Nuclear energy is obtained from splitting uranium atoms through nuclear fission. Uranium is mined and processed to extract and enrich the uranium-235 isotope, which is then fabricated into fuel pellets. These pellets are assembled into reactors where fission occurs, producing heat used to generate electricity. Used fuel is stored on site, though permanent storage solutions are still needed. Nuclear energy production results in radioactive waste that must be carefully contained and isolated over hundreds of years to prevent environmental contamination.

1. CHAPTER 13 –Nuclear Energy
Introduction
Nuclear energy is energy that is obtained from the nucleus of an atom. The
energy is released from an atom through one of two processes:
(1) nuclear fusion or
(2) nuclear fission.
Energy is released in nuclear fusion when atoms are combined or fused
together (fusion). This is how energy is generated in the sun. In nuclear fission,
energy is released when atoms are split apart. Nuclear fission is the only
method currently used by nuclear plants to generate electricity. However, the
terms nuclear fusion and nuclear fission are referred to synonymously as
nuclear energy. Both involve changes in (nuclear) mass.

2. Introduction
Regarding fission, uranium is the heaviest of the 92 naturally occurring
elements. Since it is also one of the few elements that is easily fissioned, it is
the fuel of choice used by today’s nuclear power plants.
When a uranium atom is split apart (fissioned), the mass of the fragments is
less than the mass of the original atom. The energy corresponding to this loss
of mass is defined as fission energy. It is represented in equation form by
Einstein’s equation: E = mc2
where (in SI units) E = joules (J)
m = kilograms (kg)
c = meters/second (m/s); the velocity of light, 3 × 108 m/s

3. Introduction
One can show that each kilogram of mass converted liberates approximately
1017 J. This thermal energy is enough to run a large turbine generator (a 1-GW
unit) for a year at 35 percent thermal efficiency and is equivalent to the energy
possessed by 2.5 million tons of coal.
Similarly, if two or more light elements (e.g., hydrogen) are combined (fused) to
form a heavier one, the resulting mass of the atom is less than the sum of the
two original atoms. The difference (or loss) in mass is converted to energy, as
with the fusion process. This energy is defined as fusion energy.
Nuclear energy is generated by the splitting of uranium atoms. The energy in
the form of heat from this fission process is used to drive a turbine to generate
electricity.

4. Early History
The pursuit of nuclear energy for electricity generation began in the early
twentieth century soon after the discovery that radioactive elements, such as
radium, released monumental quantities of energy, as previously described by
Einstein’s equation.
The peaceful use of the atom for power generation was delayed until after
World War II. In this process, a controlled fission chain reaction generated heat
in the fuel and transferred the heat through a fluid medium to a heat exchanger
to produce steam. A conventional steam cycle is then used to generate
electricity. Great Britain (Calder Hall in Sellafield) took an early lead in
developing nuclear power for peaceful use(s). Russia’s Obninsk nuclear power
plant became the first to generate electricity for a power grid in 1954.

5. Early History
Unfortunately, several serious nuclear and radiation accidents have involved
nuclear submarines.
Aided by the U.S. Atomic Energy Commission (AEC) and based on the nuclear
power for naval ships, the first civilian nuclear reactor went into service in
1957. The plant was in Shipping port, Pennsylvania, with a power output of 60
MW.
The second-generation plants started in 1963 when a New Jersey utility
ordered its first commercial plant
Orders were placed for more than 50 nuclear plants with outputs from 500 to
1,100 MW, for a total of 40,000 MW. Orders averaged 10,000 MW for each
new unit over the next 3 years.

6. Early History
From an economic point of view, nuclear plant capital costs were generally
higher and fuel costs were lower when compared to existing fossil fuel plants.
Overall, nuclear power costs were lower in the larger plants where fuel cost
represented a larger portion of the total costs
there were two major accidents at nuclear power plants. Unfortunately, these
two accidents have changed the public’s perception of the safety of nuclear
plants. The accidents were Three Mile Island Unit 2 (TMI2) in Harrisburg,
Pennsylvania (1979), and Chernobyl (1986) in the former Soviet Union.
During the mid-1990s, nuclear power plants matured and were competitive
with fossil fuel power generation since maintenance costs had been reduced.
While there have been few fossil and no new nuclear power plants constructed
in the United States, it should be noted that nuclear plants based on advanced
reactors are being built and brought online elsewhere

7. Availability/Distribution
At the turn of this century, 30 percent of nuclear energy in the world was
generated by the United States. France, Japan, Russia, Germany, and Korea
contributed 15, 10, 5, 5, and 5 percent, respectively, of the total.
Currently, nuclear power plants provide 6 percent of the world’s energy and
nearly 15 percent of the world’s electricity.
France produces the highest percentage of its electrical energy from nuclear
reactors—80 percent as of 2006. Nuclear energy provides 30 percent of the
electricity in the European Union. Nuclear energy policy differs among
European Union countries, and some, such as Austria, Estonia, and Ireland,
have no active nuclear power plants.

8. Characterization
As discussed in the Introduction, nuclear energy is released from an atom
through one of two processes: nuclear fission or nuclear fusion. Nuclear fission
releases energy when the nuclei of atoms are split apart, and it is the loss of
mass associated with this merging process that creates the energy that is
released.
Nuclear fusion releases energy when the nuclei of atoms are combined or
fused together. This process is how the sun produces energy. The process
involves those isotopes of hydrogen that can combine to form helium.
Hydrogen has only one proton and normally no neutrons. However, a small
fraction of naturally occurring hydrogen has a single neutron in the nucleus
along with the proton. This form of hydrogen is defined as deuterium.

