Why We CANDU Nuclear: A Review of Why Nuclear is Important for the 21st Century
Let’s talk about nuclear power, the grand technology that was supposed to pull humanity out of the barbarism of the 20th century and into the Jetson like 21st. At least, that’s until Chernobyl, Five Mile Island, and a Nuclear Arms Race, sullied its reputation and forever tarnished such technology.
Nowadays when people talk about nuclear power, the vast majority simply shrug and brush off the idea, stating something along the lines of it being too unsafe or too expensive but are otherwise indifferent. Then there are two vocal minorities. One which stands staunchly against the idea of nuclear energy, brought together in an alliance of Greenpeace and NIMBY suburbanites. Then there is the even odder group of nuclear defendants who claim that there is still a role for nuclear power in our world.
I am one of that latter group.
My grandfather was one of the pioneering control room operators in Pickering, Ontario. He worked in the early Canadian nuclear program and this article is in memory of him.
I was raised with a worldview that nuclear was safe and those vague childhood stories followed me into my adult life. When I was getting my Bachelors in Environmental Studies, I stood out as a defender of nuclear energy and even now, where my degree has failed to secure me gainful employment, I still have interest in the subject matter.
So, let’s discuss the CANadian Deuterium Uranium reactor, or CANDU reactor for short, a Canadian-made nuclear system. In this article, I will argue that it’s an environmentally-friendly, safe, and low waste alternative to the less well received reactors of the United States, Russia, and Japan.
In total there are 55 of these reactors in the world in countries such as Canada, South Korea, China, India, Argentina, Romania, and Pakistan.
But before we begin, let’s briefly discuss what makes the CANDU reactor different from other nuclear reactors. The two main differences are its fuel and moderator.
Most reactors are light-water reactors which use standard H20 and an enriched uranium. While not weapon’s grade, this uranium can range from anywhere between 3–20% enrichment levels (percentage that is U235-isotopes).
The CANDU reactor, on the other hand, uses heavy water as its moderator and either low- or non-enriched uranium for fuel (natural has around 0.7% U-235). Heavy water is used as the moderator because it doesn’t absorb spare neutrons as easily as regular water, meaning CANDU reactors can get more fissile energy out of natural uranium.
As such, CANDU reactors cut out one of the major fears of nuclear power which is the fact that enriching uranium for fuel can easily lead to enriching uranium for weapons which has made the public skeptical of this technology and especially exporting it.
Along with this, I will also be discussing the environmental benefits of nuclear power, the safety systems put in place on CANDU reactors, and the unique ability of CANDU reactors to recycle byproducts created from other reactors.
Hopefully, with this information, we can get a better understanding of what makes the CANDU reactor special and a compelling solution to our current climate crisis.
The Glowing Fuel Rods Aren’t the Only Thing That’s Green
Nuclear power generation itself doesn’t produce much carbon dioxide, yet that doesn’t mean that carbon isn’t involved in the process.
After all there is still the construction of reactors which require heavy machinery and carbon rich materials. Then there is also the mining, transportation, and processing of uranium ore which all require machinery and trucking to move from point A to point B. And lastly, there is the tedious and hard work involved with decommissioning retired reactors.
That being said, if we can better understand where the carbon-intensive energy inputs into nuclear energy are coming from, we can compare them to other energy sources.
So, let’s begin with construction.
In terms of steel and concrete, CANDU reactors require a greater number of inputs than coal power plants (in terms of units of steel and concrete per unit of energy). In comparison to other forms of energy, however, CANDU reactors use far less. For example, it uses half as much as hydro, one-fifth of winds, and less than one-tenth of solar’s requirements.
In total the construction of a CANDU reactor generates 2220 tonnes of CO2 for every Terawatt-hour that a CANDU reactor will generate over the course of its life (from now on tonnes of CO2 per Terawatt-hour will be t/Twh). Ironically, the construction of coal and natural gas facilities generate less carbon via their construction, while renewable sources (wind and solar) generate more by a magnitude of ten.
