Filed Under : by Perjalanan Hidup..........
Thursday, May 1, 2014
Definition
of Nuclear Energy
What is
nuclear energy? Nuclear energy is a way of creating heat through the fission
process of atoms. All power plants convert heat into electricity using steam.
At nuclear power plants, the heat to make the steam is created when atoms split
apart. This splitting phenomena of the atoms is what we called fission. Besides
than that, there are other types of nuclear power plants that are by burning
coal or oil for heat to make steam.
Reaction
in Nuclear Power Plant
When there are fissions in the reaction, it will also
release energy in the form of heat. The released neutrons can then repeat the
process. This releases even more neutrons and more nuclear energy. The
repeating of the process is called a chain reaction. In a nuclear power plant,
uranium is the material used in the fission process.
The heat from fission boils water and creates steam
to turn a turbine. As the turbine spins, the generator turns and its magnetic
field produces electricity. The electricity can then be carried to many houses, so people can work on the computer,
watch television, play video games, or even make toast. The most important
thing is the government must make sure that the nuclear power plant must be safe
for people who work there and live nearby, and for the environment.
In other hand, we must know
that the nuclear
material is used for many things besides nuclear power for example for detecting
and treating certain illnesses. Nuclear material also used to perform research
at universities and to help in industries for such things as locating cracks in
steel, getting rid of dust from film and even measuring the amount of air
whipped into ice cream.
What is Nuclear Reactors
To produce nuclear energy, we need to have a
nuclear reactor. So what is nuclear reactor?. A nuclear reactor is a system
that contains and controls sustained nuclear chain reactions. Reactors are used
for generating electricity, moving aircraft carriers and submarines, producing
medical isotopes for imaging and cancer treatment, and for conducting research.
Fuel, made up of heavy atoms that split when they
absorb neutrons, is placed into the reactor vessel along with a small neutron
source. The neutrons start a chain reaction where each atom that splits
releases more neutrons that cause other atoms to split. Each time an atom
splits, it releases large amounts of energy in the form of heat. The heat is
carried out of the reactor by coolant, which is most commonly just plain water.
The coolant heats up and goes off to a turbine to spin a generator or drive
shaft. So basically, nuclear reactors are exotic heat sources.
When we look at the nuclear reactors, there are many
components. The main components inside the nuclear reactor are:
1.
The core of the
reactor contains all of the nuclear fuel and generates all of the heat. It
contains low-enriched uranium
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2.
The coolant is the
material that passes through the core, transferring the heat from the fuel to a
turbine. It could be water, heavy-water, liquid sodium, helium, or something
else. In the US fleet of power reactors, water is the standard.
3.
The turbine
transfers the heat from the coolant to electricity, just like in a fossil-fuel
plant.
4.
The containment is the
structure that separates the reactor from the environment. These are usually
dome-shaped, made of high-density, steel-reinforced concrete. Chernobyl did not
have a containment to speak of.
5.
Cooling towers are
needed by some plants to dump the excess heat that cannot be converted to
energy due to the laws of thermodynamics. These are the hyperbolic icons of
nuclear energy. They emit only clean water vapour.
Types of Nuclear Reactors
There are
very many different types of nuclear reactors with different fuels, coolants,
fuel cycles, purposes. The example of nuclear reactors are pressurized water
reactor and sodium cooled fast
reactor.
1.
Pressurized Water Reactor
The most common type of reactor -- the PWR uses
regular old water as a coolant. The primary cooling water is kept at very high
pressure so it does not boil. It goes through a heat exchanger, transferring
heat to a secondary coolant loop, which then spins the turbine. These use oxide
fuel pellets stacked in zirconium tubes. They could possibly burn thorium or plutonium fuel as well.
2.
Sodium Cooled Fast Reactor
The first electricity-producing nuclear reactor in
the world was SFR (the EBR-1 in Arco, Idaho). As the name implies, these
reactors are cooled by liquid sodium metal. Sodium is heavier than hydrogen, a
fact that leads to the neutrons moving around at higher speeds. These can use metal or oxide fuel, and burn
anything you throw at them (thorium,
uranium, plutonium, higher actinides).
