Saturday, April 09, 2022

Is Nuclear Power Green?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]

A lot of people have asked me to do a video about nuclear power. But that turned out to be really difficult. You won’t be surprised to hear that opinions about nuclear power are extremely polarized and every source seems to have an agenda to push. Will nuclear power help us save the environment and ourselves, or is it too dangerous and too expensive? Do thorium reactors or the small modular ones change the outlook? Is nuclear power green? That’s what we’ll talk about today.

I want to do this video a little differently so you know where I’m coming from. I’ll first tell you what I thought about nuclear power before I began working on this video. Then we’ll look at the numbers, and in the end, I’ll tell you if I’ve changed my mind.

When the accident in Chernobyl happened I was 9 years old. I didn’t know anything about nuclear power or radioactivity. But I was really scared because I saw that the adults were scared. We were just told, you can’t see it but it’ll kill you.

Later, when I understood that this had been an unnecessary scare, I was somewhat pissed off at adults in general and my teachers in particular. Yes, radioactive pollution is dangerous, but in contrast to pretty much any other type of pollution it’s easy to measure. That doesn’t make it go away but at least we know if it’s there. Today, I worry much more about pollution from the chemical industry which you won’t find unless you know exactly what you’re looking for and also have a complete chemistry lab in the basement. And I worry about climate change.

So, I’ve been in favor of nuclear power as a replacement for fossil fuels since I was in high school. In 2008, I over-optimistically predicted the return of nuclear power. Then of course in 2011, the Fukushima accident happened, after which the German government decided to phase out nuclear power, but continued digging up coal, buying gas from Russia, and importing nuclear power from France.

However, in all fairness I haven’t looked at the numbers for more than 20 years. So that’s what we’ll do next, and then we’ll talk again later.

Fossil fuels presently make up almost two thirds of global electric power production. Hydropower makes up about 16 percent, and all other renewables together about 10 percent. Power from nuclear fission makes up the rest, also about 10 percent.

Nuclear power is “green” in the sense that it doesn’t directly produce carbon dioxide. I say “directly” because even though the clouds coming out of nuclear power plants are only water vapor, power plants don’t grow on trees. They have to be built from something by someone, and the materials, their transport, and the construction itself have a carbon footprint. But then, so does pretty much everything else. I mean, even breathing has a carbon footprint. So one really has to look at those numbers in comparison.

A good comparison comes from the 2014 IPCC report. This table summarizes several dozens of studies with a minimum, maximum, and median value. All the following numbers are in grams of carbon dioxide per kilowatt hour and they are average values for the entire lifecycle of those technologies, so including the production.

For coal, the median that the IPCC quotes is 820, gas is a bit lower with 490, solar is a factor 10 lower than gas, with about 40. Wind is even better than solar with a median of about 11. And the median for nuclear is 12 grams per kiloWatthour, so comparable to that of wind, but there is a huge gap to the maximum value which according to some sources is as high as 110, so about twice as high as solar.

An estimate that’s a little bit higher than even the highest value the IPCC quotes comes from the World Information Service on Energy, WISE, which is based in the Netherlands. They calculated that nuclear plants produce 117 grams of carbon dioxide per kilowatt-hour.

It’s not entirely irrelevant to mention that the mission of WISE is to “fight nuclear” according to their own website. That doesn’t make their number wrong, but they clearly have an agenda and may not be the most reliable source. 

But these estimates differ not so much because someone is stupid or lying, at least not always, but because there is some uncertainty in these numbers that affect the outcome. That’s things like the quality of uranium resources, how far they need to be transported, different methods of mining or fuel production, and their technological progress, and so on. In the scientific literature, the value that is typically used is somewhat higher than the IPCC median, about 60-70 grams of carbon dioxide per kilo Watthour. And the numbers for renewables should also be taken with a grain of salt because they need to come with energy storage which will also have a carbon footprint.

I think the message we can take away here is that either way you look at it, the carbon footprint of nuclear power is dramatically lower than that of fossil fuels, and roughly comparable to some renewables, exact numbers are hard to come by.

So that’s one thing nuclear has going in its favor: it has a small carbon footprint. Another advantage is that compared to wind and solar, it doesn’t require much space. Nuclear power is therefore also “green” in the sense that it doesn’t get in the way of forests or agriculture. And yet another advantage is that it generates power on demand, and not just when the wind blows or the sun shines.

Let us then talk about what is maybe the biggest disadvantage of nuclear power. It’s not renewable. The vast majority of nuclear power plants which are currently in operation work with Uranium 235.

At the moment, we use about 60 thousand tons per year. The world resources are estimated to be about 8 million tons. This means if we were to increase nuclear power production by a factor of ten, then within 15 to 20 years uranium mining would become too expensive to make economic sense.

This was pretty much the conclusion of a paper that was published a few months ago by a group of researchers from Austria. They estimate that optimistically nuclear power from uranium-235 would save about 2 percent of global carbon dioxide emissions by 2040. That’s not nothing, but it isn’t going to fix climate change – there just isn’t enough uranium on this planet.