A Terawatt-hour, for reference, is a massive unit of energy and in total humanity produces about 27500 Terawatt-hours a year.
Of course, construction is only one part of energy generation. Next, we can look at the cost of making fuel.
First, there is the actual mining of the uranium. In Canada, there are three mines, two of which use hydro while the third is diesel powered. All of these sites use gasoline powered equipment and vehicles. In total, these generate 138,000 tonnes of CO2 or to put it another way they generate 220 t/Twh.
Once mined the ore is put under a chemical treatment that produces another 60 t/Twh. Transportation to processing facilities brings about another 5 tonnes. While processing and fabrication of fuel garner another 75 tonnes and 10 tonnes respectively. In total the process of mining, processing, and transporting fuel, generates a further 370 t/Twh.
Next, I’ll talk about the CO2 generated from the energy itself. While nuclear energy produces a negligible amount of CO2, what’s important to display here is how it competes against other forms of energy, especially dirty energy. Against coal, nuclear power saves 1117.38 kilotonnes per Twh (kilotonnes is 1000 tonnes and will be denoted as kt/Twh when necessary). Against natural gas it saves between 406.17–773.06 kt/TWh. And against renewables, nuclear performs slightly worse, emitting between 11.8–32.23 kt/TWh more than these other green energy sources.
These losses mostly come from the carbon generated from the production of heavy water and can be limited if heavy water is produced using green energy sources.
Finally, there is the decommissioning of nuclear power plants. While not as energy intensive as the construction of these facilities, the decommissioning of nuclear power stations is the most carbon intensive of all energy methods, generating a total of 610 t/Twh. In comparison, decommissioning non-renewable power stations generates between 30–90 t/Twh while renewable stations generate between 210–480 t/Twh.
So, after all of that math and explanation we can prove that nuclear power is far more efficient than coal, producing only a mere 3180 t/Twh or about 0.3% of what coal produces. While other fossil fuels fare slightly better, they are also beaten handily by nuclear.
Compared to other renewables, the picture is a little blurrier. In terms of construction, nuclear power is far less energy intensive due to the lighter requirement of materials. But in terms of generation and decommissioning, it fairs a little worse due to the energy costs of making its fuel and the intensive procedures needed to decommission such facilities. Still, I’d personally believe that it’s comparable in overall scope.
That being said, the environmental argument against nuclear power is not just fought in the realm of carbon dioxide. After all, in the wake of Three Mile Island, Chernobyl, and Fukushima, it was not the sudden release of carbon dioxide that scared the public into phobia.
So, let’s turn our attention towards safety.
Now We are All Sons of a Bitches
Nuclear power has always had its reputation sullied by its close and intimate relationship with weaponry. It’s not an easy image to shake as there is not a soul alive who is not aware of Hiroshima and Nagasaki. Plus, even when used peacefully, nuclear fission can still be a destructive force.
Three Mile Island, Fukushima, and especially Chernobyl are fresh memories to many and are portrayed in popular culture as horrific accidents that caused much destruction and hardship.
Yet, let me bring forth another set of figures.
Coal kills 120 individuals for every TWh of power produced, oil kills 99.5, natural kills 71.9, wind kills between 1.78–8.5, and even solar has a death toll of 0.245. Where does nuclear fall upon this scale?
Nuclear kills 0.009 individuals per TWh.
Because failures in engineering are an unfortunate reality within any form of power generation or with any machine. But failures can be made more uncommon with good engineering and maintenance.
There’s a reason there are only three famous examples of failures in nuclear power while there are currently 680 reactors operating across the globe. Three major failures over the course of more than seventy years.
But with that being said when one does fail, it’s a big event and can’t be ignored like failures in other forms of energy generation.
So maybe a better course of action would be to discuss the safety features of the CANDU reactor system. A system which has never had a major failure during its entire operational history of more than sixty years. Maybe with these features in mind we can help dispel some of the fear around nuclear power.
