Custom Search

Friday, October 23, 2009

Nuclear Power and Global Warming



1. Nuclear Power is not Greenhouse Friendly

While nuclear electricity generation entails no direct emissions of CO2 or any other greenhouse gases, the nuclear fuel cycle does in fact release CO2. Although these emissions are, at present, quite small in comparison with coal fired power stations (4% of equivalent size generation); they are considerably larger than alternatives:

Nuclear Power -
• releases 4-5 times more CO2 than equivalent power production from renewable sources
• releases up to 20 times more CO2 than saving the same amount of power with energy efficiency measures

(By Dr Nigel Mortimer, FoE 9, 1989)

This is because of the considerable fossil fuels use during mining, fuel enrichment, manufacture, and plant construction. It might be argued that future nuclear systems could achieve lower emissions, though as demand for uranium grew, CO2 emissions would again rise as ore grades declined.

2. Unsustainable - Fast Breeder Reactors and Uranium Reserves

Most publicity promoting nuclear power acknowledges that global uranium reserves are indeed quite limited when used in conventional thermal reactors.

“..used in the type of reactors now in operation, the world's uranium supplies that are recoverable at a reasonable cost would be unlikely to last more than 50 years”. (U.S. Dept of Energy, 1989).

“However, without drawing attention to the fundamental technical problems and substantially higher economic costs, fast breeder reactors are usually cited, quite glibly, as a means of transforming severely limited uranium resources into a much larger potential source of energy. In theory, the use of fast breeder reactors could increase the energy available by a factor of 60. In practice, it is now not clear how this would be achieved on an expanded global scale without encountering basic plutonium shortages, not to mention serious problems with waste disposal, power plant decommissioning and nuclear weapons proliferation. In fact, the fast breeder reactor is an essential component of the case for nuclear power. Yet, this case is built around a technology, which is not expected, by the nuclear industry itself, to be available for commercial introduction for another 20 years”. (UK Atomic Energy Authority).

Is nuclear power a global warming solution? Are there any ways to prevent global warming?

The main cause of global warming is the increased emission of so called greenhouse gases , in particular carbon dioxide (chemical symbol CO2). These greenhouse gases have an average lifetime in the atmosphere of 50 to 200 years. This means that even if we stopped the emission of greenhouse gases completely tomorrow, global warming would still continue.

In other words: It is impossible to stop global warming, it is only possible to mitigate its effects through a drastic reduction of the emission of CO2.

Can nuclear power plants mitigate the effects of global warming?

Nuclear energy is used to generate electrical power. Therefore it is only possible to reduce the emission of CO2 if nuclear power plants are used instead of other, CO2 emitting technologies. This is in particular the case for electrical generation plants fuelled by coal, oil or gas. The CO2 emission can indeed be reduced, if electrical power plants driven by fossil fuels are being replaced by nuclear power plants. However the application of nuclear power unfortunately is highly problematic, therefore the problem of CO2 emissions must not be looked at independently of all other risks and problems. See our text about pros and cons of nuclear power for a summary of the advantages and disadvantages.

How much can nuclear energy reduce the main cause of global warming?

The International Energy Agency (IEA) records the energy consumption world-wide and produces a forecast for the next 25 years. In their last energy outlook published in autumn 2006, IEA predicts a strong increase of the carbon dioxide emissions by the year 2030 as a consequence of the increasing demand for energy world-wide.

Additionally, IEA investigated to which extent the above mentioned emissions of CO2 could be prevented if politics applied rigorous measures. One of many measures investigated was massive facilitations and incentives for building additional nuclear power plants.

From all measures proposed, nuclear energy was found to have the smallest effect (only 10%). This result is even more remarkable facing the fact that IEA is known for having no reservations whatsoever against nuclear energy.

The chart below shows the effects of each proposed measure to reduce the main cause of global warming, the emission of carbon dioxide:

The following results attract attention:

• Almost 80% of the desired effects are due to increasing the energy efficiency (36% due to increasing the efficiency of the use of fossil energy, 29% due to increasing the efficiency of electrical appliances and 13% due to increasing the efficiency at the electrical power generation).
• 12% of the desired effects are due to furthering the generation and application of renewable energies.
• Only 10% of the desired effects are due to furthering nuclear energy.

This result is surprising, in particular if you think about how nuclear power is praised as solution to global warming by politicians like George W. Bush and Tony Blair. It seems like they would (again) head into the wrong direction.

Instead of talking about measures to increase the energy efficiency, which accounts for 80% of the effects, some politicians propagandize building nuclear power plants, which according to IEA can only account for 10% of the desired effects. Here the focus is clearly on the wrong subject!

