The environmental impact of nuclear power
results from the nuclear fuel cycle, operation,
and the effects of nuclear accidents.
The greenhouse gas emissions from nuclear
fission power and are much smaller than those
associated with coal, oil and gas, and the
routine health risks are much smaller than
those associated with coal. However, there
is a "catastrophic risk" potential if containment
fails, which in nuclear reactors can be brought
about by overheated fuels melting and releasing
large quantities of fission products into
the environment. This potential risk could
wipe out the benefits. The most long-lived
radioactive wastes, including spent nuclear
fuel, must be contained and isolated from
the environment for a long period of time.
On the other side, spent nuclear fuel could
be reused, yielding even more energy, and
reducing the amount of waste to be contained.
The public has been made sensitive to these
risks and there has been considerable public
opposition to nuclear power.
The 1979 Three Mile Island accident and 1986
Chernobyl disaster, along with high construction
costs, also compounded by delays resulting
from a steady schedule of demonstrations,
injunctions and political actions, caused
by the anti-nuclear opposition, ended the
rapid growth of global nuclear power capacity.
A release of radioactive materials followed
the 2011 Japanese tsunami which damaged the
Fukushima I Nuclear Power Plant, resulting
in hydrogen gas explosions and partial meltdowns
classified as a Level 7 event. The large-scale
release of radioactivity resulted in people
being evacuated from a 20 km exclusion zone
set up around the power plant, similar to
the 30 km radius Chernobyl Exclusion Zone
still in effect. But published works suggest
that the radioactivity levels have lowered
enough to now have only a limited impact on
wildlife. In Japan, in July 2016, Fukushima
Prefecture announced that the number of evacuees
following the Great East Japan earthquake
events, had fallen below 90,000, in part following
the lifting of evacuation orders issued in
some municipalities.
== Waste streams ==
Nuclear power has at least three waste streams
that may impact the environment:
Spent nuclear fuel at the reactor site (including
fissicoalon products and plutonium waste)
Tailings and waste rock at uranium mining
mills
Releases of ill-defined quantities of radioactive
materials during accidents
== 
Radioactive waste ==
=== 
High-level waste ===
The spent nuclear fuel from uranium-235 and
plutonium-239 nuclear fission contains a wide
variety of carcinogenic radionuclide isotopes
such as strontium-90, iodine-131 and caesium-137,
and includes some of the most long-lived transuranic
elements such as americium-241 and isotopes
of plutonium. The most long-lived radioactive
wastes, including spent nuclear fuel, are
usually managed to be contained and isolated
from the environment for a long period of
time. Spent nuclear fuel storage is mostly
a problem in the United States, following
a 1977 President Jimmy Carter prohibition
to nuclear fuel recycling. France, Great Britain
and Japan, are some of the countries which
rejected the repository solution. Spent nuclear
fuel is a valuable asset, not simply waste.
Disposal of these wastes in engineered facilities,
or repositories, located deep underground
in suitable geologic formations is seen as
the reference solution. The International
Panel on Fissile Materials has said:
It is widely accepted that spent nuclear fuel
and high-level reprocessing and plutonium
wastes require well-designed storage for long
periods of time, to minimize releases of the
contained radioactivity into the environment.
Safeguards are also required to ensure that
neither plutonium nor highly enriched uranium
is diverted to weapon use. There is general
agreement that placing spent nuclear fuel
in repositories hundreds of meters below the
surface would be safer than indefinite storage
of spent fuel on the surface.
Common elements of repositories include the
radioactive waste, the containers enclosing
the waste, other engineered barriers or seals
around the containers, the tunnels housing
the containers, and the geologic makeup of
the surrounding area.The ability of natural
geologic barriers to isolate radioactive waste
is demonstrated by the natural nuclear fission
reactors at Oklo, Africa. During their long
reaction period about 5.4 tonnes of fission
products as well as 1.5 tonnes of plutonium
together with other transuranic elements were
generated in the uranium ore body. This plutonium
and the other transuranics remained immobile
until the present day, a span of almost 2
billion years. This is quite remarkable in
view of the fact that ground water had ready
access to the deposits and they were not in
a chemically inert form, such as glass.
Despite a long-standing agreement among many
experts that geological disposal can be safe,
technologically feasible and environmentally
sound, a large part of the general public
in many countries remains skeptical. One of
the challenges facing the supporters of these
efforts is to demonstrate confidently that
a repository will contain wastes for so long
that any releases that might take place in
the future will pose no significant health
or environmental risk.
Nuclear reprocessing does not eliminate the
need for a repository, but reduces the volume,
reduces the long term radiation hazard, and
long term heat dissipation capacity needed.
Reprocessing does not eliminate the political
and community challenges to repository siting.The
countries that have made the most progress
towards a repository for high-level radioactive
waste have typically started with public consultations
and made voluntary siting a necessary condition.
This consensus seeking approach is believed
to have a greater chance of success than top-down
modes of decision making, but the process
is necessarily slow, and there is "inadequate
experience around the world to know if it
will succeed in all existing and aspiring
nuclear nations". Moreover, most communities
do not want to host a nuclear waste repository
as they are "concerned about their community
becoming a de facto site for waste for thousands
of years, the health and environmental consequences
of an accident, and lower property values".In
a 2010 Presidential Memorandum, U.S. President
Obama established the "Blue Ribbon Commission
on America’s Nuclear Future". The Commission,
composed of fifteen members, conducted an
extensive two-year study of nuclear waste
disposal. During their research the Commission
visited Finland, France, Japan, Russia, Sweden,
and the UK, and in 2012, the Commission submitted
its final report. The Commission did not issue
recommendations for a specific site but rather
presented a comprehensive recommendation for
disposal strategies. In their final report
the Commission put forth seven recommendations
for developing a comprehensive strategy to
pursue. A major recommendation was that "the
United States should undertake an integrated
nuclear waste management program that leads
to the timely development of one or more permanent
deep geological facilities for the safe disposal
of spent fuel and high-level nuclear waste".
