How Does Nuclear Energy Work
How does nuclear energy works? With nuclear energy means all sorts of phenomena which has energy production due to changes in atomic nuclei . Nuclear power, along with renewable and fossil fuels, is a primary energy source, which is in nature and is not derived from the processing of other forms of energy. Although some consider it a renewable source itself, the European Commission has recently expressed by saying that nuclear power is not considered as renewable.
The reactions involving nuclear energy are mainly those of nuclear fission, nuclear fusion and those related to radioactive materials (radioactive decay).
In the fission reactions (whether spontaneous or induced) nuclei of atoms with high atomic number (heavy), for example, uranium, plutonium and thorium break producing nuclei with atomic number lower, reducing its total mass and releasing a large amount of energy. The process of induced fission is used to produce energy in nuclear power plants. The first atomic bombs of the kind dropped on Hiroshima and Nagasaki, were based on the principle of nuclear fission. It should be noted that in this context the term atomic is absolutely incorrect, or at least inappropriate because the processes involved are contrary to the nuclear, involving the nuclei of atoms and the atoms themselves.
Fusion reactions in the nuclei of atoms with low atomic number, such as hydrogen, deuterium or tritium, fuse giving rise to heavier nuclei and releasing a significant amount of energy (much higher than that released in fission, with the same number of nuclear reactions involved).
In nature, the fusion reactions are those that produce energy from the stars. So far, despite decades of efforts by researchers around the world, has not yet been achieved in a stable, controlled fusion reactions on Earth even though it is developing the ITER project, a project that will give the successor DEMO create the first nuclear fusion in the world. However, it is now possible to obtain large amounts of energy through fusion reactions such as uncontrolled, for example, the hydrogen bomb.
The reactions of radioactive decay involving the nuclei of unstable atoms that, through processes of emission / capture of subatomic particles (radiation), they tend to reach a state of greater balance in consequence of the decrease of the total mass of the system. Those in which one has the greater amount of energy released are the processes of de-excitation range: the plots are generally high-energy photons, or electromagnetic radiation at higher frequencies (more precisely, even if there is overlap between the emission frequencies of X Origin range of atomic and nuclear sources).
Nuclear power is given by the fission or fusion of the nucleus of an atom. The first person who understood the possibility of obtaining energy from the nucleus of the atom was the scientist Albert Einstein in 1905. To extract energy from the nucleus of the atom there are two opposing processes:
merging (union) of light nuclei;
fission (breaking) of a heavy nucleus.
A process for obtaining energy from the atom is nuclear fusion. It is exactly the opposite of fission, instead of heavy nuclei break into small pieces, uniting them in light nuclei (from hydrogen, composed of a single proton) in heavier nuclei: the mass of the latter is less than the sum of the original, and the difference is emitted as energy in the form of gamma rays and high-frequency kinetic energy of neutrons emitted. The percentage of mass transformed into energy is about 1%, a huge quantity.
Because the merger takes place, the nuclei of atoms must be made to approach despite the electrical repulsion force that tends to reject them from each other, and are therefore required very high temperatures, millions of degrees centigrade. Nuclear fusion occurs normally in the nucleus of stars, including the Sun, where these conditions are normal. Because of these difficulties, the present day man is not so far succeeded in making the merger happen in a controlled and reliable if not for a few seconds (what there is uncontrolled: the thermonuclear bomb). The experiments are focused today on the merger of certain isotopes of hydrogen, deuterium and tritium, that fuse hydrogen more easily than common great-uncle.
Nuclear fusion is so far in the research phase, and after over 50 years of experimentation, the experts predict that the realization of an operational fusion reactor will require a few more decades.
Fission is the breaking of the atomic nucleus to make large amounts of energy result: when a neutron hits a fissile core (such as uranium-235) that splits into two fragments and released by two or three more neutrons (average 2 , 5).
The sum of the masses of the two fragments and neutrons emitted is slightly less than that of the original group and those of the neutron fission him: the missing mass is converted into energy. The percentage of mass transformed into energy is around 0.1%, ie for each kg of fissile material, 1 g is transformed into energy.
If next to the nucleus fission if they are in sufficient quantities and in other geometric configuration suitable (critical mass), will develop a chain reaction capable of self sustaining as a result of subsequent fissions of nuclei caused by secondary neutrons emitted from the first fission.
Nuclear fission of uranium and plutonium is widely tested and engineered for nearly 50 years. In August 2007, 439 commercial nuclear power reactors, producing 16% of electricity worldwide.  In the 30 OECD countries the nuclear power represents 30% of the total electricity produced. Apart from the risk of accidents, the biggest unsolved problem is the radioactive waste that remains dangerous for thousands if not millions of years.
The Nuclear Fission
Its operation is very similar to that of a conventional power plant with the difference that the water is heated by a nuclear reactor, where uranium is nuclear fission.
There are three main parts of a nuclear plant today:
-The reactor containment building: a huge concrete cylinder and / or steel in which the center is the cooling circuit and the reactor itself;
-Engine room means a building where they housed the turbines and the generator with their auxiliary circuits;
-Auxiliary buildings: the pools contain screens for the temporary storage of spent fuel and radioactive most central of the other auxiliary circuits required for the normal operation and emergency
The operation of a nuclear fission type boiling light-water (one of the most common) is quite simple: Water is pumped through the reactor core that causes it to evaporate through the heat produced by fission of uranium. The steam is then fed into the turbines, which then transfers its mechanical energy to the alternator which generates electricity.
Ballast means a confined space in which to place the fission reactions in a controlled manner. Since the 40s of the 900 were designed many types of reactors, with different characteristics and purposes. The initial aim was to produce material suitable for the production of nuclear arsenals, and only later on that reasoning was accompanied by the production of electricity. No coincidence that the countries with the largest number of stations are also equipped with nuclear weapons.