Why is the focus on nuclear energy instead of energy efficiency?

Unfortunately, there is no lobby for energy efficiency, except perhaps some environmental organizations. The nuclear industry however, does have quite a strong lobby world-wide. If a politician asks for a higher efficiency of cars, he or she gets opposed immediately by the automobile industry (keyword work places). If the same politician suggests building nuclear power plants, he or she can even hope for some money for the next election campaign.

Why use nuclear power at all?

If the focus is put only to avoid the emission of CO2 and if all other side effects are neglected, then nuclear energy can indeed contribute to the solution. However the problem of climate change should be solved and discussed in a much wider context: It is important to limit our consumption of resources to such an amount which does not curtail future generations nor other beings on Earth. We finally must learn to live a sustainable living .

In this context, nuclear power plants are no solution at all. On the contrary, it would mean to shift from one problem (CO2 emission) to another and not less severe problem (nuclear waste, risk of nuclear catastrophes, limited resource uranium, and nuclear proliferation).

Dangers and Cleanliness of Nuclear Power Plants

Among the many departures from the truth by opponents of the Kyoto protocol, one of the most invidious is that nuclear power is “clean” and, therefore, the answer to global warming.

The cleanliness of nuclear power is nonsense. Not only does it contaminate the planet with long-lived radioactive waste, it significantly contributes to global warming.

While it is claimed that there is little or no fossil fuel used in producing nuclear power, the reality is that enormous quantities of fossil fuel are used to mine, mill and enrich the uranium needed to fuel a nuclear power plant, as well as to construct the enormous concrete reactor itself.

Indeed, a nuclear power plant must operate for 18 years before producing one net calorie of energy. (During the 1970s the United States deployed seven 1,000-megawatt coal-fired plants to enrich its uranium, and it is still using coal to enrich much of the world’s uranium.) So, to recoup the equivalent of the amount of fossil fuel used in preparation and construction before the first switch is thrown to initiate nuclear fission, the plant must operate for almost two decades.
But that is not the end of fossil fuel use because disassembling nuclear plants at the end of their 30- to 40-year operating life will require yet more vast quantities of energy. Taking apart, piece by radioactive piece, a nuclear reactor and its surrounding infrastructure is a massive operation: Imagine, for example, the amount of petrol, diesel, and electricity that would be used if the Sydney Opera House were to be dismantled. That’s the scale we’re talking about.

And that is not the end of fossil use because much will also be required for the final transport and long term storage of nuclear waste generated by every reactor.

From a medical perspective, nuclear waste threatens global health. The toxicity of many elements in this radioactive mess is long-lived.

Strontium 90, for example, is tasteless, odorless, and invisible and remains radioactive for 600 years. Concentrating in the food chain, it emulates the mineral calcium. Contaminated milk enters the body, where strontium 90 concentrates in bones and lactating breasts later to cause bone cancer, leukemia, and breast cancer. Babies and children are 10 to 20 times more susceptible to the carcinogenic effects of radiation than adults.

Plutonium, the most significant element in nuclear waste, is so carcinogenic that hypothetically half a kilo evenly distributed could cause cancer in everyone on Earth.

Lasting for half a million years, it enters the body through the lungs where it is known to cause cancer. It mimics iron in the body, migrating to bones, where it can induce bone cancer or leukemia, and to the liver, where it can cause primary liver cancer. It crosses the placenta into the embryo and, like the drug thalidomide, causes gross birth deformities.

Finally, plutonium has a predilection for the testicles, where it induces genetic mutations in the sperm of humans and other animals that are passed on from generation to generation.

Significantly, five kilos of plutonium is fuel for a nuclear weapon. Thus far, nuclear power has generated about 1,139 tons of plutonium.

So, nuclear power adds to global warming, increases the burden of radioactive materials in the ecosphere and threatens to contribute to nuclear proliferation. No doubt the Australian government is keen to assist the uranium industry, but the immorality of its position is unforgivable.

Safety of Nuclear Power Related to Other Common Risks

When people hear the word "nuclear," it usually conjures up a sense of intense fear. They associate that word with danger because they think of nuclear bombs, radiation sickness, cancer, Three Mile Island, and Chernobyl, to name a few. In the minds of many, nuclear power is an unsafe method of generating electricity that is to be avoided. In reality, nuclear power is much safer than other ways of creating power. Electricity can be generated from steam, and the methods to boil the water to create the steam include nuclear fission, the burning of fossil fuels (coal, natural gas, or petroleum), the combustion of natural gas or oil, biomass, geothermal power, other renewable sources such as hydroelectric power from the flowing water of dams of tidal forces, and wind. People are most familiar with the idea of getting their power from coal fired plants that move turbines by creating steam. They don't realize that this method involves much more risk to workers, the people who live nearby, and the environment than does nuclear power.

