Nuclear Power

Nuclear Power Nuclear Power Nuclear energy in California has produced 36,186 million Kilowatt/hours of electricity in 1995. The total dependable capacity of California’s nuclear-supplied power is 5,326 megawatts, including the two operating nuclear power plants in California and portions of nuclear plants in other states owned by California electric companies. There are two ways to release energy from nuclear reactions: fission and fusion of atomic nuclei. Electricity generating technologies are available, whereas fusion is still in the early stages of research and development. Nuclear fission is the process of splitting the nuclei of atoms, which releases energy from within those atoms.

Nuclear fusion is the process of joining, rather than splitting, these atoms with similar releases of energy. There are several types of fission reactors in the United States but the most common is light water reactors. The reason they are called “light water reactors” is because normal (light) water is used to cool the reactor core; some reactors use heavy water, which contains hydrogen atoms with an additional neutron in the nucleus. Pressurized water reactors (PWR) and boiling water reactors (BWR) use uranium-235, a naturally occurring radioactive isotope of uranium, as a fuel. As the nucleus of a uranium-235 atom is hit by a neutron, it splits into smaller atoms of other elements, and releases energy and extra neutrons.

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Those neutrons hit more atoms of the original uranium-235 creating a fission chain reaction that releases more energy and neutrons. In a PWR, water passes through the nuclear core and is heated. The power plant’s primary circulating system passes water through the reactor core, where the water is heated by the nuclear reaction. That water (under high temp and pressure to prevent boiling) is passed through a steam generator, where it releases its heat to the secondary circulating system. Water in secondary circulating system is allowed to boil, and the resulting steam is used to drive a steam turbine-generator.

In a BWR, there is no need for a steam generator and a secondary circulating system, as the water in primary circulating system is allowed to boil before exiting the reactor and is then routed directly to a steam turbine-generator. There are only two nuclear power plants out of six that are still used in California. The first one is owned by PG&E named Diablo Canyon Nuclear Power Plant near San Luis Obispo. The Plant has two units; the first unit is a 1,073-megawatt PWR, which began operation in May 1985. The second unit is 1,087-megawatt PWR, which began operation in March 1986.

The second plant is owned by Southern California Edison Co. and San Diego Gas & Electric named San Onofre Nuclear Generating Station. Unit two of that station is a 1,070-megawatt PWR that began operation in August 1983, while unit three is a 1,080-megawatt PWR that began operation in April 1984. Below is a chart of nuclear power plants in California: Nuclear Power Plants in California Name of Plant Capacity (MW) In Service Owner Diablo CanyonUnit 1Unit 2 1,0731,087 19851986 PG&EPG&E San OnofreUnit 1Unit 2Unit 3 4361,0701,080 1968 – 199219831984 SCE/SDG&ESCE/SDG&ESCE/SDG&E Humboldt Bay Unit 3 * 65 1963 – 1976 PG&E Rancho Seco 913 1975 – 1989 SMUD Vallecitos 30 1957 – 1967 PG&E/GE * Units 1 and 2 are natural gas-fired thermal power plants on the same site. There are many reasons and issues why we don’t have a lot of nuclear power plants in California here are a few: Nuclear plants may not be economically feasible in the United States.

No American utility has proposed to construct a new nuclear power plant since the late 1970s. Need for a spent fuel disposal facility and a decommissioning plan Use of large amounts of water for cooling purposes (if wet cooling towers are used) Biological impacts on the ocean due to thermal discharge (if seawater cooling is used) Designing for seismic safety Public safety concerns Transportation issues associated with the development of an emergency evacuation plan Changes in visual quality due to the power plant structures, including the reactor vessel containment structure, and cooling towers (if applicable) Potentially significant amounts of land Potentially significant public opposition Nuclear power plants produce a lot of energy but they serious environmental problems. I think that these plants are not the solution to our energy problems. I don’t see why we can’t just go solar. But the only way we can stop the production of these plants is to educate the people about them and the hazards of them. And that the only true way to solve this problem is to conserve energy and go solar.

Arts Essays.

Nuclear power

Nuclear power has been around since the first atomic plant was made operational on December 2, 1942. These plants are an efficient way of producing electricity. They can power every electric item we use today, from TV’s to computers and every thing in between. As great as they may seem, how do we deal with the radioactive waste left over? The answer is, we don’t. Until we, as a civilization, find a better way of dealing with this waste, we should hold off on converting fossil fuel plants to nuclear.


