The document discusses nuclear energy, which is energy obtained from nuclear reactions like nuclear fission and fusion. It explains that nuclear reactions involve the splitting or combining of atomic nuclei, which results in a mass defect that is converted to a large amount of energy according to Einstein's mass-energy equivalence formula. Specifically, the document defines nuclear fission and fusion, describes how a nuclear chain reaction powers a nuclear reactor to produce electricity, discusses the safety and environmental issues with nuclear energy, and provides an example calculation of energy released by radioactive decay.

1. NUCLEAR ENERGY
Subtitle

2. 22/2/2018 Nurul Fadhilah Alias @ MRSM PARIT 2

3. Video Discussion Questions
• Why do people disagree about the use of nuclear power/energy?
• What makes nuclear energy such a ‘complicated story?’
• How do the by products of nuclear energy compare to the by
products of burning fossil fuels?
• What are the benefits and drawbacks of nuclear energy?
• How does nuclear energy work?
• What’s the difference between nuclear fission and nuclear fusion?
• What do you think will happen in the future with nuclear energy?
What do you think should happen and why?
• Based on what you learned in the video, would you support nuclear
power?
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4. 4
NUCLEAR ENERGY
Radioactive decay causes the unstable nucleus to
disintegrate and becomes smaller and hence mass
of daughter nuclide decreases
The mass which is lost during the decay is called the
mass defect
This mass defect is converted to nuclear energy
Nuclear Energy – the energy obtained from the mass
defect during a radioactive decay
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5. 5
Mass of Atoms
• Measured in the unit called atomic mass
unit ( u or a.m.u.)
• 1 u is 1/12 of the mass of the Carbon-12
atoms
1 u = 1.66 x 10 -27 kg
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6. 6
Mass of some atoms
ATOM NOTATION MASS (U)
Hydrogen-1 1 H
1
1.007825
Helium-4 4 He
2
4.002603
Cobalt-60 60 Co
27
59.933820
Radium-226 226 Ra
88
226.025406
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7. 7
EINSTEIN PRINCIPLE
Conservation of total ‘mass-energy’
Mass and energy are not conserved
separately, mass and energy can be
exchanged one for another by the equation:
E = mc 2 where E = energy released (J)
m = mass defect (kg)
c = speed of light
( 3 x 10 8 ms-1)
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8. 8
Nuclear Fission
• Process of splitting a heavy nucleus into two lighter
nuclei.
• Accompanied with the release of enormous amount
of energy from the mass defect
• Energy is mainly in the form of kinetic energy of the
fission fragments and radioactive emission
• The fission of U-235 can be written as follows :
235 U + 1 n 141 Ba + 192 Kr + 3 [ 1 n ]
92 0 56 36 0
• The U-235 nucleus captures a slow moving neutron
to become U-236 which is unstable. It quickly splits
into 2 fission fragments, Ba-141 and Kr-192 plus 3
free neutrons
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10. 10
Chain reaction
• The free neutrons can strike other uranium
nuclei and cause them to split to produce more
fission fragments and more neutrons.
• This sets off a chain reaction in which nuclear
fission spreads
• A chain reaction is a self-sustaining reaction in
which the products of the reaction can initiate
another similar reaction
• A controlled chain reaction is used in a nuclear
reactor while an uncontrolled chain reaction is
used in nuclear bombs
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11. 11
Chain Reaction
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12. 12
Nuclear Fusion
• Process of combination of two lighter nuclei to form
a heavier nuclei.
• Accompanied with the release of enormous amount
of energy from the mass defect
• Energy is mainly in the form of kinetic energy of the
heavier nucleus, neutrons, proton or gamma rays
• Can only occur at very high temperatures and
pressure ( at the sun)
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13. 13
Radium-226 undergoes alpha decay to become
radon-222. The equation is :
226 Ra 222 Rn + 4 He.
88 86 2
Calculate the energy released
Ra-226 = 226.025406 u
Rn-222 = 222.017574 u
He = 4.002603 u
Ans :
mass defect = 226.025406 – (222.017574 u + 4.002603 u)
= 0.005229 u
= 0.005229 x 1.66 x 10 - 27
= 8.68 x 10 - 30 kg
E = mc2 = 8.68 x 10 -30 kg x ( 3 x 10 8 ) 2
= 7.81 x 10 - 13 J
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14. 14
Examples of nuclear fusion
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15. 15
Nuclear Reactor
Nuclear E Heat E Mechanical / Kinetic E Electrical E
(rotate turbine) (dynamo)
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16. 16
The working principle of a nuclear
reactor
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17. Let’s watch!
• https://www.calacademy.org/educators/nu
clear-energy-is-fission-the-future
• Length: 3.75 minutes
NGSS Disciplinary Core Ideas: MS-ESS3.A,
MS-ESS3.C
• In this video, we'll weigh the benefits and
drawbacks of nuclear energy.
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18. 18
Functions of parts of a nuclear reactor
• Uranium fuel rods –splitting of nuclei by neutron in a
controlled chain reaction
• Boron control rods –Rods are lowered to absorb neutrons
so that the rate of fission is reduced
• Graphite core – moderator to slow down the neutrons
• Concrete shield – prevent leakage of radiation from the
reactor
• Heat exchanger – heat energy from hot gas is used to boil
the water into steam
• Turbines – rotated by the flow of steam under high
pressure
• Coil and magnet – rotated by turbines to generate
electricity by electromagnetic induction
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• Problems :
- pollution if radiation is released to atmosphere
- storage of radioactive waste
- high cost for maintenance
• Advantages :
- only a little radioactive substance is required to
release enormous amount of energy
- no harmful gases released like CO2, CO and SO2
• Safety precautions :
- Safety badge
- Safety clothing like gloves, lab coats etc
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20. Reference
• https://www.calacademy.org/sites/default/files/assets/docs/pdf/flipsideener
gy_nuclearenergy_sciencetextswdiagrams.pdf
• QUIZIZ -
https://quizizz.com/admin/quiz/5a8d1becef9cb57444ea0a35/startV4
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