The document discusses the role of nuclear power in energy production, highlighting its advantages such as clean energy and low operational costs, while also addressing challenges like radioactive waste management and initial construction costs. It explains the nuclear fuel cycle, the mechanisms of reactors, and historical incidents related to nuclear power, including the Chernobyl disaster and Fukushima meltdown. The text concludes by underscoring the importance of nuclear power amidst rising energy demands and the potential transition to fusion energy in the future.

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Nuclear Power
Nuclear Energy
• Major Driving Factor
- Price of natural gas more than doubled.
- Volatilityof natural gas prices
- High long-term projections for natural gas prices
• Additional Considerations
– Energy security
– Uncertainty in the future emissions regulations (monetizationof
airborne pollutants such as carbon and mercury)
– Availabilityof advanced nuclear plant designs
– Relativestability of regulatory environment
– Public policy (political)support (Energy Legislationin the U.S.)
• Challenges
- Spent fuel disposal
- Resource availability (human and supply chain)
- Project Management

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Advantages of Nuclear Power
• Clean
• Plentiful Supply
• High energy content in uranium
–Small fuel pellet
–Can provide base load power
–Energy savings in transportation
• Operating cost is low after construction
Drawbacks to Using Nuclear Power
• Initial construction costs
• Radioactive waste byproduct
• Storage
• Natural disasters
• Public perception

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NPPs AROUND THE WORLD
• Nuclear technology takes advantage of the power
locked in structure of atoms, the basic particle of
matter.
– The nucleus of an atom
contains all of its
positively-charged protons
and non-charged neutrons.
– Negatively-charged electrons
orbit the nucleus.
• Atoms always contain equal numbers of protons
and electrons, , making them electrically neutral.
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Atomic Structure

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• Atoms can have different
numbers of neutrons in
their nuclei.
– Nuclei from the same
element with different
numbers of neutrons are
called isotopes.
• Most isotopes are stable,
but some can
spontaneously break apart,
emitting energy and
particles.
– This is radiation.
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• Nuclear weapons harness a specific type of
decay called nuclear fission.
– This is the splitting of the nucleus into two smaller
fragments.
• The fuel used by the first
nuclear weapons was
Uranium-235, a naturally
occurring isotope.
– Uranium-235 has an
extremely large nucleus
that can be split when it
is hit with a high-speed
neutron.
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• In a nuclear bomb, a large amount of uranium-
235 is clustered together, so that when fission is
initiated in one of the atoms, it splits and
released more neutrons, which then cause
fission in other atoms.
– This creates a fission chain
reaction.
• Each time a nucleus splits,
a large amount of energy is
released.
– Multiplied across the entire
chain reaction…
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Fission of U-235

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Only certain kinds of atoms are suitable for the developmentof a nuclear chain reaction.
The two materialsmost commonly used are uranium-235 and plutonium-239.
Tricks of the trade
• Slow moving (thermal) neutrons are more
effective at inducing fission, but, fissions
produce fast moving electron. We need to
slow neutrons down.
• Fissions typically produce several neutrons but
a linear chain reaction only needs one. We
need to get rid of a good fraction of our
neutrons.

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Moderator
• Neutrons are slowed
down by having them
collide with light atoms
(Water in US reactors).
• Highest level of energy
transfer occurs when
the masses of the
colliding particles are
equal (ex: neutron and
hydrogen)
Control Rods
• Control rods are made
of a material that
absorbs excess
neutrons (usually Boron
or Cadmium).
• By controlling the
number of neutrons, we
can control the rate of
fissions

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Basic Ideas
• The Uranium is both the fuel and the source
of neutrons.
• The neutrons induce the fissions
• The Water acts as both the moderator and a
heat transfer medium.
• Control rods regulate the energy output by
“sucking up” excess neutrons
Practicalities
• Processing of Uranium
• Each ton of Uranium ore
produces 3-5 lbs of Uranium
compounds
• Uranium ore is processed
near the mine to produce
“yellow cake”, a material rich
in U3O8.
• Only 0.7% of U in yellow
cake is 235U. Most of the rest
is 238U which does not work
for fission power.

