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Friday, October 23, 2009

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.

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