The debate over nuclear power reflects bigger questions about a decarbonized future

A series of highly publicized nuclear power plant accidents have stalled nuclear’s expansion at various times. But as the climate crisis has worsened and technological developments have made nuclear power generation safer and more reliable than ever before, the tide is turning on nuclear power.

The science of atomic radiation developed gradually around the turn of the 20th century before escalating during World War II. After World War II, the technological focus shifted from atomic weapon development to harnessing nuclear energy in a controlled fashion for naval propulsion and electricity generation. 

Since 1956, almost all development in nuclear energy has focused on the technological evolution of reliable nuclear power plants. However, since the onset of commercial nuclear power generation, opposition has been strong. An anti-nuclear energy movement catalyzed in the 1960s and 1970s driven by fears of nuclear weapon proliferation and national security concerns. 

A series of highly publicized nuclear power plant accidents have stalled nuclear’s expansion at various times. The construction of new nuclear plants reversed as nuclear energy lost favor and pop culture reinforced a perception of nuclear energy as dangerous and not worthwhile.

But as the climate crisis has worsened and technological developments have made nuclear power generation safer and more reliable than ever before, the tide is turning on nuclear power. As the road to a decarbonized energy future unfolds, a fierce debate is brewing as to how large of a role nuclear power ought to play in a cleaner, more sustainable energy mix.

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Nuclear Power is Much Safer and Less Polluting Than You Might Think

Per unit of electricity produced, oil, coal, and natural gas each generate hundreds of times more greenhouse gas emissions than nuclear.Nuclear power is the use of nuclear reactions to produce electricity. In the universe, this happens either by fusion (fusing atoms together) or fission (splitting them apart). On Earth, fission has powered all commercially viable nuclear power to date. 

Uranium is the main element used in nuclear fission. It is mined and then converted (and often enriched to make natural uranium more likely to undergo fission) before being stacked into fuel rods where fission creates nuclear reactions that generate excessive thermal energy. This thermal energy (i.e. heat) then warms the reactor’s cooling agent (typically water) to produce steam, which is then channeled to spin turbines, activating an electric generator to create electricity.

Over time, those fuel rods contain progressively less fissile material and more waste. Spent fuel is then moved to a spent fuel pool for a few months or years before it becomes radioactively and thermally cool enough to be either reprocessed or moved to long-term storage, typically via dry storage casks.

Of course, thermal energy is not the only byproduct of nuclear fission. Radiation is also produced, and unlike heat, it’s not useful. We encounter radiation throughout our lives (including from our own bodies as well as technologies like cell phones, X-ray machines, and microwaves) but nuclear radiation is much more potent. In sufficient concentrations, radiation can cause a number of long-term health effects. In worst-case scenarios, it can kill people.

In essence, nuclear power is quite powerful but the process to generate it is also risky. Over the years, a tug-of-war has perpetuated between those who favor it and those who oppose it. Much of this tug-of-war centers on how safe nuclear power is, but the data makes it plain just how much safer and cleaner nuclear energy is compared to fossil fuels. In fact, from a safety perspective, nuclear energy is just as safe as any other form of energy - wind, solar, geothermal, hydropower, you name it. Measured on a deaths per terawatt-hour basis (equivalent to the annual electricity consumption of 150,000 European Union citizens), nuclear energy is similarly dangerous to wind and solar energy, causing about 0.03 deaths per terawatt-hour. 

In contrast, oil produces about 18.4 deaths per terawatt-hour while coal produces 24.6 deaths per terawatt-hour. A growing body of research has shown that pollution driven by fossil fuel use kills close to 10 million people every year. This is an astounding statistic that is nonetheless barely discussed because it’s not as captivating as a nuclear power plant accident.

In essence, nuclear energy is hundreds of times less deadly than fossil fuels. This relative safety extends to the minimal greenhouse gas emissions generated by nuclear energy. Per unit of electricity produced, oil, coal, and natural gas each generate hundreds of times more greenhouse gas emissions than nuclear.

Of course, the disparate nature of how these forms of energy kill people influences how we perceive their respective riskiness. Fossil fuels kill silently whereas nuclear energy kills loudly. 

