• Raphaël Champeimont

Is nuclear power sustainable?

Updated: Nov 27, 2020

On the issue of global warming, two radical worldviews face each other. On the conservative side, people either deny global warming or think that the number one priority is growth and development because the benefits outweigh the risks. On the other side, environmentalists argue that we should rely exclusively on renewable energy and make the necessary sacrifices to adapt to the new constraints they impose. But what if there was a third way with nuclear power?


Like in my previous article about the risks of nuclear power, I explore preconceptions that people have about the sustainability of nuclear power and how they compare to reality.


See also: French version 🇫🇷


No conflict of interest: The author of this article and this blog do not receive any money from, nor have any financial interests in the nuclear industry.


#1 “It contributes to global warming”


Reality: Not at all! Nuclear power is one of the most climate-friendly ways to produce electricity, even more than some renewable sources.


A lot of people think nuclear energy contributes to global warming. Even in France, which has the highest share of energy produced with nuclear power in the world (around 80% of its electricity), a vast majority of the population believes nuclear power contributes to global warming.


In fact, nuclear power is one of the technologies with the lowest CO2 emissions. Below are the order of magnitudes of greenhouse gases emissions for the same quantity of electricity produced (units are gCO2eq/kWh).

  • Wind: ~ 10

  • Nuclear: ~ 10

  • Water power: ~ 20

  • Solar photovoltaic: ~ 40

  • Gas: ~ 500

  • Coal: ~ 800

Source: IPCC 2014 report of WG3 - Annex iii p7


As we can see, nuclear power emits almost no greenhouse gases, like wind and water power. It is not exactly zero, because some emissions occur when mining uranium, building and decommissioning the plants. However, it is 4 times less than solar cells (manufacturing solar cells consumes energy) and 80 times less than coal (the most polluting source).


France is a good example of the effect of nuclear power on CO2 emissions. With 80% of its electricity produced with nuclear power, its electricity production emits 5 times less CO2 than the european average (60 vs 300 gCO2/kWh), and about 8 times less than the world average (475 gCO2/kWh).


#2 “We don’t know what to do with nuclear waste”


Reality: We already bury some nuclear waste deep underground, and this solution is considered safe by experts.


There are different types of nuclear waste. Some of it will be radioactive for a few years only, so we only need to wait for radiation to become low enough. Some of it is only weakly radioactive and can simply be buried near the surface. What is really a complex issue is what to do with waste which is both high-level (highly dangerous) and long-lived (it will remain radioactive for thousands of years). This is typically the case of the used nuclear fuel.


Taking care of high-level waste

Some people advocate leaving it in high-security buildings on the surface, where most of it is stored today. Radioactivity decreases over time, so if we wait long enough, it will return to the same level of radioactivity that the natural uranium had when we first extracted it from the ground (which is very low, you can actually touch it without risk). However, the order of magnitude for that to happen is 100,000 years, which is extremely long. Even though we hope peace will last forever, it seems crazy to assume that there will be peace all over the globe during 100,000 years. That’s why the experts think that a safer long-term solution is to bury this waste deep underground.


Leaving nuclear waste on the surface would also require future generations to take care of them for a very long time, while storing it underground does not require any special care once it’s buried. They can just forget about it. Actually there is even some research on how to make sure that future generations would not accidentally dig it up, using signs, messages in different languages and even art. This solution is already in use in the United States for military waste, and several other countries are building such storage facilities too.

Natural nuclear reactors

It might be hard to believe that nuclear waste buried in the ground can stay there for hundreds of thousands of years. But actually, we have experimental proof that this can be the case! How can this be possible? When the Earth was younger, there was more uranium-235 than today in the ground, and the composition of natural uranium was the same as today's enriched uranium which is used in power plants. If there happened to be some water and oxygen around the uranium, the conditions could theoretically exist for a natural nuclear reactor, that would work just like a light-water man-made reactor. Physicists had predicted this possibility, and real ones have actually been discovered! It was found that nuclear reactions happened in a uranium ore layer in Gabon, 1.7 billion years ago and during several hundred thousand years.