There are four fundamental safety philosophies of a CANDU reactor: the shutdown of a reactor and maintenance of safe shutdown conditions, the removal of decay heat from the fuel, providing a secure barrier to limit radioactivity, and the steady supply of information to monitor facility status.
To help in this endeavor, there are four special safety systems: Shutdown Systems 1 and 2, Emergency Core Cooling System, and Containment.
Let’s start with the shutdown systems and how they work.
The first shutdown system is a series of 28 shutdown rods which are spring-launched into the reactor core and made of a material known as cadmium that sucks up excess neutrons, slowing or stopping a nuclear reaction. They can also be deployed without electricity, ensuring that the sudden loss of power to safety systems would not stop a reactor shutdown.
The second shut down system dumps a neutron absorbing gas (gadolinium nitrate) into the reactor chamber. This has the same effect as the first shutdown system but is independent of it, ensuring that if either system is knocked out of commission there is a backup in place.
The Emergency Core Cooling System is designed to cool the core in the event of a sudden loss-of-coolant. It essentially uses water for this purpose in one of three methods. For small coolant accidents it removes water from the reactor floor and uses it to cool the core. For more severe accidents it has dousing tanks that can administer a medium-pressure spray. And in the most severe cases there are high-pressure water injectors that can spray water right into the core itself. Like with the shutdown system, these three water systems are all independent of each other. Thus, the loss of one means there are two more waiting to support it.
And finally, there’s the structure of the facility, the final line of defense. And were not just talking about the building, nor the reactor, but down to the fuel itself. Everything about the CANDU system is engineered as a safety precaution.
Let’s start with the fuel.
In a CANDU reactor, the fuel pellets are made up of uranium dioxide which does not emit radiation unless it’s hot. So, when the fuel is not being used for generation it is stored in climate-controlled storage (pre-reaction) or in cooling ponds (post-reaction) both of which ensure that pellets aren’t emitting needless radioactivity.
Then beyond the pellets are the fuel rods which are made out of zircaloy and graphite which are tested to endure heat and traumatic blunt force. Already that’s two layers of protection before it’s even within the reactor.
The reactor itself is surrounded by a containment structure made of reinforced metal and concrete. In the event of an accident both the reactor and this structure would need to be breached in order for radiation to leak out. And this structure is regularly monitored to ensure it is not leaking or emitting excess radioactivity.
Then there is the building itself which is made of a post-tensioned prestressed concrete with epoxy liners, energy sinks, hydrogen control systems, and enough other technical jargon to make me feel safe, providing a final layer of stalwart defense against a breach. And if this were breached, there is an exclusion zone around every CANDU facility to further protect the public. Not that one of these reactors has ever been breached.
And these are just the special systems and don’t include the redundancies in features, religious monitoring of facilities, and evermore sophisticated engineering that goes into these reactors. So, with such systems in place, it’s easy to understand why the CANDU reactor system can hold the claim of not causing a single fatality from radiation in its entire operational history.
In fact, CANDU reactors often go well below their limits in terms of radioactivity. The Atomic Energy Control Board of Canada determined that individuals working in atomic facilities should only be exposed to a maximum of 0.5 rems of radioactivity over the course of a year. And in CANDU reactors this figure is more like 0.005 rems annually. A mere percentage point of this goal.
But with that quick examination of safety features out of the way, let’s turn to the subject of waste. An issue that poses the biggest problem for nuclear power but also reveals the biggest benefit of the CANDU system.
Recycling the Unrecyclable
On March 23rd, 2010 a CANDU reactor started another day of operation in Qinshan, China, starting on a fresh set of fuel rods to provide power to Chinese cities and communities. Except today’s fuel rods were different, they were using recycled uranium.