One of the first concerns about nuclear power is the possible risk to the people who work there. Most think that workers in nuclear plants suffer from problems with radiation. Many think that these employees will be radiated so much that they will all get cancer or have deformed offspring. In reality, nuclear power plant workers do not get much exposure to radiation because of safety regulations and work practices. The average U.S. radiation worker exposure is less than 300 milligram, which is not enough to increase cancer risk or other health risks.(UWM). All Americans in general get about 360 milligram of radiation exposure a year from natural radiation sources like cosmic rays, terrestrial, radon, and internal and from man-made sources like medical radiation and consumer products (UWM). Nuclear workers, as shown above may get as much as double that rate, but their cancer risk is not significantly increased.

In addition to cancer risks, people are concerned about the risk of death from accidents at a nuclear power plant. Compared to other industries, nuclear power death and injury rates are low. The mining industry records 24 fatalities per 100,000, agriculture 23, and construction 12, compared to an overall rate worker fatality rate of 4 for all workers ("High Risk Industries"). Other methods of generating electricity are not safer than nuclear power. A chart provided by the Next Big Future website compares risk of death per TWh for power generation as follows: oil37, coal25, lignite 18, peat 12, biomass 12, natural gas 5, wind 3, nuclear power 2, and hydro 1 ("Deaths per TWh',). With the exception of hydro power, nuclear power is the safest. A major nuclear accident is a concern, but safety regulations, training, and the nature of the nuclear fission process make such accidents almost impossible. No deaths or injuries occurred in the Three Mile Island incident, and as Stanford University Professor John McCarthy writes. The immediate death toll of 31 people at Chernobyl was small compared to the hundreds that die in regularly occurring coal mine cave-ins (5).

Workers at nuclear plants are subjected to many fewer risks than those who work in coal-fired plant sand substantially fewer risks than those who mine the coal for those plants. Even wind power, which might be thought to be harmless and safe, results in more and more gruesome injuries from toppling towers, broken blades and ice shards. The way a nuclear plant is run compared to any other type of energy plant is drastically different in amount of safety precautions. The nuclear plants are safer, have lower injury rates, and higher health standards. Excellent and extensive training in these plants ensures that workers know how to be safe.
Enhanced safety from nuclear plants not only includes that of workers but also that of people who live nearby. Inhabitants are exposed to less air and water pollution than those who live near a coal mine or coal-fired plant. No increased radiation exposure results to people who live near nuclear plants, studies find (BBC). The radiation that a normal person gets exposed to is not much more than a worker at a nuclear plant.

Additionally, people who live near nuclear plant shaven o increased health risks, especially as compared to other common neighborhood risks such as living near coal fired plants, coal mines, chemical plants, or large dams, or living within high-crime or high-poverty areas. Should a nuclear accident occur and land become inhabitable from contamination, Dr. McCarthy reminds us that at Chernobyl "about 20 square miles of land became uninhabitable for a long time. This isn't a lot". He goes on to say that although the radiation from the accident caused radiation exposure to Europeans", the largest estimates are in the low thousands which would make Chernobyl a disaster comparable to the Bhopal chemical plant or the Texas City explosion of a shipload of ammonium nitrate or the Halifax disaster during World War I. It is comparable to the
Number killed in coal mining accidents in the Soviet Union over the years Chernobyl was operating" (McCarthy 5).

As shown in McCarthy's article and in other studies, nuclear power plants simply do not increase health risk to anyone. As explained by Dr. Bernard Cohen of the University of Pittsburgh, "radiation due to nuclear technology should eventually increase our cancer risk by 0.002% (one part in 50,000), reducing our life expectancy by less than one hour. By comparison, our loss of life expectancy from competitive electricity generation technologies burning coal, oil, or gas is estimated to range from 3 to 40 days".

In addition to causing little or no risk to workers and residents, nuclear power also does not harm the environment. It is much safer environmentally than coal-fired plants. A small example of the kind of pollution that occurs from one coal-fired plant can be seen in the current argument over a new coal-fired plant in South Carolina. The head of SC's Department of Natural Resources opposes that plant because of its "grave" threat to human health. John Frampton is concerned about mercury pollution, carbon dioxide releases, and ash pond damage, which "present unacceptable impacts, costs and risks for the natural environment" (Monk l). Nuclear power plants have near-zero carbon emissions and, according to Paul Meier, director of the Energy Institute at the University of Wisconsin-Madison, are on the order of only I to 5 per cent of a coal plant…[preventing] 631 million tons of carbon from being emitted every year in the United States alone" (Kleiner 1). The advantages of nuclear power in the war against global warming are clear.

