Nuclear Reactions

Balancing Nuclear Equations Conservation of: Conservation of: Atomic Number (subscript) Atomic Mass (superscript)

Balancing Nuclear Equations 16 N  0 e + 16 O 7 8 Conservation of mass number: 16 = Conservation of atomic number: 7 =

Natural Transmutation 1 term on reactant side 1 term on reactant side Original isotope Original isotope 2 terms on product side 2 terms on product side Emitted Particle Emitted Particle New Isotope New Isotope Happens all by itself - Not affected by anything in environment

Natural Transmutation 16 N  0 e + 16 O term reactant side 2 terms product side

Artificial Transmutation Man: causes it to happen by smashing particles into one another Man: causes it to happen by smashing particles into one another 2 terms on reactant side 2 terms on reactant side Original Isotope Original Isotope Particle that hit it: neutron, proton, or  -particle Particle that hit it: neutron, proton, or  -particle Product side usually 2 terms Product side usually 2 terms

Artificial Transmutation 27 Al + 4 He  30 P + 1 n Original isotope (target nucleus) “Bullet”

Bombarding with Protons,  protons and  -particles - do damage when hit target nucleus protons and  -particles - do damage when hit target nucleus (+) charge & large mass: must be accelerated to high speeds to overcome repulsive forces (+) charge & large mass: must be accelerated to high speeds to overcome repulsive forces magnetic and electric fields used to acceleratemagnetic and electric fields used to accelerate

What is an accelerator? accelerator is vacuum chamber (long pipe) surrounded by vacuum pumps, magnets, high voltage instruments & electronic circuits accelerator is vacuum chamber (long pipe) surrounded by vacuum pumps, magnets, high voltage instruments & electronic circuits inside pipe, particles are accelerated to very high speeds & smashed into each other inside pipe, particles are accelerated to very high speeds & smashed into each other

FermiLab ring circumference = 4mi ! (≈ 21km)

Neutron Capture Neutrons: Neutrons: neutral - aren't repelled by (+) nucleusneutral - aren't repelled by (+) nucleus no need to be acceleratedno need to be accelerated good thing since can’t accelerate them! good thing since can’t accelerate them!

Artificial Transmutation 27 Al + 4 He  30 P + 1 n N + 4 He  17 O + 1 H As + 4 He  78 Br + 1 n Cl + 1 n  38 Cl All have 2 reactants!

Fission Reaction Involves splitting heavy nucleus into 2 lighter nuclei Involves splitting heavy nucleus into 2 lighter nuclei

Fission Fission = Division Fission = Division heavy nucleus: FM > 100 amu heavy nucleus: FM > 100 amu reactant side 2 terms: reactant side 2 terms: 1 heavy isotope (U-235, Pu-239) 1 heavy isotope (U-235, Pu-239) Bombarding particle – usually neutron Bombarding particle – usually neutron product side at least 2 terms: product side at least 2 terms: 2 medium-weight isotopes 2 medium-weight isotopes 1 + neutrons 1 + neutrons Huge amount energy released Huge amount energy released

Fission 235 U + 1 n  91 Kr Ba n + energy U + 1 n  72 Zn Sm n + energy >200 different product isotopes have been identified small amount mass is converted to energy by E = mc 2

Fission Chain Reaction

Fission Chain Reaction Fission Chain Reaction Controlled – nuclear reactor Controlled – nuclear reactor Uncontrolled – bomb Uncontrolled – bomb

Fusion nuclei unite nuclei unite reactant side 2 small nuclei reactant side 2 small nuclei H + H; H + He; He + He … (no larger than Li)H + H; H + He; He + He … (no larger than Li) Product side: Product side: 1 nucleus (still pretty small) &1 nucleus (still pretty small) & maybe a particlemaybe a particle Source of sun’s energy Source of sun’s energy 2 H + 3 H  4 He + 1 n + energy 1120

CERN particles travel just below speed of light; particles make 400 million revs of ring in 10 hrs 27 km ring

SLACLBL