=== Other waste ===
Moderate amounts of low-level waste are through
chemical and volume control system (CVCS).
This includes gas, liquid, and solid waste
produced through the process of purifying
the water through evaporation. Liquid waste
is reprocessed continuously, and gas waste
is filtered, compressed, stored to allow decay,
diluted, and then discharged. The rate at
which this is allowed is regulated and studies
must prove that such discharge does not violate
dose limits to a member of the public (see
radioactive effluent emissions).
Solid waste can be disposed of simply by placing
it where it will not be disturbed for a few
years. There are three low-level waste disposal
sites in the United States in South Carolina,
Utah, and Washington. Solid waste from the
CVCS is combined with solid radwaste that
comes from handling materials before it is
buried off-site.In the United States environmental
groups have said that uranium mining companies
are attempting to avoid cleanup costs at disused
uranium mine sites. Environmental remediation
is required by many states after a mine becomes
inactive. Environmental groups have filed
legal objections to prevent mining companies
from avoiding compulsory cleanups. Uranium
mining companies have skirted the cleanup
laws by reactivating their mine sites briefly
from time-to-time. Letting the mines sites
stay contaminated over decades increases the
potential risk of radioactive contamination
leeching into the ground according to one
environmental group, the Information Network
for Responsible Mining, which started legal
proceedings about March 2013. Among the corporations
holding mining companies with such rarely
used mines is General Atomics.
== Power plant emission ==
=== 
Radioactive gases and effluents ===
Most commercial nuclear power plants release
gaseous and liquid radiological effluents
into the environment as a byproduct of the
Chemical Volume Control System, which are
monitored in the US by the EPA and the NRC.
Civilians living within 50 miles (80 km) of
a nuclear power plant typically receive about
0.1 μSv per year. For comparison, the average
person living at or above sea level receives
at least 260 μSv from cosmic radiation.All
reactors in the United States are required
by law to have a containment building. The
walls of containment buildings are several
feet thick and made of concrete and therefore
can stop the release of any radiation emitted
by the reactor into the environment. If a
person is to worry about an energy source
that releases large amounts of radiation into
the environment, they should worry about coal-fired
plants. "The waste produced by coal plants
is actually more radioactive than that generated
by their nuclear counterparts. In fact, the
fly ash emitted by a [coal] power plant—a
by-product from burning coal for electricity—carries
into the surrounding environment 100 times
more radiation than a nuclear power plant
producing the same amount of energy." Coal-fired
plants are much more hazardous to people's
health than nuclear power plants as they release
much more radioactive elements into the environment
and subsequently expose people to greater
levels of radiation than nuclear plants do.
"Estimated radiation doses ingested by people
living near the coal plants were equal to
or higher than doses for people living around
the nuclear facilities. At one extreme, the
scientists estimated fly ash radiation in
individuals' bones at around 18 millirems
(thousandths of a rem, a unit for measuring
doses of ionizing radiation) a year. Doses
for the two nuclear plants, by contrast, ranged
from between three and six millirems for the
same period. And when all food was grown in
the area, radiation doses were 50 to 200 percent
higher around the coal plants."The total amount
of radioactivity released through this method
depends on the power plant, the regulatory
requirements, and the plant's performance.
Atmospheric dispersion models combined with
pathway models are employed to accurately
approximate the dose to a member of the public
from the effluents emitted. Effluent monitoring
is conducted continuously at the plant.
==== Tritium ====
A leak of radioactive water at Vermont Yankee
in 2010, along with similar incidents at more
than 20 other US nuclear plants in recent
years, has kindled doubts about the reliability,
durability, and maintenance of aging nuclear
installations in the United States.Tritium
is a radioactive isotope of hydrogen that
emits a low-energy beta particle and is usually
measured in becquerels (i.e. atoms decaying
per second) per liter (Bq/L). Tritium can
be contained in water released from a nuclear
plant. The primary concern for tritium release
is the presence in drinking water, in addition
to biological magnification leading to tritium
in crops and animals consumed for food.Tritium,
the mass 3 isotope of hydrogen is deliberately
created for thermonuclear weapons use, at
government-owned reactors like Watts Bar,
by irradiating lithium 6 with neutrons to
fission i1. Light water reactors, the standard
kind in the US, generate small quantities
of deuterium by neutron capture in the water.
This consumes enough neutrons that the natural
uranium needs enrichment to raise its fissile
U-235 content from 0.72% to 3.6% for Pressurised
Water Reactors. Canada's CANDU design uses
"heavy water", deuterium oxide, and can use
un-enriched uranium because deuterium captures
so very few of the neutrons. So the rate of
production of tritium from the small amount
of deuterium in US reactors must be quite
low.