In considering risks to workers, residents, and the environment, nuclear power is as safe or safer as other common risks that occur at work, at home, and in daily life. The burning of fossil fuels is considered fine by most Americans; however, in actuality it is very harmful to people and the environment. Burning coal and other fossil fuels releases poisonous, destructive gasses that harm humans and destroy the atmosphere. In comparison nuclear energy is less harmful and more efficient than using fossil fuel.

Equal-sized amounts of uranium and coal do not produce an equal amount of energy. Nuclear energy yields far more power than coal, solar, wind, or any other alternative energy sources. Also, nuclear energy causes little if any environmental damage except in the very unlikely case of a nuclear accident or in disposal of waste products. It is free of air emissions which are the major cause of greenhouse gasses and global warming. Its benefits are high and its risks are low.
People, however, can be funny about evaluating risk. According to one travel site, the fatality rate per billion passenger miles traveled in a care is 7.2; the rate for an airplane is 2.0. ("Is It Better to Drive, Fly, Take the Train, or Take a Bus?"). However, many people who are tenified of flying to Texas, for example, will happily drive there without a thought about the true risk of their decision. If we can educate people about the actual risks of nuclear power compared to those of other power generation methods and make them really understand what it means, we can convince them that nuclear power will make them safer, healthier, and ultimately, happier. Nuclear power is much safer than other common risks, and it may be our only way to solve the global warming crisis that threatens our survival.


References Dr. Helen Caldicott. 2001. Nuclear Power Isn’t Clean; it’s Dangerous. Unknown. (w.y.). Energy information administration (EIA), official energy statistics from the U.S. Government. Unknown. March 2002. Environmental Policy Issues. Nuclear Energy Issues. Unknown. (w.y.). Is Nuclear Power a Global Warming Solution?. Time of Change.


The Interaction of Fossil Fuel and Nuclear Power Waste Decisions


There are three practical and significantly expandable forms of electricity generation: coal, natural gas, and nuclear. Oil and oil product based generation is less thoroughly discussed in this section because relatively high oil prices discourage use in quantity for power generation and are anticipated to continue to do so in the future. This is especially the case for base load power generation, the sub-market where nuclear power has been most attractive. Alternative and renewable power sources are insufficiently expandable to compete significantly with coal, natural gas, and nuclear power.

Coal and natural gas present parallel environmental problems, though the volume and proportion of particular emissions, for example sulfur dioxide or carbon dioxide, vary between them. Nuclear power is sufficiently different from oil and natural gas that the tradeoffs between nuclear power and fossil fuels (oil and natural gas) vary whether it is coal or natural gas that is replaced. In the case of coal, there is also a capacity to choose among fuels which are high or low in sulfur, ash, and other emission contents. Fossil fuels also permit variations in emission based on burner types, technology choices, and emission control equipment.

Sulfur dioxide emissions from coal-based power plants have been subject to “allowances” since 1995 under guidelines arranged under the Clean Air Act of 1990. An allowance is a permit for a power plant to emit one ton of a pollutant such as sulfur dioxide (SO2) per year. Allowances are allocated to specific power plants that produce SO2 emissions. Thus, if a plant has 5000 allowances for the year, at the end of the year its SO2 emissions must have must not exceed 5000 tones. Allowance allocation criteria have varied over time. Presently there is a “cap and trade” arrangement for power plant emissions. Allowances are marketable (tradable) among SO2 producing firms. If one plant produces less SO2 than its allowance limits, it can sell that allowance to a plant that cannot meet its limits. Overall emission levels (the cap) are regulated by government policy. Nothing is ever so simple, of course, and there are further components of the process that are not addressed here. In addition some regional allowance systems account for emissions other than SO2.

Allowances are usually allocated based on the energy content of the plant’s heat input, though there are exceptions and additions to these limits. There is thus less reward in the form of allowances to power plants that have higher thermal efficiencies. Allowances are granted primarily to power generation units that burn coal because natural gas burning units produce little SO2. Similarly, nuclear power plants are also excluded from the allowance system. New allowances have generally not been allocated to new power plants or for upgrades of existing emitting units. (This relates to the highly controversial topic of “new source review” regarding coal plant modifications.) The allowance system regulates overall emissions (caps) from units that presently operate. The allowance system does not directly reward firms that build non-emitting units because these units are not usually granted allowances, though the impact is similar, though indirect, as caps are tightened or as plants within the emitting category are permitted to expand.

