Nuclear processes and their effects
SEC 2 ACE 2011
Dickson Lim 2P214
Content Page
Introduction
Nuclear fission
Nuclear fusion
Nuclear Power Plant
Radioactivity and its risks
Case study: Japan’s Recent 9.0 Earthquake
Reflections
Citations
Introduction
Our economy has been a carbon based one since the Industrial Revolution began in the 18th
century. Along the way, mankind has explored other alternatives for our energy needs,
including solar, wind, geothermal, tidal and notably nuclear power.
Our lives, as we are familiar and comfortable with, have become entirely dependent on a
steady and abundant supply of energy. Indeed, it would be impossible to imagine having to
live a day without any electricity. The quality of life is proportional to the supply of energy,
as such extensive development and research have been ongoing to discover the holy grail of
energy production.
In this work, we will discuss nuclear energy and eventually evaluate and weigh the
pros and cons of nuclear power from a neutral and unbiased perspective. Hopefully, this
would aid the discerning readers in making an informed choice when the decision to retain or
abolish nuclear power has to be made.
Energy generation has gone a long way in its development, evolving from being
driven by horses or water to hydrocarbon energy generation to today’s nuclear fission.
Though nuclear fission is a clean and reliable energy supply, it poses a plethora of other
problems, such as nuclear waste disposal concerns and risk of radiation leakage. However,
electricity is quintessential to the maintenance of an acceptable quality of life.
At the start of the 21st century, two of those six billion people live without electricity.
Energy poverty equates with financial poverty and developing energy supplies to the world's
poorest is vital if their lives are to improve. But fossil fuels, which drove the industrial
revolution in Europe and the US and allowed millions in the temperate world to escape
poverty, have a down side. The carbon released to the atmosphere during combustion is the
main cause of global warming, a phenomenon which becomes ever more apparent with each
passing hurricane, flood or drought. Within the last six months tens of thousands have died in
Venezuela and India from natural disasters which may be an expression of global warming.
Experts generally believe that climatic extremes are more likely in a greenhouse world.
The last two centuries were dominated by fossil fuels; firstly coal, then oil and gas. If the
world is to avoid the most damaging impacts of global warming, such as major melting of the
polar ice caps and rapid shifts in climatic regions, an alternative to fossil fuel has to emerge.
Ending dependence on oil for transport and coal and gas for electricity is one of society's
most fundamental challenges. Alas, our society is too deeply entrenched in the current
hydrocarbon economy, notwithstanding the current infrastructure in terms of our power
stations and machinery. Much time is required before we can successfully transit from a
hydrocarbon to a fusion economy.
Nuclear fission
Fission is induced by a neutron and can be regarded as a form of spontaneous
radioactive decay. The composition of the products are somewhat unpredictable in a broad
probabilistic and chaotic manner.
Fission of heavy elements is an exothermic reaction which can release large amounts
of energy in the form of electromagnetic radiation and kinetic energy of the fragments. In
other words, the total binding energy of the resulting elements is less than that of the starting
element. The resulting fragments are not the same element as the original atom.
Nuclear fission is the de facto process for generating energy in the nuclear power
stations and the main driver behind the destructive explosion of nuclear weapons. Both uses
are possible because certain substances called nuclear fuels undergo fission when struck by
fission neutrons, and in turn emit neutrons when they break apart. This makes possible a selfsustaining chain reaction that releases energy at a
controlled rate in a nuclear reactor or at a very rapid
uncontrolled rate in a nuclear weapon.
Using the same basis for comparison, an
equivalent amount of nuclear fuel would be able to
release millions of times of energy than the same amount of chemical fuel. The products of
nuclear fission give rise to a serious issue of nuclear waste disposal. Concerns over nuclear
waste accumulation and over the destructive potential of nuclear weapons may
counterbalance the desirable qualities of fission as an energy source.
Nuclear fusion
The fusion of two nuclei with lower masses than
iron (which, along with nickel, has the largest binding
energy per nucleon) generally releases energy while the
fusion of nuclei heavier than iron absorbs energy. The
opposite is true for the reverse process, nuclear fission.
In the simplest case of hydrogen fusion, two protons must be brought close enough for the
weak nuclear force to convert either of the identical protons into a neutron, thus forming the
hydrogen isotope deuterium. In more complex cases of heavy ion fusion involving two or
more nucleons, the reaction mechanism is different, but the same result occurs— smaller
nuclei are combined into larger nuclei.
Nuclear fusion occurs naturally in all active stars. Synthetic fusion as a result of
human actions has also been achieved, although this has not yet been completely controlled
as a source of nuclear power.
Uncontrolled nuclear fusion has been carried out many times in nuclear weapons
testing, which results in a deliberate explosion. These explosions have always used the heavy
isotopes of hydrogen, deuterium (H-2) and tritium (H-3), and never the much more common
isotope of hydrogen (H-1), sometimes called "protium".
