Nuclear Fission and Nuclear Fusion Enormous Energies Nuclear

Nuclear Fission and Nuclear Fusion Enormous Energies

Nuclear Fission � Take a large atom and impact the nucleus with a particle. � Split the atom releasing high energy, more high energy neutrons, and two daughter nuclides. � Fission occurs only rarely in nature. Alpha decay is much more common.

Uranium-235 � Elements with an atomic number greater than 80 are capable of undergoing fission. � 235 U absorbs a neutron, 1 n, temporarily 92 0 producing unstable 23692 U. � Almost immediately 23692 U splits into two more stable daughter nuclides plus large amounts of energy and two to three fast neutrons depending on the reaction.

Fission and energy � The fast neutrons produced by fission fly off to impact other atoms of 23592 U resulting in a chain reaction. � The fission of uranium-235 releases ~200 Me. V. That equals ~100 x energy release by burning a coal molecule.

Concepts � � � Fissile: atoms (235 U or 239 Pu)that are capable of undergoing fission when an atom captures a thermal slower neutron. Fissionable: atoms (238 U)able to undergo fission when bombarded with high energy neutrons such as in a thermonuclear weapon, bomb. Nuclear fuels: elements that can sustain a fission chain reaction such as uranium-235 and plutonium-239. Spontaneous fission: the slowly occurring process of fission in nuclear fuels unaltered by human intervention. Critical mass: enough nuclear fuel present and emitting neutrons in quantities to sustain a chain reaction.

Chain Reaction � Once the fission reaction is initiated, the high energy neutrons released keep the reaction going. This is a chain reaction. � The mousetrap model. › http: //www. youtube. com/watch? v=0 v 8 i 4 v 1 mie. U Student project 2: 54 minutes › http: //www. youtube. com/watch? v=vjq. IJW_Qr 3 c Nat. Sci. Demo 2: 28 minutes

Power Production �A coal fired plant and a nuclear plant share the same power generation type: conversion of heat to electricity via pressurized steam. � The fission reaction releases energy which is absorbed by water converting some of the water to steam. � Steam is used to drive the turbine connected to a generator.

Schematic of Nuclear Plant

The Bomb http: //www. youtube. com/watch? v=CGRx 2 c. Pj. U XM Navy Film of Bikini Crossroads Test A bomb typically uses a contained explosion or impact to induce a chain reaction. No controls limit the progress of the reaction.

Fusion � Fusion reactions are the combining of two nuclei to form a more massive nucleus. � Many fusion reactions release large amounts of energy. › An example is the combining of two isotopes of hydrogen (tritium and deuterium) to form helium and a neutron plus a large amount of kinetic energy in the reaction products: 3 H + 2 H 4 He + n + 17. 6 Me. V

� http: //www. youtube. com/watch? feature=end screen&v=y. Tkoj. ROgt 8&NR=1&safety_mode=true&persist_safety _mode=1&safe=active Best of Science, Fission and Fusion 8: 38 minutes

Resources � http: //www. lbl. gov/abc/wallchart/teachersgui de/contents. html DOE Teacher’s Guide