Is Nuclear Power a Viable Option For The Future
Nuclear Waste
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.
What is Radioactivity?
Radioactivity occurs when unstable nuclei of atoms decay and
emit particles. These particles may have high energy and can
have bad effects on living tissue. There are many types of radiation.
How does radioactivity get to you?
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. Radio nuclides 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 radio nuclides 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!
What can we do
about nuclear waste?
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."
Forms of Radioactive Waste
Radioactive wastes come in many different forms including the
following:
- cooling water, used fuel rods, and old tools and parts
from nuclear power plants
- the reactor housing, core and coolant circuits from decommissioned
power plants
- protective clothing of people in contact with radioactive
materials
- mill tailings from uranium-enrichment factories
- old medical radiation equipment from hospitals and clinics
- the remains of lab animals used in experiments with radio
nuclides
- used smoke detectors which contain radioactive americium-241
sensors
Types of nuclear waste
High-level waste
Nuclear waste is divided into several categories. High-level
waste consists mostly of spent nuclear reactor fuel from both
commercial 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 generally store their spent fuel rods in lead-lined
concrete 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 launch
pad or in space could expose the earth and atmosphere 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
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 sand like 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 Waste
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:
Fuel wastes are fission products that leak out of fuel rods
and into cooling water.
Non-fuel wastes result when stray neutrons bombard anything
in the core other than fuel--such as the reactor vessel itself--and
cause them to become radioactive.
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 landfills. 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 currently 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?
Will technology improve the nuclear waste problem
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.
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