Nuclear fission and fusion reactions can be used to generate energy. Fission occurs when heavy atomic nuclei split into lighter nuclei, releasing energy. In 1939, Hahn and Strassman discovered nuclear fission through bombarding uranium-235 with neutrons. Fusion occurs when two light atomic nuclei combine to form a heavier nucleus, which also releases energy and occurs naturally in stars. Controlling fission or fusion reactions allows the energy to be harnessed for applications like nuclear power plants or weapons. Nuclear reactors contain a fuel core, coolant, moderator, and control rods to manage the chain reaction in a controlled manner.

1. Nuclear Fission & Fusion

2. History:
Hahn & Strassman (1939)
•Bombarded Uranium-235 samples with neutrons
expecting the Uranium-235 to capture neutrons
•Instead, the products showed different chemical
properties that they could not explain

3. •Explained Hahn & Strassman results.
•Instead of heavier Uranium, it had split
into smaller elements = Nuclear Fission
Meitner & Frisch

4. Nuclear Forces
1. Electric repulsion – ________ charge particles
repel each other
same
1. Strong Nuclear Force – causes protons and
neutrons to ________ each otherattract
•Stable Nuclei = strong nuclear force is ________
than repulsion force
greater
•Unstable Nuclei = strong nuclear force is
________ than repulsion force
oHave too many or too few neutrons in nucleus
oHave more than 83 protons in nucleus
oWill decay into a more stable nucleus
less

5. Nuclear Fission – splitting of
heavier nuclei into lighter
nuclei.
U235
92 n1
0 Ba137
56 Xe84
36 n1
0
energy+ +15+ +
How much energy? E=mc2
_______= _______ x (_____ _ _____)2
c=3.0x108
Energy mass speed of light
E=mc2
explains _____ _____ (total mass of
nucleus is less than sum of individual particles)
mass defect

7. Nuclear Chain Reactions:
•Nuclear fission releases more neutrons which trigger
more fission reactions
•The number of ________ released determines the
success of a chain reaction
neutrons

9. Applications of Controlling
Chain Reactions
• Must have a minimum amount of radioactive isotope
to sustain a chain reaction =_________ _______
1. Atomic Bomb (fission bomb) – Triggering a chain reaction in
U-235 or Pu-239
CRITICAL MASS
1. Nuclear Power Plants – Convert heat energy from fission
chain reaction into __________.electricity
Control chain reaction with ________ _____ that
absorb ________ emitted after fission reaction.
control rods
neutrons

10. Nuclear Fusion - Energy released when
two light nuclei combine or fuse
•However, a large amount of energy is
required to start a fusion reaction:
o Need this energy to overcome ________ forces
of protons.
o Extremely high temperatures can provide start-up
energy.
repulsion
More energy in fusing hydrogen that fission of uranium

11. Nuclear Fusion

12. Stars energy is produced
through fusion reactions
Fusion occurs until Fe is
produced because less energy is
released than required to fuse
Fe nuclei = _____ ____ ____
Star burns out

13. Difference between nuclear fission
and fussion
• Fission reaction does
not occur naturaly.
• It produces many
highly radioactive
particles.
• Energy released is
million times grater
that that in chemical
reactions, but lower
that the energy released
by nuclear fusion
• Fusion occurs in stars
such as sun.
• Few radioactive
particles are produced
by fusion reaction, but
requires fussiom
trigger
• Energy released is
three to four times
greater than the energy
released by fission

14. • One class of nuclear
weapon is a fission
bomb
• Definition
• Takes little energy to
split two atoms in a
fission reaction
• Hydrogen bomb,
which used fission
reaction to trigger
a fusion reaction
• Definition
High density, high
temperature
environment is
required.