All reactors are equipped with a control bar system that allows you to adjust the reaction and therefore the power generated, as well as openings to allow insertion of fissile material and the extraction of "fuel" used. The whole is enclosed in a container full of water ferritic steel or another moderator (usually graphite) that allows the reaction to develop a regular basis. The water is very often used as a fluid, that is to cool the reactor core (which would otherwise fund) and at the same time-heater to generate steam to be sent to the turbines. In some reactors instead of plain water is used other substances, such as gas or metal alloys with low melting point (for example, containing sodium or lead). In any case, such as cooling fluids-radioactive-circulates in a closed circuit.
The "fuel" by far the most common is the enriched uranium (ie with a percentage of uranium-235 greater than normal), but not the only usable fissile materials: the reason we have developed reactors is U235 they produce plutonium, which is useful in times of an arms race. By contrast, the slag has a "life" much longer than non-example-if you were using thorium, as proposed by Nobel Carlo Rubbia.
The process of nuclear fission (like that of fusion, albeit much lower) produces highly radioactive waste materials. These pads of spent fuel (uranium, plutonium and other radioactive elements) that are extracted from the reactor to be replaced, and fission products. This material, emits penetrating radiation, it is very radiotoxic and therefore requires precautions in the treatment of disposal. The radioactivity of the materials extracted from a reactor is reduced over time according to the natural phenomenon, but half the time it takes to make it fit within standard acceptable organic to the human body are long. The radioactive decay times also vary depending on the element ranging from a few days to hundreds of thousands or millions of years.There are currently two main ways to dispose of waste, strictly linked to preliminary studies of geological hazards at the site of destination for low-level radioactive waste is a tendency to resort to the so-called surface deposit, or confinement in terrestrial protected areas and contained barriers within engineering; for waste with higher radioactivity level is used instead of the geological disposal, or storage in underground bunkers shielded. Also explored are the regeneration plants able to extract uranium, plutonium and other attinoidi (those children, mainly neptunium, americium and curium) from the dross and make it reusable in the process of nuclear fission.
The slag can also be reprocessed into other types of reactors (nuclear transmutation transmuters or conversion factor c <0.7) with desired collateral production of electricity. If they are reprocessed with the sole objective of reducing the radioactivity, you will need a period of at least 40 years to witness a decline of 99.9% of the radioactivity.
Another method being studied for transmutation of nuclear waste (ADS) is based on an accelerator of high energy protons (600 MeV - 2 GeV), coupled with a subcritical nuclear reactor, whose fuel rods as the material to be transmuted in the form of MOX or other. Again we assume the possibility that the system is energy self-sufficient, with the production side of energy.
The Nuclear Batteries
The nuclear batteries are small devices that can generate power through the radioactive decay of elements contained in them, mostly plutonium. They are used mainly in medicine (in some pacemakers) and in the aerospace industry, as it can provide a stable current and long-lasting (the stability is given by the decay of the radioisotope used and the durability is given by the stress of bombing ionizing particles from the material that generates electricity, typically a semiconductor).
Recently, promising studies have been done to improve the life of these batteries, using for example liquid semiconductors, which degrade more slowly than a solid state
COST OF ELECTRİCİTY FROM NUCLEAR
The generation costs per kWh are difficult to calculate because it affected mainly by the cost of the system and to a lesser extent by the price of fuel.
The costs of building a nuclear plant is known to be much greater than in any other station due to increased risks of operation and therefore of special security measures to be taken to reduce it, once built. according to some studies, a nuclear power plant can produce energy at costs similar to other energy sources. These studies base their conclusions by failing to account for certain costs would be more relevant because without a certain monetary quantification, between the costs of recall, for example, the following:
-harm to living beings in the areas of influence of facilities;
-long-term damage to the surrounding environment or interacting with the site;
-costs as radioactive waste storage;
-premiums to cover damage caused by accidents and disaster;
-risk premiums for delay in service.
Some jobs are agreed as follows:
-the impact of increased raw material costs and the entire fuel cycle, including spent fuel management, account for a modest total cost of production;
-nuclear fuel is no strong fluctuations in the cost also because of geopolitical contingencies as, instead, is the case of fossil fuels;
-uranium resources are available in sufficient amounts to continue the production of nuclear energy in the long term and stable costs (including in relation to different types of reactors currently existing or hereafter developed);
-capital investment should be recovered only in part.
According to other studies, nuclear power is economically disadvantageous, and the enormous capital required to build a plant and the complete management of the fuel cycle, can never be compensated by the production of energy. Paine said: "[...] The analysis suggests that even under the most optimistic (where costs are cut considerably and incomes rise significantly), the current generation of nuclear power plants in the course of their lives, they can succeed than to cover the costs
The main points in his argument are:
-it is unlikely that construction costs are recovered by the plant's operation, given its length and the expected gain;
-the cost of other energy sources (such as oil, natural gas, coal) is expected to rise so unrealistic that nuclear power becomes competitive (while the cost of renewables, already lower in some cases, is set to fall more and more is the improvement of technologies);
-the plant rarely operates at full capacity, it is usually only used in part (Paine says that 58% is the norm) because some facilities must be periodically stopped for security checks. Increase this percentage will inevitably expose us to a risk;
-on balance, nuclear power would be a worthwhile investment only in the most optimistic scenarios (maximum lifespan, improved technology, operating costs and energy).
Paine does not discuss issues of environmental and economic externalities, such as waste disposal. He laments the fact that accurate data on the economic cost in terms of atomic energy are not available to the public.
On the other hand, construction costs are not easily predictable: Whereas 75 U.S. plants completed, it was found that the actual total construction costs were 145 billion dollars compared with 45 expected, initially in India, the funding planned for last ten plants increased by 300%. The cost is very dependent on the time necessary, that a study of the World Energy Council (WEC) on the plant under construction in the world between 1995 and 2000 were found to be increased from 66 to 116 months. This should be the increased complexity of the systems.
The price of a nuclear kWh ultimately amounted to about 6.1 euro cents, according to conservative estimates by the U.S. Department of Energy, including an estimate of the costs of waste containment: This is not only a much higher price kWh to that of a coal or gas, but also the wind and biomass. To assess this data, you need a more general comparison with the costs of all other alternative energy sources, especially in the medium to long term.
