nuclear fission & fusion

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Nuclear Fission & Fusion. FISSION : a heavy nucleus splits into 2 lighter nuclei. some elements undergo fission spontaneously some elements can be induced to undergo fission when bombarded with other particles (e.g. neutrons). FUSION : 2 nuclei combine to form a heavier nucleus. - PowerPoint PPT Presentation



Nuclear Fission & Fusion1FISSION: a heavy nucleus splits into 2 lighter nucleisome elements undergo fission spontaneouslysome elements can be induced to undergo fission when bombarded with other particles (e.g. neutrons)2FUSION: 2 nuclei combine to form a heavier nucleusthe sun is a tremendous fusion reaction; the major fusion reaction in the sun is thought to be:

both fission & fusion release large amounts of energy (fusion more than fission)

3The Atomic Bomb (FISSION)when the nucleus of U-235 splits, 2 isotopes are formed, plus neutrons are emittedthese neutrons collide with other U-235 atoms, causing them to undergo fission; they release neutrons, and so onThe result - CHAIN REACTION!!



6The Atomic Bomb (FISSION)

7The Atomic Bomb (FISSION)

8CRITICAL MASSThe minimum mass of fissionable material that must be used to sustain a chain reaction9One type of bombLittle Boy: U-235 (Hiroshima)

Fat Man: Pu-239 (Nagasaki)subcritical mass of U-235subcritical mass of U-235TNT(dynamite)10

Little Boy

Nuclear Reactors (controlled FISSION)

13Nuclear Reactors (FISSION)use subcritical masses of fissionable materialCORE: contains fuel pins made of U-235; interspersed among the pins are control rodscontrol rods: absorb neutronspull rods out of core: fission increasespush rods back into the core: fission decreasesSafety feature: if power is lost, rods will automatically fall into the core and shut reaction down.14Nuclear Reactors (FISSION)The energy produced by breaking down the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine.Ernest Rutherford

15Nuclear Reactors (FISSION)

16Nuclear Power Plants

17TO GENERATE ELECTRICITY:Fission heats up water in vessel and heat is carried away.This heat is used to heat up water in a second system, which turns into steam.Steam turns turbine of a generator.Generator makes electricity.18Nuclear Power Plants

19Nuclear Power Plants

20PROS OF NUCLEAR ENERGY:no air pollutionenormous amt. of energy releasedalternative to using our rapidly decreasing fossil fuels21CONS OF NUCLEAR ENERGYcontainers for waste products may erode or breakthermal pollution (heated water returned to rivers, etc.)potential theft of fuel (Pu-239) for use in weapons22Controlled Nuclear FUSIONPROS:A very abundant supply of energy world wide.Environmentally cleanNo creation of weapon materialsNo chance of runaway reactions leading to accidentsCONS:It doesnt work; at least not yet23Nuclear Fusion"Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements, and it is an everyday reality throughout the Milky Way Galaxy." Carl Sagan, Spitzer Lecture, October 1991

24Nuclear FusionObstaclesHOT plasma at least 100 million CHigh density plasmaContainment of plasmaConfinement time



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