Prospects Of Nuclear Energy

Prospects of Nuclear Energy Thus, in discussing the prospects of nuclear power, we face two major sources of uncertainty. We do not know how the alternative energy contenders will compare on technical, economic, and environmental grounds. We know even less how public and political attitudes will evolve. There are also differences among countries that sometimes have no clear explanation. It is easy to understand why Norway has no nuclear power while Sweden has employed it extensively. The answer lies in Norway’s ample hydroelectric resources that have been providing over 99% of its electricity. However, it is hard to find such straightforward explanations for Italy’s abandoning of nuclear power while France was emphasizing it, or the difference between substantially nuclear Switzerland—which in 2003 referenda voted against giving up nuclear power—and nuclear-free Austria. In the remainder of this chapter, we will discuss some of the factors that will influence the future development of nuclear power. However, at every turn, it will be necessary to recognize that there are large uncertainties on both the technical and political sides. Internal Factors Impacting Nuclear Power The future acceptability of nuclear energy, which we restrict to energy from nuclear fission here, will depend, in part, on internal factors—the strengths and weaknesses of nuclear power itself. Key factors are as follows: 1: Nuclear accidents. The sine qua non for the acceptance of nuclear power is a long period of accident-free operation, worldwide. Any major nuclear accident will heighten fears of nuclear power and each decade of accident free operation helps to alleviate them. 2: Reactor designs. For nuclear power to be attractive, next-generation reactors must be manifestly safe and also must be economical to build. These could be either large evolutionary reactors, of the sort recently built in France, Japan, and South Korea, or smaller reactors that may be a better match to markets of modest size. 3: Waste disposal. The completion of integrated and fully explained waste disposal plans would encourage people to believe that the problem is “solved.” In particular, smooth progress with the Yucca Mountain project would suggest that waste disposal problems are surmountable. However, for a large expansion of nuclear power, it will be necessary to demonstrate the ability to handle the wastes from many more years of reactor operation. 4: Resistance to proliferation and terrorism. For nuclear power to be acceptable, its facilities must be well protected against terrorists and the nuclear fuel cycle must be proliferation resistant. 5: Assessments of radiation hazards. Most professionals believe that public fears of radiation—and, in particular, radiation from nuclear power—are out of proportion to the actual risks. A more realistic understanding of the dangers would, in this view, lessen some of the opposition to nuclear power. External Factors Impacting Nuclear Energy Verdicts on the “internal factors” discussed earlier will be influenced by perceptions of need. Here, factors external to nuclear power determine the apparent need. These include the following: -Energy and electricity demand. Economic expansion and population growth act to increase the demand for additional energy, including nuclear energy. Effective conservation measures reduce it. -Limitations on oil and gas resources. The need for alternatives is enhanced if these resources are seen to be inadequate. -Global climate change. If the increasing concentration of carbon dioxide in the atmosphere looms large in the public consciousness as an environmental threat, then the pressures to find alternatives to fossil fuels will intensify. Complicating the equation is the prospect of carbon sequestration, which, at least in principle, offers the possibility of “carbon-free” coal. -Renewable energy. The technical and economic feasibility of renewable sources and assessments of their environmental impacts are critical to judging the need for nuclear power. Possible Difficulties in Nuclear Expansion The Pace of Reactor Construction Population is increasing so energy per capita is also increasing Uranium Resources However, it would make little sense to bring reactors on line that would run out of fuel Nuclear Wastes The nuclear waste problem will increase with its expansion Weapons Proliferation More countries could assert the need for uranium-enrichment facilities, ostensibly for low-enriched uranium for civilian reactors but potentially easing the path to high-enriched uranium for weapons. SAFETY The main safety concern is the emission of uncontrolled radiation into the environment which could cause harm to humans both at the reactor site and off-site The Nature of Reactor Risks 1: Criticality accidents. These are accidents in which the chain reaction builds up in an uncontrolled manner, within at least part of the fuel. In