Two accidents stand out in the history of nuclear power that have directly reversed its development: Chernobyl in 1986 and Fukushima in 2011. Estimates of the respective death tolls vary, ranging from hundreds to tens of thousands of people. But both disasters led to pauses in plant construction as well as plant closures. 

These memorable events contrast sharply to the steady death toll inflicted by burning fossil fuels, which have likely killed hundreds of millions of people in modern times. The human brain isn’t well-adapted to thinking about risks, probabilities, and tradeoffs. We are much better at contextualizing and responding to immediate, short-term threats like terrorist attacks or car accidents than distant, long-term threats like climate change or chronic disases. 

A large body of research has proven how poorly our brains are adapted to assess risk on a level commensurate with the scale of human civilization. As one author put it, “The application that allows us to respond to visible (threats) is ancient and reliable, but the add-on utility that allows us to respond to threats that loom in an unseen future is still in beta testing.” The heuristics (i.e. shortcuts) our brains use to think about risks, probabilities, and tradeoffs are much better suited to living in primitive and small family groups than in a modern society with as much uncertainty and technological advancement as we now face. This neurological shortcoming explains much of our collective apathy in responding to the climate crisis, whose impacts are often hard to perceive since they can unfold slowly rather than urgently.

Our cognitive deficiencies have fueled a collective paranoia about nuclear energy that frankly isn’t justified by an overwhelming body of data. The bottom line is that if decades of history are any guide, nuclear power is plenty safe compared to every other form of energy we’ve ever deployed at scale.

Nuclear Power has Major Land and Infrastructure-Related Advantages

One of the biggest advantages of fossil fuels is the energy density of hydrocarbon atoms. The fact that a gallon of gasoline can propel a giant hunk of metal 40 or 50 miles attests to this attribute. You simply don’t need much fossil fuel to get a lot done.

The same advantage applies to nuclear power given the properties of the uranium atom. This means that whereas other clean energy sources - solar, wind, and hydropower in particular - require a lot of land per unit of electricity generated, nuclear does not. And since nuclear material is so power-dense, nuclear power demands far less transmission infrastructure than its clean competition.

When you combine the land use and infrastructure benefits of nuclear power with its lack of intermittency (the fact that it can run 24/7 rain or shine), it turns out that almost any sensible path toward a globally decarbonized energy future will include a considerable mix of nuclear power. 

Global electricity demand is expected to soar in the coming decades as many sectors electrify and many countries become more industrialized. Renewable energy with battery storage can meet a good chunk of that demand but may be unable to meet all of it and almost certainly wouldn’t do so as cheaply as nuclear power would given its lower physical and environmental footprint. If nuclear’s use doesn’t grow in line with this surge of electricity demand, fossil fuels will likely take their place.

If nuclear’s use doesn’t grow in line with this surge of electricity demand, fossil fuels will likely take their place.

This happens time after time around the world when the closure of nuclear reactors leaves a gaping hole in the grid, and it’s what a comprehensive 2019 report from the International Energy Agency concluded would happen if countries don’t sufficiently invest in reactor lifetime extensions or new nuclear projects. 

In sum, nuclear power will almost certainly be part of the likely cheapest path toward decarbonization on a global scale, which requires firm generation of clean power from energy sources such as hydropower, geothermal power, and nuclear power of course. Firm generation refers to sources of power that are controlled and reliable as opposed to energy sources like wind and solar that are episodic or reliant on environmental variables. While renewable energy will likely meet most of our power needs down the line, firm power sources like nuclear would make a fully decarbonized future more feasible and affordable.

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Nuclear Power Carries Massive Long-Term Risks Beyond Catastrophic Accidents

As with any source of energy, nuclear does come with downsides. First and foremost is the physical danger posed by radioactivity. No matter how safe and advanced we make nuclear power, human error and natural disasters mean that a catastrophic accident will always be possible. And like mining in general, uranium mining is highly environmentally destructive, with the added risk of radioactivity. The amount of uranium fuel needed to keep a typical large reactor operating for a year entails the extraction of half a million tonnes of waste rock and over 100,000 tonnes of mill tailings. These are toxic for hundreds of thousands of years.

Historically, uranium mining has spawned serious environmental justice concerns. For instance, uranium mining in the American Southwest during World War II and the Cold War decimated Indigenous communities across the region. Uranium miners ingested harmful uranium dust that sickened and killed many of them and their family members. Many abandoned uranium mine and mill sites dot the region, presenting long-term health risks for one of the poorest and most marginalized parts of the U.S.