Legal concentration limits have differed greatly
from place to place (see table right). For
example, in June 2009 the Ontario Drinking
Water Advisory Council recommended lowering
the limit from 7,000 Bq/L to 20 Bq/L. According
to the NRC, tritium is the least dangerous
radionuclide because it emits very weak radiation
and leaves the body relatively quickly. The
typical human body contains roughly 3,700
Bq of potassium-40. The amount released by
any given nuclear plant also varies greatly;
the total release for nuclear plants in the
United States in 2003 was from nondetected
up to 2,080 curies (77 TBq).
==== Uranium mining ====
Uranium mining is the process of extraction
of uranium ore from the ground. The worldwide
production of uranium in 2009 amounted to
50,572 tonnes. Kazakhstan, Canada, and Australia
are the top three producers and together account
for 63% of world uranium production. A prominent
use of uranium from mining is as fuel for
nuclear power plants. The mining and milling
of uranium present significant dangers to
the environment."An average value for the
thermal energy of coal 
is approximately 6150 kilowatt-hours(kWh)/ton.
.... The thermal energy released in nuclear
fission produces about 2 x 10E9 kWh/ton."
It follows that, for the same amount of energy,
much less uranium needs to be mined than coal,
cutting the environmental impacts of uranium
mining on nuclear energy generation.
In 2010, 41% of the world's uranium production
was produced by in-situ leaching, which uses
solutions to dissolve the uranium while leaving
the rock in place. The remainder was produced
by conventional mining, in which the mined
uranium ore is ground to a uniform particle
size and then the uranium extracted by chemical
leaching. The product is a powder of unenriched
uranium, "yellowcake," which is sold on the
uranium market as U3O8. Uranium mining can
use large amounts of water — for example,
the Roxby Downs Olympic Dam mine in South
Australia uses 35,000 m³ of water each day
and plans to increase this to 150,000 m³
per day.The Church Rock uranium mill spill
occurred in New Mexico on July 16, 1979 when
United Nuclear Corporation's Church Rock uranium
mill tailings disposal pond breached its dam.
Over 1,000 tons of solid radioactive mill
waste and 93 millions of gallons of acidic,
radioactive tailings solution flowed into
the Puerco River, and contaminants traveled
80 miles (130 km) downstream to Navajo County,
Arizona and onto the Navajo Nation. The accident
released more radiation, although diluted
by the 93 million gallons of mostly water
and sulfuric acid, than the Three Mile Island
accident that occurred four months earlier
and was the largest release of radioactive
material in U.S. history. Groundwater near
the spill was contaminated and the Puerco
rendered unusable by local residents, who
were not immediately aware of the toxic danger.Despite
efforts made in cleaning up cold war nuclear
arms race uranium sites, significant problems
stemming from the legacy of uranium development
still exist today on the Navajo Nation and
in the states of Utah, Colorado, New Mexico,
and Arizona. Hundreds of abandoned mines,
primarily used for the US arms race and not
nuclear energy production, have not been cleaned
up and present environmental and health risks
in many communities. The Environmental Protection
Agency estimates that there are 4000 mines
with documented uranium production, and another
15,000 locations with uranium occurrences
in 14 western states, most found in the Four
Corners area and Wyoming. The Uranium Mill
Tailings Radiation Control Act is a United
States environmental law that amended the
Atomic Energy Act of 1954 and gave the Environmental
Protection Agency the authority to establish
health and environmental standards for the
stabilization, restoration, and disposal of
uranium mill waste.
=== Risk of cancer ===
Numerous studies have been done on possible
effect of nuclear power in causing cancer.
Such studies have looked for excess cancers
in both plant workers and surrounding populations
due to releases during normal operations of
nuclear plants and other parts of the nuclear
power industry, as well as excess cancers
in workers and the public due to accidental
releases. There is agreement that excess cancers
in both plant workers and the surrounding
public have been caused by accidental releases
such as the Chernobyl accident. There is also
agreement that some workers in other parts
of the nuclear fuel cycle, most notably uranium
mining – at least in past decades – have
had elevated rates of cancer. However, numerous
studies of possible cancers caused by nuclear
power plants in normal operation have come
to opposing conclusions, and the issue is
a matter of scientific controversy and ongoing
study.There have been several epidemiological
studies that say there is an increased risk
of various diseases, especially cancers, among
people who live near nuclear facilities. A
widely cited 2007 meta-analysis by Baker et
al. of 17 research papers was published in
the European Journal of Cancer Care. It offered
evidence of elevated leukemia rates among
children living near 136 nuclear facilities
in the United Kingdom, Canada, France, United
States, Germany, Japan, and Spain. However
this study has been criticized on several
grounds – such as combining heterogeneous
data (different age groups, sites that were
not nuclear power plants, different zone definitions),
arbitrary selection of 17 out of 37 individual
studies, exclusion of sites with zero observed
cases or deaths, etc. Elevated leukemia rates
among children were also found in a 2008 German
study by Kaatsch et al. that examined residents
living near 16 major nuclear power plants
in Germany. This study has also been criticised
on several grounds. These 2007 and 2008 results
are not consistent with many other studies
that have tended not to show such associations.
