Starting in the 1950s, U.S. scientists began to research ways to manage
highly radioactive materials accumulating at power plants and other
sites nationwide. Long-term surface storage of these materials poses
significant potential health, safety, and environmental risks.
A variety of options were considered
Scientists studied a broad range of options for managing spent nuclear
fuel and high-level radioactive waste. The options included:
- Leaving it where it is
- Disposing of it in various ways
- Sub-seabed disposal
- Very deep-hole disposal
- Space disposal
- Ice-sheet disposal
- Island geologic disposal
- Deep-well injection disposal
- Making it safer through advanced technologies
International scientific consensus holds that these materials should
eventually be disposed of deep underground in what is called a geologic
repository. In a recent special report, the National Academy of Sciences
summarized the various studies and emphasized that geologic disposal is
ultimately necessary.1
Leaving it where it is
Currently, America’s spent nuclear fuel and high-level radioactive
waste are temporarily stored above ground at 131 locations in 39 states.
There are many disadvantages associated with long-term surface storage,
even if only for another 100 years.
If left where they are indefinitely, the materials could become a serious
hazard to nearby populations and the environment. This could be an even
greater concern if global climate change causes the oceans to rise, as
many scientists believe is happening.
Most of the storage sites are near population centers, and because nuclear
reactors require abundant water, these sites are also located near rivers,
lakes, and seacoasts.
If not continuously maintained and safeguarded, this stored material could
deteriorate and travel through groundwater and surface water runoff to
rivers and streams that people use for domestic and agricultural purposes.
Should this occur, 20 major waterways and all U.S. seacoasts could be
adversely impacted.
Sub-seabed disposal
Scientists considered burying radioactive waste under the ocean floor,
but there are problems associated with this option.
Whether waste buried under the seabed could be recovered, if necessary,
is questionable. Developing an effective international, legal, and administrative
structure to develop, regulate, and monitor a sub-seabed repository would
be challenging as well.
Beyond technical and political considerations, the United States signed
the London Convention in October 1993. This international agreement, which
remains in force until 2018, bans disposing of radioactive materials at
sea. After that time, the sub-seabed disposal option can be revisited
at 25-year intervals.
Very deep-hole disposal
Another option scientists investigated was disposal in very deep holes:
placing high-level radioactive waste containers as deep as about six miles
(10,000 meters) underground. At such depths, the radioactivity theoretically
could be isolated until it decayed to a safe level.
Very deep-hole disposal was rejected as an option, however. While it would
keep radioactive waste below most groundwater, the surrounding rock would
have to retain its structure under extreme heat and radiation.
Scientists do not know enough about how radioactive waste would behave
under the exceptionally high pressures and temperatures of very deep holes.
Space disposal
The National Aeronautics and Space Administration (NASA) and the DOE also
researched several methods of disposal in space. Possibilities included
launching waste containers into the sun or putting them on the moon.
Space disposal offers the attraction of permanent separation of waste
from the human environment.
However, the disadvantages of space disposal are great.
The possibility of an accident during launch and the potential for radioactive
waste to be scattered by such an accident make this an unacceptable option.
In addition, space disposal is impractical because of the number of launches
that would be required.
Establishing international agreements on how such a program would be operated
and regulated would also be difficult.
Ice-sheet disposal
Scientists also considered burying radioactive waste in polar ice.
Advantages to this option include the lack of population in polar regions
and the stability and thickness (several miles, thousands of meters) of
polar ice.
One drawback to this option is the uncertain disposal and/or retrieval
processes.
Another is the potential effect of future climate changes on the stability
and size of polar ice masses. Radioactive wastes could be released into
the environment if global climate changes increased polar ice melting.
This option also would be extremely expensive due to the remote location
and adverse weather.
Finally, the Antarctic Treaty of 1959 prohibits disposing of radioactive
waste on the Antarctic continent.
Island geologic disposal
Scientists looked at burying radioactive waste beneath remote islands
that lacked valuable resources and were far from large continental landmasses.
One drawback to island geologic disposal concerned the risks associated
with ocean transport, especially during bad weather.
Also, many islands experience frequent and intense earthquake and volcanic
activity.
In addition, some islands have geologic structures that allow seawater,
as well as fresh water, to penetrate underlying rock. The presence of
water could contribute to waste container corrosion, releasing and eventually
transporting radioactive particles into the environment.
The potential for opposition from nearby countries was an additional consideration.
Deep-well injection disposal
Scientists studied a disposal option called deep-well injection, which
involves pumping pressurized liquid high-level radioactive waste to depths
of about 3,500 to 16,000 feet (1,000 to 5,000 meters).
The waste theoretically would move throughout a porous rock formation
protected by a layer of solid (impermeable) rock. Sandstone overlaid by
shale is considered a good choice for deep-well injection because of shale’s
ability to isolate the waste from groundwater and the environment.
One disadvantage to this option was the need for either mechanical or
chemical processing of the spent nuclear fuel prior to injection.
Another concern was the potential movement of liquid waste outside the
porous rock formation. This could increase the chances that the irretrievable
waste might escape into the environment.
Reprocessing
Some nations reprocess their spent nuclear fuel. Reprocessing requires
a complex set of mechanical and chemical treatments to separate out the
uranium from the plutonium, which is produced by the atom-splitting in
the reactor. The material can then be reconstituted as fresh fuel pellets
to produce more electricity.
1 Board on Radioactive Waste Management, National Research
Council, National Academy of Sciences, Disposition of High-Level Waste
and Spent Nuclear Fuel: The Continuing Societal and Technical Challenges.
National Academy Press: Washington, D.C. 2001.
U.S. Department of Energy
Office of Civilian Radioactive Waste Management
Yucca Mountain Project
1551 Hillshire Drive
Las Vegas, NV 89134
1-800-225-6972
http://www.ocrwm.doe.gov
DOE/YMP-0017
November 2003 |