Download Nuclear Reactions

Nuclear Reactions
Topic 7.3 Continued, 8.4 – Nuclear Power
Review: Properties of Radiation
Create a chart to summarize for the 3 types of
Radiation:
 Relative Charge (Compared to a single proton)
 Mass
 Speed
 Ionizing effect
 Penetrating affect
 Effects of Fields
Stability
 What is the main
difference between
smaller nuclei
(lower left) and the
bigger ones (upper
right)?
 Why do heavier
nuclei need more
neutrons to be
stable?
Decay Chains
 A radio-nuclide often produces an unstable daughter
nuclide.
 The daughter will also decay, and the process will
continue until finally a stable nuclide is formed.
 This is called a decay chain or a decay series.
 Part of one decay chain is shown below
 When determining the
products of decay series,
the same rules apply as in
determining the products
of alpha and beta, or
artificial transmutation.
 The only difference is
several steps are involved
instead of just one.
Unified Atomic Mass Unit (u)
 Defined as 1/12 of the mass of an atom of
Carbon-12
u = 1.6605402 x 10-27 kg
How much energy is in 1u?
Mass Energy Equivalence
 Using the principles of conservation, what is the
implication of this equation?
Energy of 1 u
 E = mc2
 E = 1.6605402 x 10-27 kg x (2.9979 x 108 ms-1)2
 E = 1.4923946316 x 10-10 J
 Remembering 1 eV = 1.602177 x 10-19 J
 1 u = 931.5 MeV
Mass Energy Equivalence
 If mass and energy are considered to be equal,
could there be reactions in which mass is not
conserved?
Mass Defect
Mass Defect
Where is the
missing mass?
Mass Defect
The missing mass (mass defect) has been stored as
energy in the nucleus. It is called the binding
energy of the nucleus.
Energy stored in the nucleus:
2
mc
E=
2
(ΔE = Δmc )
Binding Energy Released
Binding Energy per Nucleon
Mass defect calculation
 Find the mass defect of the nucleus of
gold, 196.97 – Au
 From data booklet:
Mass defect calculation
 The mass of this isotope is 196.97u
 Since it has 79 electrons its nuclear mass is
196.97u – 79x0.000549u = 196.924u
 This nucleus has 79 protons and 118 neutrons,
individually these have a mass of 79x1.0007276u
+ 118x1.008665u = 198.080u
 The difference in mass (mass defect) is therefore
1.156u
Mass Defect
 Where is the missing mass?
1 u = 931.5 MeV
Your Turn
 Use the following information to calculate the
mass defect of Lithium-7
 Proton: 1.00728 u
 Neutron: 1.00866 u
 Periodic table is on MyClass
Your Turn
Fission
 In a fission reaction a large nucleus splits in two.
 What happens to the binding energy per nucleon of U-
235 when it undergoes fission?
Fission
 What does it mean to have a higher binding energy per
nucleon ?
 What happens to the excess energy?
Uranium
Uranium 235 has a large unstable nucleus.
Capture
A lone neutron hitting the nucleus can be
captured by the nucleus, forming Uranium 236.
What happens next?
Fission
The Uranium 236 is very unstable and splits into
two smaller nuclei (this is called nuclear fission)
Free neutrons
As well as the two smaller nuclei (called daughter
nuclei), three neutrons are released (with lots of
kinetic energy)
What happens next?
Fission
These free neutrons can strike more uranium nuclei,
causing them to split.
Fission Example
Chain Reaction
If there is enough
uranium (critical mass)
a chain reaction
occurs. Huge amounts
of energy are released
very quickly.
Chain Reaction
Chain Reaction
Simulation Videos
 Tank Video
 500 of them!
Bang!
This can result in a nuclear explosion!
Video:
Fusion
 What is it?
 Which nuclei are involved in fusion reactions?
 Which part of the binding energy curve does
fusion fit it?
 How does the energy you get from fusion
compare with fission?
The binding energy curve
Nuclear fusion – Star power!
Nuclear fusion – Star power!
 Each second, in our Sun, more than 560 million
tonnes of hydrogen fuse together to make helium.
 One series of reactions for this is shown here:
Star power… on Earth?
 One possible reaction is the fusion of deuterium and
tritium.
 These are isotopes of hydrogen
 What are some advantages of fusion over fission?
The Fusion Challenge
 We have yet to produce usable energy through
fusion
 What are some of the challenges?
ITER Project