A detailed presentation on Nuclear reactions - fission & fusion and how they are used to form energy. Pros and cons of Nuclear energy and perminent examples.

1. Nuclear energy
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2. Atomic structure – Atoms are fundamental subunits of matter. Matter is anything that
takes up space and has mass. Air, water, trees, cement, and gold are examples of matter.
Figure 4.2 diagram of oxygen
All atoms have a central region know as the
nucleus, which is composed of two kinds of
relatively heavy particles: positively charged
particles called protons and uncharged particles
called neutrons. Surrounding the nucleus is a cloud
of relatively light weight, fast moving, negatively
charged particles called electrons. The atoms of
each element differ in the number of protons,
neutrons, and electrons present.
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3. Isotopes
• All atoms of the same element have the same
number of protons and electrons but the number
of neutrons may differ.
• Atoms of the same element that differ in the
number of neutrons are called isotopes, For eg.
Uranium-235, 236, 238 (atomic no. 92)
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4. Fissile and Fissionable nuclides
• fissile nuclides: those nuclides that can be made
to undergo nuclear fission (i.e., are fissionable)
and also produce neutrons from such fission that
can sustain a nuclear chain reaction in the correct
setting.
• Fissionable: the only nuclides that are fissionable
are those nuclides that can be made to undergo
nuclear fission but produce insufficient neutrons,
in either energy or number, to sustain a nuclear
chain reaction.
• As such, while all fissile isotopes are
fissionable, not all fissionable isotopes are
fissile.
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5. Introduction
1. Nuclear power is the fourth-largest source
of electricity in India after thermal, hydro and wind power.
2. As of 2012, India had 20 nuclear reactors in operation in 6 nuclear power plants.
3. India's Nuclear plants generate 3.75% of total electricity produced in India.
4. 17% of electricity in the world is generated by nuclear energy.
Tarapur Atomic Power Station, Maharashtra
Madras Atomic Power Station (Kalpakkam), Tamil Nadu
Rajasthan Atomic Power Station
Kaiga Atomic Power Station, Karnatka
Narora Atomic Power Station, Uttar Pradesh
Kakrapar Atomic Power Station, Gujarat
Kudankulam Nuclear Power Plant, Tamil Nadu
Proposed Nuclear Energy Parks:
Jaitapur Nuclear Power Plant, Maharashtra
Mithi Virdi Nuclear Power Plant, Gujarat
Kovvada Nuclear Power Plant, Andhra Pradesh
Haripur Nuclear Power Plant, West Bengal
Kumharia Nuclear Power Plant, Haryana
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6. History of Nuclear Energy Development
• The first controlled fission of an atom occurred in
1938 in Germany
• The US was the first to develop an atomic bomb
• In 1945, the US military dropped bombs on the
Japanese cities of Hiroshima and Nagasaki
• A legacy of the military research is that a great deal of
soil, water, and air are contaminated with radioactive
material (Hanford, Savannah River sites).
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7. History - Continued
•The world’s first electricity generating reactor was constructed in
the US in 1951 (Arco, Idaho).
•First commercial power plant, England 1956.
•The first commercial nuclear generator to become operational in the
United States was the Shipping port Reactor (Pennsylvania,
December 1957).
•“APSARA” – THE FIRST NUCLEAR RESEARCH RECATOR IN
Trombay
•“CIRUS” (Canadian Indian reactor, US): supplied by Canada but
used heavy water supplied by U.S.A. It was shut down on 31st
December 2010, because of INDO-US nuclear accord
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8. Nuclear fuel reserves
India's domestic uranium reserves are small and the country is dependent on uranium
imports to fuel its nuclear power industry. Since early 1990s, Russia has been a major
supplier of nuclear fuel to India.
Large deposits of natural uranium, which promises to be one of the top 20 of the world's
reserves, have been found in the Tummalapalle belt in the southern part of the Kadapa basin
in Andhra Pradesh in March 2011.
http://www.ecolo.org/photos/uranium/uranium-black.jpg
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9. To appreciate the consequences of using nuclear fuels to generate
energy it is important to recognize the nuclear fuel cycle. Mining
produces low grade uranium ore. The ore contains 0.2 % uranium
by weight. After it is mined, the ore goes through a milling process.
It is crushed and treated with a solvent to concentrate the
uranium. Milling produces yellow-cake, a material containing 70-
90% uranium oxide. 9

10. Naturally occurring uranium ore contains about 99.3%
nonfissionable U-238 and only 0.7% fissionable U235 (the
U235 is the uranium isotope needed in nuclear reactors).