For many, the final and incontrovertible proof of the non-cost electricity from nuclear fission is that for decades no private company has decided to build a new power plant, except where there are large state subsidies as a result of a deliberate choice purely political (see in the case of Finland), as certain sources (eg solar), which without State funding would have no economic benefit, except in special cases. In 2009 there were in fact different waivers by power companies: for example, MidAmerican Nuclear Energy Co, which operates in Idaho, gave up the realization of its plans to expand the number of reactors, the AmerenUE, which operates in Missouri and Illinois, also has given up the construction of an EPR.Both companies have shown that the high cost of implementation for the time would not result in a reduction in the cost of electricity. However it also pointed out in recent decades, many plants have been strengthened with the addition of new reactors at the same site and increased significantly the production of electricity from nuclear plants.
The Cost Of Electricity From Nuclear Plants
Modern experience shows that the cost of each kWh of electricity generation remains uncertain until the actual start of the installation in almost all Western countries. Although estimates construction costs affecting between 70% and 80% of the electricity generated only when the system started, you can attribute the higher cost of funding due to construction delays. Fuel costs and the operational impact and then the remaining part (20-30%). The fluctuations of the uranium market still tend to have little influence on the final price of energy generated.
In 2008, for example, Areva said that the cost of fuel for its reactors EPR only accounted for 17% of generation costs. In January 2010, according to the World Nuclear Association (WNA), the approximate cost of 1 kg of UO2 (uranium as fuel burning rate (burnup) amounted to 45,000 MWD / MTU) was $ 2,555 / kg, while the cost of refined ore (8.9 kg U3O8), which is required to produce 1 kg of uranium oxide fuel, amounted to $ 1,028 / kg, about 40% of the final cost of nuclear fuel, from which it follows that 'impact on costs of electricity generation is equal to $ 0.0071 / kWh. Changes in the retail price of refined mineral extraction (yellowcake) have modest influence on the total cost of generation.
A recent (2009) study of the Massachusetts Institute of Technology has shown, for installations of new construction, the cost per kWh is higher than nuclear, gas and coal. These costs of electricity generation have grown in recent years, although those relating to nuclear power less than gas and coal. The main difference between the cost of generation of nuclear plants and those of coal and gas are the following:
-nuclear power plants require a substantial investment significantly more than the others;
-in the western states suffer long construction times and unpredictable expansion in time due to popular protests and design problems (phenomena "not present" in countries such as South Korea, Japan and China);
-in addition to higher costs resulting from frequent delays in operation, assessed the financial costs leaving more for nuclear power plants than the other, serving as the highest risk with higher interest rates to investors (interest on capital provided valued at 10% for nuclear against 7.8% for gas and coal and entire cost of the financed with no money of their own).
He concludes that: "Reduce or eliminate this risk premium makes a significant contribution to make nuclear competitive. With the risk premium and without a carbontax, nuclear is more expensive and coal (without CCS) or natural gas (7 $ / MBTU). If this risk premium can be eliminated, nuclear power and decrease its cost becomes competitive with coal and natural gas, even in the absence of carbontax. The report of 2003 found that a reduction of the initial capital is possible but not proven and that the risk premium is removed, only with proven performance [in the construction of amenities in terms of estimated
The location of the site affects the economic outcomes of a unit: in the presence of a large number of nuclear power stations and a production already in use (as in the U.S.) the unit cost of generation is lower.
At the cost of creating the installation, maintenance, power generation and decommissioning (this item has a very wide range of cost per kWe, since the variables at stake are the power, the type and the operational life of the plant) there be added the costs of waste disposal. These costs are still unclear since we do not find definitive solutions are still working for the long term for waste Category III (if different to those of I and II, of which there are many storage sites already in operation for decades), because are either under study or in the process made some final repositories, but none of them are still active. Inside this variable is to add the factor of reprocessing spent fuel, on the one hand this greatly decreases the volume of radioactive waste from having to store the other decreases significantly the period of radiotoxicity, as it is removed the plutonium decays very slowly and is very radiotoxic, thus giving less of a problem for storage (but not deleted).
Nuclear Energy Balance Electric
You can not say with absolute certainty the energy balance of the entire nuclear power, because the entire process, from extraction of fuel until the fission, can consume more energy than produced. In addition to this not all the uranium mining is derived exclusively from uranium mines, but is also partly a byproduct of other mineral processing (in the case of the uranium mine in South Africa or the Australian Olympic Dam), in which is difficult to calculate the energy cost of production only separated from the uranium production of other minerals.
This end is called EROEI energy balance and a nuclear power plant can vary from less than 1 (negative output) up to 100 or beyond (report very convenient). The factors leading to this are many: the concentration of the mineral in the rock, the fuel enrichment, the method of enrichment (the gaseous diffusion consumes about 2500kWh for SWU, compared with about 60 kWh of centrifugation), the life of the system ( Since the energy cost of construction and decommissioning of fixed, spread their electricity production on a greater or lesser degree), the conversion ratio of the reactor (the higher, more fissile uranium you can not burn, and if> 1, the breeder reactor becomes ), the energy efficiency of reactor. A negative EROEI can be advantageous only in certain areas, such as naval propulsion, because you concentrate so much energy in a short volume.