The second big problem with nuclear power is that it’s expensive. A medium sized nuclear power plant currently costs about 5-10 billion US dollars, though large ones can cost up to 20 billion.

Have a look at this figure is from the World Nuclear Energy Status report 2021 (page 293). It shows what’s called the levelized cost of energy in US dollar per megawatt hour, that’s basically how much it costs to produce power over the entire lifetime of some technology, so not just the running cost but including the production. As you can see, nuclear is the most expensive. It’s even more expensive than coal, and at the moment roughly 5 times more expensive than solar or wind.  If the current trend continues, the gap is going to get even wider.

On top of this comes that insurance for nuclear power plants is mandatory, the premium is high, and those expenses from the plant owners go on top of the electricity price. So at the moment nuclear power just doesn’t make a lot of economic sense. Of course this might change with new technologies, but before we get to those we have to talk about the biggest problem that nuclear power has. People are afraid of it.

Accidents in nuclear power plants are a nightmare because radioactive contamination can make regions uninhabitable for decades, and tragic accidents like Chernobyl and Fukushima have arguably been bad publicity. However, the data say that nuclear power has historically been much safer than fossil fuels, it’s just that the death toll from fossil fuels is less visible.

In 2013, researchers from the NASA Goddard Institute for Space Studies and Columbia University calculated the fatalities caused by coal, gas and nuclear, and summarized their findings in units of Deaths per TeraWatthour. They found that coal kills more than a hundred times more people than nuclear power, the vast majority by air pollution. They also calculate that since the world began using nuclear power instead of coal and gas, nuclear power has prevented more than 1.8 million deaths. 

Another study in 2016 found a death rate for nuclear that was even lower, about a factor 5 less. The authors of this paper also compared the risk of nuclear to hydro and wind and found that these renewables actually have a slightly higher death rate, though in terms of economic damage, nuclear is far worse.

I am guessing now you all want to know just how exactly people die from renewables. Well, since you ask. For wind it’s stuff like “a bus collided with a truck transporting a turbine tower” or an aircraft crashed into a wind turbine, or workers falling off the platform of an offshore windfarm. For solar, it’s accidents in manufacturing sites, electric shocks from improper wiring, or falls from roofs.

The number for hydropower is dominated by a single accident when a dam broke in China in 1975. The water flooded several villages and killed more than 170 thousand people.

The Chernobyl accident, in comparison, killed less than 40 people directly. The World Health Organization estimates long-term deaths from cancer as a consequence of the Chernobyl accident to be 4000-9000. There is a group of researchers which claims it’s at least a factor 10 higher but this claim has remained highly controversial.

The number of direct fatalities from the Fukushima accident is zero. One worker died 7 years later from lung cancer, almost certainly a consequence of radiation exposure. About 500 died from the evacuation, mostly elderly and ill people whose care was interrupted. And this number is unlikely to change much in the long run.

According to the WHO, the radiation exposure of the Fukushima accident was low except for the direct vicinity of the power plant which was evacuated. They do not expect the cancer risk for the general population to significantly rise. The tsunami which caused the accident to begin with killed considerably more people, at least 15 thousand.

I don’t want to trivialize accidents in the nuclear industry, of course they are tragic. But there’s no doubt that they pale in comparison to fossil fuels, which cause pollution that, according to some estimates kills as much as a million people per year. Also, fun fact, coal contains traces of radioactive minerals that are released when you burn it. Indeed, radioactivity levels are typically *higher* near coal plants than near nuclear power plants.

Again, you see, there are some differences in the details but pretty much everyone who has ever seriously looked at the numbers agrees that nuclear is one of the safest power sources we know of.

Okay, so we have seen that the biggest two disadvantages of nuclear power are that it’s not renewable and that it’s expensive. But this is for the conventional nuclear power plants that use uranium 235 which is only 0 point 7 percent of all uranium we find on Earth.

Another option is to use fast breeder reactors which work with the other 99 point 3 percent of uranium on earth, that’s the isotope uranium-238.

A fast breeder transmutes uranium-238 to plutonium-239, which can then be used as reactor fuel like uranium-235. And this process continues running with the neutrons that are produced in the reaction itself, so the reactor “breeds” its own fuel, hence the name

Fast breeders are not new; they have been used here and there since the 1940’s. But they turned out to be expensive, unreliable, and troublesome. The major problems are that they are cooled with sodium which is very reactive, and they also can’t be shut down as quickly as the conventional nuclear power plants. To make a long story short, they didn’t catch on, and I don’t think they ever will.

But technology in the nuclear industry has much advanced in the past decades. The most important innovations are molten salt reactors, thorium reactors, and small modular reactors.

Molten salt reactors work by mixing the fuel into some type of molten salt. The big benefit of doing this is that it’s much safer. That’s partly because molten salt reactors operate at lower pressure, but mostly because the reaction has a “negative temperature coefficient”. That’s a complicated way of saying that the energy-production slows down when the reactor overheats, so you don’t get a runaway effect.