This concentration of U-235 is not high enough for most
types of reactors, so the amount of U-235 must be
increased by enrichment. Since the masses of the isotopes
U-235 and U-238 vary only slightly, enrichment is a difficult
and expensive process. However, enrichment increases the
U-235 content from 0.7% to 3%.
Fuel fabrication converts the enriched material into a
powder, which is then compacted into pellets about the
size of a pencil eraser. These pellets are sealed in metal
rods and transported to the reactor site.
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11. Nuclear Fission
• Nuclear fission is the
process of splitting a
nucleus into two nuclei
with smaller masses.
• Fission means “to divide”
• The process of splitting a
heavy nucleus into a
number of fragments of
much smaller mass by
suitable bombardment with
sub-atomic particles is
called nuclear fission.
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12. Fission cont.
• Only large nuclei with
atomic numbers above 90
can undergo fission.
• Products of fission reaction
usually include two or
three individual neutrons,
the total mass of the
product is somewhat less
than the mass of Uranium-
235.
• During this process some of
the mass of the original
atom is converted into
energy in accordance with
the equation E = mc2
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13. By appropriate calculations, 1 g of URANIUM-235 releases
8.22x107 kJ of energy which is equal to that released by 2.5
metric tones of good quality coal
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14. A chain reaction is an ongoing series of fission reactions. Billions of reactions occur each
second in a chain reaction. Only certain kinds of atoms are suitable for the development of
a nuclear chain reaction. The two materials most commonly used are uranium-235 and
plutonium-239.
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15. Chain Reaction cont.
• On earth, nuclear fission
reactions take place in
nuclear reactors, which
use controlled chain
reactions to generate
electricity.
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16. Chain Reaction cont.
• Uncontrolled chain
reactions take place
during the explosion of
an atomic bomb.
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17. Nuclear Reactors
A nuclear reactor is a device that permits a controlled fission chain reaction. In the
reactor, neutrons are used to cause a controlled fission of heavy atoms such as Uranium
235 (U-235). U-235 is a uranium isotope used to fuel nuclear fission reactors.
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18. Components of a nuclear power reactor: a moderator, controlling rods,
fuel element and coolant. All these parts are enclosed in a chamber.
How to slow down the speed of secondary neutrons: use of moderators:
The three neutrons that are released in the fission of U-235 are fast neutrons (14,000 km/s)
and cannot further cause fission. To sustain a nuclear chain reaction these fast neutrons
need to be converted into thermal neutrons (2.2 km/s) which are slower as compared to
fast ones. When high speed neutrons collide with moderator they lose some kinetic
energy. Examples of moderators are water, heavy water, graphite.
How to decrease the number of secondary neutrons: use of controlling rods
If the number of neutrons are more then it will result in explosion. In order to regulate the
excess no. of neutrons controlling rods are used (cadmium or boron rods).
Their length is a crucial aspect. This is adjusted from outside the reactor. If no. of neutrons
is to be decreased then they are pushed further.
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19. Fuel element:
U-235 CAN BE FISSIONED. Natural uranium consists of chiefly 99.3 % of U-238 and only
0.7% of U-235. U-238 can be fissioned by fast moving neutrons (breeder reactors).
Enriched uranium uses both isotopes and is used in the form of long rods or plates. The
uranium rods are inserted into the graphite core in such a way that cadmium or boron rods lie
between the uranium rods.
Coolant (heat transfer agent): the energy produced in the reactor is heat energy. It should be
immediately transferred to the heat exchanger. This is done by circulating a coolant which is
attached to both reactor and heat exchanger. It must have a high boiling point. For eg. Water,
liquid sodium
Protective chamber: thick walls made from cement and concrete
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20. Various possibilities in a nuclear reactor
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21. Critical mass: minimum mass required to sustain a chain reaction
Neutron multiplication factor (K): the average number of released neutrons which cause
further fission
Critical: K=1 (chain reaction is sustained)
Subcritical (K<1): (chain reaction is not sustained; safe; maybe some secondary neutrons
have escaped into the atmosphere)
Supercritical (K>1): (leads to explosion, bomb)
The critical mass for lower-grade uranium depends strongly on the grade: with 20% U-235 it
is over 400 kg; with 15% U-235, it is well over 600 kg.
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22. Nuclear Fission from Slow Neutrons and Water
Moderator
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24. How does a Nuclear Power Plant Work?