Nuclear power was also one of the lowest external costs, for example in terms of environment and people, although such estimates are extremely unreliable because the main cost, namely the confinement for centuries or millennia of thousands of tons of radioactive waste in secure sites (along with the decommissioning of old power plants), presents insuperable uncertainties. For supporters of atomic energy, however, it is the only source of energy in total costs explicitly includes the estimated costs for the containment of nuclear waste and decommissioning the plant (but these costs are difficult to estimate and past estimates to downward will force governments to spend public money to pay for the disposal of hazardous waste), and said the cost of fossil fuel plants is low so misleading for this reason, the Kyoto Protocol, putting in the costs of environmental externalities in terms of effect emissions, should correct this issue: nuclear power, considering the external effects associated with each way of producing energy, would be an economically competitive and environmentally friendly way to produce energy by replacing fossil fuels.According to some estimates, the United Kingdom for example, the external costs for nuclear power, with regard to global warming, public health, occupational health and property damage amounted to 0.25 euro cents per kWh, that is little more than 's Wind (0.15 euro cents per kWh), but much less than for coal (from 4 to 7 euro cents per kWh), oil (3 to 5 euro cents per kWh), gas (1 to 2 euro cents per kWh) and biomass (1 euro cent per kWh)
The Problem Of Insurance Costs And Legal
Given the extent of the risks involved, in most countries, nuclear power can not be ensured only by private insurers, because of high projected costs in the case of a serious accident: no insurance company. In 2005, the U.S. government has set at $ 300 million the maximum amount stipulated for insurance in this field, while the risk of a serious nuclear accident would be much higher (although this has not happened in the case of Three Mile Island). For this reason, governments need to support their insurance costs. This practice is similar to that for banks, which are also supported by government guarantees of compensation for depositors in the event of failure.
The law Price-Anderson Act, the first comprehensive law on nuclear liability to the world, is crucial in resolving the issue of liability for nuclear accidents since 1957. Is renewed every ten years or so, with strong support pole, and establishes that individuals are responsible for two levels of insurance coverage:
1. The first level concerns the requirement for each nuclear site to sign a policy with coverage of $ 300 million from private insurers;
2. the second level, if required, meet together all operators of reactors in the United States, this level is financed through retroactive payments of up to $ 96 million for each reactor, collected in annual installments of 15 million and adjusted for inflation tenenedo .
The total exceeds 10 billion dollars (9.5 billion the Department of Energy provides to its nuclear activities). Regardless of responsibility, the Congress, as insurer of last, must decide how to arrange compensation if the requests exceed the amount covered 10 billion. In 2005, the law has again been renewed by Congress in the Energy Policy Act of 2005.
A criticism that is sometimes raised is that more than 40 years of research have failed to create an area safe enough to cover its insurance costs. Proponents of nuclear power, however, assert that this issue will be addressed by projects such as safer pebble bed modular reactor.
Comparison With Other Energy Sources
The cost of nuclear power also depends on the costs of alternative sources: for this in many countries, if atomic energy is not popular in times of rising prices for fossil fuels, the arguments in support of nuclear power re-emerge .
In some places, especially where the mines are far away from the ski, atomic energy is less expensive, while in others it is to have a price approximately equal to or greater. The same comparisons can be made with oil and gas.
In addition, the declared cost of many renewable energy would increase if it had included the provision of sources of reserves needed during periods when the intermittent nature of sun, wind, waves, and so does not allow to produce energy. Considering this has been calculated that wind power, one of the greatest hopes for the abandonment of nuclear power, would cost three times the average cost of electricity in Germania.D 'On the other hand the connection of all the national electricity system is used to compensate the lack of production of a temporary site with the surplus of another, making it manageable, the issues of these sources. It should also be pointed out that production from solar energy would be perfect for powering air conditioning systems because the energy input would be "synchronized" with the availability.
ENERGY POLİCY İSSUES
In some nations may be no alternative, according to some. As the French say, "we do not have coal, we do not have oil, we do not have gas, we have no choice." Critics argue that the abandonment of nuclear power plants could not be replaced and provide an energy crisis, or argue that only nuclear power could replace coal, but CO2 emissions will increase alarmingly (with the use of oil and fossil fuels) and you should import energy or nuclear or oil. Nuclear energy was not significantly affected by embargoes, and uranium is mined in countries as "safe" countries like Australia and Canada, in contrast to other, as some large natural gas suppliers, including the former USSR .
As regards cost, it is known that in recent years fossil fuels like oil had a significant increase, which led for example in 2005 the average cost of electricity in the United States to 5 euro cents a kW. h. In the production of electricity from nuclear power, the cost of fuel is, at least currently, a dominant voice of the total costs (construction, security, etc..), But see below for the availability of uranium.
For many, the reasons for the rejection of the use of this energy source are to be found mostly in the strong pressure that the oil lobby has on governments, since the use of nuclear energy would lead to a significant reduction of dependence on fuel fossils, and of course industry groups that base their work on their business.
Avaılabılıty Of Uranıum
The fissile fuel costs could increase considerably in the future as it is difficult to accurately estimate the reserves of uranium still pull in an economic way. Some consider that the reserves will be enough for a few decades at current prices. Some estimates say then proven reserves of uranium economically exploitable with current technology be enough for another millennium, valuing Gtoe 200 (billion tons of oil equivalent), compared to 300 Gtoe total oil and natural gas.
For nearly five decades, from 1950 to 2000, the price of natural uranium oxide (uraninite and pitchblende UO2 U3O8, also called yellowcake) was generally low and almost always down considering the price adjusted for inflation, except for the second half of the seventies, when he came to equal that of all other raw materials following the oil crises of 1973 and 1979 . This favorable situation was a clear sign of increasing availability, despite steady growth in consumption.
However, in the first decade of the century this trend was abruptly reversed by increasing the price of the equipment to levels never reached before (even considering the inflationary effect on the dollar) in a few years it has gone from less than $ 10 / lb in 2002 to more than 130 $ / lb in mid 2007, with a subsequent drop to around $ 85 / lb in 2008 had increased because of the overlap in new nuclear programs and closure of some Canadian moniere, which led to a contraction of
The nuclear power plants currently consume about 81.000t of uranium oxide, which is then slightly enriched (2% -4%), compared with a production of 60,000. Many speculators are betting on a rise in short-term uranium price and then invest their money in the exploitation rights, mining companies are considering the idea to reopen many mines or seams abandoned as uneconomic in the past (eg ' extraction of phosphate) and on the contrary that may now be very profitable.
It is believed that this sudden increase in price is attributable to the reduction of uranium from the dismantling of Russian nuclear weapons and increasing demand of uranium, which reduced the producers' stocks. The increase in mining activities should also reduce the cost of raw materials in 2001 (before revaluation in recent years) accounted for only 5-7% of total production costs of nuclear power.
