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Fission and Fusion of Atomic Nuclei

The sun is not actually burning. If the energy given off by the sun were the product of a combustion reaction, the sun would have burned out approximately 2000 years after it was formed, long before today. You will learn how energy is produced in the sun.

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Fission and Fusion of Atomic Nuclei >

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Nuclear Fission

Nuclear Fission

splitting of a nucleus into smaller fragments

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

When the nuclei of certain isotopes are bombarded with neutrons, they undergo fission,

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

Chain Reactions

some of the neutrons produced react with other fissionable atoms, producing more neutrons which react with still more fissionable atoms.

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

Nuclear Fission

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Fission and Fusion of Atomic Nuclei > Nuclear Fission25.3

A Nuclear Power Plant

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

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.

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

Neutron Absorption

- is a process that decreases the number of slow-moving neutrons. Control rods, made of a material such a cadmium, are used to absorb neutrons.

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Nuclear Waste

Nuclear Waste

spent fuel rods from a nuclear reaction stored in water

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Fission and Fusion of Atomic Nuclei > Nuclear Waste

-Water cools the spent rods

-also acts as a radiation shield to reduce the radiation levels.

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Nuclear Fusion

Nuclear Fusion

How do fission reactions and fusion reactions differ?

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Fission and Fusion of Atomic Nuclei > Nuclear Fusion

Fusion- nuclei combine to produce a nucleus of greater mass.

In solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei and two positrons.

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Fission and Fusion of Atomic Nuclei > Nuclear Fusion

Fusion reactions, release much more energy than fission reactions

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Fission and Fusion of Atomic Nuclei > Nuclear Fusion

The use of controlled fusion as an energy source on Earth is appealing.

• The potential fuels are inexpensive and readily available.

• The problems with fusion lie in achieving the high temperatures necessary to start the reaction and in containing the reaction once it has started.

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25.3 Section Quiz.

1. One of the control mechanisms for a sustainable nuclear chain reactor involves slowing down the released neutrons so they may be captured by other nuclei. This is done using

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25.3 Section Quiz.

2. Spent fuel rods are stored in

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25.3 Section Quiz.

3. Choose the correct words for the spaces. In solar fusion, _______ nuclei fuse to form _______ nuclei.