The creation of huge quantities of long-lived radioactive waste is the most formidable problem facing the nuclear power industry today. The difficulty of waste disposal was not considered to be a big problem during the time when power plants were first introduced; it was assumed that waste could be recycled or buried. Unfortunately, finding safe ways of storing radioactive wastes so that they do not leak radiation into the environment has proved to be a much more difficult task than anticipated.
The planet's water cycle is the main way radiation gets spread about the environment. When radioactive waste mixes with water, it is ferried through this water cycle. Radionuclides in water are absorbed by surrounding vegetation and ingested by local marine and animal life. Radiation can also be in the air and can get deposited on people, plants, animals, and soil. People can inhale or ingest radionuclides in air, drinking water, or food. Depending on the half life of the radiation, it could stay in a person for much longer than a lifetime. The half life is the amount of time it takes for a radioactive material to decay to one half of its original amount. Some materials have half-lives of more than 1,000 years!
Paths of Radiation to the Body
According to a report from the U.S. National Academy of Sciences, it will take 3 million years for radioactive waste stored in the United States as of 1983 to decay to background levels. So, presently, the only solution is to store the waste in a place so that the environment won't be contaminated. The problem with storing nuclear waste is both political as well as technological. In terms of politics, no one wants it stored near them. So there's much dispute as to where radioactive waste should be stored. In addition, storing so much waste is a major technological challenge. According to a report issued by the British Parliament, "In considering arrangements for dealing safely with such wastes, man is faced with time scales that transcend his experience."
Nuclear waste is divided into several categories. High-level waste consists mostly of spent nuclear reactor fuel from both commerical power plants and military facilities, as well as reprocessed materials which can emit large amounts of radiation for hundreds of thousands of years. Commercial nuclear power plants in the U.S. alone produce 3,000 tons of high-level waste each year. The amount of spent fuel removed annually from the approximately 100 reactors in the U.S. would fill a football field to a depth of one foot. When spent fuel is removed from a reactor core, it still emits millions of rems of radiation. For more information on units of measurement (such as the rem), see the radiation effects page.
In the absence of high-level waste repositories, nuclear power plants genearlly store their spent fuel rods in lead-lined conceete pools of water. These pools somewhat contain the spread of gamma radiation by keeping the rods relatively cool. They also help prevent fission. The average commercial power plant puts 60 used assemblies into temporary storage each year and will probably continue to do so until the year 2000, when responsibility for spent fuel will be transferred to the Department of Energy. Space is running out at many plants though. The plants have another option of storing their spent fuel at other plants still under construction. It is theoretically possible to reduce the amount of storage space that spent fuel rods require by removing them from their assemblies, bundling them tightly, and then packing them into heavily shielded dry storage, but repacking these highly radioactive rods may present too much of a challenge.
For long-term storage of high-level waste, a waterproof, geologically stable repository and leak-proof waste container is required. Packaging has to be tailored to the volume of the waste, the actual radioactive isotopes of elements it contains, how radioactive it is, its isotopes' half-lives, and how much heat it still generates. One technique for packaging high-level wastes involves melting them with glass and pouring the molten material into impermeable containers. The containers could be buried in soil or in a rock pile and surrounded by fill material and a barrier wall. From the 1940s through the 1960s, barrels of radioactive waste were frequently dumped in oceans. This ended in 1970 when the EPA (Energy Protection Agency) determined that at least one-fourth of these barrels were leaking. A new, possibly safer proposal under consideration for long-term ocean storage includes offshore drilling and a procedure known as self-burial. In offshore drilling, holes would be drilled into the seabed and filled with barrels of waste. In self-burial, specially shaped barrels would be dumped and left to sink to the ocean floor.
Geologic disposal is currently the most popular solution for waste disposal. During the 1980s, the U.S. government invested more than $2 billion into geologic disposal. In this form of disposal, mined tunnels with deep holes for waste canisters would be built using conventional mining techniques. Monitoring and waste retrieval would be relatively easy. In 1987, a site was chosen for the first permanent high-level commercial nuclear waste storage repository in the United States--Yucca Mountain, 100 miles northwest of Las Vegas, Nevada. Expected to cost up to $15 billion, this repository is scheduled to go into operation by the year 2010.
