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UEET 603 Introduction to Energy Engineering Spring 2010 Nuclear Power Nuclear Energy Nuclear energy is a way of creating heat through the fission process of atoms. Nuclear energy originates from the fission of atomic nucleus in a chain reaction.
Introduction to Energy Engineering
Nuclear energy is a way of creating heat through
the fission process of atoms.
Nuclear energy originates from the fission of
atomic nucleus in a chain reaction.
Nuclear fission reaction is controlled in a
nuclear reactor to produce thermal energy.
of a heavy atom like uranium or plutonium is
split when struck by a neutron.
The fission of the nucleus releases two or
more new neutrons.
It also releases energy in the form of heat.
The released neutrons can then continue to split
additional nucleus .
- This releases even more neutrons and more
- The repeating of the process leads to a chain
All nuclear power plants convert heat into electricity
The heat is created when atoms are split apart – called
The heat from fission reaction is used to produce
steam, which is then used to turn a turbine and
produce electricity using a generator.
Power from nuclear fission accounts for about 19% of
the nation’s total energy.
Number of operating nuclear power plants is 120 ??
Mostly safe, successful and well regulated
No new power plant has been built in last 30 years
Nuclear power is generated primarily in stationary
applications like in a nuclear power plants, propulsion of
mobile system like naval vessels, especially submarines as
well as several surface vessels.
Since nuclear plants do not consume oxygen like
conventional plants, it is quite attractive for use under sea.
Also, ships powered by nuclear plants need to be refueled
only after long period of operation.
Nuclear power has also been developed for the propulsion
of aircrafts and rockets.
Safe operation of the plant and safe handling and disposal of nuclear fuels.
Concern of environmentalists about the dangers of storing the radioactive byproducts of the process.
Cost of building a new nuclear reactor is about $10 billion each – One of the main reason for a stagnant industry.
Recent reduced cost of other fuels like coal, natural gas and oil, make the nuclear power production less competitive.
Each project has to pass through a rigorous scrutiny and check through Nuclear Regulatory Commission (NRC) before construction can begin.
Without any support from the government it seems
difficult for the utility companies to start any new projects.
Government recently committed $8.33 billion
in loan guarantees for the construction of two
new reactors at the Alvin W. Vogtle Electric
Generating Plant in Georgia
- Expected to provide electricity to
over a million people by next 5-6 years.
- Expected to create new job opportunities.
The physical world is composed of various subatomic or fundamental particles.
There are variety of different fundamental particles, and scientists are still finding newer ones .
However , only few of these are important in nuclear engineering:
- Electrons - Proton - Neutron
- Photon - Neutrino
This particle has rest mass of
and carries a charge
Mass of a particle is a function of its speed relative to the
In giving the mass of fundamental particle, it is necessary to
specify the mass at rest with respect to the observer -
termed as rest mass.
Negatrons or negative electrons:
Carries a negative charge
Normal electrons encountered in this
Positrons or positive electrons:
Carries a positive charge
Relatively rare in this world
These two are identical except the sign of the charge
When under circumstances, a positron collide
with a negatron, the electrons disappear and
two (occasionally more) photon (particles of
electromagnetic radiation) are emitted.
This particle has a rest mass of
and carries a positive charge equal in magnitude
to the charge on the electron.
Protons with negative charge have also been
discovered, but these particles are of no
importance in nuclear engineering.
The mass of a neutron is
which is slightly larger than the mass of the
It is electrically neutral.
The neutron is not a stable particle, except
when it is bound into an atomic nucleus.
A free neutron decays to a proton with the
emission of a negative electron (Known as )
Particle equivalent of electromagnetic wave.
This is a particle with zero rest mass and zero
charge, which travels in a vacuum at only one
speed, namely the speed of light
This also a particle with zero rest mass and no electrical
This appearsin the decay of certain nuclei.
There are two types of Neutrinos: neutrinos and
Atoms are the building blocks of all gross matter
Atoms, in turn, consists of a small but massive nucleus surrounded by a cloud of rapidly moving (negative) electrons
The nucleus is composed of protons and neutrons
The total number of protons in the nucleus is called the atomic number (Z) of the atom.
In a neutral atom there are as many electrons as
protons, i.e. Z-number of electrons moving around the
It is the number electrons that dictates the chemical behavior of atoms and gives identify of a element.
Hydrogen (H) has one electron
Helium (He) has two electrons
Lithium (Li) has three electrons
The number of neutrons in a nucleus is known as
theneutron number (N)
Atomic mass number: A = Z+N
Each nuclides is denoted by the chemical symbol of the element (this specifies Z) with the atomic mass number as superscript.
This determines the number of neutrons N = A-Z
: Hydrogen nuclide with ( Z=1) a single proton as nucleus
is the hydrogen nuclide with a neutron and as well as a proton in the nucleus. This called the deuterium of heavy hydrogen .
For better clarity, Z is also included in the symbol as a subscript.
Atoms such as and whose nuclei contains same number of protons but different numbers of neutrons ( Same Z but different N and hence different A) are known asisotopes.
Naturally occurring elements may exist in the nature with some stable isotopes and some unstable isotopes and expressed as percentage atoms of the element.
Oxygen, for example, has three stable isotopes ,
, ( Z = 8, N = 8, 9 , 10 ) and five known unstable ( i.e. radioactive) isotopes , , , and (Z = 8, N=5, 6, 7, 11, 12).