The British Committee on Medical Aspects of
Radiation in the Environment issued a study
in 2011 of children under five living near
13 nuclear power plants in the UK during the
period 1969–2004. The committee found that
children living near power plants in Britain
are no more likely to develop leukemia than
those living elsewhere Similarly, a 1991 study
for the National Cancer Institute found no
excess cancer mortalities in 107 US counties
close to nuclear power plants. However, in
view of the ongoing controversy, the US Nuclear
Regulatory Commission has requested the National
Academy of Sciences to oversee a state-of-the-art
study of cancer risk in populations near NRC-licensed
facilities.A subculture of frequently undocumented
nuclear workers do the dirty, difficult, and
potentially dangerous work shunned by regular
employees. The World Nuclear Association states
that the transient workforce of "nuclear gypsies"
– casual workers employed by subcontractors
has been "part of the nuclear scene for at
least four decades." Existent labor laws protecting
worker's health rights are not properly enforced.
A 15-country collaborative cohort study of
cancer risks due to exposure to low-dose ionizing
radiation, involving 407,391 nuclear industry
workers showed significant increase in cancer
mortality. The study evaluated 31 types of
cancers, primary and secondary.Nuclear power
reactor accidents can result in a variety
of radioisotopes being released into the environment.
The health impact of each radioisotope depends
on a variety of factors. Iodine-131 is potentially
an important source of morbidity in accidental
discharges because of its prevalence and because
it settles on the ground. When iodine-131
is released, it can be inhaled or consumed
after it enters the food chain, primarily
through contaminated fruits, vegetables, milk,
and groundwater. Iodine-131 in the body rapidly
accumulates in the thyroid gland, becoming
a source of beta radiation.The 2011 Fukushima
Daiichi nuclear disaster, the world's worst
nuclear accident since 1986, displaced 50,000
households after radiation leaked into the
air, soil and sea. Radiation checks led to
bans of some shipments of vegetables and fish.Production
of nuclear power relies on the nuclear fuel
cycle, which includes uranium mining and milling.
Uranium workers are routinely exposed to low
levels of radon decay products and gamma radiation.
Risks of leukemia from acute and high doses
of gamma radiation are well-known, but there
is a debate about risks from lower doses.
The risks of other hematological cancers in
uranium workers have been examined in very
few studies.
=== Comparison to coal-fired generation ===
In terms of net radioactive release, the National
Council on Radiation Protection and Measurements
(NCRP) estimated the average radioactivity
per short ton of coal is 17,100 millicuries/4,000,000
tons. With 154 coal plants in the United States,
this amounts to emissions of 0.6319 TBq per
year for a single plant.
In terms of dose to a human living nearby,
it is sometimes cited that coal plants release
100 times the radioactivity of nuclear plants.
This comes from NCRP Reports No. 92 and No.
95 which estimated the dose to the population
from 1000 MWe coal and nuclear plants at 4.9
man-Sv/year and 0.048 man-Sv/year respectively
(a typical Chest x-ray gives a dose of about
0.06 mSv for comparison). The Environmental
Protection Agency estimates an added dose
of 0.3 µSv per year for living within 50
miles (80 km) of a coal plant and 0.009 milli-rem
for a nuclear plant for yearly radiation dose
estimation. Nuclear power plants in normal
operation emit less radioactivity than coal
power plants.Unlike coal-fired or oil-fired
generation, nuclear power generation does
not directly produce any sulfur dioxide, nitrogen
oxides, or mercury (pollution from fossil
fuels is blamed for 24,000 early deaths each
year in the U.S. alone). However, as with
all energy sources, there is some pollution
associated with support activities such as
mining, manufacturing and transportation.
A major European Union-funded research study
known as ExternE, or Externalities of Energy,
undertaken over the period of 1995 to 2005
found that the environmental and health costs
of nuclear power, per unit of energy delivered,
was €0.0019/kWh. This is lower than that
of many renewable sources including the environmental
impact caused by biomass use and the manufacture
of photovoltaic solar panels, and was over
thirty times lower than coals impact of €0.06/kWh,
or 6 cents/kWh. However, the energy source
of the lowest external costs associated with
it was found to be wind power at €0.0009/kWh,
which is an environmental and health impact
just under half the price of Nuclear power.
=== Contrast of radioactive accident emissions
with industrial emissions ===
Proponents argue that the problems of nuclear
waste "do not come anywhere close" to approaching
the problems of fossil fuel waste. A 2004
article from the BBC states: "The World Health
Organization (WHO) says 3 million people are
killed worldwide by outdoor air pollution
annually from vehicles and industrial emissions,
and 1.6 million indoors through using solid
fuel." In the U.S. alone, fossil fuel waste
kills 20,000 people each year. A coal power
plant releases 100 times as much radiation
as a nuclear power plant of the same wattage.
It is estimated that during 1982, US coal
burning released 155 times as much radioactivity
into the atmosphere as the Three Mile Island
accident. The World Nuclear Association provides
a comparison of deaths due to accidents among
different forms of energy production. In their
life-cycle comparison, deaths per TW-yr of
electricity produced from 1970 to 1992 are
quoted as 885 for hydropower, 342 for coal,
85 for natural gas, and 8 for nuclear. The
figures include uranium mining, which can
be a hazardous industry, with many accidents
and fatalities.
=== Waste heat ===
As with all thermoelectric plants, nuclear
power plants need cooling systems. The most
common systems for thermal power plants, including
nuclear, are:
Once-through cooling, in which water is drawn
from a large body, passes through the cooling
system, and then flows back into the water
body.
Cooling pond, in which water is drawn from
a pond dedicated to the purpose, passes through
the cooling system, then returns to the pond.