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26. How a Nuclear Reactor works
• 235U fissions by absorbing a neutron and producing 2 to 3 neutrons, which
initiate on average one more fission to make a controlled chain reaction
• Normal water is used as a moderator to slow the neutrons since slow
neutrons take longer to pass by a U nucleus and have more time to be
absorbed
• The protons in the hydrogen in the water have the same mass as the
neutron and stop them by a billiard ball effect
• The extra neutrons are taken up by protons to form deuterons
• 235U is enriched from its 0.7% in nature to about 3% to produce the
reaction, and is contained in rods in the water
• Boron control rods are inserted to absorb neutrons when it is time to shut
down the reactor
• The hot water is boiled or sent through a heat exchanger to produce
steam. The steam then powers turbines.
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27. Types of nuclear reactor: (classified according to the fuel, coolant and moderator)
Light water reactor
(water acts as a coolant, moderator, heat exchange liquid)
Boiling water reactor Pressurized water reactor
Heat from the fuel rods
causes water to boil,
producing steam at the top
of the reactor
The water is under sufficiently high pressure to prevent
boiling even at a temperature above the normal boiling
point. The high temperature water still under high
pressure leaves the reactor vessel and enters a device
called a heat exchanger which contains a separate,
secondary water system. The lower pressure in the
secondary water system causes the water the boil and this
steam is then fed to the steam turbines.
Advantage of pressurized water reactor: As steam is
generated outside the reactor; it is radiation free
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28. .
Cooling Tower
Emergency core
cooling system
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29. •Pressurized heavy water reactor
•Gas cooled reactors (heat exchange fluid can be a gas)
•Liquid metal cooled breeder reactors (breeder reactors are used to prepare fissile
nuclides)
Types of nuclear reactor..Contd…
U-uranium
Np- neptunium
Pu- plutonium
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30. How much energy is produced?
• Nuclear power is an
extremely rich energy
source.
• One gram of Uranium-
235 delivers as much
energy as 2.5 metric
tons of coal!!!
• One in every 5 houses
in the U.S. is supplied
with nuclear energy.
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31. Nuclear Fusion
• Nuclear fusion is the
combining of two nuclei with
low masses to form one
nucleus of larger mass.
• Nuclear fusion reactions are
also called thermonuclear
reactions (because they
require high temperature,
generally greater than
4x106 oC, in order to
overcome electrostatic
repulsion between 2 nuclei
when they come together)
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32. Nuclear Fusion cont.
• Fusion reactions exist in stars.
• Our sun is a good example of
a thermonuclear (fusion)
reaction.
• It is almost impossible to
create fusion reactions on
earth since they need
temperatures above one
million degrees Celsius in
order to take place.
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33. Nuclear Fusion cont.
• Nuclear fusion produces
less nuclear waste than
nuclear fission and the
materials are easier to
obtain.
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34. The energy that would be released by combining the deuterium in one
cubic meter of ocean water would be greater than that contained in all of
the world’s entire fossil fuels. Even though in theory fusion promises to
furnish large amounts of energy, technical difficulties appear to prevent its
commercial use in the near future. Even the governments of nuclear
nations are budgeting only modest amounts of money for fusion research.
And, as with nuclear fission and the breeder reactor, economic costs and
fear of accidents may continue to delay the development of fusion
Nuclear Fusion
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35. U-235 U-236 U-238
Half-life (t½) is the
amount of time
required for a
quantity to fall to
half its value as
measured at the
beginning of the
time period
7.038 ×108 years 2.348 x107 years 4.468×109
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36. Nuclear Power Countries
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37. NPPs AROUND THE WORLD
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39. Pros for Nuclear Power
• Rich energy source.
• 1 gram of Uranium-235 delivers as much
energy as 2.5 metric tons of coal.
• Reactors run for years without refueling or being shut
down and need little maintenance.
• No air pollution! (Nuclear energy annually prevents 5.1
million tons of sulfur 2.4 million tons of nitrogen oxide
164 metric tons of carbon dioxide)
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40. Cons about Nuclear Power
• Produces Radioactive Waste
• There is no permanent long-
term disposal site for
commercial nuclear waste.
• There is a relatively short
supply of 235U
• Nuclear Power Plants are
expensive to build.
• Minor maintenance problems
can be very expensive to fix.
• Safety concerns!!!
• Nuclear Proliferation
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41. Nuclear Proliferation: Nuclear proliferation is
the spread of nuclear weapons, fissile
material, and weapons-applicable nuclear
technology and information to nations not
recognized as "Nuclear Weapon States" by
the Treaty on the Nonproliferation of Nuclear
Weapons, also known as the Nuclear
Nonproliferation Treaty or NPT.
