The Dangers of
Radiation
Canadian nuclear energy generation
entails risk of illness and death through radiation at all stages of
production: mining and processing into fuel rods; nuclear power generation; and
disposal of nuclear waste. These risks are not entirely understood due to the
lack of clear understanding of the means by which radiation causes illness.
However, more than 6 decades of nuclear power production in Canada as well as
the experiences of other countries provide a context for understanding the
risks that Canada is likely to face due to this industry. And this will shed
some light on how risky nuclear power is compared to other sources of energy.
Nuclear waste is
dangerous partly because of chemical toxicity and partly due to the ionizing
radiation of the waste. Avoiding chemical toxicity is mainly addressed during
the mining stage when small radioactive materials are air-bound and potentially
enter the water supply. Radiation is an ongoing concern to the nuclear
industry, advocacy groups and the regulatory agencies. The absorption of ionizing
radiation is measured in millisieverts (mSv). The typical background radiation
people receive is around 1.8 mSv / year and the Canadian Nuclear Safety
Commission’s guideline for additional radiation for the public is less than 1
mSv/year (Canadian Nuclear Safety Commission 2017a).
It is uncertain
how much radiation is safe, as the mechanisms through which ionizing radiation
lead to increased cancer risk are not well-understood. One model is that there
is a critical threshold of 100 mSv at which increasing radiation exposure
increases risk and that would suggest that low levels of nuclear exposure is
not problematic (Cuttler 2014). However, Canadian safety guidelines assume the
more conservative model in which any ionizing radiation exposure increases
risk.
The initial
evidence that nuclear radiation was dangerous came from observing the
after-effects of the nuclear fallout after the atom bombs were dropped on Japan
in 1945. Among those exposed to 6000 millisieverts, all of them died. Of those
exposed to 4500 mSv, half died (MIT). Additional evidence came from observing
effects of the Chernobyl nuclear power plant meltdown in 1986 and the Fukushima
meltdown in 2009. At somewhat lower levels of 1000 mSv, radiation sickness
occurs. Emergency workers are limited to 500 mSv/year and workers at nuclear
power plants are limited to 100 over a 5-year span, and 50 mSv in a giver year
(Canadian Nuclear Safety Commission 2017a).
Uranium mining and
processing
Canada’s uranium ore is mined in
the Athabasca Basin in northern Saskatchewan. It contains very high grade
uranium ore, between 10 and 100 times richer than uranium ore mined elsewhere
and is on average 18% uranium (NRCAN 2017a). This occurs at a mere 3 mines. The
MacArthur River Mine produced 8173 tonnes of uranium oxide in 2016; the Cigar
Lake Mine 7863 tonnes; and the Rabbit Lake Mine 505 tonnes. Numerous sites have
been decommissioned and 3 more are proposed.
https://www.cnsc-ccsn.gc.ca/eng/resources/maps-of-nuclear-facilities/results.cfm?category=radioactive-waste-management-facilities
The mining process
entails certain pollution problems, however. The uranium itself is damaging to
tissues if inhaled or ingested, so mining it requires certain precautions.
Uranium leakage itself is a risk, but worse are the associated by-products of
thorium-230 and radium 236, in the form as large waste rocks of mill-tailings. Despite
the potential for harm however, workers at mines and mills only receive an
additional 1 mSv of radiation per year, on average (Canadian Nuclear
Association 2017).
Winfield, et al. (2006)
estimate that in 2001, there were 108 million tonnes of waste rock, and such
waste was being added at about 3 million tonnes a year. Using this yearly
figure to estimate ensuing years provides an estimate of about 153 million
tonnes of waste rock in 2016. They also estimate tailings of 575,000 tonnes in
2003. However they erroneously use 1.8% uranium grade rather than 18%. Making
this adjustment would suggest that better estimate would be 481,340 tonnes in
that year. Adding 13 years at that rate to the stock of 213 million tonnes in
2003, suggests a stock of about 219 million tonnes of tailings in 2016.
Currently, mill
tailings are managed by placing them back on the site of mined out pits, after
partly dewatering the area in order to minimize contamination of the water
table. Groundwater channels are directed toward the site, rather than away from
it (NRCAN 2007c).
The mill tailings
can theoretically seep into groundwater, producing toxic drinking water to
surrounding communities. This has proved to be a major concern in the United
States with more uranium mines and more densely populated areas (Institute For
Energy and Environmental Research 2017). Still, since Canadian mines are in the
Athabasca river region, there is danger of contamination of nearby water areas.
