Radioactive Wastes
In the early 1980’s, the United States federal legislature created two acts dealing with radioactive wastes: the Low-Level Radioactive Waste Policy Act and the Nuclear Waste Policy Act. The Low-Level Waste Policy Act put low-level radioactive waste disposal in the hands of each state while encouraging states to unite to form regional waste compacts. The Nuclear Waste Policy Act represents the process to define permanent disposal for spent nuclear fuel.
There are roughly five categories of radioactive waste. How a waste is categorized is not necessarily based on the amount of radioactivity, but instead where the waste is generated.
Low-Level Radioactive Wastes
Low-level radioactive wastes consist of radioactively contaminated items from research centers, hospitals, industries, power plants, and educational organizations. These items include paper, gloves, booties, protective gowns, paper or plastic bags, and empty containers (empty except that the walls of the container are radioactively contaminated). Generators of these wastes have done several things over the past decades to decrease the amount of waste to be shipped to a licensed waste-disposal site. Some ways to decrease the amount of waste include holding short half-lived material until the radioactivity is gone, better separation of non-radioactive items from radioactive items, using tools that can be decontaminated and reused, incinerating some waste items at licensed sites, and compacting the waste. Compacting the waste does not decrease the amount of waste generated, but by compressing the waste that is put into 55-gal drums for shipment, more waste can be put in a drum, decreasing the total number of drums to be shipped and buried.
If the wastes must be shipped to a licensed burial site, the wastes must be properly packaged and transported. Licensed burial sites, historically, have put the wastes into deep trenches which are then buried under clay. After a trench is full, it is capped with clay and, above that, some topsoil. Trenches are continuously monitored after they are closed.
Spent Nuclear Fuel and other High-Level Wastes
Spent nuclear fuel and other high-level wastes generally will come from nuclear reactors and nuclear weapon facilities. Items in this category would include, as the name implies, spent nuclear fuel—the radioactivity originally used to run the nuclear reactor that is no longer radioactive enough to be useful—and waste materials left from the production and processing of nuclear weapons.
Currently, much of the spent nuclear fuel is being kept on-site at nuclear reactor facilities either in water pools (the water acts as a shield and also helps dissipate the heat generated by the fuel rods) or in dry casks. The fuel in these rods are waste because they no longer having enough uranium to be useful. Within approximately 90 days, nearly half of the radioactivity is gone and within about a year, about 80 percent of the radioactivity is gone. The remaining radioactivity has half-lives ranging from several years to thousands of years.
The reason spent nuclear fuel and other high-level wastes are being kept on-site is that the United States has no disposal site for this waste. Some sites have been evaluated, but controversies remain. While members of the scientific community believes that safe disposal options currently exist, they also believe that a waste site should not be considered a permanent site (one where the waste would or could be there forever) but instead should be a site where the waste could be retrievable. This would allow the application of new technologies and methodologies that we haven’t even yet discovered to make the process better. Even if the waste is retrievable, however, it would need to be continuously monitored to assure there is no contamination of the environment.
Nuclear weapons waste is the responsibility of the Department of Energy. Most of this waste is generated from the “cleanup” of sites where nuclear weapons were manufactured. At these sites, parts of buildings, soils, and ground and surface waters are radioactively contaminated. Some sites have been cleaned up and cleared for other uses, while the decontamination process continues for many of them.
Mixed Wastes
Mixed wastes refer to wastes that are a mixture of hazardous wastes (i.e. chemicals) and radioactive wastes and, as such, are dually regulated. Hazardous-waste treatment and disposal is regulated by the U.S. Environmental Protection Agency; while radioactive waste is regulated by the U.S. Nuclear Regulatory Commission or the state of origin.
Transuranic Wastes
Transuranic wastes are generated within the nuclear weapons industry and wastes from reprocessing spent fuel. They contain radionuclides with an atomic number higher than uranium (atomic number 92). These wastes are mostly sludge, tools, and contaminated protective clothing. These wastes, like spent nuclear fuel, are temporarily stored at the sites where they are generated. There is a waste-disposal facility for these wastes and, eventually, what has been maintained on-site will be shipped to the facility.
Uranium Mining and Mill Tailings
Uranium mining and mill tailings are pulverized rock and soils that remain after mining for uranium. The radionuclides present usually include uranium, radium, radon, and thorium.
Radioactive Waste Transport
The Nuclear Regulatory Commission, Agreement States, and Department of Transportation have oversight for the safe transport of radioactive wastes from the place of origin to the place of disposal. Within this oversight lies regulations regarding the proper packaging and labeling of shipments, proper loading and unloading, shipment manifests, and training for anyone who would package, label, load, unload, or transport the wastes. Packaging varies depending on the waste, but some of the packaging must have passed several tests for strength and toughness including being put in a high-heat fire, dropped onto a steel spike, and even submersed in water. This packaging helps to assure that wastes are not dispersed in the event of an accident.