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42. Nuclear wastes
Type Mildly active Moderately active Highly active
Examples residues from filter
and purification
plants
radioactive residues from
purification plants (ion
exchange resins)
spent fuel (burnt)
which is sent for
reprocessing
Way of
disposal
“Dilute and Disperse”.
Disposed off in oceans
or buried in soil.
“Delay and Decay”. Delay
disposal by storing at the site
in sealed tanks till radioactivity
levels falls somewhat. After the
period of decay they are
packed in double wall
containers and sunk in the
ocean or stored in disused salt
mines (because salt mines will
be free from water and thus
radioactive contamination of
groundwater is unlikely)
“Concentrate and
contain”. Reduce
volume as much as
possible. It is
contained above
ground in double
walled steel and
concrete tanks,
constantly
refrigerated and
agitated with air
because if they
settle down they
might corrode the
floor due to heat
energy released.
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43. Hazards of above nuclear waste disposal: refrigeration
might fail due to power failure, earthquake, flood, human
error, chemical corrosion of tanks, etc
Other ways of disposal: under polar ice sheets, buried in
the sea bed, interplanetary disposal.
Waste can be minimized by usage of breeder reactors
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44. DRY STORAGE IN CASKS ON SITE
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45. YUCCA MOUNTAIN SITE
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46. Yucca Mountain
The Future of Nuclear Waste Storage
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47. Problems with Yucca Mountain
• The nuclear waste currently sitting around is enough to fill the
repository (commonly refers to a location for storage, often for
safety or preservation)
• Danger to the public with the transportation of the waste to yucca
mountain
• Possible health risks to those living near Yucca Mountain
• Eventual corrosion of the metal barrels which the waste is stored in
• Located in an earthquake region and contains many
interconnected faults and fractures
• These could move groundwater and any escaping radioactive
material through the repository to the aquifer below and then to the
outside environment
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48. Is Nuclear Energy Safe?
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49. Three Mile Isle
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51. Chernobyl nuclear accident
• 4 reactors (2 built in 1970’s, 2 in 1980’s,
graphite moderated water coolant reactor)
• Combination of design and operator error
during electrical power safety check resulted
in cascade of events leading to core breach of
Reactor 4 with subsequent chemical (not
nuclear) explosion
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52. Chernobyl is a small city
in Ukraine near the
border with Belarus,
north of Kiev.
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56. The largest lump of graphite shows
an intact control rod channel.
A mutated piglet 56

57. One impact of Chernobyl is that it deepened public concern about the safety of nuclear
reactors. Even before Chernobyl, between 1980 and 1986, the governments of Australia,
Denmark, Greece, Luxembourg, and New Zealand had officially adopted a “no nuclear”
policy. Since 1980, 10 countries have cancelled nuclear plant orders or mothballed plants
under construction. Argentina canceled 4 plants, Brazil 8, Mexico 18, and the US, 54. There
have been no orders for new plants in the US since 1974. Sweden, Austria, Germany, and
the Phillipines have decided to phase out and dismantle their nuclear power plants.
Decommissioning Costs
Decommissioning a a fossil fuel plant is relatively easy a wrecking ball is about all that is
required. Nuclear power plants are not demolished they are decommissioned.
Decommissioning involves removing the fuel, cleaning the surfaces, and permanently
preventing people from coming in contact with the contaminated buildings and equipment.
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58. The Fukushima Daiichi
nuclear accident (2011)
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59. http://www.greenfacts.org/en/chernobyl/, Chernobyl Forum(2006)
Pathways Of Exposure To Man From Release of
Radioactive Materials
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60. Safety of Nuclear Plants
•Steel-reinforced concrete and a dome-shaped
containment buildings surround all US reactors (inner
wall several feet thick and outer wall at least 15 inches
thick)
• Designed to withstand hurricanes, earthquakes, high
winds
• Reactors have detectors to quickly shut down in event of
tremor (about 20% are in regions with seismic activity
like Pacific Rim)
• In considering safety, must address…
• Faults in plant design
• Human error
• Risks associated with terrorism/political instability
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61. “The energy produced by the breaking down of the atom is a very poor kind of thing.
Anyone who expects a source of power from the transformation of these atoms is talking
moonshine."
However, within 10 years the world's first nuclear reactor had been built and by the mid-
1950s nuclear power stations started supplying electrical power for industrial and
domestic use.
Ernest Rutherford (1871-1937)
The discoverer of the nucleus of the atom.
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