HPAVC/HPAVC CD-ROM.iso/pc/HOMEWORK.ZIP/NUKE-USA.TXT

Text File | 1998-07-25 | 8.6 KB | 149 lines

Date sent:        Sat, 27 Apr 1996 08:19:33 -0400



Nuclear Power

 Over the past few years the increase in the use of energy all over the world has
increased by incredibly huge amounts.  This means, that as the population continues to
grow, the increase in energy usage will also continue to grow.  So scientist all over the
world, are continuously searching for ways to produce the huge amount of energy required by
the world.  Up until now, a large portion of the energy produced has been from fossil fuel
such as oil and gas, that are non replaceable and are running out very quickly.  In fact,
even with a world policy on the use of fossil fuels, the present increase in the use of
energy, all the worlds coal, oil, gas, and uranium will be used up by the year 2023.  The
fastest increase at the moment is in the use of nuclear power, And all known uranium
reserves would be exhausted by the year 2000.


 This graph shows the consumption of world energy sources
 Nuclear energy actually refers to the energy consumed or produced in changing
the composition of the atomic nucleus.  The force that arms the atomic bomb and
hydrogen bomb and other nuclear weapons, nuclear energy also powers electricity-
generating plants in countries throughout the world.  It is seen by many as the source of
inexpensive, clean power;  but, because of the hazardous radiation emitted in producing that
power and the radioactivity of the materials used, others feel that it may not be a viable
energy alternative to the use of fossil fuels or solar energy.


The following text discusses the science involved in the release of nuclear energy, and the
use of that science by the industries that produce electric power.

Scientific Definitions
 The processes that change the state or composition of matter are inevitably
accompanied by the consumption or production of energy.  Common processes such as
combustion produce energy by the chemical rearrangement of atoms or molecules.  For
example, the combustion of methane (natural gas) is represented by the chemical
reaction

CH(4) + 2O(2) = CO(2) + 2H(2)O + energy

 For this example the energy release is 8 electron volts (ev). The electron volt is a
unit of energy used by nuclear physicists and represents the gain in kinetic energy when an
electron is accelerated through a potential drop of one volt.

 The most well-known nuclear reaction is fission, in which a heavy nucleus
combines with a neutron and separates into two other, lighter nuclei.  A typical fission
reaction involving uranium-235 is;

92 U235 + 1 neutron = 38 Sr96 + 54 XE138 + 2 neutrons+energy
where the energy release is about 200 million electron volts (meV), a factor of 25 million
greater than the combustion reaction of methane.

 Another important nuclear reaction is fusion, in which two light elements
combine to form a heavier atom.  An important fusion reaction is ;

1 H(2) + 1 H(3) = 2 He(4) + 1 neutron + energy

where the energy release of the reaction is 18 million eV.

 Nuclear power plants harness the enormous energy releases from nuclear
reactions for large-scale energy production.  In a modern coal plant the combustion of
one pound of coal produces about 1 kilowatt hour (kWh) of electric energy.  The
fissioning of one pound of uranium in a modern nuclear power plant produces about 3
million kWh of electric energy.  It is the incredible energy density (energy per unit mass)
that makes nuclear energy sources of such interest.

At present, only the fission process is used in the commercial production of energy,
usually to make electricity, but also occasionally to produce steam for district heating or
other industrial applications.  Fusion research has not yet produced a feasible power
production technology.




Advantages and Disadvantages
Advantages
 -Cheapest form of power to date
 -Lots of power produced
 -Renewable
 -Runs for a long time
 -No air pollution
 -Fairly low risk of radioactivity
 -Fairly safe
Disadvantages
 -Radioactive waste
 -Small chance of radiation
 -Increased risk of cancer
 -Radiation is hard to detect
 -Some chance of meltdown
 -Many people against it due to previous disasters
 -Expensive to set up
 -Large amounts of space needed to occupy the reactor
 -Chance of large scale disasters
Chernobyl
 The Chernobyl nuclear power plant, about 130 km north of Kiev, in Ukraine, was
the site of the world's worst nuclear-reactor disaster on April 26, 1986, when the plant's
No. 4 reactor exploded. The accident occurred while an experiment was being conducted with
the graphite-moderated reactor running but its emergency water-cooling system turned off. A
series of miscalculations permitted neutron build up in one area of the core, where the
nuclear reaction suddenly went out of control. The power surge shattered the fuel. This and
a second, steam-induced explosion blew the lid off the reactor, whose containment structure
was not designed for such pressures. A third, chemical explosion followed, and scattered
fragments caused further local fires.
 The disaster killed 31 persons immediately or shortly thereafter and caused the
hospitalization of about 500 others. Over the next few days, persons living within 30 km of
the site were evacuated. The force of the explosion and fire carried much of the
radioactivity away from the site to relatively high altitudes, where it spread across the
Northern Hemisphere. The heaviest fallout descended on the western Soviet Union and portions
of Europe, where preventive steps were taken by several nations to protect food supplies.
Data on worldwide effects of this fallout remain inconclusive.

 Although heavily contaminated soil and trees were removed from the 30-km (19-
mi) zone near the power plant, authorities acknowledged in 1990 that several million
persons were still living on contaminated ground. The incidences of thyroid cancer,
leukemia, and other radiation-related illnesses are higher than normal among this
population. At the plant itself, reactor No. 4 was entombed in concrete. Two of the three
remaining reactors continued in operation, but a series of accidents at Chernobyl persuaded
Ukraine's parliament in 1991 to press for a complete shutdown--an unlikely event until
another source of power for the region is developed. Three Mile Island
 The most serious U.S. commercial reactor failure occurred on Mar. 28, 1979, at
the Three Mile Island (TMI) reactor near Harrisburg, Pa.  The TMI-2 accident began as a
small break in which a valve stuck open, allowing coolant to escape from the vessel.  The
emergency core cooling system (ECCS) operated as designed and provided makeup water for the
core. Unfortunately, the operators misinterpreted the information available to them in the
control room and shut off the ECCS for several hours.  The decay heat from the core boiled
off the available water in the vessel, and without adequate cooling, the cladding and fuel
started to melt.  Before the operators resumed the flow of emergency coolant, a sizeable
portion of the core, about one-half to one-third, melted. The molten fuel and cladding
dropped into the bottom of the vessel, which was full of water.  This water was adequate to
quench the molten material.  The vessel itself maintained its integrity and kept all of the
debris contained.

 A sizable amount of gaseous fission products escaped from the vessel through the
open valve into the containment building. The containment functioned as the ultimate
barrier and prevented a release into the local environment.  The small amount of activity
that did escape was carried by coolant water that leaked out the valve into the containment
and then overflowed into an auxiliary building where the gases leaked into the environment.
The releases were almost entirely noble gases (such as xenon), which are chemically inert
and not retained within the human body.  The health effects of the accident proved to be
quite small, and virtually undetectable against the normal incidence of background
radiation. Our Evaluation of Nuclear Energy
 After taking a careful look at all the different kinds of options of energy
production, we both have decided that despite the chances of radiation leakage, and
nuclear meltdown, that nuclear is power is the key to the worlds energy problem,
although a fusion reactor would be far the superior to the current fission ones, as there is
almost no waste given off.   Seeing as now scientist are finding ways to cut the amount of
uranium needed, this should mean that there will probably be plenty of uranium around, and
that it will take a while to run out.