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World Distribution of Uranium
Enrichment
• To be used in US
reactors, fuel must be
3-5% 235U.
• Yellow cake is converted
into UF6 and this
compound is enriched
using gaseous diffusion
and/or centrifuges.
• There are some reactor
designs that run on
pure yellow cake.

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• NOTE: A nuclear bomb requires nearly
100% pure 235U or 239Pu. The 3% found
in reactor grade Uranium CANNOT create
a nuclear explosion!
Fuel Pellets
• The enriched UF6 is
converted into UO2 which
is then made into fuel
pellets.
• The fuel pellets are
collected into long tubes.
(~12ft).
• The fuel rods are collected
into bundles (~200 rods
per bundle
• ~175 bundles in the core

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Cladding
• The material that the
fuel rods are made out
of is called cladding.
• It must be permeable to
neutrons and be able to
withstand high heats.
• Typically cladding is
made of stainless steel
or zircaloy.
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.

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Summary: How Nuclear Energy Works
NUCLEAR REACTOR
A nuclear reactoris a device in which nuclear chain
reactionsare initiated, controlled,and sustained at a
steadyrate, as opposed to a nuclear bomb, in which the
chain reaction occurs in a fraction of a second and is
uncontrolled causingan exploitation.

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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.
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.

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STEAM TURBINE
A steam turbine is a mechanical device that extracts
thermal energy from pressurized steam, and converts it into
useful mechanical
 Various high-performancealloys and superalloys have
been used for steam generator tubing.
COOLANT PUMP
The coolant pump pressurizes the coolant to pressures of
the order of 155bar.
The pressure of the coolant loop is maintained almost
constant with the help of the pump and a pressurizer unit.

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FEED PUMP
Steam coming out of the turbine, flows through
the condenser for condensation and recirculated
for the next cycle of operation.
The feed pump circulates the condensed water
in the working fluid loop.
CONDENSER
Condenser is a device or unit which is used to condense
vapor into liquid.
The objective of the condenser are to reduce the turbine
exhaust pressure to increase the efficiencyand to recover
high qyuality feed water in the form of condensate & feed
back it to the steam generator without any further
treatment.

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In addition to fuel rods containinguranium, reactors contain control rods of cadmium,
boron, graphite,or some other non-fissionablematerial used to control the rate fission
by absorbing neutrons. Lowering the rods decreases the rate of reaction.
The heat
generatedby the
fission of or
uranium releases
energy that heats
waterto produce
steamto turn
turbinesto
generate
electricity.
Cooling Tower
Reactor is inside a large containment
building

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ContainmentStructure
Natural Draft
HyperbolicCooling
Towers
The light water reactors
(LWR) make up 90% of the
reactors operating today,
use ordinary water as the
moderator and as the
coolant. The BWR and
PWR are light water
reactors. In a BWR (20% of
reactors in the world).
Steam is formed within
the reactor and
transferred directly to the
turbine.
The steam must be treatedand the generating building must be shielded. In the PWR (70%
of reactors in the world) the water is kept under high pressure so that steam is not formed in
the reactor.Such an arrangement reduces the risk of radiation in the steam but adds to the
cost of constructionby requiring a secondary loop for the steam generator.
Emergency core
cooling system

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Breeder Reactors
• A big problem with nuclear power is the
creation of Plutonium in the reactor core.
• This is a long lived radioactive element that is
difficult to store.
• Q: Why not use it as a fuel too?
Basic Idea
• Process that creates the Pu.
• During fission use one of the extra neutrons to create
a Pu atom




 
 



0
1
239
944.2
239
93
0
1
239
93min23
239
92
239
92
238
92
PuNp
NpU
UUn
days

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• Somewhat difficult in that we want fast
neutrons to “breed” the 239Pu out of the 238U,
but we want slow neutrons to induce the
fission of 235U.
• Requires a different design of reactor.
• Doubling time: Time required to produce
twice as many 239Pu atoms as 235U destroyed.
A good design will have a 6-10 doubling time.
• There are no currently operating breeder
reactors in the US.
38
• Three Mile Island accident
– A relief water valve stuck open, allowing water to
escape from the core.
– A meltdown, when the fuel and control rods
physically begin to melt due to the heat surge
within the reactor, partially occurred.
– No major leak to the
environment occurred.