Nuclear Reactor and the
Environment
Small amounts of radioactivity can be released into
the environment but only under controlled and monitored conditions. The only
major accident in a nuclear power plant in this country was at Three Mile
Island near Harrisburg, Pennsylvania, in March 1979. At Three Mile Island,
there was major fuel damage, and radioactive gases and contaminated cooling
water filled the containment building. Some radioactivity was released into the
atmosphere, but it didn't hurt people or the environment.
A much more serious accident happened in 1986 at
Chernobyl in the former Soviet Union. That reactor was built differently than
those in the U.S. Most importantly, it had no containment system. The reactor
core was severely damaged and a large amount of radioactivity was released into
the environment.
Decommissioning
of Nuclear Reactor
Nuclear power plants can be decommissioned using
three methods:
- Dismantling -- Parts of the reactor are removed or decontaminated soon after the plant closes and the land can be used.
- Safe Storage -- The nuclear plant is monitored and radiation is allowed to decay; afterward, it is taken down.
- Entombment -- Radioactive components are sealed off with concrete and steel, allowing radiation to "decay" until the land can be used for other purposes.
Radioactive
Waste
High-Level Radioactive Waste
High-level waste includes the fuel used in the
nuclear reactor -- called spent fuel . It is highly radioactive and very
dangerous. It must be cooled for several years in deep pools inside the plant
or in special storage facilities outside of the plant site. It can remain in
the pool or later be transferred to special casks, which are like big, concrete
barrels. Some of the fission products in the spent fuel will take many years to
lose their radioactivity. A special disposal site is needed for this type of
spent fuel. The U.S. Department of Energy wants to build such a site at Yucca
Mountain, Nevada. The spent fuel, in heavy casks, would remain buried there for
thousands of years. The NRC must approve and license this site to make sure it
is safe.
Low-Level Radioactive Waste
Low-level waste can come from nuclear reactors or
from hospitals or universities. Low-level waste is not as dangerous as
high-level waste. It can be shipped to low-level waste disposal facilities.
There, it is packaged, buried in trenches and covered with soil. States are
responsible for selecting new disposal sites or using those that already exist.
Effects of Nuclear Radiation on Environment
Humans and Animals
The effects of radiation on
humans and animals are well-documented as having an extremely detrimental
effect. When exposed to radiation in large amounts, humans can develop cancer.
If the amount of radiation is controlled, it can be used to treat cancer, but
if a leak or accidental exposure occurs, it would be nearly impossible to
control the exposure. Radiation can also cause birth defects in humans and
animals, so an exposure to radiation in the wild could lead to generations of
difficulties throughout an entire ecosystem.
Plant Reproduction
One of the largest environmental
exposures to nuclear radiation was the Chernobyl disaster in 1986. This
accident caused 125,000 square miles in the Ukraine and Russia to be exposed to
radiation. One of the largest damaging effects over the next few weeks were the
reproductive tissues of the plants. Similar effects have occurred with hydrogen
bomb testing in other parts of the world. It took these trees around three
years to regain their reproductive abilities. Some scientists believe that three
years was much sooner than when they believed the plants would be able to
reproduce again.
Nuclear Fusion in Astronomy
In physics and nuclear
chemistry, nuclear fusion is the process by which multiple atomic particles
join together to form a heavier nucleus. It is accompanied by the release or
absorption of energy. Iron and nickel nuclei have the largest binding energies
per nucleon of all nuclei and therefore are the most stable. The fusion of two
nuclei lighter than iron or nickel generally releases energy, while the fusion
of nuclei heavier than iron or nickel absorbs energy. The opposite is true for
nuclear fission. Nuclear fusion is naturally found in stars.
References:
Nuclear Reactor.
Retrieved on May, 1, 2012
from http://www.whatisnuclear.com/articles/nucreactor.html
Report on Nuclear Energy
Usage. Retrieved on May, 1, 2012
from http://www.epa.gov/ttn/caaa/t3/reports/eurtc1.pdf
Review oh the Usage of
Nuclear Energy. Retrieved on May, 1, 2012
http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html
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