There is also the theoretical possibility of extracting uranium from seawater according to the scheme devised by the Japanese T. Kato. If this system will mature technical and economic availability of uranium will become virtually unlimited on a human scale, when this process is uneconomic compared to mining. Another way is to extract uranium from the ashes of coal, road has already been done successfully in China
Beyond the amount of uranium available in the world, there are some types of nuclear reactors already commercially available that reduce or even eliminate entirely the need for new uranium mining.
They are primarily three:
1. i reactors that can use MOX as a fuel;
2. fast breeder reactors (FBR, Fast Breeder Reactor) in uranium-plutonium cycle that significantly raise the efficiency of uranium usage since they produce more fuel than they consume . The innovation introduced by this technology takes advantage of converting non-fissile isotope uranium-238 (about 140 times more abundant fissile isotope with mass number 235) of plutonium-239. However, the plutonium (depending on its isotopic composition, and very poor if different from the isotope plutonium-239) is material suitable for making weapons is generally classified as toxic if inhaled or ingested, due to its radioactivity and the Being a heavy metal, its production is difficult because of the complexity of the specific reactors used. One of these reactors was French Superphénix (owned by ENEL to 30%), now closed for political reasons and to have completed its cycle of experimentation, while others are still operating. Recently, interest has grown because the depletion of uranium and its price increase would make them very affordable and are therefore underway to new generations who are expected to be available from 2030;
3. T he slow-neutron breeder reactors using thorium mixed uranium as nuclear fuel through a process of fertilization of thorium-232 (to convert it into fissile uranium-233) similar to that of uranium-plutonium cycle. Since thorium is more common than uranium in the crust, then it could provide more fuel for centuries. Another advantage is with regard to proliferation because they are not yet been studied techniques to produce nuclear weapons from the scraps of thorium-uranium cycle. In India, the study breeder reactors of this type. The choice of this fuel is good due to the presence of exploitable mines on its territory.
Key in the future, other types of nuclear power plants, where they will reach maturity in technical and commercial, can make even more irrelevant to the question of the availability of uranium. They mainly consist of:
1. Fast fission reactors of the fourth generation (planned for 2030) they will use as fuel, metals other than uranium;
2. Amplifier power (in English EA Energy Amplifier or ADS Accelerator Driven System), based on assisted subcritical fission, which will only use thorium as a fuel (given the difficulties of operating experience so far and especially the low amount of energy reactor that produces, but it seems much more useful to burn radioactive waste produced by a traditional LWR, as required by the projects TRASCO and EUROTRANS);
3. Thermonuclear fusion reactors (hot), with the first row in the ITER project that is estimated to produce a first working prototype (called "DEMO") by 2050;
4. Cold nuclear fusion reactors (which, at present, however, are a total unknown, moreover, the same as cold fusion).
The promoters of nuclear power argue that it is possible to increase relatively rapidly the number of plants: on average the construction of reactors next generation lasts three to four years, according to others they are no less than five, and in any case is very more than it takes to build such a power plant to natural gas (one or two years). The only construction costs, which amount to at least two billion dollars to the central, combined with long-time, make in any case very difficult to significantly increase the production of electricity from nuclear power in the short term: to double the U.S. production as many argue that should be done would cost a trillion dollars.
Some supporters of nuclear demolish objections based on the characteristics of future nuclear fusion power plants: the project (ITER) but aims to reach only a prototype in 2030 and a commercial center in 2050, although the date of possible use of thermonuclear fusion for power production was postponed for decades), so it is unrealistic to consider them within a national energy policy for decades to come.
Centralized And Distributed Generation
Since nuclear power plants usually have a higher power than any other type of power plant (you can of course also build small "size" but for reasons of economy of scale, we prefer almost always produce larger plants), this generating method of putting a greater emphasis is the concentration of production.
According to some thinkers, the current model of centralized energy production makes first major investments necessary for the construction and maintenance of distribution networks and secondly it would create a strong power of control by a few producers on the security and continuity of energy supply utilities.
With this in mind, these thinkers believe that the only way to avoid this is to distribute widely the production (and the rising price of fossil fuels would be a good opportunity to adopt this new model) for scattering throughout the small production facilities close to consumers, something made possible by the development of technological knowledge on the renewable energy (and type nuclear reactors pebble bed) which are those which lend themselves to development in light of the objective mentioned above.
In fact, a careful examination of the facts, the situation would prove to be diametrically opposed as:
1. In a liberalized energy market with centralized production and distribution at a distance is possible for users to choose from time to time the vendor that provides the best service and the small plant in a logic of distributed generation would inevitably be the local monopolist ;
2. With centralized generation can have economies of scale, with no distributed generation;
3. Renewables alone can satisfy only a fraction of the energy requirements and therefore most of the production would be distributed using fossil fuels;
4. The greater the number of plants, the higher is the pollution that they produce a total.
So far from being the panacea hoped for by some, distributed generation would in essence only to increase the price of energy, decrease the quality of service and increase pollution.
The main concerns due to the use of nuclear energy for electricity generation about the impact on the environment and safety.
Some nuclear accidents in the past have caused radioactive contamination. The most serious accident, the Chernobyl disaster, 'he killed people, caused injuries and damaged and rendered unusable for decades large tracts of land. It is feared that other incidents could happen in the future (even if the recurrence of a serious accident such as Chernobyl 'is technically impossible).
Other criticisms focus on the risks of radioactive contamination during the extraction, enrichment, waste disposal and long-term storage of spent nuclear fuel. Accidents in these areas are much less known, but not rare and include some of the most serious incidents in the postwar period to today (Windscale / Sellafield, Tricastin etc...) The strict observance of the precautionary principle would suggest to take into account only those technologies that prove not to cause significant harm to the health of the living or the biosphere.
