Nuclear Energy - Radioactive Waste Disposal
level low facilities reactor
Disposing of radioactive waste is unquestionably one of the major problems associated with the development of nuclear power; radioactive waste is also a by-product of nuclear weapons plants, hospitals, and scientific research. Although federal policy is based on the assumption that radioactive waste can be disposed of safely, new storage and disposal facilities for all types of radioactive waste have frequently been delayed or blocked by concerns about safety, health, and the environment.
The highly toxic wastes must be isolated from the environment until the radioactivity decays to a safe level. In the case of plutonium, for example, the half-life is 26,000 years. At that rate, it will take at least 100,000 years before radioactive plutonium is no longer dangerous. Any facilities built to store such materials must last at least that long.
Regulation of Radioactive Waste Disposal
The Nuclear Regulatory Commission, other federal agencies, and the states regulate radioactive materials. As of 2004, the NRC had entered into agreements regarding radioactive waste with 33 states, which are called Agreement States. These states, under their agreements with the NRC, regulate the management, storage, and disposal of certain nuclear waste within their states.
Disposal of Uranium Mill Tailings
Mill tailings are usually deposited in large piles next to the mill that processed the ore. In 1978 Congress passed the Uranium Mill Tailing Radiation Control Act (PL95–604). This law requires mill owners to follow Environmental Protection Agency (EPA) standards for cleanup of uranium and thorium after milling operations have permanently closed. They must cover the mill tailings to control the release of radon gas; the cover must effectively control radon releases for 1,000 years. Figure 5.8 shows the locations of uranium mill tailings disposal sites. The sites are located in the western United States because deposits of uranium ore are more plentiful there.
Disposal of Low-level Waste
Low-level waste is classified according to its potential hazards. Commercial sites that dispose of these wastes must be licensed by either the NRC or Agreement States. In 2004 three low-level waste facilities were operational in the United States. These facilities accept a broad range of low-level radioactive waste and are located in Barnwell, South Carolina, and Richland, Washington. In addition, Envirocare of Utah accepts large amounts of mill tailings and low-level waste, such as contaminated soil or debris from demolished buildings and from facilities that have shut down. Four low-level radioactive waste facilities have been closed: West Valley, New York (closed 1975); More-head/Maxey
Flats, Kentucky (closed 1977); Sheffield, Illinois (closed 1978); and Beatty, Nevada (closed 1993).
The design of a low-level waste facility is shown in Figure 5.9. Wastes are buried in shallow underground sites in the specially designed canisters in which they are shipped as shown in the diagram. Underground storage may or may not include protection by concrete vaults.
The Low-level Radioactive Waste Policy Amendments Act of 1985 (PL 99–240) encouraged states to enter into compacts, which are legal agreements among states for low-level radioactive waste disposal. Figure 5.10 shows these compacts. Although each compact is responsible for the development of disposal capacity for the low-level waste generated within the compact, new disposal sites have yet to be built. As Figure 5.10 shows, two of the three operational low-level sites are located in the Northwest Compact and one is in the Southeast Compact. Facilities located in compacts with no current low-level waste disposal sites must petition the compact to export their low-level radioactive waste to one of the three operating disposal sites.
Disposal of High-level Waste
A major step toward shifting the responsibility for disposal of high-level radioactive wastes (spent fuel) from the nuclear power industry to the federal government was taken in 1982, when Congress passed the Nuclear Waste Policy Act (PL 97–425). It provided the first comprehensive national policy and detailed timetable for the management
and disposal of high-level nuclear waste and authorized construction of the first high-level nuclear waste repository. A 1987 amendment to the Nuclear Waste Policy Act directed investigation of Yucca Mountain in Nevada as a potential site. In 2004 no long-term, high-level permanent waste disposal repository for spent fuel existed. While
waiting for the development of the Yucca Mountain site, spent fuel was being stored at away-from-reactor storage facilities, such as the General Electric Company facility in Morris, Illinois, or at the nuclear power plants that generated the waste. (See Figure 5.7 for the locations of operating nuclear reactors in the United States.)
On July 9, 2002, the U.S. Senate joined the U.S. House of Representatives in approving the Yucca Mountain site. The State of Nevada, however, challenged the constitutionality of this resolution. Nevertheless, in 2004, federal courts dismissed all challenges to the site selection of Yucca Mountain but did call into question the legality of the 10,000-year standard for the facility set by the Environmental Protection Agency because the EPA did not accept the National Academy of Sciences recommendation of a higher standard of perhaps 300,000 years. While the agency works on a new standard, Congress could decide to allow the old one to stay in place. Congress approved $2 million for the state's work on the project and $8 million for local governments for fiscal year 2005, an increase from the state's $1 million and local government's $4 million received for fiscal year 2004. The DOE must still submit its license application for the proposed Yucca Mountain nuclear repository. It will take about five years to construct the facility, which is already more than a decade behind schedule.