Over the years, a number of other ideas for high-level waste disposal have been proposed and, at least temporarily, abandoned. One was disposal in space, in which sealed containers of radioactive material would be sent up into distant orbits. This would be an expensive and risky operation, as problems on the launchpad or in space could expose the earth and atmostphere to an enormous amount of radiation. Another suggestion was burying waste under the Antarctic ice sheets. However, this would risk irradiating that area and the surrounding sea. A much safer idea, which would render disposal unnecessary, is to bombard radioactive waste with subatomic particles to transform it into less harmful isotopes. Unfortunately, this attractive proposal awaits still unrealized technology.
Mill tailings, left over when ore is refined and processed is the largest by volume of any form of radioactive waste. Only 1% of uranium ore contains uranium--the rest is left on-site as sandlike residue. These tailings are generally left outdoors in huge piles, where they blow around, releasing radioactive materials into the surrounding air and water. By 1989, some 140 million tons of mill tailings had accumulated in the United States alone, with 10 to 15 million tons added each year. Although their radiation is generally less concentrated than other types of waste, some of the isotopes in these tailings are long-lived and can be hazardous for many thousands of years.
Until their radioactive risk was known, mill tailings were sometimes used as foundation and building materials, especially in western states. When their risk was discovered, these materials in the buildings had to be monitored. These monitored sites are generally safer, although some groundwater contamination still occurs at them. It has been recommended that tailings be stored underground in clay pits, far from population centers.
Low-level wastes are usually defined in terms of what they are not. They are not spent fuel, milling tailings, reprocessed materials, or transuranic materials. Low-level waste includes the remainder of radioactive wastes and materials generated in power plants, such as contaminated reactor water, plus those wastes created in medical laboratories, hospitals, and industry. Wastes in this category usually, although not always, release smaller amounts of radiation for a shorter amount of time. "Low level" does not mean "not dangerous," though. Although its radioactivity is usually less concentrated than that of high-level waste, low-level waste can be dangerous for up to tens of thousands of years.
Most low-level wastes come from reactors. These wastes can be divided up into two categories:
The remainder of low-level wastes comes from industry and institutional sources, including pharmaceutical plants, universities, and medical facilities. Instead of going to low-level waste dumps, these wastes are often kept on-site for the short time it takes for them to decay to safe levels. Then they are deposited into sanitary landsfills. However, it is likely that liquid wastes are literally poured down the drain, whether or not they are still radioactive.
Low-level waste landfills were first built in the 1960s. In near-surface land burial, containers of waste fill a trench and are covered and surrounded by compacted earth. There are currently a few burial grounds in the U.S. to which most commercial low-level waste materials emitting detectable amounts of radiation are sent. A few other landfills are currenly inactive due to severe waste-containment problems and radioactive leakage. Waste containers in near-surface landfills are prone to corrosion, particularly in moist climates. Landfills provide a false sense of comfort because they are "out of sight, out of mind." More worthwhile alternatives include above-ground landfills and to store waste at existing nuclear plant sites.
There are a number of unresolved issues regarding disposal of low-level wastes. The current institution control period (the amount of time a waste site must remain under guard after it has been filled and closed) is only 100 years. Yet the hazards presented by some low-level wastes can continue for thousands of years. What will keep future generations from uncovering and being contaminated by these substances?
Currently, better methods are being developed to decrease waste volume and make methods of separating the waste by decay rate more efficient. Development of waste storage is far from complete. There are many alternatives to consider and many techniques to develop and improve upon. There has also been much controversy about site selection and disposal methods. Although urban areas consume most of nuclear-generated electricity, radioactive wastes are dumped in rural settings, where property values decline and public health is jeopardized. However, the problem of radioactive waste disposal is not unique to the United States. Other countries are facing the same waste dilemmas. Although hazards of radioactive waste are less visible than some other problems associated with nuclear energy, such as reactor accidents and nuclear weapons, they are no less dangerous, and decisions made concerning this waste will be felt far into the future. For more information on the pros and cons of nuclear energy, contact the nuclear politics page. Let us know what you think! Go to the forum.