Some local and regional nitrogen oxide allowances have been selectively considered for nuclear power plants during 2002 for upgrades in capacity. These allowances are minor in volume but would reward the plants for avoided emissions. Nuclear plant owners would be able to sell such allowance improving the profitability of their plants. Within the cap and trade environment this would mean proportionally less allowances being allocated to SO2 emitting plant owners or operators, provided the total cap is not expanded.

The results of any allowance re-allocations to nuclear plants would be complicated by the fact that owners of coal and nuclear plants are often the same corporations though the proportions of nuclear to coal plant ownership vary. Some fossil plant owners might see granting allowances to nuclear plant operators as increasing their own operating costs. Others might see allowances to nuclear power plants as a mechanism that would permit the prolonged and perhaps upgraded operation of their existing coal plants. The actual allocation system and any emissions cap might be anticipated to determine individual operator attitudes.

The Environmental Protection Agency (EPA) identifies the following average emission levels in the production of 1 MWh of electricity

Pounds of Emissions per MWh

Coal Oil Natural Gas Nuclear
Carbon Dioxide 2249 1672 1135 0
Sulfur Dioxide 13 12 0.1 0
Nitrogen Oxides 6 4 1.7 0

Source: www.epa.gov/clean energy/impacts

For fossil fuel-burning power plants, solid waste is primarily a problem for coal-based power. Approximately 10% of the content of coal is ash. Ash often includes metal oxides and alkali. Such residues require disposal, generally burial, though some recycling is possible, in a manner that limits migration into the general environment. Volumes can be substantial. When burned in a power plant, oil also yields residues that are not completely burned and thus accumulate. These residues must also be disposed as solid wastes. Natural gas does not produce significant volumes of combustion-based solid wastes. Nuclear does produce spent fuels.

Nuclear power produces around 2,000 metric tons/per annum of spent fuel. This amounts to 0.006 lbs/MWh. If a typical nuclear power plant is 1000 MWe in capacity and operates 91% of the time, waste production would be 45,758 lbs./annum or slightly less than 23 tons. The solid waste from a nuclear power plant is thus not the volume of the waste, which is very small, but the special handling required for satisfactory disposal. A similar amount of electricity from coal would yield over 300,000 tons of ash, assuming 10% ash content in the coal. Processes (specifically scrubbing) for removing ash from coal plant emissions are generally highly successful but result in greater volumes of limestone solid wastes (plus water) than the volume of ash removed.

The preceding discussion used averages. Different plants operate differently. This case is most stark for oil where products used to generate electricity range from rather heavy fuel oil to liquefied petroleum gas (LPG). These products produce different sulfur dioxide and metals emissions profiles. Sulfur content of oil products also varies considerably within category group, most notably fuel oil and gasoil (diesel). Coal is even more variable in energy, ash, sulfur, and metal content. Natural gas and LPG are more consistent in fuel character.

Any environmental gains from switching from fossil-based fuels to nuclear fuel thus depend on which fuel is replaced and which emission is of principal concern. While the gain in most airborne emissions between nuclear and coal is significant across the board, emission reductions increasingly focus on carbon emissions as one moves from solid to liquid to gaseous fuels. Within each fuel category there is also a potential to burn lower sulfur content varieties. Lower sulfur fuels thus present a partial alternative to replacement of generation capacity by nuclear power, if the aggregate (cap) emission level of sulfur is the policy goal. A more strict emission cap would be more attractive regarding nuclear power industry than a less severe cap.

The economic and environmental choice in regard to emissions reduction thus focuses on the relative value placed on fossil fuel emission vs. spent fuel production at a nuclear power plant and on the alternative sources of emissions mitigation compared to any added cost from nuclear power production. This view accepts the historic experience that nuclear power is more expensive to build than conventional fossil fuel units. The decline of new nuclear power plant construction since the 1970s and 1980s culminated in the completion of the last new nuclear power reactor in the United States in 1996 (Watts Bar 1). While as many as four construction licenses remain in effect (or are to be extended) until the early 2010s, there is little anticipation that any new nuclear plant reactor be completed prior to the end of the present decade. Reasons given for this decline include the relatively high capital costs of building new nuclear power reactors and an array of financial risks in building new nuclear plants.