Figure 5.11 shows the location of the proposed radioactive waste disposal facility at Yucca Mountain. The proposed repository would look like a large mining complex. It would have facilities on the surface for handling and packaging nuclear waste and a large mine about 1,000 feet underground. Here, plans call for the waste to be placed in sealed metal canisters arranged vertically in the floor of underground tunnels. Above-ground facilities would cover approximately 400 acres and be surrounded by a three-mile buffer zone. Underground, about 1,400 acres would be mined, consisting of tunnels leading to the areas where waste containers would be placed and service areas near the shafts and ramps that provide access from the surface. This type of "deep geologic" disposal is widely considered by governments, scientists, and engineers to be the best option for isolating highly radioactive waste.
The repository would be designed to contain radioactive material by using layers of human-made and natural barriers. Regulations require that a repository isolate waste until the radiation decays to a level that is about the same as that from a natural underground uranium deposit. This decay time was originally estimated at be about 10,000 years, but the National Academy of Sciences has more recently recommended a higher standard of about 300,000 years.
After the repository has been filled to capacity, regulations require the DOE to keep the facility open and to monitor it for at least fifty years from the fill date. This will allow experts to monitor conditions inside the repository and retrieve spent fuel if necessary. Eventually, the repository shafts will be filled with rock and earth and sealed. At the ground level, facilities will be removed, and, as much as possible, the DOE will take steps to return the site to its original condition.
Scientists assume that over thousands of years, some of the human-made barriers in a repository will break down. Once that happens, natural barriers will be counted on to stop or slow the movement of radiation particles. The most
|Total commercial spent nuclear fuel discharges, 1968–2002|
|Number of assemblies|
|Reactor type||Stored at reactor sites||Stored at away-from-reactor facilities||Total|
|MTU = Metric tonnes of uranium.|
|Notes: A number of assemblies discharged prior to 1972, which were reprocessed, are not included in this table (no data is available for assemblies reprocessed before 1972). Totals may not equal sum of components because of independent rounding.|
|SOURCE: "Table 1. Total U.S. Commercial Spent Nuclear Fuel Discharges, 1968–2002," in Energy Information Administration Spent Nuclear Fuel Data, Detailed United States as of December 31, 2002, U.S. Department of Energy, Energy Information Administration, October 1, 2004, http://www.eia.doe.gov/cneafr/nuclear/spent_fuel/ussnfdata.html (accessed November 18, 2004)|
|High-temperature gas cooled reactor||1,464||744||2,208|
|Metric tonnes of uranium (MTU)|
|High-temperature gas cooled reactor||15.4||8.8||24.2|
likely way for particles to reach humans and the environment would be through water, which is why the low water tables at Yucca Mountain are so crucial. Yucca Mountain also has certain chemical properties that act as another barrier to the movement of radioactive particles. Minerals in the rock called zeolites would stick to the particles and slow their movement throughout the environment.
The long delay in providing disposal sites for spent nuclear fuel, coupled with the accelerated pace at which nuclear plants are being retired, has created a crisis in the industry. Several aging plants are being maintained at a cost of $20 million a year for each reactor simply because there is no place to send the waste once the plants are decommissioned. Table 5.3 shows that as of 2002 more than 47,000 metric tons of nuclear uranium waste were sitting in spent fuel pools at the 104 operating and nineteen permanently closed nuclear power plants. When a nuclear plant shuts down, the nuclear waste and the radioactive equipment stay on the premises because there is no place to put them. As a result, every nuclear power plant in the United States has become a temporary nuclear waste disposal site. Plants that close must wait until a repository opens to be decommissioned or dismantled.
Disposal of Transuranic Waste
The first disposal facility licensed to dispose of transuranic waste opened on March 26, 1999. The Waste Isolation Pilot Plant (WIPP) is located in the desert in southeastern New Mexico. WIPP facilities include disposal rooms mined 2,150 feet underground in a 2,000-foot-thick salt formation that has been stable for more than 200 million years.
Disposal of Mixed Waste
As mentioned previously, mixed waste is jointly regulated by the Environmental Protection Agency, which regulates the hazardous waste component of mixed waste, and the Nuclear Regulatory Commission and the Department of Energy, which regulate the radioactive component of mixed waste. There are a variety of commercial facilities in the United States, including Envirocare (see "Disposal of Low-level Waste"), that accept mixed waste.