Examples include the South Texas Nuclear Generating
Station.The North Anna Nuclear Generating
Station uses a cooling pond or artificial
lake, which at the plant discharge canal is
often about 30 °F warmer than in the other
parts of the lake or in normal lakes (this
is cited as an attraction of the area by some
residents). The environmental effects on the
artificial lakes are often weighted in arguments
against construction of new plants, and during
droughts have drawn media attention. The Turkey
Point Nuclear Generating Station is credited
with helping the conservation status of the
American Crocodile, largely an effect of the
waste heat produced.
Cooling towers, in which water recirculates
through the cooling system until it evaporates
from the tower. Examples include the Shearon
Harris Nuclear Power Plant.A 2011 study by
the National Renewable Energy Laboratory determined
that the median nuclear plant with cooling
towers consumed 672 gallons of water per megawatt-hour,
less than the median consumption of concentrating
solar power (865 gal/MWhr for trough type,
and 786 gal/MWhr for power tower type), slightly
less than coal (687 gal/MWhr), but more than
that for natural gas (198 gal/MWhr). Once-through
cooling systems use more water, but less water
is lost to evaporation. In the median US nuclear
plant with once-through cooling, 44,350 gal/MWhr
passes through the cooling system, but only
269 gal/MWhr (less than 1 percent) is consumed
by evaporation.Nuclear plants exchange 60
to 70% of their thermal energy by cycling
with a body of water or by evaporating water
through a cooling tower. This thermal efficiency
is somewhat lower than that of coal-fired
power plants, thus creating more waste heat.
It is possible to use waste heat in cogeneration
applications such as district heating. The
principles of cogeneration and district heating
with nuclear power are the same as any other
form of thermal power production. One use
of nuclear heat generation was with the Ågesta
Nuclear Power Plant in Sweden. In Switzerland,
the Beznau Nuclear Power Plant provides heat
to about 20,000 people. However, district
heating with nuclear power plants is less
common than with other modes of waste heat
generation: because of either siting regulations
and/or the NIMBY effect, nuclear stations
are generally not built in densely populated
areas. Waste heat is more commonly used in
industrial applications.During Europe's 2003
and 2006 heat waves, French, Spanish and German
utilities had to secure exemptions from regulations
in order to discharge overheated water into
the environment. Some nuclear reactors shut
down.With Climate change causing weather extremes
such as heat waves, reduced precipitation
levels and droughts can have a significant
impact on all thermal power station infrastructure,
including large biomass-electric and fission-electric
stations alike, if cooling in these power
stations, namely in the steam condenser is
provided by certain freshwater sources. A
number of thermal stations use indirect seawater
cooling or cooling towers that in comparison
use little to no freshwater, while during
heat waves, those that were designed to heat
exchange with rivers and lakes, are under
regulations to reduce output or cease operations
to protect water levels and aquatic life.
This presently infrequent problem common among
all thermal power stations may become increasingly
significant over time.
If global warming continues, disruption of
electricity may occur if station operators
do not have other means of cooling, like cooling
towers available, these in the decades before
newer squat mechanical draft designs, were
frequently large structures and therefore
sometimes unpopular with the public.
== Water consumption and risks ==
During the process of nuclear power generation,
large volumes of water are used. The uranium
fuel inside reactors undergoes induced nuclear
fission which releases great amounts of energy
that is used to heat water. The water turns
into steam and rotates a turbine, creating
electricity. Nuclear plants must collect around
600 gallons/MWh for this process, so the plants
are built near bodies of water.
A 2011 study by the National Renewable Energy
Laboratory found that nuclear plants with
cooling towers consumed 672 gal/MWhr. The
water consumption intensity for nuclear was
similar to that for coal electricity (687
gal/MWhr), lower than the consumption rates
for concentrating solar power (865 gal/MWhr
for CSP trough, 786 gal/MWhr for CSP tower),
and higher than that of electricity generated
by natural gas (198 gal/MWhr).When intaking
water for cooling, nuclear plants, like all
thermal power plants including coal, geothermal
and biomass power plants, use special structures.
Water is often drawn through screens to minimise
to entry of debris. The problem is that many
aquatic organisms are trapped and killed against
the screens, through a process known as impingement.
Aquatic organisms small enough to pass through
the screens are subject to toxic stress in
a process known as entrainment. Billions of
marine organisms, such as fish, seals, shellfish,
and turtles, essential to the food chain,
are sucked into the cooling systems and destroyed.
== Greenhouse gas emissions ==
Many stages of the nuclear fuel chain — mining,
milling, transport, fuel fabrication, enrichment,
reactor construction, decommissioning and
waste management — use fossil fuels, or
involve changes to land use, and hence emit
carbon dioxide and conventional pollutants.
Nuclear energy contributes a very small amount
of emissions into the atmosphere which can
cause many environmental problems such as
global warming. Uranium is not burned in a
nuclear power plant as coal is so there are
no emissions from it. All of the waste that
comes from the fission of uranium stays in
the plant and is therefore able to be disposed
of in a safe way in which the uranium is kept
out of the environment. “About 73 percent
of emissions-free electricity in the United
States comes from nuclear plants.” Nuclear
energy produces far less carbon dioxide than
coal, 9 grams per kilowatt hour compared with
790–1017 grams per kilowatt hour for coal.
Also, nuclear energy produces the same amount
if not less greenhouse gasses than renewable
resources.