Building upon the nuclear transmutation experiments by Ernest Rutherford, carried
out several years earlier, the fusion of the light nuclei (hydrogen isotopes) was first
accomplished by Mark Oliphant in 1932. Then, the steps of the main cycle of nuclear fusion
in stars were first worked out by Hans Bethe throughout the remainder of that decade.
The advantages of fusion technology are numerous. Firstly, it does not have the
disadvantages of nuclear fission technology. Also, it is superior as compared to renewable
energy sources such as wind or solar power as their energy generation capabilities are too
limited to be of practical application. And global energy availability has to increase if poverty
is to decrease. Fusion offers the possibility of high power density, no high level radioactive
waste and no greenhouse gases. For decades, scientists have been trying to harness this
energy safety for our usage and now this is within our reach.
The fuels that could be used are relatively inexpensive and readily available. 1 The
products of a fusion reaction are not radioactive, thus there are no nuclear waste problems. 2
Fusion is not a chain reaction, therefore it can be stopped at anytime and there is no threat of
a meltdown. 3 Fusion would be a virtually inexhaustible energy supply that could eliminate
most of the world's dependence on other fuels. fairly expensive to create but virtually
inexpensive energy.
The last two centuries were dominated by fossil fuels; firstly coal, then oil and gas. If
the world is to avoid the most damaging impacts of global warming, such as major melting of
the polar ice caps and rapid shifts in climatic regions, an alternative to fossil fuel has to
emerge. Ending dependence on oil for transport and coal and gas for electricity is one of
society's most fundamental challenges. Alas, our society is too deeply entrenched in the
current hydrocarbon economy, notwithstanding the current infrastructure in terms of our
power stations and machinery. Much time is required before we can successfully transit from
a hydrocarbon to a fusion economy.
In summary, nuclear fusion is the panacea to our energy problems. However, there are
quite a few obstacles that are hindering the progress of the research into making nuclear
fusion a viable energy production method on a wide scale basis. Only if the entire world is
united in committing to taking the first step towards a change to nuclear fusion
Nuclear Power Plant
The nuclear power plant stands on the border between humanity's greatest hopes and
its deepest fears for the future. On one hand, atomic energy offers a clean energy alternative
that frees us from the shackles of fossil fuel dependence. On the other, it summons images of
disaster: quake-ruptured Japanese power plants belching radioactive steam, the dead zone
surrounding Chernobyl's concrete sarcophagus.
You'd encounter the generator that produces the spark and the turbine that turns it.
Next, you'd find the jet of steam that turns the turbine and finally the radioactive uranium
bundle that heats water into steam. Welcome to the nuclear reactor core.
The water in the reactor also serves as a coolant for the radioactive material,
preventing it from overheating and melting down.
As of March 1, 2011, there were 443 operating nuclear power reactors spread across the
planet in 47 different countries. In 2009 alone, atomic energy accounted for 14 percent of the
world's electrical production. Break that down to the individual country and the percentage
skyrockets as high as 76.2 percent for Lithuania and 75.2 for France. In the United States,
104 nuclear power plants supply 20 percent of the electricity overall, with some states
benefiting more than others.
A nuclear power plant is not that different from a conventional one besides the energy
source being quite different. Both power plants heat water into pressurized steam, which
drives a turbine generator. While older plants burn fossil fuels, nuclear plants depend on the
heat that occurs during nuclear fission, when one atom splits into two and releases energy.
Nuclear fission happens naturally every day. Uranium, for example, constantly undergoes
spontaneous fission at a very slow rate. This is why the element emits radiation, and why it's
a natural choice for the induced fission that nuclear power plants require.
Uranium is a common element on Earth and has existed since the beginning. While there are
several varieties of uranium, uranium-235 (U-235) is the one most important to the
production of both nuclear power and nuclear bombs. U-235 decays naturally by alpha
radiation: It throws off an alpha
particle, or two neutrons and two
protons bound together. It's also one
of the few elements that can undergo
induced fission. Fire a free neutron
into a U-235 nucleus and the nucleus
will absorb the neutron, become
unstable and split immediately.
The number of ejected neutrons depends on how the U-235 atom splits). The process
of capturing the neutron and splitting happens very quickly.
The decay of a single U-235 atom releases approximately 200 MeV (million electron volts).
That may not seem like much, but there are lots of uranium atoms in a pound (0.45 kilograms)
of uranium. So many, in fact, that a pound of highly enriched uranium as used to power a
nuclear submarine is equal to about a million gallons of gasoline.
The splitting of an atom releases an incredible amount of heat and gamma radiation, or
radiation made of high-energy photons. The two atoms that result from the fission later
release beta radiation (superfast electrons) and gamma radiation of their own, too.