The stable isotopes ( and a few of the unstable isotopes) are
found as naturally occurring elements in nature.
However, they are not found in equal amounts; some isotopes
of a given element are more abundant than others.
For example: 99.8 % of naturally occurring
oxygen atoms are the isotope . Rest are:
0.037% and 0.204%
Einstein’s theory of relativity
Mass and energy are equivalent and
convertible, one into other.
Complete annihilation of a particle or other body
of rest mass releases an amount of energy
which is given by Einstein’s formula
c is the speed of light
- This is equivalent to 25 million kilowatt-hours
Another unit of energy that is often used in nuclear engineering is the electronVolt(eV)
This is defined as the increase in the kinetic energy of an electron when it falls through an electrical potential of one volts.
This is in turn is equal to the charge of the electron multiplied by the potential drop
Total energy of a particle, that is, its rest mass plus its kinetic energy
Kinetic energy is given as
For v<< c
Same as in Classical Mechanics
Photon: Travels at the speed of light and has no rest mass, its total energy is given as
Particle Wave Length
For Photon and all other particles of zero rest mass
Where E is the kinetic energy in eV
The z atomic electrons that cluster about the nucleus move in a well defined orbits
However, some of these electrons are more tightly bound in the atom than other.
For example only 7.38 eV is required to remove the outermost electron from a lead (Z=82), while 88 keV (or 88,000 eV) is required to remove the inner most or the k-electron.
The process of removing an electron from an atom is call ionization and 7.38 eV and 88k3V are known as the ionization energies.
It slow decays back to the ground state.
When such transition occurs, a photon is emitted by the atom with an energy equal to the difference in the energies of the two states.
Depending on the energy level of the excited state or the removed electron orbit level, radiation wavelength ( ultraviolet etc. ) can be determined.
Light -Water Reactor (LWR)
Gas Cooled Graphite moderated Reactor
- High temperature gas cooled reactor (HTGR)
Heavy -Water Reactor (HWR)
Breeder Reactor (BR)
The first generation of reactor that is moderated and cooled by ordinary (light) water.
There are two types of light - water reactors:
Pressurized-water reactor (PWR)
Boiling-water reactor (BWR)Light-Water reactor (LWR)
The water in a PWR is maintained at a high pressure in the range of 2000-2500 psi to prevent water from boiling.
High pressure water is circulated through the reactor core to pick up heat without any boiling of water.
Pressurize hot water is then circulated through the steam generator where heat is transferred to a secondary water stream that enters as liquid water and exits steam.
Large PWR system uses as many as four steam generators, which produce steam at about 560 F and 900 psi.
This gives an overall efficiency of 32-33 % for a PWR plant.
The condenser is cooled by a cooling water loop using pumps and cooling tower that rejects heat to environment
Referred to as the direct cycle.
Water is boiled directly in the reactor vessel and produces steam to turn the turbine.
Steam is produced directly inside the reactor and there is no need of a separate steam generator.
Steam from the rector goes directly to the turbine to produce power.
More effective in removing heat from the fission reaction using latent heat rather than sensible heat.
However, the water becomes radioactive in passing through the reactor core.
Since this radioactive water is utilized in the electricity producing side of the plant, all of the components like the turbines, condensers, reheaters, pumps, piping be shielded in a BWR Plant.
The pressure in a BWR is approximate 1000 psi, about half the pressure in a PWR.
However the power density (Watt/cm^2) is smaller in a BWR than a PWR, and so overall dimension of a pressure vessel for BWR must be larger than for PWR.
Heavy-water moderated and cooled reactor (HWR) has been under development in several countries, especially in Canada.
Heavy-water moderated reactor is suitable for use with natural uranium.
Canada has large resources of natural uranium.
Removes the need for expansive uranium enrichment plant.
However, deuterium in is twice as heavy as hydrogen in , so that is not as effective in moderating neutrons as .
They require more collisions and travel greater distances before reaching thermal energies than
In order to avoid the use of large and expensive pressure vessel, Canadian design uses pressure tube concept that encapsulated fuel within a hollow tubes.
The coolant passes through the tubes and coolant do not come in direct contact with the heavy water moderator.
In Canadian HWR design, heavy water is also used as the coolant.
Thus an accidental increase in power leads automatically to further increase in power and rapid external intervention is required to bring reactor under control
The world reserve of are not adequate to meet the indefinite needs of the growing nuclear power industry ( may be for 100 years)
Only the advent of the breeder reactor can achieve the full potential of the world’s uranium and thorium supply.
It is possible to manufacture certain fissile isotopes from abundant non-fissile materials by a process know an conversion.
The fissile isotope is obtained from fissile isotope of thorium by the absorption of neutrons.
is obtained from nonfissile , which is one of the major component of natural resource of uranium.
has to be irradiated in a reactor, which normally occurs in most the reactors. So most of the reactor are fueled with uranium which is only slightly enriched in .
Practically all of the fuel in these reactors is therefore and conversion of into takes place during the normal operation of the rector.
- Defined as the average number of fissile atoms produced in a reactor per fissile fuel atom consumed.
In a breeder reactor every effort is made to prevent fission neutrons to slow down. So, light-water is excluded from the core.
There is no moderator in the core and the core contains only fuel rods and coolant.
In these reactors, different other types of coolants such as sodium are used.
Liquid-metal Cooled fast Breeder Rector
Gas cooled fast breeder Reactor (GCFR)
Molten salt breeder reactor (MSBR)
Light water breeder reactor