The fuel in these rods came from spent fuel pellets from light water reactors and depleted uranium from enrichment facilities. As I mentioned earlier, CANDU reactors operate on natural or low-enriched uranium, meaning that the leftover fuel from enriched nuclear power planets can find a second life within CANDU reactors.
There is also the efficiency of CANDU reactors to bring into play. Because of how they operate, they manage to use 30% less fuel than competing reactor technologies ensuring that they use less uranium and create less radioactive waste.
CANDU reactors also provide a solution to the issue of dealing with plutonium stocks, offering a future to nuclear power once easy to recover uranium stockpiles are depleted.
The first is obviously a more pressing issue to our cultural zeitgeist due to the fears of plutonium in weapon’s manufacturing and has been one of the largest issues with converting the public opinion towards nuclear power. After all, nuclear power has created 1700 tonnes of plutonium over the years.
That is what we’d call: ‘a bad look’.
But what’s this about depleted uranium stocks?
Well uranium isn’t the most abundant mineral in the world and is pretty hard to access. It’s estimated that at current rates of consumption we have roughly 230-years of the stuff left. And that’s at current consumption levels and not at the heightened consumption it would take to effectively combat climate change (the World Nuclear Association stated that we’d have to triple our atomic power generation in order to meet climate change targets).
That’s where a magic little rock called thorium comes into play. It’s three-to-four times more abundant than uranium and could offer a solution to atomic power generation. While not fissile on its own, research is being done to see if it can be made fissile when combined with plutonium.
Research which is quite promising.
It’s estimated that a fuel rod made up of 10% plutonium and 90% thorium-232 could provide fission and replace the need for uranium. This solves the problem related to the shortage of uranium and also provides a use for excess plutonium.
Now you’re asking yourself “what does this have to do with CANDUs.”
Well, CANDU reactors are proving to be the testing bed for this technology as their heavy-water moderator means they are ideally suited for the lower reactivity of this fuel bundle.
That being said, there are still waste by-products created by CANDU reactors. I will not deny that this is the case. But the fact that CANDU can generate power with less material, recycle used materials, and use alternative fuel sources makes it an interesting technology to look into going forward.
All energy sources have waste by-products but those by-products, if properly managed, should not limit uptake of useful technologies. Especially when said technologies could be crucial at combating climate change.
With that being said…
Concluding Thoughts
In order to meet global demand for sustainable energy the UN estimates that 25% of the world’s energy stocks will need to come from nuclear sources by 2050. This would mean tripling the amount of nuclear energy currently being generated over the course of 29 years.
Nuclear is more affordable than most renewable energy sources in terms of cost, being cheaper to produce than wind and solar. It also has a comparable carbon footprint to both of these energy sources.
The current amount of carbon offset by nuclear power is equivalent to 1/3 of the CO2 generated from all cars on earth in a year, every year, removing a huge chunk of carbon from the atmosphere. In France, a nation which derives 70% of its energy from nuclear, its electricity-related carbon emissions are 1/6 of the European average.
At first, we discussed the environmental benefits of nuclear power, showing that nuclear power produces a tiny sliver of the carbon that fossil fuels do and has a comparable carbon footprint to renewables, being less carbon intensive in terms of construction while being slightly more carbon intensive in energy generation and decommissioning. Nuclear is also less resource intensive in terms of steel and concrete than renewables, limiting waste and carbon emissions from producing these materials.
Secondly, we discussed the safety features of the CANDU reactor system, displaying the four core special features that ensure that CANDU reactors never go supercritical. A fact which has been proven in practice due to the impressive track record of zero radiation deaths from CANDU reactors.
And finally, we ventured into the murky subject of nuclear waste, where we discussed CANDU’s role in recycling spent fuel from light-water reactors. A project which has been underway since 2010 and is looking to expand into the realm of recycling plutonium and using thorium for fuel.
While I know that nuclear energy has a very messy history with links to weaponry and apocalyptic events, I hope that this article can provide a counterpoint to help discuss some of the safer utilities of this technology when properly handled.
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