an LWR of normal design, such accidents are highly improbable, due to negative feedbacks and shutdown mechanisms. They are less unlikely in some other types of reactor, given sufficient design flaws. The 1986 Chernobyl accident was a criticality accident, although much of the energy release was from a steam explosion following the disruption of the core. 2: Loss-of-coolant accidents. When the chain reaction is stopped, which can be accomplished quickly in the case of an accident by inserting control rods, there will be a continued heat output due to radioactivity in the reactor core. Unless adequate cooling is maintained, the fuel temperature will rise sufficiently for the fuel cladding and the fuel to melt, followed by the possible escape of radioactive materials from the reactor pressure vessel and perhaps from the outer reactor containment. The TMI accident was a loss-of-coolant accident. There was substantial core melting, but no large escape of radioactive material from the containment Radiations. The UO2 fuel pellets retain most radionuclides, although some gaseous fission products (the noble gases and, at elevated temperatures, iodine and cesium) may escape. -The zircaloy cladding of the fuel pins traps most or all of the gases that escape from the fuel pellets. -The pressure vessel and closed primary cooling loop retain nuclides that escape from the fuel pins due either to defects in individual pins or, in the case of an accident, overheating of the cladding. -Other harm includes physical damage to the reactor plant and contamination of the surrounding environment that may force the evacuation of large regions Avoiding accidents The reactivity of the system Reactivity os system is kept low enough to make delayed neutrons crucial for criticality. Thus, even if the reactivity rises, the rates of increase of the neutron flux and of the power output are relatively slow Heat Removal and Loss-of-Coolant Accidents The central problem in loss-of-coolant accidents arises from the need to remove the heat produced by radioactivity during the period after reactor shutdown decay heat is removed by a coolent otherwise it would melt the fuel Core-Cooling Systems During normal operation, reactor cooling is maintained by the flow of a large volume of water through the pressure vessel. This flow can be disrupted by a break in a pipe, failure of valves or pumps, or, in PWRs, a failure of heat removal in the steam generators. Such accidental disruptions of the normal cooling system are generically termed loss-of-coolant accidents (LOCAs emergency core-cooling systems intended to maintain water flow to core of reactor coolant can be water, sodium, sodium salts. Release of Radionuclides from Hot Fuel The radionuclides include both fission products and actinides. They can be grouped according to differences in their volatility. The most volatile are the noble gases. These can diffuse out of the fuel into the fuel pins even at normal fuel temperatures. If radionuclides escape from the cooling system or from the reactor vessel, the next barrier is the containment structure. The integrity of the containment can be compromised by overpressure, most likely from the buildup of steam. To avoid this containment cooling systems intended to condense the steam. For example, PWRs commonly have spray systems for condensation. Also there should be the maintenance of barriers that prevent the release of radiation HAZARDS Radiation :How Dangerous Is Radiation?high dose cancer is certain.Routine emission from nuclear industries also from reactor accident Reactor waste : There are several types of radioactive waste generated by the nuclear industry, but we will concentrate largely on the two most important and potentially dangerous, high-level waste and radon. -High-Level Waste: The residue, containing nearly all of the radioactivity produced in the reactor, is called high-level waste. The waste can be converted into a rock-like form and buried deep underground in a carefully selected geological formation. The waste generated by one large nuclear power plant in one year and prepared for burial is about six cubic yards. The ground is full of naturally radioactive materials, no large effect on increase in radioactivity of ground.The principal concern about buried waste is that it might dissolve in groundwater and contaminate food and drinking water supplies. How dangerous is this material to eat or drink - Radon problem: the release of radon, a radioactive gas that naturally evolves from uranium. There has been some concern over increased releases of radon due to uranium mining and milling operations. These problems have now been substantially reduced by cleaning up those operations and covering the residues with several feet of soil. The health effects of this radon are several times larger than those from other nuclear wastes

Prospects Of Nuclear Energy

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