15. Radius of Gyration
Protons travel in the doughnut with constant
radius. Proton are injected into the
doughnut from a linear accelerator or van
de Graff generatore and are recovered by
magnetic deflection as a pulsed beam.When
protons reach their maximum energy, the
oscillator frequency is distorted so taht the
orbit expands or contracts and the protons
strike the target.
It gives the proton 10 GeV energy

16. General features of Nuclear
reactor

17. REACTOR

18. COMPONENTS OF A REACTOR
1. Control Rods
Control rods made of a material that absorbs neutrons are inserted into the bundle using a
mechanism that can rise or lower the control rods.
The control rods essentially contain neutron absorbers like, boron, cadmium or indium.
2. Steam Generators
Steam generators are heat exchangers used to convert water into steam from heat
produced in a nuclear reactor core.
Either ordinary water or heavy water is used as the coolant.

19. 3. Steam Turbine
A steam turbine is a mechanical device that extracts
thermal energy from pressurized steam, and
converts it into useful mechanical.
Various high-performance alloys and super alloys have
been used for steam generator tubing.
4. Coolant Pump
The coolant pump pressurizes the coolant to pressures
of the order of 155 bar.
The pressure of the coolant loop is maintained almost
constant with the help of the pump and a pressurize
unit.

20. 5. Feed Pump
Steam coming out of the turbine, flows through the condenser
for condensation and recalculated for the next cycle of
operation.
The feed pump circulates the condensed water in the working
fluid loop.
6. Condenser
Condenser is a device or unit which is used to condense
vapour into liquid.
The objective of the condenser are to reduce the turbine
exhaust pressure to increase the efficiency and to recover
high quality feed water in the form of condensate & feed
back it to the steam generator without any further
treatment

21. 7. Cooling Tower
Cooling towers are heat removal devices used to transfer
process waste heat to the atmosphere.
Water circulating through the condenser is taken to the
cooling tower for cooling and reuse.

22. Types of nuclear reactor
An assembly of nuclear fuel and moderator which is able
to sustain reaction is called a nuclear reaction.
It is a controlled chain reacting system supplying
nuclear energy.
It is a nuclear furnace that burns fuels like U-235, U-
233, Pu-239.

23. All the reactors consists of
following components
1. Reactor coil
2. Reflector
3. Reactor vessel
4. Radiation shield
5. Structural materials
6. Coolant loops
7. Heat exchangers

24. 1. Reactor core. The central region of a reactor where the
fussion takes place is known as core. It consists of nuclear
fuel. In fast reactors it consists of a coolant, control rods and
structural materials. A moderator is also present in thermal
reactors.
Fuel is in the form of ceramic
Fuel Rods –An ideal fuel should have high thermal conductivity,
high melting point, high resistance to radiation demage and
chemically inert. To prevent th e fission fragments into the
coolant or the moderators, corrosion , the fuel rods are
covered with protective materials – cladding.
An ideal fuel clad material must be – highly resistant to
corrosion, a poor neutron absorption, cheap, easily available,
good mechanical strength, high melting point.
Zirconum, steel Al, Mg, Ni. Zr is the best one, LWR- steel
Resarch reactors- Al

25. 2. Coolant – To remove fission heat from the core, it is
necessary to circulate a fluid – liquid or gas through
the reactor. This fluid is referred to as coolant. It
must have high thermal capacity, low cost, low
neutron absorption,, good radiation and thermal
stability and compatibility with fuel and clad.
Water, liquid sodium, gases like CO2, He
3. Moderator: to slow down the fast neutrons, to
increase their fission cross section with uranium. It
must have low mass number and should not absorb
neutrons.
Heavy water, D2O, graphite, beryllium, paraffin which
are reach in protons

26. When a reaction takes place in uranium rod, most of
the fast neutrons enters in moderator. They collide
with the protons of moderator by interchanigng
their energies and are slowed down.
4. Control rods: for maintaining the desired state of
fission reactions within a nuclear reactor. To
control the chain reaction from becoming violent,
rods of boron or cadmium are inserted in the holes
of reactor core. As a result of which the desired
number of neutrons are absorbed and only limited
numbers of neutrons are left to produce fission.

27. Cold Fusion:
Efforts are being
made to start and
sustain a fusion
reaction at lower
temperatures, in
other words with a
lower amount of
input energy