You might consider the environmental risks of nuclear energy unacceptable. It’s undeniable that large nuclear power plants can be awful for the environment on many different levels. But the hard truth is that no energy source is perfect. Hydropower usually requires massive dams that can displace millions of people and wreak havoc on local ecologies. Solar and wind power require a lot of land relative to their power output and produce plenty of waste. Balancing these concerns on a global scale won’t be easy but even without the greenhouse gas emissions generated by burning fossil fuels, we will eventually need clean, renewable energy to sustainably power our civilization. These debates require nuance and foresight to a degree that has often been lacking in how we have powered our civilization since the Industrial Revolution.

In regards to the energy transition, nuclear’s more salient downsides relate to the economic viability of conventional nuclear power plants, which take a very long time to build and are expensive to operate. Building a new conventional plant takes about 10 years on average and nuclear energy is materially more expensive than solar and wind power. Renewable energy has seen consistent cost declines thanks largely to technological developments. The same cannot be said for nuclear energy, which many argue is the biggest reason for nuclear’s stalled growth (rather than safety concerns).

It’s undeniable that large nuclear power plants can be awful for the environment on many different levels. But the hard truth is that no energy source is perfect.

Furthermore, the nature of nuclear power requires many levels of stability - geopolitical, geophysical, etc - that we take for granted. The operation of large nuclear power plants lends itself to centralized, militarized management that stands in the way of more decentralized and resilient responses to the climate crisis that address some underlying societal ills that have contributed to the climate crisis and other civilizational crises. In a warmer, less stable world, the prospect of containing radioactive nuclear waste for hundreds of thousands of years without a glitch seems uncomfortably uncertain. 

One immediate threat is sea level rise; a recent study concluded that “if seas rise about six feet—which is possible by the end of the century—more than half of the waste storage sites would be directly along the water’s edge or even surrounded by water.” Extreme heat events can also threaten nuclear power generation’s viability, and those are becoming more frequent and severe as we continue to emit greenhouse gases.

The 2011 Fukushima incident underlines the threat to nuclear power posed by natural disasters. The most powerful earthquake in Japanese history triggered a tsunami with waves almost 50 feet high. Those waves overwhelmed the protective seawall of a nuclear power plant in Fukushima, flooding parts of the plant and instigating the most severe nuclear disaster since Chernobyl in 1986. As with Chernobyl, human error exacerbated the toll of the Fukushima disaster, but no amount of human heroism could have prevented it. Most nuclear power plants are placed near major sources of water for cooling purposes, so flooding risk is inevitable.

Given the urgency of the climate crisis, all of these obstacles limit nuclear power’s potential to save the planet so to speak. For one, since nuclear power is often unprofitable, its growth will require massive state investment and support, which is far from guaranteed. And nuclear power doesn’t lend itself to a rapid global energy transition; it’s slow, inflexible, and costly, requiring big and highly complex power plants that stand in stark contrast to wind turbines and solar panels.

Small Modular Reactors

Despite nuclear’s flaws, innovation promises to make it more viable and practical in a decarbonized, decentralized grid. One of the most tantalizing advancements in the nuclear world is the advent of small modular reactors (SMRs). The core technology is the same as conventional nuclear power: nuclear fission. But SMRs are a fraction of the size of conventional nuclear reactors, and their modular design allows their systems and components to be factory-assembled and transported as one unit to be installed on site

As you might expect, SMRs produce less energy than large reactors: less than 300 megawatts compared to over 1,000 megawatts. For scale, a typical SMR produces the power equivalent of dozens of utility-scale wind turbines while a conventional reactor produces as much power as hundreds of those turbines. And smaller size removes some of the economies of scale advantages that larger reactors enjoy. 

But their size and modular design means SMRs can be located on sites not suited for large nuclear power plants. In this respect, SMRs might be better suited to take advantage of arguably nuclear power’s greatest strength relative to wind and solar: its power density. 