Another problem is the large amount of water needed for cooling and hot water entering the water bodies that in some ecosystems may be hazardous to the health of aquatic life, as certain species of fish already at risk of extinction. These difficulties can be greatly reduced using cooling towers, which are usually located in places where it is considered unacceptable excessive heating of the water or there is shortage of water to cool the condenser of the plant, or building power plants near the sea where the availability of water is almost always assured.
This problem only partially shared by the nuclear plants in the thermoelectric power plants. On the one hand, the thermodynamic performance of a nuclear plant is much lower than that of a modern thermal power plant (30-35% vs. 60%), and therefore the same thermal electricity discharges are about double. The other, a power plant may, by type and location, be connected to district heating (CHP), taking as an additional dividend of heat instead of dispersing into the environment. These applications are not practically feasible for nuclear installations.
Air Emissions And Greenhouse Gases
Nuclear power plants, despite not having the flue gas emissions from power plants such as common, they release small amounts of radioactivity into the atmosphere in the form of both liquid and gaseous discharges, in particular tritium, isotopes of cesium, cobalt, iron, radio and strontium, and these issues persist even after decades of plant closures in amounts ranging from thousands to hundreds of millions of becquerels). There are also emissions of large quantities of water vapor coming from the cooling towers (only present in some plants).
Recently there has been a renewed interest in nuclear energy as a solution to diminishing supplies of oil, because the demand for electricity is increasing, and nuclear power generates few greenhouse gases (during extraction, preparation and transport of nuclear fuel and construction, maintenance and decommissioning of plants), contrary to common alternatives such as coal have been discussed nuclear energy as a solution to the greenhouse effect). On this basis the European Union recently called on nuclear power as an important tool in the fight against global warming. This claim is disputed by many environmental organizations.
Nuclear reactors do not emit greenhouse gases directly during normal operations, but the uranium mining and processing generate considerable emissions. According to the association of the nuclear industries (WNA), emissions throughout the life cycle would be comparable to that of wind energy and hydro power, but much lower than photovoltaic. However, a controversial issue is that greenhouse gas emissions due to mining, processing and enrichment could be much higher in the future as the world's uranium reserves of high quality will gradually peter out and will use more uranium low quality.
In a 2000 document commissioned by the Greens in the European Parliament entitled Is Nuclear Power Sustainable? ("Nuclear power is sustainable?") And in the document following the May 2002 initolato Can Nuclear Power Provide Energy for the Future, Would it solve the CO2-emission problem? ("Nuclear energy can provide energy for the future? Would solve the problem of CO2 emissions?"), Jan Willem Storm van Leeuwen and Philip Smith argued that the cost of nuclear power in the end will exceed that of fossil fuels in the emissions of greenhouse gases as ore uranifero shortage of high quality. The two have questioned its sustainability within an environmental protection plan.This document has been dismissed as false by the nuclear industries because the published results on the extraction of the mineral shows a benefit of 99% of the generation of nuclear energy against fossil fuels on the slope of CO2 emissions. The authors have alleviated a lot of the allegations contained in their document and they re-released in 2005, omitting most of the numerical values used, but the remaining claims are still contradicted by some studies on the life cycle (eg Vattenfall). All this puts into question the very article for which forecasts are thought to be wrong because they are based on evidence belied by current data, sometimes 3:1. It should be noted that the statements are based on the mineral industry of high quality currently available, while those of Storm van Leeuwen and Smith based their projections on the quality of ore available in the future.
Germany has supported the abandonment of nuclear energy and renewable energy development will increase the efficiency of fossil power plants to reduce reliance on coal. According to the German minister Jürgen Trittin in 2020 that will cut carbon dioxide emissions by 40% compared to 1990 levels. Germany has become a model country for its efforts to comply with the Kyoto Protocol. Among other things, Germany achieved excellent results in energy savings, thanks to efforts from the energy crisis of the seventies. Critics of German politics is regarded as a contradiction to the abandonment of nuclear energy for renewable energy, as both have very low emissions of CO2.
All other waste products of nuclear power plants are collected and stored in isolation, unlike other energy sources like oil and coal residues of which pollutants are released directly into the surrounding environment. Without nuclear power, if they were forced to replace them with fossil power plants, each year the United States produce nearly 700 million metric tons of carbon dioxide in addition, an amount roughly equal to the amount of carbon dioxide produced annually by U.S. automobiles.
Have not yet been completely solved the problems related to the containment of nuclear waste in the long term. In fact, once the fissile material present in the spent fuel, are products of chain reaction, but which are not fissile radioactive. These products are a range of isotopes with half-life varied, but may even be a few thousand years: the waste produced by reactors remain radioactive for a long time, until the extreme case of Cesium 135 (135Cs), which employs 2.3 million years for half of its radioactivity. Nuclear waste also have a minimum volume (a typical nuclear power reactor produces about 25 tonnes of spent fuel amounts to about 3 cubic meters, equivalent to 28 m³ once deposited in a barrel ) and terms of volume are less than 1% of highly toxic waste in industrialized countries over time, although their toxicity is not comparable.
The amount of waste could be reduced in several ways, either by reprocessing and nuclear fast breeder reactors, subcritical reactors (fission or assisted, power amplifiers, accelerator driven system or drag EUROTRANS if you prefer) and the fast breeder reactors ( FBR) can greatly reduce the confinement time is waste neoprodotte, both existing ones. 96% of highly radioactive waste could be recycled and reused if the additional risks of proliferation should be deemed acceptable. These projects are further elaborated in the early nineties, and provide two alternatives:
1. Incineration , ie the bombardment of radio-isotopes with neutrons produced by "spallation" to hit a target with protons accelerated by a special particle accelerator (accelerator driven system);
2. Hit the radioisotopes with gamma rays produced by a special laser.
Despite considerable investment in time and money, has not yet come to final results on these procedures, which still require investment in the order of half billion euro per plant, thus casting further heavy cost of the unknown ' nuclear electricity. Plutonium, which is contained in spent fuel rods, in the plant extract is similar to that Areva La Hague (France) or to BNFL at Sellafield (United Kingdom).