Molten salt reactors have their own problems though. The biggest one is that the molten salt fuel is highly corrosive and quickly degrades the material meant to contain it.  How much of a problem this is in practice is currently unclear.

Molten salt reactors can be run with a number of different fuels, one of them is thorium. Thorium is about 4 times more abundant than uranium, however, fewer resources are known, so in practice this isn't going to make a big difference in the short run.

The real advantage is that these reactors can use essentially the entire thorium, not just a small fraction of it, as is the case with the normal uranium reactors. This means, thorium reactors produce more energy from the same amount of fuel and, as a consequence, thorium could last for thousands of years.  Thorium is also a waste product of the rare-earth mining industry, so trying to put it to use is a good idea.

However, the problem is still that the technology is expensive. There is currently only one molten salt thorium reactor in operation, and that’s in China. It started operating in September 2021.

It’s just a test facility that will generate only 2 Megawatt, but if they are happy with the test the Chinese have plans for a bigger reactor with 373 Megawatt for the next decade, though that is still fairly small for a power plant. It’ll be very interesting to see what comes out of this.

And the biggest hope of the nuclear industry is currently small modular reactors. The idea is that instead of building big and expensive power plants, you build reactors that are small enough to be transported. Mass-producing them in a factory could bring down the cost dramatically.

A conventional plant generates typically a few Gigawatt in electric energy. The small modular reactors are comparable in size to a small house, and have an energy output of some tens of Megawatt. For comparison, that’s about ten times as much as a wind turbine on a good day. That they are modular means they are designed to work together so one can build up power plants gradually to the desired capacity.

Several projects for small modular reactors are at an advanced stage in the USA, Russia, China, Canada, the UK, and South Korea. Most of the current projects use uranium as fuel, partly in the molten salt design.

But the big question is, will the economics work out in the end? This isn’t at all clear, because making the reactors smaller may make them cheaper to manufacture, but they’ll also produce less energy during their lifetime. Certainly at this early stage, small modular reactors aren’t any cheaper than big ones.

A cautious example comes from the American company NuScale. They sit in Utah and have been in business since 2007. They were planning to build twelve small reactors with 60 MegaWatt by 2027. Except for being small they are basically conventional reactors that work with enriched Uranium.

Each of those of those reactors is a big cylinder, about 3 meters in diameter and 20 feet tall. Their original cost estimate was about 4.2 billion dollars. However, last year they announced that had to revise their estimate to $6.2 billion and said they’d need three years longer.

In terms of cost per energy that’s even more expensive than conventional nuclear power plants. The project is subsidized by the department of energy with 1.4 billion, but several funders backed out after the announcement that the cost had significantly increased.

Ok, so that concludes my rundown of the numbers. Let’s see what we’ve learned.

What speaks in favor of nuclear energy is that it’s climate friendly, has a small land use, and creates power on demand. What speaks against it is that it’s expensive and ultimately not renewable. The disadvantages could be alleviated with new technologies, but it’s unclear whether that will work, and even if it works, it almost certainly won’t have a significant impact on climate change in the next 20 years.

It also speaks against nuclear power that people are afraid of it. Even if these fears are not rational that doesn’t mean they don’t exist. If someone isn’t comfortable near a nuclear power plant, that affects their quality of life, and that can’t just be dismissed.

There are two points I didn’t discuss which you may have expected me to mention. One is nuclear proliferation and the risk posed by nuclear power plants during war times. This is certainly an important factor, but it’s more political than scientific, and that would be an entirely different discussion.  

The other point I didn’t mention is nuclear waste. That’s because I think it’s a red herring which some activist groups are using in the attempt to scare people. For what I am concerned, burying the stuff in a safe place solves the problem just fine. It’s right that there aren’t any final disposal sites at the moment, but Finland is expected to open one next year and several other countries will follow. And no, provided adequate safety standards, I wouldn’t have a problem with a nuclear waste deposit in my vicinity.

So, what did I learn from this. I learned that nuclear power has become economically even more unappealing than it already was 20 years ago, and it’s not clear this will ever change. Personally I would say that this development can be left to the market. I am not in favor of regulation that makes it even more difficult for us to reduce carbon emission, to me this just seems insane. In all fairness it looks like nuclear won’t help much, but then again, every little bit helps.

Having said that, I think part of the reason the topic is so controversial is that what you think is the best strategy depends on local conditions. There is no globally “right” decision. If your country has abundant solar and wind power, it might not make sense to invest in nuclear. Though you might want to keep in mind that climate change can affect wind and precipitation patterns in the long run.

If your country is at a high risk of earthquakes, then maybe nuclear power just poses too high a risk. If on the other hand renewables are unreliable in your region of the world, you don’t have a lot of space, and basically never see earthquakes, nuclear power might make a lot of sense.

In the end I am afraid my answer to the question “Is nuclear power green?” is “It’s complicated.”

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