbing dangerous radiation
Fission and Fusion of Atomic Nuclei
Nuclear Fusion
Fusion occurs when nuclei combine to produce a nucleus of greater mass. In
solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei and two
positrons.
Fusion reactions, in which small nuclei combine, release much more
energy than fission reactions, in which large nuclei split.
The sun has been supplying energy via nuclear fusion for about 4.567
billion years, and is about half way through its life cycle
Fission and Fusion of Atomic Nuclei
Nuclear Fusion
•The use of controlled fusion as an energy source on Earth is appealing as the
potential fuels are inexpensive and readily available.
•The problems with fusion lie in achieving the high temperatures necessary to
start the reaction (40,000,000,000 C) and in containing the reaction once it has
started.
2.3 Vocabulary 25.3 Vocabulary
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•
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Fission: the splitting of a nucleus into smaller fragments
Neutron moderation: process of slowing down neutrons do they will be
absorbed by nuclei.
Neutron absorption: process of decreasing the number of slow moving
neutrons by using control rods
Fusion: when light nuclei fuse together to form a single nuclei
END OF SHOW