It is necessary to provide storage areas in which radioactive isotopes (radioactive third class) have the time to decay, is the ultimate storage sites for storing the remaining radioactive material (waste first and second category, ie with a 'half-life of less than 300 years). In the case of reprocessing of irradiated fuel, the latter are preserved in the superficial deposits of cement that after nearly three centuries, when the radioactivity of waste becomes comparable to natural background, are permanently covered with earth. Despite being a very controversial point, supporters of nuclear power argue that the solution of underground disposal (geological), standing (that is reversible or irreversible) of waste "dry" (ie without prior reprocessing) or those of third category in the case of reprocessing - an idea that several countries have already taken into account - is well tested and proven, point to the Oklo natural example of the natural deposit of radioactive waste, where waste is confined to about 2 billion years with a contamination minimal surrounding ecosystem.
Nuclear waste, although very little in terms of lasting radiotoxicity are also large parts of the structures of nuclear power plants. The radioactivity induced by neutrons and elements, but short-lived high activity, issued daily by the operation of the cooling cycle parts in contact with the primary fluid, determine the technical necessity to avoid high costs and risks to staff, wait for long periods after the end of manufacturing operations and shutting down the reactor before dismantling.In England, where plants such as Calder Hall are planned closure of one hundred years after shutdown, the cost of dismantling promises much lower (several tens of times smaller) than serving reactors such as the Italian, whose dismantling "accelerated" was decided for political reasons in the thirteenth legislature, by a decree of the then Minister Bersani, for which the cost of dismantling will be the end of two or three times that of construction.
In many countries has not yet been established who is to cover the operating costs of nuclear waste containment areas. At the moment it seems likely that, at least in Germany, the state will pay the direct costs for waste (empty bars) and contaminated materials or plant products in the extraction of plutonium and uranium, as well as other nuclear waste, because ' industry does not have sufficient means. In the United States, utility companies pay a fixed tax per kilowatt hour in a fund administered by the Department for disposal for energy.
In Britain, in April 2005 this issue led to the creation of the National Authority for dismantling.
The safety of nuclear power plants has often been questioned, since the most visible structures, such as cooling towers, are fragile and could be easy targets for terrorist attacks, for example by using kamikaze airliners to hit them (this has been much heated debate in Germany). According to the proponents of nuclear power, such attacks would render the central inactive but could not produce radioactive contamination as the nucleus of the plants is protected by walls of reinforced concrete several feet thick: any kamikaze planes would not be able to break through the exterior walls unless use of extremely powerful explosives. On the other hand it is said that the attacks should be implemented through an explosion outside the building. Nuclear power plants, according to their supporters, are monitored very closely, although many doubt. A study conducted by the U.S. commission that controls the nuclear (Nuclear Regulatory Commission) revealed that more than half of U.S. nuclear power plants have not been able to prevent a simulated attack.
The safety of nuclear technology is guaranteed, although in a less showy, not only in burning in the center, but on the whole production cycle, which includes processing and storage. However, more attention must still be given to aspects concerning the transport and storage of nuclear waste.
Proponents of nuclear power also emphasize the high level of safety regulations for workers employed in industry (which, moreover, are inevitably less, being a nuclear power attributed to other sources: 342 energy produced from coal to natural gas and 883 to 85 'hydropower’
According to those opposed to nuclear power, given that the uncontrolled release of radioactive material put at risk the safety of nuclear power plants, the risk of radioactive leaks would be intolerable. To address these concerns, all the nuclear operators are obliged to measure the radiation inside and around these sites and to disclose all the particles and radiation. This must be certified by an independent assessment body. This practice is essentially identical in all member countries of the IAEA. If the substances escape in considerable quantities, ie above the limits set by the NCRP (National Council on Radiation Protection and Measurements, National Council on Radiation Protection and Measurement) of the United States and compulsory for all members of IAEA, we must put informed the IAEA and must be assigned at least one level 5 on the INES scale, a very rare event. All equipment is checked regularly. In addition, all operators are obliged to publicly disclose the full list of measures. A person living near a power station will receive on average about 1% of the levels of natural radiation, well below safety limits.
In Britain, detailed studies conducted by the Committee on Medical Aspects of Radiation in the Environment (COMARE) in 2003 found no evidence of an increased incidence of cancer among children living near nuclear power stations. Instead, they have detected an abnormally high number of leukemia and non-Hodgkin lymphoma (NHL) near other nuclear installations, such as those at AWE Burghfield, the UKAEA at Dounreay to Sellafield and BNFL COMARE has considered unlikely although a link between this and the nuclear material. According to gossip, "it is unlikely that the abnormal incidences around Sellafield and Dounreay to be a coincidence, although there is currently no convincing explanation of the phenomenon."
The Chernobyl accident 'that occurred due to a combination of several breaches of security by the lack of staff and a project about certain aspects of security, is not physically repeatable in a reactor moderated by water, which is characterized by other types of accident. The Chernobyl plant 'also had a type of secondary containment system only partial: a complete structure might have limited the dispersal of radioactive discharges outside.
A containment system was complete, however, present in the central of the Three Mile Island (Pennsylvania, USA), who suffered an accident in 1979 with the release of significant quantities of radionuclides and the partial core meltdown. The radiation leak was mitigated (but not canceled) by the presence of appropriate structures of the reactor containment American than Soviet.
These are among the best known and most serious incidents of accidents at civilian power plants, although a number of serious incidents also occurred over the past years (eg at Sellafield in Britain or Browns Ferry in the U.S.) and continues to occur still, for example, with various scandals in Japan.
Another safety issue concerns the danger of radioactive leaks not caused by internal faults in the central, but by external events that may compromise the structures. A catastrophic weather event, such as a tornado or an earthquake of strong intensity, could destroy the containment building, if not properly sized. In Japan, the facilities of the Kashiwazaki-Kariwa nuclear power station, were damaged in 2007 following an earthquake of intensity greater than that considered in the project and there were no release of radioactivity into the environment completely and uniquely quantified (see the entry for details).