As of today, there is no real way to dispose of nuclear waste. While theories of ridding our earth of this harmful radioactive substance vary, the many attempts, have included every thing from simply burying it, to sending it out of our orbit into space. The most popular method to date seems to be “long term storage.” But what, exactly, does the “long term storage” mean? It means storing air tight barrels of nuclear waste in facilities until they lose their potency. As good as this method may sound on paper, the process I’ve just described to you can take up to 20,000 years. This means that the waste storage facilities will have to be secured from robbers, terrorists, and the effects of nature for a period of time in which not only their designers will die, but also, quite possibly the countries in which they are located will crumble.

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Other, more reasonable methods include transmutation: a process in which toxic elements are transformed into less toxic substances. For instance, plutonium can be turned to uranium. This is done by using “fast consumer” reactors, which use the discarded radioactive isotopes of nuclear reactors and “consume” them, leaving isotopes which are less dangerous and have only about half the life and potency of the original waste. Another method is short term storage. This method can significantly reduce the potency of spent nuclear fuel. In this method, waste is stored for ten years. Since nuclear waste decays in exponential increments, it would take another hundred years to do the work of the first ten. Short term storage, however, does not in any way reduce the threat that these substances pose to our environment.

Nuclear Power

Radioactive wastes, must for the protection of mankind
be stored or disposed in such a manner that isolation from
the biosphere is assured until they have decayed to
innocuous levels. If this is not done, the world could face
severe physical problems to living species living on this
planet.
Some atoms can disintegrate spontaneously. As they do,
they emit ionizing radiation. Atoms having this property are
called radioactive. By far the greatest number of uses for
radioactivity in Canada relate not to the fission, but to
the decay of radioactive materials – radioisotopes. These
are unstable atoms that emit energy for a period of time
that varies with the isotope. During this active period,
while the atoms are ‘decaying’ to a stable state their
energies can be used according to the kind of energy they
emit.
Since the mid 1900’s radioactive wastes have been
stored in different manners, but since several years new
ways of disposing and storing these wastes have been
developed so they may no longer be harmful. A very
advantageous way of storing radioactive wastes is by a
process called ‘vitrification’.