Like all energy sources, various life cycle
analysis (LCA) studies have led to a range
of estimates on the median value for nuclear
power, with most comparisons of carbon dioxide
emissions show nuclear power as comparable
to renewable energy sources.To better quantify
and compare greenhouse gas emissions reported
by researchers using many different assumptions
and techniques, the US National Renewable
Energy Laboratory is sponsoring meta-analysis
studies using harmonization, in which reported
life-cycle emissions are adjusted to consistent
assumptions. The results commonly narrow the
range of carbon emissions for a given energy
source. The resulting 2012 study published
in the Journal of Industrial Ecology analyzing
CO2 life cycle assessment emissions from nuclear
power determined that "the collective LCA
literature indicates that life cycle GHG emissions
from nuclear power are only a fraction of
traditional fossil sources and comparable
to renewable technologies". It also said that
for the most common category of reactors,
the light water reactor (LWR): "Harmonization
decreased the median estimate for all LWR
technology categories so that the medians
of BWRs, PWRs, and all LWRs are similar, at
approximately 12 g CO2-eq/kWh".With this data
in hand, therefore historically, nuclear power,
primarily from ~1970 to 2013, is estimated
to have prevented the atmospheric emission
of 64 gigatonnes of CO2-equivalent.Many commentators
have argued that an expansion of nuclear power
would help combat climate change. Others have
argued that it is one way to reduce emissions,
but it comes with its own problems, such as
risks related to severe nuclear accidents,
war attacks on nuclear sites, nuclear terrorism
and currently no generally accepted solution
for the disposal of radioactive waste which
needs to be heavily guarded for hundreds of
thousands of years. These advocates also believe
that there are better ways of dealing with
climate change than investing in nuclear power,
including the improved energy efficiency and
greater reliance on decentralized and renewable
energy sources.There is also some uncertainty
surrounding the future GHG emissions of nuclear
power, which has to do with the potential
for a declining uranium ore grade without
a corresponding increase in the efficiency
of enrichment methods. In a scenario analysis
of future global nuclear development, as it
could be effected by a decreasing global uranium
market of average ore grade, the analysis
determined that depending on conditions, median
life cycle nuclear power GHG emissions could
be between 9 and 110 g CO2-eq/kWh by 2050,
with the latter figure regarded as an unrealistic
"worst-case scenario" by the authors of the
study.Although this future analyses deals
with extrapolations for present Generation
II reactor technology, the same paper also
summarizes the literature on "FBRs"/Fast Breeder
Reactors, of which two are in operation as
of 2014 with the newest being the BN-800,
for these reactors it states that the "median
life cycle GHG emissions ... [are] similar
to or lower than [present] LWRs and purports
to consume little or no uranium ore.
== Environmental effects of accidents and
attacks ==
The worst accidents at nuclear power plants
have resulted in severe environmental contamination.
However, the extent of the actual damage is
still being debated.
=== Fukushima disaster ===
In March 2011 an earthquake and tsunami caused
damage that led to explosions and partial
meltdowns at the Fukushima I Nuclear Power
Plant in Japan.
Radiation levels at the stricken Fukushima
I power plant have varied spiking up to 1,000
mSv/h (millisievert per hour), which is a
level that can cause radiation sickness to
occur at a later time following a one-hour
exposure. Significant release in emissions
of radioactive particles took place following
hydrogen explosions at three reactors, as
technicians tried to pump in seawater to keep
the uranium fuel rods cool, and bled radioactive
gas from the reactors in order to make room
for the seawater.Concerns about the possibility
of a large-scale release of radioactivity
resulted in 20 km exclusion zone being set
up around the power plant and people within
the 20–30 km zone being advised to stay
indoors. Later, the UK, France and some other
countries told their nationals to consider
leaving Tokyo, in response to fears of spreading
nuclear contamination. New Scientist has reported
that emissions of radioactive iodine and cesium
from the crippled Fukushima I nuclear plant
have approached levels evident after the Chernobyl
disaster in 1986. On March 24, 2011, Japanese
officials announced that "radioactive iodine-131
exceeding safety limits for infants had been
detected at 18 water-purification plants in
Tokyo and five other prefectures". Officials
said also that the fallout from the Dai-ichi
plant is "hindering search efforts for victims
from the March 11 earthquake and tsunami".According
to the Federation of Electric Power Companies
of Japan, "by April 27 approximately 55 percent
of the fuel in reactor unit 1 had melted,
along with 35 percent of the fuel in unit
2, and 30 percent of the fuel in unit 3; and
overheated spent fuels in the storage pools
of units 3 and 4 probably were also damaged".
As of April 2011, water is still being poured
into the damaged reactors to cool melting
fuel rods. The accident has surpassed the
1979 Three Mile Island accident in seriousness,
and is comparable to the 1986 Chernobyl disaster.
The Economist reports that the Fukushima disaster
is "a bit like three Three Mile Islands in
a row, with added damage in the spent-fuel
stores", and that there will be ongoing impacts:
Years of clean-up will drag into decades.
A permanent exclusion zone could end up stretching
beyond the plant’s perimeter. Seriously
exposed workers may be at increased risk of
cancers for the rest of their lives...