The cost of building new nuclear power plants has historically been much higher than the cost of building fossil fuel based power plants. Vendors have recently advertised construction costs for building new plants that would ultimately cost less per MWe than new coal plants, especially coal plants with full practical emission controls in place. Advertised nuclear power costs per kWh delivered would also compete with natural gas based power plants. Presently no orders are in place for these reactors and the Nuclear Regulatory Commission has not yet licensed many of the newest designs. If the vendors correctly identify new nuclear power plant construction costs and if costs include full adjustments for financial risks, then there is diminished policy importance regarding the environmental gains of replacing fossil fuels with nuclear power. The nuclear plants would be economically viable and environmental gains would be an additional benefit rather than the deciding investment issue.

Conversely, if building new nuclear plants remains significantly more expensive than the cost of building fossil fuel-based power plants, environmental arguments for building nuclear power plants would carry less weight. Equivalent environmental mitigation might then be achieved at lower cost through refitting fossil fuel plants with emission controls, burning lower sulfur fuels, or replacing coal-fired plants with natural gas-fired plants.

Any environmental gains in switching power generation from fossil to nuclear fuels would thus be of greatest interest as nuclear power become economically competitive regarding operating and construction costs. The extent of such gains would vary with which fossil fuel is under consideration and how one evaluates the emissions avoided and gained. Coal has many unwanted emissions. Replacing natural gas with nuclear power would depend more on the relative evaluation of carbon emission compared to spent fuel disposal.

Nuclear Power Plant Wastes


There are restrictions on the disposition of such wastes. Restrictions are imposed through legislation, regulation, and the commitments of plant owner/operators. From a public perspective, such restrictions represent a collective measure of the cost and value of each type of emission. The rules do not represent the values that each individual places on the emission, thus opinions will vary on the adequacy of particular emission policies.

Restrictions usually vary with the type of waste. Because wastes produced from power plants vary with the fuel, potential environmental controls consequently vary with the type of power plant. There are also variations in the desired level control of some emissions from nuclear power plants. For example, coolant water discharges might affect temperature conditions in neighboring bodies of water. Such discharges alter the ecology of these bodies of water and it becomes a policy issue whether the change has a negative value and what that value is. The answer to such questions will determine what controls and expenses will be required related to that coolant water disposal. The levels of permitted discharge rules do vary by jurisdiction.
By far the greatest environmental waste concern at an operating nuclear power plant is spent fuel disposal. Because nothing is burned (oxidized) during the fission process, little fuel volume or mass is changed during nuclear power generation. The fuel exists under controlled conditions from the first insertion into the reactor until its removal from the reactor. This control continues until “final disposition” of the spent fuel. Disagreements can exist as to what constitutes final disposition though with most nuclear spent fuel that disposition is some form of burial. Burial is also the “final disposition” for most solid wastes from fossil fuel plants though restrictions on nuclear solid wastes are usually much stricter.
The nature of the nuclear fuel changes during power generation because generation produces fission and fusion products within the fuel units and also in materials neighboring the fuel units. Nuclear fuel becomes spent fuel when these fission and fusion products accumulate to an extent that the nuclear fuel is no longer adequate for additional power generation use. Considerable energy content of the fuel is unused in this process. There is ongoing disagreement whether such unused content is economically usable in the form of reprocessed fuel.

The spent fuel has different radiation and chemical characteristics from the initial nuclear fuel. These characteristics necessitate special handling of the waste above and beyond the handling of the initial fuel. Such handling requires expenses that are part of the costs of nuclear power production. Potential procedures for handling spent fuel vary. Procedures include recycling (reprocessing) substantial portions of the spent fuel as usable nuclear fuels and transmuting problem components of nuclear fuel into less harmful components. In some countries, for both policy and economic reasons, final disposition has targeted the ultimate burial of all spent fuels from nuclear power plants. Reprocessing and transmutation remain options that are under periodic policy consideration though such processes also involve the ultimate burial of spent fuel components. Reprocessing and transmutation would alter the timing, volume, duration, and conditions of such burials. They would also increase the costs of the nuclear power plant operation, probably significantly. The choice is between the costs of reprocessing and transmutation compared to the higher operating costs that these processes involve. Additional costs are involved because reprocessing has the potential of facilitating weapons proliferation.
The point and timing of Department of Energy custody of such waste is an active subject for the court system and for negotiations between power generators and the Department. Nuclear fuel disposal costs are funded by a surcharge on the cost of nuclear fuels. Charges are intended to cover the costs of disposal of nuclear wastes, though they are levied on power generation and not waste. The funds accumulated for spent fuel disposal have sometimes been identified as a public subsidy to the nuclear power industry. Whether this is the case depends very much on perspective and definition. Spent fuel disposal constitutes more extensive and direct federal government involvement in waste disposal than is the case for most other forms of power generation. Views favoring government involvement include special hazards from spent fuel and national security issues arising from reprocessed spent fuels which might be upgraded to weapons-grade conditions.

