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Transmutation of Waste Overview Tour

Transmutation of Waste Technology Road map:
A Report to Congress

Transmutation-Related Links

Recent Papers
on Transmutation

AAA Pamphlet

The Nuclear Waste Issue

Nuclear waste is predominately comprised of used fuel discharged from operating nuclear reactors. In the United States, the roughly 100 operating reactors (which currently produce about 20% of the nation’s electricity) will create about 87,000 tons of such discharged or “spent” fuel over the course of their lifetimes. Sixty thousand tons of this waste is destined for geologic disposal at the Yucca Mountain site in Nevada, along with another ~10,000 tons of so-called defense waste. Worldwide, more than 250,000 tons of spent fuel from reactors currently operating will require disposal.

These numbers account for only high-level nuclear waste generated by present-day power reactors. Rather conservative projections of nuclear power growth worldwide in the coming decades indicate that by year 2050, almost 1 million tons of discharged fuel requiring disposal could exist. Such projections would indicate the need to build and commission a repository on the scale of Yucca Mountain somewhere in the world roughly every three to four years.

Nearly all issues related to risks to future generations arising from long-term disposal of such spent nuclear fuel is attributable to ~1% of its content. This 1% is made up primarily of plutonium, neptunium, americium, and curium (called transuranic elements) and long-lived isotopes of iodine and technetium created as products from the fission process in power reactors. When transuranics are removed from discharged fuel destined for disposal, the toxic nature of the spent fuel drops below that of natural uranium ore (that was originally mined for nuclear fuel) within a period of several hundred years. Removal of plutonium and other transuranics from material destined for geologic disposal also eliminates issues related to long-term (centuries) heat management within geologic environments. The removal of neptunium, technetium, and iodine render negligible the possibility of radioactive material penetration into the biosphere far in the future. Finally, removal of plutonium negates any incentive for future intrusion into repositories driven by overt or covert recovery of material for nuclear proliferation.

In brief, a large nuclear waste-disposal challenge is driven by a relatively small amount of long-lived materials. Their removal makes long-term disposal of remaining, more benign materials increasingly straightforward and robust. The problem of addressing the long-term residues can be done in controlled environments having time scales of a few centuries rather than millennia.

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Transmutation of Nuclear Waste

Transmutation Explained - Transmutation is defined as nuclear transformation and describes processes that have occurred naturally since the origin of the universe. Radioactive dating of fossils is based on a measurement of the natural decay of carbon-14 to nitrogen, reflecting the amount of transmutation that has occurred over time, and thereby implying how much time has passed since the object was formed. Transmutation occurs every time the nucleus of an atom changes because of natural radioactive decay, nuclear fission, nuclear fusion, neutron capture, or numerous other processes.

Man has had the ability to cause transmutations to occur throughout most of the twentieth century, relying on the fission transmutation process to release and harness nuclear energy since the 1950s. Most transmutation processes that are induced involve the use of nuclear reactors or particle accelerators. For example, many radioisotope used in medical procedures today are produced in reactors or by using particle beams from accelerators. In principle, any radioisotope can be produced or destroyed using nuclear transformations, although some transmutations are easier to induce than others.

Advantages of Transmutation - Used nuclear fuel contains several unstable nuclei in sufficient quantities to render the material quite hazardous for a prolonged period of time. The process of disposing of the spent nuclear fuel carries an obligation to isolate these materials from the environment for a period estimated to range from 10,000 years to perhaps millions of years. These time periods challenge man’s abilities to engineer long-lasting containers and barriers, and therefore force some reliance on predictions of geologic behavior to assure the required long-term isolation from the environment.

Nuclear waste transmutation is an option that arises when one examines the hazards in the spent nuclear fuel. The long-term hazards are posed by about 1% of the content of the spent fuel, including the plutonium, neptunium, americium, curium, iodine, and technetium, leaving the other 99% relatively harmless over the long term. Further, the isotopes that are present in the problematical 1% can be converted to either stable or short-lived hazards when exposed to neutrons in an appropriate energy range. Finally, most of the materials in the 1% (the transuranics) will fission, releasing large amounts of energy.

There are three major beneficial impacts that can result from transmuting these problematic waste components. First, we can greatly reduce the amount of long-lived hazards and the need to provide for nearly total isolation for many thousands (perhaps millions) of years. It also reduces the need to attempt to provide control of geologic (and climatic) behavior in the distant future, shifting the isolation burden into the time frame of man-made containers and barriers. Second, the partitioning and transmutation process allows for the use of optimized waste forms, which can be highly resistant to leaching and other natural processes that might transport hazardous materials. Third, by transmuting most of the transuranics, such as plutonium, one greatly reduces any incentive for future generations to re-enter (or mine) the repository.

Summary - In brief, transmutation applied to nuclear waste allows us to:

• reduce the volume, toxicity, and fissile content of waste now requiring repository disposal;
• reduce materials that create proliferation and environmental risks; and
• support a simpler repository.

Spent fuel is the fuel for a transmutation system

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