Vitrification is a semi-continuous process that enables
the following operations to be carried out with the same
equipment: evaporation of the waste solution mixed with the
additives necesary for the production of borosilicate glass,
calcination and elaboration of the glass. These operations
are carried out in a metallic pot that is heated in an
induction urnace. The vitrification of one load of wastes
comprises of the following stages. The first step is
‘Feeding’. In this step the vitrification receives a
constant flow of mixture of wastes and of additives until it
is 80% full of calcine. The feeding rate and heating power
are adjusted so that an aqueous phase of several litres is
permanently maintained at the surface of the pot. The second
step is the ‘Calcination and glass evaporation’. In this
step when the pot is practically full of calcine, the
temperature is progressively increased up to 1100 to 1500 C
and then is maintained for several hours so to allow the
glass to elaborate. The third step is ‘Glass casting’. The
glass is cast in a special container. The heating of the
output of the vitrification pot causes the glass plug to
melt, thus allowing the glass to flow into containers which
are then transferred into the storage. Although part of the
waste is transformed into a solid product there is still
treatment of gaseous and liquid wastes. The gases that
escape from the pot during feeding and calcination are
collected and sent to ruthenium filters, condensers and
scrubbing columns. The ruthenium filters consist of a bed of
glass pellets coated with ferrous oxide and maintained at a
temperature of 500 C. In the treatment of liquid wastes, the
condensates collected contain about 15% ruthenium. This is
then concentrated in an evaporator where nitric acid is
destroyed by formaldehyde so as to maintain low acidity. The
concentration is then neutralized and enters the
vitrification pot.
Once the vitrification process is finished, the
containers are stored in a storage pit. This pit has been
designed so that the number of containers that may be stored
is equivalent to nine years of production. Powerful
ventilators provide air circulation to cool down glass.
The glass produced has the advantage of being stored as
solid rather than liquid. The advantages of the solids are
that they have almost complete insolubility, chemical
inertias, absence of volatile products and good radiation
resistance. The ruthenium that escapes is absorbed by a
filter. The amount of ruthenium likely to be released into
the environment is minimal.
Another method that is being used today to get rid of
radioactive waste is the ‘placement and self processing
radioactive wastes in deep underground cavities’. This is
the disposing of toxic wastes by incorporating them into
molten silicate rock, with low permeability. By this method,
liquid
wastes are injected into a deep underground cavity with
mineral treatment and allowed to self-boil. The resulting
steam is processed at ground level and recycled in a closed
system. When waste addition is terminated, the chimney is
allowed to boil dry. The heat generated by the radioactive
wastes then melts the surrounding rock, thus dissolving the
wastes. When waste and water addition stop, the cavity
temperature would rise to the melting point of the rock. As
the molten rock mass increases in size, so does the surface
area. This results in a higher rate of conductive heat loss
to the surrounding rock. Concurrently the heat production
rate of radioactivity diminishes because of decay. When the
heat loss rate exceeds that of input, the molten rock will
begin to cool and solidify. Finally the rock refreezes,
trapping the radioactivity in an insoluble rock matrix deep
underground. The heat surrounding the radioactivity would
prevent the intrusion of ground water. After all, the steam
and vapour are no longer released. The outlet hole would be
sealed. To go a little deeper into this concept, the
treatment of the wastes before injection is very important.
To avoid breakdown of the rock that constitutes the
formation, the acidity of he wastes has to be reduced. It
has been established experimentally that pH values of 6.5 to
9.5 are the best for all receiving formations. With such a
pH range, breakdown of the formation rock and dissociation
of the formation water are avoided. The stability of waste
containing metal cations which become hydrolysed in acid can
be guaranteed only by complexing agents which form ‘water-
soluble complexes’ with cations in the relevant pH range.
The importance of complexing in the preparation of wastes
increases because raising of the waste solution pH to
neutrality, or slight alkalinity results in increased
sorption by the formation rock of radioisotopes present in
the form of free cations. The incorporation of such cations
causes a pronounced change in their distribution between the
liquid and solid phases and weakens the bonds between
isotopes and formation rock. Now preparation of the
formation is as equally important. To reduce the possibility
of chemical interaction between the waste and the formation,
the waste is first flushed with acid solutions. This
operation removes the principal minerals likely to become
involved in exchange reactions and the soluble rock
particles, thereby creating a porous zone capable of
accommodating the waste. In this case the required acidity
of the flushing solution is established experimentally,
while the required amount of radial dispersion is determined
using the formula:
R = Qt
2 mn
R is the waste dispersion radius (metres)
Q is the flow rate (m/day)
t is the solution pumping time (days)
m is the effective thickness of the formation (metres)
n is the effective porosity of the formation (%)
In this concept, the storage and processing are
minimized. There is no surface storage of wastes required.
The permanent binding of radioactive wastes in rock matrix
gives assurance of its permanent elimination in the
environment.
This is a method of disposal safe from the effects of
earthquakes, floods or sabotages.
With the development of new ion exchangers and the
advances made in ion technology, the field of application of
these materials in waste treatment continues to grow.
Decontamination factors achieved in ion exchange treatment
of waste solutions vary with the type and composition of the
waste stream, the radionuclides in the solution and the type
of exchanger.
Waste solution to be processed by ion exchange should
have a low suspended solids concentration, less than 4ppm,
since this material will interfere with the process by
coating the exchanger surface. Generally the waste solutions
should contain less than 2500mg/l total solids. Most of the
dissolved solids would be ionized and would compete with the
radionuclides for the exchange sites. In the event where the
waste can meet these specifications, two principal
techniques are used: batch operation and column operation.

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The batch operation consists of placing a given
quantity of waste solution and a predetermined amount of
exchanger in a vessel, mixing them well and permitting them
to stay in contact until equilibrium is reached. The
solution is then filtered. The extent of the exchange is
limited by the selectivity of the resin. Therefore, unless
the selectivity for the radioactive ion is very favourable,
the efficiency of removal will be low.
Column application is essentially a large number of
batch operations in series. Column operations become more
practical. In many waste solutions, the radioactive ions are
cations and a single column or series of columns of cation
exchanger will provide decontamination. High capacity
organic resins are often used because of their good flow
rate and rapid rate of exchange.