9. Characterization
Hydrogen with two neutrons is referred to as tritium. Reactions liberating
energy include
Locating and extracting deuterium and/or tritium is a major problem currently.
Another option is to combined lithium-6 with a neutron in the following manner:

10. Extraction and Conversion
The process starts with mining. Uranium mines are underground, open pit, or
in situ leach mines. In any case, the uranium ore is extracted, usually
converted into a stable and compact form such as yellowcake, and then
transported to a processing facility.
the overall nuclear process may be visualized as occurring in a series of eight
steps:
1. Extraction
2. Milling
3. Conversion
4. Enrichment
5. Fabrication
6. The nuclear reaction unit
7. Waste management
8. Reprocessing

11. Extraction and Conversion
Overall uranium fuel cycle.

12. Extraction and Conversion
1- Extraction. A ton of uranium ore in the United States typically contains 3 to
10 pounds of uranium.
2- Milling. After it has been mined, uranium ore is crushed. The crushed ore is
usually mixed with an acid, which dissolves the uranium, but not the rest of the
crushed rock. The acid solution is drained off and dried, leaving a yellow
powder referred to as the yellowcake, consisting mostly of uranium.
3- Conversion. The next step in the cycle is the conversion of the yellowcake
into a gas called uranium hexafluoride, or UF6.
4- Enrichment. Because less than 1 percent of uranium ore contains uranium-
235 (the form used for energy production), uranium must be processed to
increase the concentration of uranium-235. This process—called enrichment—
increases the percentage of uranium-235 from 1 to approximately 5 percent.

13. Extraction and Conversion
5- Fabrication. The enriched uranium is taken to a fuel fabrication plant where
it is prepared for the nuclear reactor. Here, the uranium is made into a solid
ceramic material and formed into small barrel-shaped pellets.
Fuel pellets are about the size of a fingertip, yet each one can produce as
much energy as 150 gallons.
6- The nuclear reactor unit. The uranium fuel is now ready for use in a
nuclear reactor. Fission takes place in the reactor core. Surrounding the core
of the reactor is a shell called the reactor pressure vessel.
The reactor core houses about 200 fuel assemblies. Spaced between the fuel
assemblies are movable control rods. Control rods absorb neutrons and slow
down the nuclear reaction. Water also flows through the fuel assemblies and
control rods to remove some of the heat from the chain reaction.

14. Extraction and Conversion
7- Waste management. Like most industries, nuclear power plants produce
waste. One of the main concerns about nuclear power plants is not the amount
of waste created, which is quite small compared to other industries, but rather
the radioactivity of some of that waste.
Utility companies generally replace one-third of the fuel rods every 12 to 18
months to keep power plants in continuous operation.
The used fuel contains both radioactive waste products and unused fuel. The
used fuel is usually stored near the reactor in a deep pool of water called the
used fuel pool.
The used fuel pool serves as a temporary method for storing used nuclear fuel.
However, there is no permanent storage solution yet for used nuclear fuel, and
space for fuel pools may be running out.

15. Extraction and Conversion
The nuclear industry has designed dry cask storage as another temporary
solution. Here, the used fuel stays in the pool for 5 to 7 years. Then, it is
moved elsewhere on the nuclear power plant site to be stored in vaults or dry
casks. Each of these methods for managing used nuclear fuel puts the fuel into
airtight, steel, and concrete structures.
8- Reprocessing. Reprocessing separates the unused nuclear fuel from the
waste products so that it can be reused in another reactor.
Reprocessing is more expensive than producing new fuel from uranium ore.

16. Transportation/Transmission
High-level waste requires safe, undisturbed confinement of material for
hundreds of years. Low- level waste has less stringent requirements but must
be handled and stored appropriately.
A key issue is preventing leakage of radioactive material to the ground water
where it can spread easily. The basic design is to prepare the waste for long-
term disposal in safe storage sites.

17. Environmental Issues
Waste Disposal
Disposal of nuclear waste is often said to be the main environmental concern
of both society and industry. Presently, waste is usually stored at individual
reactor sites where radioactive material continues to accumulate. Experts
agree that centralized underground repositories that are well managed,
guarded, and monitored are presently the most cost-effective approach to this
problem.

18. Waste Disposal
The waste sites are divided into three categories:
1- Those referred to as low-level in terms of their radioactivity are piped directly
into surface ponds on the site.
2- Intermediate-level wastes are treated more cautiously and are emptied into
concrete-covered trenches known as cribs; the cribs are open to the soil at the
bottom, and the water in the wastes gradually seeps downward, taking the
radioactive isotopes with it.
3- The most radioactive wastes, known as high level, are buried in steel-lined
concrete tanks in the ground; the storage of these wastes is the major
challenge to the nuclear industry. ( important :Describe how to treat each of
them)

19. Environmental Issues
Plant accidents/Safety
It should again be noted that nuclear power plants are designed and
constructed to a very high standard of safety. To meet such standards and
assure a high-quality product, strict quality assurance (QA) in design and
quality control (QC) in the manufacture of components and in the plant,
construction are required.
Nuclear reactors are designed so that, in the case of component failure, the
reactor can still be safely shut down.

20. Environmental Issues
Radiation effects
Perhaps the greatest potential risk from nuclear power plants is the release of
high-level radiation and radioactive material.
Emergency plans are in place to alert and advise nearby residents if there is a
release of radiation into the local environment.