This is a risk mainly to a small population in northern Saskatchewan where
mining currently occurs. However 10 of the tailing management facilities are
near Eliot Lake, Ontario, population 10,000 (Canadian Nuclear Safety Commission
2017b).
The mined uranium ore is shipped to Blind
River to be processed into uranium trioxide. Then it is further to Port Hope,
Ontario, where it is converted into uranium hexafluoride for export, as well as
uranium dioxide. The uranium dioxide is used to create uranium fuel in Port
Hope, Toronto and Peterborough and then shipped to CANDU reactors at each of
Canada’s 4 active nuclear power plants.
Nuclear Power Plants
https://www.cnsc-ccsn.gc.ca/eng/resources/maps-of-nuclear-facilities/results.cfm?category=radioactive-waste-management-facilities
Canada’s nuclear power is generated
at 4 nuclear power plants. These are the Bruce Nuclear Generating Station in
Tiverton, Ontario on Lake Huron; the Darlington Nuclear Generating Station in
Clarington Ontario, on Lake Ontario; the Pickering Nuclear Generating Station
in Pickering Ontario, also on Lake Ontario and the Point Lepreau Nuclear
Generating Station, near Point Lepreau, New Brunswick, on the Bay of Fundy. The
Gentily Generating Station in Quebec was decommissioned in 2012 (NRCAN 2017b). These
currently operating plants collectively contain 19 CANDU reactors. These
reactors are Canadian inventions, and use deuterium-oxide to catalyze uranium
fuel reactions. Additionally, the CANADU reactors are capable of using Thorium
as a fuel source, which is 4 times as abundant as uranium and may be exploited
in the future.
Whether nuclear
power workers have a significant increased health risk is controversial. Lemstra
(2009) in a meta-analysis of the risks of nuclear power globally found that
Canada posted much higher risks of developing fatal cancers, but the sample of
affected workers was low enough that this effect might have been by chance.
Lemstra suggests that Canadian nuclear workers faced increased risk of fatal
cancer of near 665% higher than average Canadians and 97% on average of a 15
country study. However, researchers such as Chambers (2009) have pointed out
that this is the increased risk per
Sievert. But since workers are only subjected to about 20 mSv per year, it
implies that the additional risk that the international cohort power plant
workers face is about 2% greater (Chambers 2009). Even using Lemstra’s figures,
those workers getting less than 100 mSv don’t have a statistically significant
additional risk (Cuttler 2014).
Canada has not yet
had any serious nuclear accidents. In 1952 and 1958 Canada experienced its most
serious accidents at the Chalk River Laboratories but even in those cases no
fatalities were caused, nor was there any increased risk to the public established.
The most serious impact was on a Bjarnie Paulsen, cleanup worker, who was found
to have developed non-fatal skin cancer as a result of his cleanup activities
(Curan 1985). Since the 1950’s, there have been minor incidents, but mostly
they involved leakages of heavy water or coolant. There was an incident in 1997
in which a small amount of nuclear waste (i.e. 0.1% of the plant’s allowance)
was dumped into Lake Ontario in error. But the CNSC determined this posed
negligible risk to the nearby community.
The
ongoing radiation from normal nuclear power plant operation is not an area of
great concern. Before being decommissioned, Chalk River Laboratories emitted
the most radiation of any of the plants. It amounted to 0.135 mSv to the public
at large; 5 mSv for the most at risk plant workers (Canadian Nuclear Safety
Commission 2017a).
Disaster
scenarios like that at Fukushima are not considered very likely by Canadian
Nuclear regulators or the industry, but the risks are not entirely trivial.
Historical geological dangers to consider involve earthquakes and tsunamis.
Earthquakes are not currently a major risk. In the last 500 years, Canada has
only had 8 earthquakes that measured 7.0 or above on the Richter Scale. The
only one within 1000 km of a nuclear power plant or storage facility occurred
in Charlevoix, Quebec in 1663. Even at the time, the property damage was
minimal (Natural Resources Canada 2011). Geological changes over the course of
tens of thousands of years will alter these risks, but do not appear to be a
significant risk over a timeframe of mere centuries.
Tsunamis
are of some long-term concern, though perhaps not with current sea levels. The
Point Lepreau Nuclear Generating Station is on the Bay of Fundy, which has the
highest tides in the world. Because of this, it attracted a considerable amount
of attention from the media and anti-nuclear activists such as Greenpeace
following the Fukushima disaster (Dunphy 2014). There are no protective tsunami
barriers like those that existed at Fukushima, but the power plant is 14 meters
above sea level. Also, New Brunswick is at much less risk than Japan, on
account of the land mass of Nova Scotia acting as a kind of buffer from ocean
waves.