John Price, a former member of the Safety
Policy Unit at the UK's National Nuclear Corporation,
has said that it "might be 100 years before
melting fuel rods can be safely removed from
Japan's Fukushima nuclear plant".In the second
half of August 2011, Japanese lawmakers announced
that Prime Minister Naoto Kan would likely
visit the Fukushima Prefecture to announce
that the large contaminated area around the
destroyed reactors would be declared uninhabitable,
perhaps for decades. Some of the areas in
the temporary 12 miles (19 km) radius evacuation
zone around Fukushima were found to be heavily
contaminated with radionuclides according
to a new survey released by the Japanese Ministry
of Science and Education. The town of Okuma
was reported as being over 25 times above
the safe limit of 20 millisieverts per year.Instead,
5 years later, the government expects to gradually
lift the designation of some “difficult-to-return-
zones”, a total 337 square kilometres (130
sq mi) area, from around 2021. Rain, wind
and natural dissipation have removed radioactive
contaminants, lowering levels, like at the
central district of Okuma town, to 9 mSv/year,
one-fifth the level of five years ago.
=== Chernobyl disaster ===
As of 2013 the 1986 Chernobyl disaster in
the Ukraine was and remains the world's worst
nuclear power plant disaster. Estimates of
its death toll are controversial and range
from 62 to 25,000, with the high projections
including deaths that have yet to happen.
Peer reviewed publications have generally
supported a projected total figure in the
low tens of thousands; for example an estimate
of 16,000 excess cancer deaths are predicted
to occur due to the Chernobyl accident out
to the year 2065, whereas, in the same period,
several hundred million cancer cases are expected
from other causes (from International Agency
for Research on Cancer published in the International
Journal of Cancer in 2006). The IARC also
released a press release stating "To put it
in perspective, tobacco smoking will cause
several thousand times more cancers in the
same population", but also, referring to the
numbers of different types of cancers, "The
exception is thyroid cancer, which, over ten
years ago, was already shown to be increased
in the most contaminated regions around the
site of the accident". The full version of
the World Health Organization health effects
report adopted by the United Nations, also
published in 2006, included the prediction
of, in total, no more of 4,000 deaths from
cancer. A paper which the Union of concerned
scientists took issue with the report, and
they have, following the disputed linear no-threshold
model (LNT) model of cancer susceptibility,
instead estimated, for the broader population,
that the legacy of Chernobyl would be a total
of 25,000 excess cancer deaths worldwide.
That places the total Chernobyl death toll
below that of the worst dam failure accident
in history, the Banqiao Dam disaster of 1975
in China.
Large amounts of radioactive contamination
were spread across Europe due to the Chernobyl
disaster, and cesium and strontium contaminated
many agricultural products, livestock and
soil. The accident necessitated the evacuation
of the entire city of Pripyat and of 300,000
people from Kiev, rendering an area of land
unusable to humans for an indeterminate period.As
radioactive materials decay, they release
particles that can damage the body and lead
to cancer, particularly cesium-137 and iodine-131.
In the Chernobyl disaster, releases of cesium-137
contaminated land. Some communities, including
the entire city of Pripyat, were abandoned
permanently. One news source reported that
thousands of people who drank milk contaminated
with radioactive iodine developed thyroid
cancer. The exclusion zone (approx. 30 km
radius around Chernobyl) may have significantly
elevated levels of radiation, which is now
predominantly due to the decay of cesium-137,
for around 10 half-lives of that isotope,
which is approximately for 300 years.Due to
the bioaccumulation of cesium-137, some mushrooms
as well as wild animals which eat them, e.g.
wild boars hunted in Germany and deer in Austria,
may have levels which are not considered safe
for human consumption. Mandatory radiation
testing of sheep in parts of the UK that graze
on lands with contaminated peat was lifted
in 2012.In 2007 The Ukrainian government declared
much of the Chernobyl Exclusion Zone, almost
490 square kilometres (190 sq mi), a zoological
animal reserve. With many species of animals
experiencing a population increase since human
influence has largely left the region, including
an increase in moose, bison and wolf numbers.
However other species such as barn swallows
and many invertebrates, e.g. spider numbers
are below what is suspected. With much controversy
amongst biologists over the question of, if
in fact Chernobyl is now a wildlife reserve.
=== SL-1 meltdown ===
The SL-1, or Stationary Low-Power Reactor
Number One, was a United States Army experimental
nuclear power reactor which underwent a steam
explosion and meltdown on January 3, 1961,
killing its three operators; John Byrnes,
Richard McKinley, and Richard Legg. The direct
cause was the improper manual withdrawal of
the central control rod, responsible for absorbing
neutrons in the reactor core. This caused
the reactor power to surge to about 20,000MW
and in turn, an explosion occurred. The event
is the only known fatal reactor accident in
the United States and the first to occur in
the world. The accident released about 80
curies (3.0 TBq) of iodine-131, which was
not considered significant due to its location
in a remote desert of Idaho. About 1,100 curies
(41 TBq) of fission products were released
into the atmosphere.Radiation exposure limits
prior to the accident were 100 röntgens to
save a life and 25 to save valuable property.
During the response to the accident, 22 people
received doses of 3 to 27 Röntgens full-body
exposure. Removal of radioactive waste and
disposal of the three bodies eventually exposed
790 people to harmful levels of radiation.
The hands of the initial victims were buried
separately from their bodies as a necessary
measure in response to their radiation levels.
=== Attacks and sabotage ===
Nuclear power plants, uranium enrichment plants,
fuel fabrication plants, and even potentially
uranium mines are vulnerable to attacks which
could lead to widespread radioactive contamination.
The attack threat is of several general types:
commando-like ground-based attacks on equipment
which if disabled could lead to a reactor
core meltdown or widespread dispersal of radioactivity;
and external attacks such as an aircraft crash
into a reactor complex, or cyber attacks.