Safety Of Geological Repositories
The geological Axis in Germany, housed in a potash mine opened by early 1900, was originally studied in the 60s. Following the excavation of additional rooms for storage of low and intermediate level waste, was reached the outer part of the mine. Given the shape of the rocks and fairly intensive use of the mine, as well as the use of fill, over the years has had a marked increase in infiltration of water, going to affect the sealing of any container containing the waste radioactive cesium showing losses.Despite the fact that the salt mines generally are immune to water infiltration and geologically stable, and therefore suitable to host thousands of years for nuclear waste, in the case of the Axis are infitrazioni and losses of radioactive substances were detected for the first time in 1988. Preliminary studies carried out in the 60's back axle considered a suitable location for the storage of LAW and MAW; to eliminate the leaks, we are studying various methods for stabilization of the rocks that form the deposit. Although the level of proof, there is also the possibility that waste is recovered, if this does not lead to greater risks for the population and the personnel who will handle the waste. Were also found the risk of collapse of the tunnel, with obvious enormous risks of a strong dispersion of radioactive.
ISSUES OF PROLIFERATION
Another argument against nuclear power is the risk posed by the increase in radioactive waste produced, moved and temporarily stored in warehouses of luck. Even low-grade radioactive material can be used to build the so-called "dirty bombs" (more accurately called "radiological bomb," where all the explosive power is provided by conventional explosives surrounded by radioactive materials that varied at the time of 'explosion, spreads in the environment), which would make an excellent tool for terrorism because of its ease of preparation.
Eventuality even more dangerous is the potential link between civil and military use (which in most countries are kept strictly separate), which could lead to an increase in countries holders of atomic bombs. The know-how gained in the construction of nuclear power plants could be used for launching nuclear weapons programs. The production of nuclear energy is based on a mechanism of chain reaction is controlled, which is technically more difficult to manage the use of uranium for military purposes.
In the industrial nuclear fuel rods, the fraction of fissile 235 isotope of uranium must be increased by the natural rate of 0.7% to 5% in order to create a chain reaction, with the exception those installations that use heavy water or graphite as moderators such as the CANDU reactor or reactors RBMK. A plant for uranium enrichment (for example the German Gronau) could - with difficulty - to increase the amount up to 80% U 235 or more in order to make nuclear weapons. As a result, some of the techniques to enrich uranium are kept secret (eg, gaseous diffusion, gas centrifuge, and the AVLIS nuclear reprocessing).
Opponents of nuclear power argue that it is not possible to distinguish between civilian and military use of nuclear energy and therefore contributes to the proliferation of nuclear weapons. While it is possible to operate a nuclear power plant with materials related to weapons, possession of a reactor involves access to materials and technologies that can be used in special military reactors at low combustion and reprocessed to produce plutonium, the essential element for the construction of high-yield nuclear weapons. This is what happened in Israel, India, South Africa (which later gave its nuclear weapons) and North Korea all have launched programs to "peaceful" nuclear energy reactors that were later used to produce plutonium suitable for weapons.Israel and North Korea do not currently have nuclear power plants, while South Africa has a very open after being equipped with nuclear weapons. To many it seems a blatant contradiction in 2006 that George Bush has strongly supported the nuclear option as an energy source safe, affordable and clean at the same time resisting with all its forces to the Iranian nuclear program to the point of threatening a military intervention: if, despite Iran's assurances that all the project's purpose is purely civil the only option that is not so simply because the risk of producing nuclear weapons is regarded as serious enough to impose such heavy work, then it is untenable position of those who argue that nuclear power plants do not pose a risk of nuclear proliferation.
Much of the popular fears about the possible proliferation of weapons comes from the consideration of fissile materials. For example, about the plutonium contained in spent fuel each year is generated by commercial nuclear reactors around the world, is correct but misleading the assertion that serve only a few kilograms of plutonium to make a bomb: all countries have in fact of uranium in quantities that could build some weapons (uranium should be enriched, however).
Plutonium is a substance with variable properties depending on the source. It is composed of several isotopes such as Pu-238, Pu-239, Pu-240 and Pu-241. It is still plutonium but not all of these types are fissile, only Pu-239 and Pu-241 can be submitted to the normal fission in a reactor. Plutonium 239 is an excellent nuclear fuel, has also been widely used in nuclear weapons because it has a relatively low fission rate and a low critical mass as a result, plutonium 239, with only a small percentage of other isotopes present (up to a maximum of 7%), plutonium is often referred to as "weapons-grade in English (for weapons). It has been used in the Nagasaki bomb in 1945, and in many other nuclear weapons.
On the other hand, this plutonium is totally different from what is normally produced in all reactors of commercial light-water nuclear power plants (called "reactor-grade") which can be separated and reprocessed spent fuel. The plutonium reactor contains a high proportion (up to 40%) of the heavier isotopes of plutonium, especially Pu-240 because it had to remain in the reactor for a relatively long period of time. This is not a particular problem for the reuse of the plutonium into mixed oxide fuel (MOX) for reactors, but impact heavily on the suitability of the use of the material in nuclear weapons. Due to the spontaneous fission of Pu-240, the material for the production of weapons will be tolerated only a very limited quantity.The design and construction of the nuclear explosive plutonium reactor-grade "would be difficult and unreliable, and so far no one has ever pursued, but was created a nuclear bomb with plutonium at low combustion from a Magnox nuclear reactor. Tested in 1962, its composition has never been officially disclosed, but clearly was around 90% fissile Pu-239. This method of production was very expensive, unreliable and easily detectable (the fuel must remain in the reactor for a relatively short period of time, ie a few weeks, compared to normal use, that a few years, and with a relatively low yield). All these factors have contributed to the fact that indiscriminate other experiences similar to that of the bomb in 1962.
The high concentration of plutonium can be used to build nuclear weapons, but in practice it is still used in nuclear power plants into fuel rods of MOX. Proponents of nuclear power in meeting stating that there are different types of nuclear power plants that use technologies that may have military applications and the first world countries could sell these technologies to other countries to prevent nuclear proliferation. In fact, many studies on nuclear Torio to depart from this kind of considerations.