Waste management
facilities
https://www.cnsc-ccsn.gc.ca/eng/resources/maps-of-nuclear-facilities/results.cfm?category=radioactive-waste-management-facilities
Short to
Intermediate-term Storage
The management of nuclear waste is
the responsibility of the firms that produce it—that is, the 4 active nuclear
power plants, the decommissioned ones, and researchers who use small amounts of
radioactive material. Approximately 94% of the waste is from the 4 active plants
and about 5% from the 2 Gentily plants, which were decommissioned in 2012 (National
Waste Management Organization 2017). There are 20 sites for nuclear waste
disposal in Canada: 4 in Tiverton, Ontario; 4 in Port Hope, Ontario; 2 in Chalk
River, Ontario; 2 in Trois-Rivieres, Quebec; 1 in Pickering, Ontario, 1 in
Saint John, New Brunswick; 1 in Darlington, Ontario; 1 in Brampton, Ontario, 1
in Branford, Ontario; 1 in Toronto, Ontario; 1 in Edmonton, Alberta; and 1 in
Pinawa, Manitoba (National Waste Management Organization 2017).
In mid-2015,
Canada had 2.6 million used fuel bundles. At close to 22 kilograms each, that
totals about 52000 tons of nuclear waste. About 58% of these is being stored in
“wet storage” and 42% in “dry storage.” Spent fuel rods are initially stored in
water pools for cooling for a period of 7 to 10 years. At the beginning, the waste is approximately
3,000,000 times more radioactive than the source uranium. It is at this stage
that nuclear energy poses its greatest risk. But the cooling process reduces
the radioactivity to approximately 30,000 times as radioactive. After this process, they are stored in
concrete storage containers which are ½ inch of steel, encased in 20 inches of
cement, coated in ½ inch of steel again. These containers are designed to last
for 50 years, at which point they might be reinforced, or discarded with the
nuclear waste transferred to new containers. The containers are regularly
monitored. After 100 years of storage it is still more than 1000 times as
radioactive as uranium and after 1000 years, more than 100 times as radioactive
(National Waste Management Organization 2017).
Long-term storage
The current federal discussion
surrounding long-term storage of Canada’s nuclear waste are about how to
transition to long-term storage, and to some extent, what the long-term is.
Estimates for operating a storage facility for 300 years, starting around 2035,
run between $18 billion and $28 billion (Globe and Mail, 2009). Unfortunately,
300 years is not sufficient to dissipate the radioactivity of the waste. The
cost of $30 billion per 300 years is therefore for an indefinite period.
It
is also not yet clear where the optimal storage facility will be. The federal
government convened a panel under the aegis of the Canadian Nuclear Safety
Commission and they recommended a facility underground, in limestone. But the
panel faced criticism suggesting that seepage was inevitable over the long-term
and this might change the geology of the area. Moreover, in the indefinite
time-horizon, we don’t really know what the geology of an area will be, so this
is not a permanent solution (Mittlestaedt 2009).
The
leading proposed site for long-term waste disposal is the Deep Geologic Repository
(DGR), near the Bruce power plant, and also about 1 km from Lake Huron. The DGR
is proposed to rest 680 meters below the surface and about 500 meters below the
deepest part of Lake Huron. At such depths, the risks to the lake were found to
be negligible (Ontario Power Generation 2017). Apart from being deep, the land
is a combination of limestone and shale and hence not very permeable for
radiation. There is also very little seismic activity there.
Health Risks Relative
to Other Energy Sources
Although there is a health risk of
approximately 0.07 fatalities per terawatt of nuclear energy, the comparable
risk for natural gas based energy is 2.8 fatalities and 24.8 for coal
(Lemstra). This is based on several studies published in the Lancet up to 2007
in Europe and does not consider the risks of severe nuclear accidents at a
scale not yet witnessed. But it equally leaves out projected effects of global
warming due to the burning of fossil fuel. One cannot be extremely confident
about whether chemical or nuclear power generation poses a great risk, due to
the large uncertainties about the long-run impacts of radioactive nuclear
isotopes on the one hand, and the evolution of CO2-fueled global warming on the
other. But a provisional evaluation might be that nuclear power seems to
generate localized risks whereas chemical energy entails risks of global
magnitudes.
Conclusion
Based on the recent scale of power
generation across several industries, including effects to nuclear power plant
workers as well as those affected by nuclear accidents, nuclear power has
proven remarkably safe. Although future risks are very difficult to quantify
for a substance that will remain as waste material for millennia, nuclear power
has been far safer than fossil fuel based energy—our principle source of
energy.
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