Economic subsidy issues also arise regarding whether the funds provided by nuclear power generators adequately cover the costs of the ultimate disposal of the nuclear wastes. Most spent fuels will be in temporary storage at the reactors where they were produced or in intermediate storage either at the reactors or alternative sites.

Nuclear Power and the Environment


Nuclear power has been presented as providing net environmental benefits. Specifically, nuclear power makes no contribution to global warming through the emission of carbon dioxide. Nuclear power also produces no notable sulfur oxides, nitrogen oxides, or particulates. When nuclear power is produced, nothing is burned in a conventional sense. Heat is produced through nuclear fission, not oxidation. Nuclear power does produce spent fuels of roughly the same mass and volume as the fuel that the reactor takes in. These spent fuels are kept within the reactor’s fuel assemblies, thus unlike fossil fuels, which emit stack gasses to the ambient environment, and solid wastes at nuclear power plants are contained throughout the generation process. No particulates or ash are emitted.

Waste from a nuclear plant is primarily a solid waste, spent fuel, and some process chemicals, steam, and heated cooling water. Such waste differs from a fossil fuel plant’s waste in that its volume and mass are small relative to the electricity produced. The waste is under the control of the plant operators and subsequent waste owners or managers, including the Department of Energy, until it is disposed. Nuclear waste also differs from fossil fuels in that spent fuel is radioactive while only a minute share of the waste from a fossil plant is radioactive. Solid waste from a nuclear plant or from a fossil fuel plant can be toxic or damaging to the environment, often in ways unique to the particular category of plant and fuel. Waste from the nuclear power plant is managed to the point of disposal, while a substantial part of the fossil fuel waste, especially stack gases and particulates are unmanaged after release from the plant.

Some fossil fuel-based emission can be limited or managed through pollution control equipment or procedures that generally increase the cost of building or managing the power plant either to the plant owner or to the public. Similarly, nuclear plant operators and managers must spend money to control the radioactive wastes from their plants until the wastes are disposed in an appropriate manner. An environmental component of any decision between building a nuclear or a fossil fuel plant is the cost of such controls and how they might change the costs of building and operating the power plant. Controversial decisions must also be made regarding what controls are appropriate.

The issue of whether nuclear plants actually present a net positive environmental gain compared to fossil fuels depends on the values that are placed on the wastes that each type of plant produces. Nuclear power provides an environmental benefit by almost entirely eliminating airborne wastes and particulates generated during power generation. Nuclear power creates a cost in the form of relatively small volumes of radioactive wastes that are produced that must be managed prior to ultimate disposal. Fossil fuels also produce unwanted solid wastes though the problems associated with these wastes differ from spent nuclear fuel. Neither waste stream is desirable. On a pound per pound basis the potential environment costs of waste produced by nuclear plant is usually viewed as higher than the environmental cost of most wastes from fossil fuels plants. The volume of waste from the nuclear plant is substantially less and better controlled. Any claim of environmental gain from nuclear power compared to fossil fuels asserts that the nuclear waste stream in aggregate is the lesser of two unwanted evils and that the electricity produced is worthwhile.

There are at least two alternatives for managing the waste streams from power generation. First, renewable or alternative fuels are available for power generation in addition to nuclear and fossil fuel generation. Such fuels carry their own positive and negative environmental effects. These power sources have not however demonstrated a potential to provide electricity in volumes that can compare to nuclear and fossil fuels, though they can contribute to any environmental mitigation programs.

The second consideration is demand management. Wastes associated with power generation would decline if less power were demanded. Because there are many ways to carry out specific economic activities, the energy requirements for each alternative also vary. Using less energy (or electricity) can result in desired environmental gains at lower costs. Demand management also recognizes that electricity follows daily, weekly, and seasonal cycles. Flattening such cycle can affect fuel use and fuel choice. Demand management is a separate question from fuel choice, though the two processes can be complementary. This is especially relevant to nuclear power vs. fossil fuel choices when demand cycles are flattened. Nuclear power is generally seen as a better fuel for base load (stable demand) conditions than for meeting cyclical peak loads. The same can however also be said for coal as a better base load fuel than as a peaking fuel. Leveling demand cycles might thus favor coal or nuclear power over gas or oil. Demand management might thus be an effective tool for controlling environmental emissions. It might lead to emissions, if more coal is consumed. Demand management is excluded here as a separate issue from fuel choice itself.