Monobed or mixed bed columns contain cation and anion
exchangers in the same vessel. Synthetic organic resins, of
the strong acid and strong base type are usually used.
During operation of mixed bed columns, cation and anion
exchangers are mixed to ensure that the acis formed after
contact with the H-form cation resins immediately
neutralized by the OH-form anion resin. The monobed or mixed
bed systems are normally more economical to process waste
solutions.
Against background of growing concern over the exposure
of the population or any portion of it to any level of
radiation, however small, the methods which have been
successfully used in the past to dispose of radioactive
wastes must be reexamined. There are two commonly used
methods, the storage of highly active liquid wastes and the
disposal of low activity liquid wastes to a natural
environment: sea, river or ground. In the case of the
storage of highly active wastes, no absolute guarantee can
ever be given. This is because of a possible vessel
deterioration or catastrophe which would cause a release of
radioactivity. The only alternative to dilution and
dispersion is that of concentration and storage. This is
implied for the low activity wastes disposed into the
environment. The alternative may be to evaporate off the
bulk of the waste to obtain a small concentrated volume. The
aim is to develop more efficient types of evaporators. At
the same time the decontamination factors obtained in
evaporation must be high to ensure that the activity of the
condensate is negligible, though there remains the problem
of accidental dispersion. Much effort is current in many
countries on the establishment of the ultimate disposal
methods. These are defined to those who fix the fission
product activity in a non-leakable solid state, so that the
general dispersion can never occur. The most promising
outlines in the near future are; ‘the absorbtion of
montmorillonite clay’ which is comprised of natural clays
that have a good capacity for chemical exchange of cations
and can store radioactive wastes, ‘fused salt calcination’
which will neutralize the wastes and ‘high temperature
processing’. Even though man has made many breakthroughs in
the processing, storage and disintegration of radioactive
wastes, there is still much work ahead to render the wastes
absolutely harmless.

Nuclear Power

Nuclear Power Most of the world’s electricity is generated by either thermal or hydroelectric power plants. Thermal power plants use fuel to boil water which makes steam. The steam turns turbines that generate electricity. Hydroelectric power plants use the great force of rushing water from a dam or a waterfall to turn the turbines. The majority of thermal power plants burn fossil fuels because thermal power plants are cheaper to maintain and have to meet less of the governments requirements compared to nuclear power plants. Fossil fuels are coal and oil.

The downfall of using fossil fuels is that they are limited. Fossil fuels are developed from the remains of plants and animals that died millions of years ago. Burning fossil fuels has other downfalls, too. All the burning that is required to turn the turbines releases much sulfur, nitrogen gases, and other pollutants into the atmosphere. The cleanest, cheapest, and least polluting power plant of the two types is the hydroelectric power plant. The main reason most countries use thermal versus the hydroelectric is because their countries don’t have enough concentrated water to create enough energy to generate electricity. (World Book vol.

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14, 586) Nuclear power plants generate only about eleven percent of the world’s electricity. There are around 316 nuclear power plants in the world that create 213,000 megawatts of electricity. (INFOPEDIA) Radioactive, or nuclear, waste is the by-product of nuclear fission. Fission occurs when atoms’ nucleus’ split and cause a nuclear reaction. (General Information) When a free neutron splits a nucleus, energy is released along with free neutrons, fission fragments that give off beta rays, and gamma rays.

A free neutron from the nucleus that just split splits another nucleus. This process continues on and is called a chain reaction. (World Book vol. 14, 588) The fission process is used to create heat, which boils water inside the nuclear reactor. The steam that boiling the water makes is used to turn turbines, which in turn, generate electricity. Fission happens inside a carefully monitored nuclear reactor, when being used in a nuclear power plant.

The fission process that nuclear power plants use spends approximately 30,000 tons of highly radioactive waste a year. (General Information) In a nuclear power plant, Uranium is used as fuel to boil the water for the steam that makes the turbines turn. So, uranium is, in a sense, the coal of a coal-fired power plant. When fueling nuclear power plants, the uranium arrives as uranium-enriched pellets. These pellets are an equivalent to one ton of coal. The pellets are sealed in tubes that are made of a strong heat- and corrosion-resistant metal alloy. This metal alloy will protect people and the environment from the high levels of radiation that the uranium is giving off.

The tubes are bundled together to make a fuel assembly. The assemblies are put inside the reactor to create heat that will boil the water. The fuel assemblies are used until they are depleted. A fuel assembly is depleted when it no longer gives off enough energy to turn the turbines. Once every year, one third of the nuclear fuel in a reactor is replaced with fresh fuel.

The used-up fuel is called spent fuel. Spent fuel is highly radioactive and is the primary form of high-level nuclear waste. (General Information) High-level radioactive waste is the by-product of commercial nuclear power plants generating electricity, and from nuclear materials production at defense facilities. This high-level waste must be isolated in a safe place for thousands of years so its radioactivity can die down and not be harmful to people and the environment. The name of the “safe place” that the Department of Energy is trying to make is called a repository. But until a repository is made, spent fuel and high-level waste is being stored in temporary storage facilities called dry casks and cooling pools.

