Disposal Of Nuclear Waste Essay, Research Paper
The disposal of nuclear waste is quickly becoming the most important issue facing the environmental community today. Nearly twenty percent of our nation s electricity is being supplied by the approximately 100 nuclear power plants that are in everyday operation in the United States. So far, almost all of the nuclear waste created by these power plants is being housed in temporary storage facilities at each power plant. Although the total volume of nuclear waste produced in one year is small when compared to the amount of other poisonous wastes produced in the same time period, the need to find a permanent method of disposing this waste is rapidly growing. Nuclear waste is extremely difficult to handle. New technologies and advancement in waste treatment processes have made waste disposal safer, but it is still not absolutely safe. Not only do scientists have to worry about treating and containing the wastes; they also have to find sites to store the waste that will not allow the wastes to spread, even under the worst circumstances. There are many classifications of waste. Spent nuclear fuel is the radioactive by-product of making electricity at commercial nuclear power plants. It is highly radioactive and must be stored in special facilities. High-level waste is the by-product from production at defense facilities. This form of waste is highly radioactive and contains hazardous chemicals and toxic heavy metals. This waste is environmentally hazardous for thousands of years and must be kept in special storage facilities. High-level waste accounts for 95% of all the waste produced. Transuranic waste is the waste generated from the production of nuclear weapons that contain transuranic elements (elements with an atomic number greater than Uranium). Some forms of this waste have a half-life of thousands of years and are currently stored in on-site drums. Low-level waste is the generic category for waste, which does not fit any of the above categories. One source of this waste is from irradiated metal parts from the reactor. Most low-level waste is stored in shallow pits located on the reactor site. Uranium-mill tailings are the leftover materials from the milling and mining process. These tailings release radon into the environment. The amount of waste produced each year in the U.S. is 300 million tons and growing. All of the nuclear waste ever produced in the U.S. would only cover one football field to a depth of 15 feet. However, the potential dangers of this waste must not be overlooked. The current method of disposing of these waste materials is to store then in steel-lined concrete tanks filled with water. However, this form of storage is not permanent and the nuclear plants will eventually run out of storage space. In 1983, the U.S. Department of Energy selected nine locations in six states for consideration as potential repository sites. This was based on data collected for nearly 10 years. The nine sites were studied and results of these preliminary studies were reported in 1985. Based on these reports, the president approved three sites for intensive scientific study called site characterization. The three sites were Hanford, Washington; Deaf Smith County, Texas; and Yucca Mountain, Nevada. The Yucca Mountain Project is now being put through the necessary steps for implementation. Yucca Mountain is located on government owned land in a remote area of Nevada. The proposed plan is the first national permanent waste repository and will cost an estimated 6.3 billion dollars. The project will include borrowing 25-foot diameter tunnels through the mountain s inner rock. The finished tunnel would be 5.5 miles in length at its completion, and will house sealed metal canisters of high-level wastes. Obviously, there is much public concern over the project. One of the largest concerns is the possibility of seismic activity rupturing the tunnel and/or canisters. At present, the 104th US Congress, house Resolution 1924 proposed to make Hanford, Washington, the western US site for temporary storage, by default permanent disposal, of spent nuclear fuel from US reactors. This resolution stemmed from a growing recognition that Yucca Mountains, in Nevada, is a less than brilliant location for a US repository. The US government has no fallback position should Yucca Mountains not pan out therefore the Hanford Reservation is likely to be targeted again in the current Congress. The rational is that Hanford, at the doorstep of British Columbia and Alberta, has been degraded to such an extent already, it should be deemed a national sacrifice zone. Another leading contender for approval is a project similar to Yucca Mountain. Masoa Kasuya, a nuclear scientist, has a similar idea of boring tunnels into rock to house the waste canisters. The difference with Mr. Kasuya s plan is that these tunnels will be drilled into rock in the ocean floor. The reason for this variation is based on Quaternary history. The Quaternary history (1.7 million years ago to the present) can be reconstructed both chronologically and spatially by geologists. These studies will show what areas have had the least movement and seismic activity. From this data, they believe that they will be able to predict which areas will remain the least active in the future. They have found that Quaternary beds found on the land tend to vary in depositional speed and are subject to erosion, weathering, and disturbances from human activity. The geologists have found the most stable Quaternary beds lie in the deep-sea (depths of more than 1000m). Because of the need for waste to be stored from isolated periods of 10,000 to 100,000 years, stability is a necessity. Another great advantage is constant environmental factors such as temperature, pressure, mineral exposure, and movement. Two methods of depositing the waste canisters have been discussed. One is to drop, in torpedo fashion, the highly reinforced canisters that will lodge them directly below the seabed. Of course, environmentalists are hitting the roof over this idea. The possibility of a canister breaking, killing a fish on the way down, or leaking into the marine environment, has caused much concern. The second method is to deposit the canisters via a tunnel, which leads from the shore to under the seabed. The cost that would arise in order to deposit the canisters more than a few hundred yards from shore would be immense. The third, and most interesting, of the current proposals is called The Subductive Waste Disposal Method , and was invented and patented by Jim Baird. First, subductive must be defined. It is the process in which one tectonic plate slides beneath another and is eventually reabsorbed into the earth s mantle. The Subductive Waste Disposal Method (SWDM) involves forming a high-level radioactive waste repository, or storage facility, in a subducting tectonic plate so that the waste will be carried beneath the earth s crust where it will be diluted and dispersed through the mantle. Mr. Baird states many reasons that his method is superior to the others. They include: (Radionuclides disposed of by this method could not mix with the water table. (The method provides inaccessibility to eliminated weapons material. (The method removes waste from the biosphere faster than it can return. (Any waste that might escape a repository constructed in accordance with this method would be bound-up in the overlaying buffer of turbidity sediments that, it has been demonstrated, have a propensity to cling to radionuclides that have fallen onto the ocean floor as a result of accidents or atmospheric testing of nuclear weapons. The subducting plate is predestined for consumption in the Earth s mantle and is constantly renewed at its originating oceanic ridge. The slow movement of the plate would seal any vertical fractures over a repository at the interface between the subducting plate and the overriding plate. Wastes deposited by this method, 2000 meters beneath the seabed, would take 2 million years to reenter the biosphere. In Mr. Kasuya s plan the wastes deposited 2000 meters below the seabed will eventually work there way back into the biosphere. The main advantages Mr. Baird s plan include providing no chance of radioactive mixing with the water table. Also, SWDM will render eliminated weapons material inaccessible. The finished process will leave the waste material beneath 2000 meters of water, 2000 meters of oceanic sediment, and up to 50 kilometers offshore. This is the only method of disposal that actually eliminates the waste and is cause for excitement in the nuclear waste field.