Forces in plane Redundant Truss - EXPERIMENT


INTRODUCTION

Definition; A truss is a structure comprising one or more triangular units which are constructed with straight slender members whose ends are connected at joints. A plane truss is one where all the members and joints lie within a 2-dimensional plane, while a space truss has members and joints extending into 3 dimensions.

In engineering, a structural member usually fabricated from straight pieces of metal or timber to form a series of triangles lying in a single plane. (A triangle cannot be distorted by stress.)
A truss gives a stable form capable of supporting considerable external load over a large span with the component parts stressed primarily in axial tension or compression. The individual pieces intersect at truss joints, or panel points. The connected pieces forming the top and bottom of the truss are referred to respectively as the top and bottom chords. The sloping and vertical pieces connecting the chords are collectively referred to as the web of the truss.
OBJECTIVE OF THE EXPERIMENT

To determine the forces in members of a redundant plane truss.

APPARATUS

1. A Redundant plane cantilever truss with seven members and 2 pinned supports.
2. A Screw jack for applying load to the truss.
3. An eight channels data acquisition system.



METHODOLOGY

1. Ensure that the pinned support is properly secured to the frame.
2. Attached the screw jack to the joint to be loaded.
3. Loosen the screw jack so that the truss is free from applied load.
4. Connect the wire from loaded cell to the data acquisition module, each load cell occupying one channel of the module. Connection of the load cell to the data acquisition module is shown on the data acquisition panel.
5. Run the wincp32 software.
6. Change the sampling rate from 10 seconds per sample to 1 second per sample of any other desired time interval.
7. Select the setting option to set the channels to be acquired and the conversion factor to covert mV output from load cell to Newton.
8. When the setting is complete, return to the main menu and press the start button.
9. Note the reading of the screw hack
10. Preload the truss by turning the screw jack handle tin the counter clockwise direction to apply load downward and observe the readings of the screw jack (for preload apply approximately 10N to 20N).
11. Allow the data to be recorded for approximately 20 Sec. this is the initial reading for each member. Alternatively record the data manually and fill the table below.
12. Increase the apply load by turning the screw jack handle in the counter clockwise direction and wait for 20 sec for the data to be recorded.
13. Increase the load for another 5 readings
14. Unload the truss by turning the jack in the clockwise direction.

RESULT


CONCLUSION

The force in member 1 and member 2 is having a less chance of error, however the rest of the members seems to be having a error when compared with theoretical calculations. In member 3, the percentage of error decreased as the force was increased, as well in member 4. Member 5 error was there at the beginning at slightly increasing as it progressed and than it decreased slightly when the load was increased. Member 6 and member 7 played a similar roll since they are both redundant members.

There can be error in the practical readings, possible instruments error, reading error since the values keeps on changing for all the members.

Tuesday, October 13, 2009

Role of Civil Engineers



Manage and direct staff members and the construction, operations, or maintenance activities at project site.

• Provide technical advice regarding design, construction, or program modifications and structural repairs to industrial and managerial personnel.

• Inspect project sites to monitor progress and ensure conformance to design specifications and safety or sanitation standards.

• Estimate quantities and cost of materials, equipment, or labor to determine project feasibility.

• Test soils and materials to determine the adequacy and strength of foundations, concrete, asphalt, or steel.

• Compute load and grade requirements, water flow rates, and material stress factors to determine design specifications.

• Plan and design transportation or hydraulic systems and structures, following construction and government standards, using design software and drawing tools.

• Analyze survey reports, maps, drawings, blueprints, aerial photography, and other topographical or geologic data to plan projects.

• Prepare or present public reports on topics such as bid proposals, deeds, environmental impact statements, or property and right-of-way descriptions.

• Direct or participate in surveying to lay out installations and establish reference points, grades, and elevations to guide construction.

Thursday, October 8, 2009

Modern Bridge







Modern Bridge, tested with 5 Kg (50 Newtons) and deflects 0.14mm approx. Using Balsa wood of 200 Kg/m3 and jointed with Adhesive. all the members are hollow and braced at the middle. Bridge designed using STAAD Pro 207 software with factor of safety 3.5.

competing the model with 70 other universities this model won 3rd place. competition was held in UTM, International UTM bridge competition was held every 2 years, and this is the 7th competition.

Bridge Designer ; Mohamed Vishal
"Cant FIND what your looking for!! Try Google search"
Custom Search