When there was not enough uranium-235 left and reaction stopped, the “used nuclear fuel” stayed there. These reaction products are basically the same as in man-made nuclear reactors, making it a “natural” nuclear waste. What is particularly interesting is that this “waste” barely moved in a billion years (a few centimeters/inches). This shows that buried radioactive waste can actually stay there for a very long time if the place is correctly chosen. Remember that we need the waste to stay in place for “only” a few hundred thousand years, that is 10,000 times less than this natural waste was able to stay there. Radioactive waste can therefore remain safely in the ground for a lot longer than what we actually need.


#3 “Uranium is like oil, we’ll soon run out of it”


Reality: We have enough uranium for 250 years at the current rate of use. If we develop breeder reactors, we will be able to use resources at least 30 times bigger.


Conventional resources

The IAEA has calculated that at the current rate of use, we have 130 years of uranium if we consider resources which we are pretty sure exist, and 250 years if we model resources that probably exist. This is at the current rate of usage, but what if we wanted to use nuclear power a lot more? Today, nuclear power provides about 10% of the world's electricity, but what if we wanted it to provide a lot more, to replace fossil fuels in order to prevent too much global warming? Let’s say we want 50% of the world’s electricity to be provided by nuclear power, which would multiply it by 5. These 250 years would become only 50 years and nuclear energy would be doomed in the long term, wouldn't it?


Going further with Fast Breeder Reactors

In fact, there are long-term possibilities with nuclear power, but I need to explain a bit more about uranium. The uranium we find in nature, called natural uranium, is actually a mix of two different types of uranium. Most of it is uranium-238 which represents 99.3%, and a more rare type called uranium-235 which represents 0.7%. The bad thing is, only the rare uranium-235 is used to produce energy in power plants. But what if we could make electricity with uranium-238? This is actually what a special type of reactor, called a Fast Breeder Reactor (FBR), can actually do.


Fast Breeder Reactors (FBRs) are able to transform the uranium-238 into plutonium, and in turn use the plutonium to produce electricity. This is particularly interesting, because it can consume unused uranium-238 and plutonium found in the used nuclear fuel of current reactors (see chart). A large part of the current nuclear waste therefore becomes usable fuel, which also greatly reduces the amount of high-activity waste that needs to be buried underground.

All things considered, FBRs multiply the amount of usable uranium by at least 30. This would give us power for several thousand years, long enough the time to develop new technologies to replace it in the long-term like fusion.


Are Fast Breeder Reactors widely used? In the 60s, people were more enthusiastic about nuclear power and were expecting faster development of nuclear plants, which would have led to a rapid depletion of uranium resources. There was therefore a lot of interest in FBRs as a long-term solution, leading to the construction of many prototypes. But after the Chernobyl accident, construction of nuclear plants slowed down. New uranium resources were also discovered, pushing further the date at which uranium resources would be depleted. Because of this, interest for FBRs decreased, and many of them were decommissioned. However, there is still some research and development on them, with 4 FBRs in operation in the World and 1 is being built.


Beyond uranium

We have talked a lot about uranium, because the already industrialized nuclear reactors all use materials derived from uranium ore. However, thorium is another element which could also be used as nuclear fuel. There is more thorium than uranium on Earth, and using it would allow to at least double the resources. India’s long-term plan for nuclear power includes thorium as the 3rd step of nuclear power, after Fast Breeder Reactors (step 2) and current reactors (step 1). Currently, there are no thorium-powered reactors in operation, but experimental reactors have shown that this is clearly a usable fuel too.


Conclusion

As long as pollution is concerned, nuclear power does not produce greenhouse gases, and its long-lived radioactive waste can be managed by storing it deep underground. In the next 100 years, there is no reason to believe that we will run out of uranium resources, even without any major technological breakthrough. In the longer term, nuclear power can provide energy for thousands of years if we improve reactor technology. This gives us plenty of time to develop new technologies, like fusion, or efficient electricity storage, which would make nuclear (fission) power irrelevant in the very long term.

Possible future scenarios if we choose to use nuclear energy.

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