By the end of the year 2000, there will be more than 40,000 metric tons of high-level waste in casks and storage pools. There will also be more than 8,000 metric tons of high-level waste from defense programs. The high-level waste from defense programs is currently being stored in Idaho, South Carolina, and Washington. (General Information) Reprocessing is the chemical process by which uranium and plutonium are recovered from spent fuel. This means that it is the recycling process of high-level waste.

The reason private industries aren’t reprocessing their high-level waste is because reprocessing costs more than mining and making new fuel. Several countries that actually care about their environment reprocess their high-level waste. (General Information) Dry casks and cooling pools are being used to store spent fuel in power plants everywhere. (Shulman, 14) Dry casks and cooling pools are only meant to be temporary storage facilities until a permanent repository is made. The need for a permanent disposal for high-level radioactive waste is becoming more urgent every year because the dry casks and cooling pools at nuclear power plants are filling up.

A dry cask is a concrete of steel container that protects the outside world from its radioactive innards. A cooling pools is a pools of water that the spent fuel is put into. The water is a radioactive shield and coolant. (General Information) The cooling pools were supposed to contain no more than 400 fuel assemblies, approximately 80,000 rods. The pools contain over four times as much of the spent fuel that they’re supposed to.

Nearly all of the nations older power plants are in this state of overload. In the late 1980’s, government industry researchers became concerned that if the rods were too closely stored in the pools, a nuclear reaction would occur. When researched further, the chain reaction theory became very remote. News of this resulted in even more densely packed cooling pools. (Shulman, 14) The cooling pools are a type of concrete warehouse.

Inside the warehouses are steel caskets containing the spent fuel rods and cooling pools. Scientists say that the cooling pool prevents the spent fuel to explode, but the extreme weight of the fuel inside the warehouses might cause the structures to rupture, especially in the case of an earthquake. (Shulman, 15) A repository is a storage facility that stores high-level nuclear waste deep underground so the waste can not harm or effect people or the environment. (DOE’s Yucca Mountain Studies) With the technology that we [humankind] have toady. Scientists believe it to be possible to make a repository somewhere. The guidelines of a repository are mainly if the geologic location will work out (i.e.

will an earthquake be able to rupture it, will water be able to corrode the repositories outer wall.). To make sure that the repository would be able to stay unscathed for thousands of years, scientists in all areas of science are making predictions of what could happen over the time period. According to U.S. Environmental Protection Agency (EPA) standards, a repository may pose no greater threat than unmined uranium from which the high-level waste was produced. The repository the DOE is wanting to make has to be proven that it will still be isolated underground in 10,000.

After this extensive time, the high-level waste should no longer be radioactive enough to harm the public health. (General Information) A rem is a unit scientist use to measure radiation exposure. Over a persons lifetime, they usually receive 7-14 rems of natural sources of radiation, such as cosmic rays and ultraviolet rays from the sun. On a single exposure of 5-75 rems, there are few to no noticeable symptoms. For someone to receive 75-200 rems of exposure, vomiting, fatigue, and loss of appetite would occur.

Recovery would take a few weeks. If someone were to be exposed to more than 300 rems, severe changes in blood cells and hemorrhage takes place. If someone were to receive more than 600 rems, symptoms would be hairloss, loss in your bodies ability to fight infection and usually results in death. (World Book vol. 16, 79) As you can see, the effects of radiation sickness is not too pleasant.

The main reason for building a repository is to keep people and the environment safe from deadly radiation. Bibliography “DOE’s Yucca Mountain Studies.” A repository is an enormous challenge. URL: http://www.ymp.gov/faq/facts/geninfo/y0343p.htm (4 Feb. 1997) “General Information.” What is nuclear fuel and waste? URL: http://www.ymp.gov/faq/facts/geninfo/Y338P.HTM (4 Feb. 1997) INFOPEDIA.

Vers. 1.5. Computer software. Future Vision Multimedia, 1995. IBM Windows 3.1, 30KB, CD-ROM.

Shulman, Seth. “Waiting Game for Nuclear Waste.” Technology Review Aug. – Sept. 1992: 14-15. World Book.

22 Volumes. Vol.14 and 16. Chicago: World Book, Inc., 1988.

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