Case study: Japan’s Recent 9.0 Earthquake
Prior to the recent Japan's deadly earthquake and tsunami last week which resulted in
the still-unfolding disaster of Fukushima Daiichi, Three Mile Island and Chernobyl have
served as shorthand for the nightmare of nuclear power generation gone awry. It has come
closer than any nuclear crisis in history to making it a fearsome trio.
It remains to be seen how much damage will be caused by the crisis at the Fukushima nuclear
power complex, where four of the six reactors have seen a range of woes including three
explosions in four days, damage to two containment vessels, possible overheating from spent
fuel rods, and mounting peril for the last remaining 50 workers due to dangerous spikes in
radiation emissions.
Reactor Type
Japan's Fukushima Daiichi nuclear power complex, which began operating in the
1970s, is made up of six boiling-water reactors, or BWRs—a type of "Light Water Reactor."
(Using ordinary water, it is distinguished from "heavy water reactors," which
use deuterium oxide, or D2O, instead of H2O.) Three Mile Island used another type of Light
Water Reactor known as a pressurized-water reactor, or PWR.
Both of these reactors use water for two purposes. It acts as a coolant, carrying heat away
from the nuclear fuel, and as a "moderator," slowing down the release of neutrons during
fission reactions.
Accident Cause
For the Fukushima disaster, the tsunami appeared to be the immediate culprit, since
the plants shut down as they were designed to do following the earthquake. When the tsunami
hit an hour later, it damaged the site infrastructure, he said. So while the earthquake had cut
the reactors' external power supply, which is needed to keep coolant pumps doing their job,
the tsunami killed the diesel backup generators needed to provide power for the cooling
system.
Radiation Containment
The Fukushima reactors have three barriers designed to prevent radiation leakage,
including metal cladding surrounding the nuclear fuel, a reactor pressure vessel, and the
primary containment vessel. Once radiation is released into the environment, it can
contaminate vast areas. Further away you don't necessarily get lower doses," he explained.
Among other factors, prevailing winds can influence what areas are affected.
Weather changed over a prolonged emission period, as a graphite fire burned for 10
days. So radioactive gases and particles were picked up by wind and carried high in the
atmosphere over long distances before raining down on communities far from the source.
Who is to be blamed?
Communication during a nuclear crisis, of course, must extend beyond industry, and
in this area plant operator Tokyo Electric Power (Tepco) is facing harsh criticism. On
Tuesday the director general of the International Atomic Agency, Yukiya Amano, called for
Japanese counterparts to facilitate stronger communication. According to the Kyodo News
Agency, Prime Minister Naoto Kan admonished Tepco executives in a meeting Tuesday after
he learned about an explosion from TV, rather than receiving a call from Tepco. He
reportedly demanded to know, "What the hell is going on?"
Conclusion
In light of the risks and disadvantages of nuclear fission, it would be worthy if we can
pay more attention to nuclear fusion instead. The last two centuries were dominated by fossil
fuels; firstly coal, then oil and gas. If the world is to avoid the most damaging impacts of
global warming, such as major melting of the polar ice caps and rapid shifts in climatic
regions, an
alternative to fossil fuel has to emerge.
Ending
dependence on oil for transport and coal
and gas for
electricity is one of society's most
fundamental
challenges. Alas, our society is too deeply
entrenched in
the current hydrocarbon economy,
notwithstanding the current infrastructure in terms of our power stations and machinery.
Much time is required before we can successfully transit from a hydrocarbon to a fusion
economy.
In summary, nuclear fusion is the panacea to our energy problems. However, there are
quite a few obstacles that are hindering the progress of the research into making nuclear
fusion a viable energy production method on a wide scale basis. Only if the entire world is
united in committing to taking the first step towards a change to nuclear fusion
Reflection
After doing this ACE on nuclear fusion and fission, I finally realised the importance of such a
indispensible energy source across the world. However, such benefits comes with the price of
safety issues and the life and death of surrounding creatures. With the recent explosion of the
nuclear power plants in Japan, not only has human been affected but also the innocent fishes
living in the ocean. Hence, I can now understand why the Singapore has been pondering over
the issue of building a nuclear power plant in Singapore
Citations
^ "The National Ignition Facility: Ushering in a New Age for Science". National Ignition
Facility. https://lasers.llnl.gov/programs/nif/. Retrieved 2009-09-13.
^ J.K. Shultis, R.E. Faw (2002). Fundamentals of nuclear science and engineering. CRC
Press. p. 151. ISBN 0824708342.
http://books.google.com/books?id=SO4Lmw8XoEMC&pg=PA151.
^ "The National Ignition Facility: Ushering in a New Age for Science". National Ignition
Facility. https://lasers.llnl.gov/programs/nif/. Retrieved 2009-09-13.