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• In 1986, a full meltdown occurred at the
Chernobyl nuclear plant located in Ukraine
(formerly Soviet Union).
• A test was being conducted on the reactor to
see how the backup water pump generators
would respond to a full power outage.
– The control rods were fully removed.
– At some point, the fission chain reaction began
occurring uncontrollably.
– An explosion ripped apart the containment building,
spreading radioactive fallout throughout the area
and into the atmosphere.
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• There were multiple design flaws at the Chernobyl
plant:
– The containment building was inadequate.
– Graphite was used as a
moderator instead of
water. When the
meltdown occurred, it
ignited, releasing more
fallout.
– A water storage pool
was located under the
reactor. If the core had
melted down into this
pool, an even greater
explosion would have occurred.
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• The burning core was eventually extinguished.
• The nearby employees’ town, Pripyat, was
permanently evacuated.
• A 30km radius around the plant, called the
exclusion zone, has been designated as
uninhabitable to people.
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• The most recent meltdown
occurred following a
massive earthquake and
tidal wave off the coast of
Japan.
• The generators powering
the water pumps of some
of the Fukushima Daiichi
reactors were flooded.
– Without cooling water, the
core overheated and
experienced a meltdown.
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Fukushima

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• Contaminated water from the plant leaked into
the Pacific.
• Top predators, like bluefin tuna, caught in the
Pacific have positively tested for small amounts
of radioactive fallout.
– A single serving of tuna has less than half of the
exposure from an arm x-ray.
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Radioactive Waste Management
• About 100,000 tons of low-level
waste (clothing) and about
15,000 tons of high-level waste
(spent-fuel) waste is stored in
the U.S. from reactor usage.
• Spent fuel rods are temporarily
placed in deep water pools
while they cool down and the
fission reaction slows.
– Waste is then moved to large
casks of metal and concrete near
the reactor.

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• The U.S. Department of Energy
announced plans to build a high-
level waste repository near Yucca
Mountain, Nevada in 1987.
• The facility met three important
criteria for long-term waste
storage:
– Low moisture.
– Geologically stable.
– Far away from major population
centers.
• Plans to use Yucca have since
been halted, due to objections
from Nevada residents.
– No long-term storage plan has
been accepted by the U.S.
• Some alternative methods of nuclear
waste disposal have been researched.
– Transmutation uses the waste as fuel in a
different type of reactor, which converts it
to a less-dangerous waste.
– Geologic disposal involves
depositing the waste
deep below the Earth’s
crust in stable rock
formations.
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Advantages and Disadvantages
• Advantages
– Low-cost electricity due to
Gov’t subsidies, services, &
insurance
– Provides “baseload”
constant power to carry
most of the load
– Clean power without air
pollution (no CO2?)
– Requires highly paid work
force (job votes)
– Source of local taxation
revenue
• Disadvantages
– Potential for radiation
leakage and health
effects
– Possible terrorist target
• Useful just as threat
– Apparent cheap power
retards renewable
energy development
– What to do with the
spent fuel?
090124
Most nuclear power plants originally had a nominal life span of
40 years, but engineering assessments of many plants over the
last decade have established that many can operate longer. In
the US most reactors now have confirmed life spans of 40 to 60
years. In Japan, 40 to 70 years. In the US the first two reactors
have been granted license renewals, which extends their
operating lives to 60 years. A few tidbits:
 No new plants commissioned in US since 1974
 17% of electricityfrom nuclear power plants
 103 plants currently operating at 64 sites in 31 states
 nuclear power plants ran 92% of the time in 2002
 average age is 22 years, programmedage 40 years extended to 60
 Spent fuel at Texas’s plants stored in water filled vats
 Since 1993, 175 metric tons of uranium from weapons have been transformed
into fuel for nuclear power plants.

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Conclusion
• Nuclear plants provide a significant global energy
• Some antinuclear organizations want all plants closed
right now and vocally oppose them
• Nuclear energy provides too much energy to readily
close them without a substitute (~1600 MW/plant)
• Nuclear energy may be a transitional approach from
fission plants to fusion plants some far away day
• Nuclear plants likely will be built again since
population growth demands more energy, natural gas
prices will be higher in the future, and fossil fuel plants
pollute
060127