Terrorists could target nuclear power plants
in an attempt to release radioactive contamination
into the environment and community.
Nuclear reactors become preferred targets
during military conflict and have been repeatedly
attacked by military air strikes:
In September 1980, Iran bombed the incomplete
Osirak reactor complex in Iraq.
In June 1981, an Israeli air strike completely
destroyed Iraq's Osirak reactor.
Between 1984 and 1987, Iraq bombed Iran's
incomplete Bushehr nuclear plant six times.
In Iraq in 1991, the U.S. bombed three nuclear
reactors and an enrichment pilot facility.The
United States 9/11 Commission has said that
nuclear power plants were potential targets
originally considered for the September 11,
2001 attacks. If terrorist groups could sufficiently
damage safety systems to cause a core meltdown
at a nuclear power plant, and/or sufficiently
damage spent fuel pools, such an attack could
lead to a widespread radioactive contamination.
According to a 2004 report by the U.S. Congressional
Budget Office, "The human, environmental,
and economic costs from a successful attack
on a nuclear power plant that results in the
release of substantial quantities of radioactive
material to the environment could be great."
An attack on a reactor's spent fuel pool could
also be serious, as these pools are less protected
than the reactor core. The release of radioactivity
could lead to thousands of near-term deaths
and greater numbers of long-term fatalities.Insider
sabotage occurs because insiders can observe
and work around security measures. In a study
of insider crimes, the authors repeatedly
said that successful insider crimes depended
on the perpetrators’ observation and knowledge
of security vulnerabilities. Since the atomic
age began, the U.S. Department of Energy’s
nuclear laboratories have been known for widespread
violations of security rules. A better understanding
of the reality of the insider threat will
help to overcome complacency and is critical
to getting countries to take stronger preventative
measures.Researchers have emphasized the need
to make nuclear facilities extremely safe
from sabotage and attacks that could release
massive quantities of radioactivity into the
environment and community. New reactor designs
have features of passive safety, such as the
flooding of the reactor core without active
intervention by reactor operators. But these
safety measures have generally been developed
and studied with respect to accidents, not
to the deliberate reactor attack by a terrorist
group. However, the US Nuclear Regulatory
Commission does now requires new reactor license
applications to consider security during the
design stage.
== Natural disasters ==
Following the 2011 Fukushima I nuclear accidents
there has been an increased focus on the risks
associated with seismic activity and the potential
for environmental radioactive release. Genpatsu-shinsai,
meaning nuclear power plant earthquake disaster
is a term which was coined by Japanese seismologist
Professor Katsuhiko Ishibashi in 1997. It
describes a domino effect scenario in which
a major earthquake causes a severe accident
at a nuclear power plant near a major population
centre, resulting in an uncontrollable release
of radiation in which the radiation levels
make damage control and rescue impossible,
and earthquake damage severely impedes the
evacuation of the population. Ishibashi envisages
that such an event would have a global impact
seriously affecting future generations.The
1999 Blayais Nuclear Power Plant flood was
a flood that took place on the evening of
December 27, 1999. It was caused when a combination
of the tide and high winds from the extratropical
storm Martin led to the sea walls of the Blayais
Nuclear Power Plant in France being overwhelmed.
The event resulted in the loss of the plant's
off-site power supply and knocked out several
safety-related systems, resulting in a Level
2 event on the International Nuclear Event
Scale. The incident illustrated the potential
for flooding to damage multiple items of equipment
throughout a plant, with the potential for
radioactive release.
== Sustainability ==
According to Joshua M. Pearce of Michigan
Technological University, on a global-scale
a “sustainable nuclear power system” would
entail: (i) dramatically improving efficient
energy use and greenhouse gas emissions intensity
by updating technology and functionality through
the entire life cycle; (ii) improving nuclear
security to reduce nuclear power risks and
making sure that the nuclear industry can
operate without large public nuclear accident
insurance subsidies; (iii) eliminating all
radioactive waste at the end of life and minimizing
the environmental impact during the nuclear
fuel cycle; and (iv) the nuclear industry
must regain public trust or face obsolescence,
as a diverse range of renewable energy technologies
are quickly commercialized. Pearce also believes
that the nuclear industry must address the
issue of equity, both in the present and for
later generations.
== Decommissioning ==
Nuclear decommissioning is the process by
which a nuclear power plant site is dismantled
so that it will no longer require measures
for radiation protection. The presence of
radioactive material necessitates processes
that are occupationally dangerous, and hazardous
to the natural environment, expensive, and
time-intensive.Most nuclear plants currently
operating in the US were originally designed
for a life of about 30–40 years and are
licensed to operate for 40 years by the US
Nuclear Regulatory Commission. The average
age of these reactors is 32 years. Therefore,
many reactors are coming to the end of their
licensing period. If their licenses are not
renewed, the plants must go through a decontamination
and decommissioning process. Many experts
and engineers have noted there is no danger
in these aged facilities, and current plans
are to allow nuclear reactors to run for much
longer lifespans.
Decommissioning is an administrative and technical
process. It includes clean-up of radioactivity
and progressive demolition of the plant. Once
a facility is fully decommissioned, no danger
of a radiologic nature should persist. The
costs of decommissioning are to be spread
over the lifetime of a facility and saved
in a decommissioning fund. After a facility
has been completely decommissioned, it is
released from regulatory control, and the
licensee of the plant will no longer be responsible
for its nuclear safety. With some plants the
intent is to eventually return to "greenfield"
status.
== See also
