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Friday, October 23, 2009

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.

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