Wind and solar require a lot of land and raw materials to produce a given amount of power. Nuclear material is much more power-dense, so a global proliferation of SMRs could neatly complement a renewable-dominated grid without the large footprints and regulatory complexities of conventional reactors. Some SMRs can produce the same amount of power as a solar or wind farm on strikingly less land. SMRs could work well in locations unable to support large reactors, in addition to powering smaller electrical markets and grids, isolated areas, and sites with limited water. With smaller size comes a friendlier environmental footprint on surrounding areas.

Since they can be pre-fabricated and then installed on site, SMRs are generally cheaper and faster to build than large reactors. Simpler designs allow for simpler and more automated safety protocols, greatly reducing the risk of accidents.

All in all, SMRs build on the best aspects of nuclear energy with added benefits from their smaller size. Nonetheless, they might actually produce more radioactive waste than larger reactors according to recent research. A Stanford study made this conclusion specifically in regards to two aspects of nuclear waste: neutron leakage and spent fuel discharge. The researchers found that overall, small modular designs are inferior to conventional reactors with respect to radioactive waste generation, management requirements, and disposal options. 

The first truly modular SMR prototype became operational in Russia in 2020 so the technology is quite new and unproven from a commercial standpoint. Dozens of designs have been proposed or are in progress but it remains to be seen just how widely SMRs will be adopted across the world over the coming decades. 

In short, SMRs counteract many of the aforementioned downsides of large nuclear reactors, which are cumbersome and ill-adapted to a more resilient and decentralized energy future. But the cold reality is that nuclear power, no matter how big or small, must be carefully managed to prevent catastrophic damage to surrounding communities.

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The Holy Grail - Nuclear Fusion

Up until now, nuclear power has been generated by nuclear fission, which splits atoms into two or more smaller nuclei. But since the dawn of atomic science, scientists and other industry experts have dreamed about making nuclear fusion technology commercially viable. 

Fusion uses the same process that powers stars like the Sun: fusing the nuclei of atoms such as hydrogen at extremely high temperatures. Keep in mind that without fusion, you would not exist!

The old joke in the nuclear community is that fusion is 20 years away and always will be. 

Beyond our planet, the immense gravitational force within stars is needed to overcome the repulsion between positively charged atomic nuclei of hydrogen. But Earth doesn’t have nearly enough gravitational force to replicate that natural process, so tokamaks (i.e. nuclear fusion machines that operate like artificial suns) must instead generate fusion in plasmas (rings of hot gas) at incredibly hot temperatures to drive nuclei close enough to fuse. And superheated plasma must be contained, which tokamaks accomplish with very powerful magnetic fields that currently require more energy to generate than the fusion process produces. In a nutshell, tokamaks must withstand extreme conditions: temperatures ten times hotter than the core of the sun and twice the force required to launch a space shuttle.

Most tokamaks seek to fuse deuterium and tritium atoms together. Tritium can be extracted from lithium, which is widely available and accessible. Deuterium can be extraced from seawater with remarkable yield; the International Atomic Agency (IAEA) estimates that enough deuterium can be extracted from 0.26 gallons (one liter) of water to provide as much energy as the combustion of 79 gallons (300 liters) of oil. And the main byproducts of fusion (neutrons and helium) are not radioactive, making it much more appealing from a safety standpoint than fission, which generates radioactivity.

Bit by bit, scientists are achieving better combinations of stability and heat generation. According to a study published in September of this year, a fusion reactor in South Korea managed to keep a nuclear fusion reaction going for 30 seconds at temperatures beyond 100 million degrees Celsius, an unprecedented combination of stability and heat generation. In 2021, a similar facility in China operated for over 17 minutes at 70 million degrees Celsius.

This achievement echoes a growing belief that fusion is shifting from a problem of physics to a problem of engineering. If fusion can be harnessed at scale, it promises virtually limitless energy to power human civilization for many millions of years. In contrast, today’s nuclear fission technology depends on fissile materials that are nonrenewable, namely uranium-233, uranium-235, and plutonium. At current rates of consumption, there may be between 130 and 230 years of recoverable uranium available globally.

In southern France, scientists have been working for over a decade on an international nuclear fusion research and engineering megaproject aimed at creating energy by replicating fusion. It’s called the International Thermonuclear Experimental Reactor (ITER for short) and the reactor they’re building, which will be the world’s largest fusion reactor upon completion (expected in 2025), could “change the way we power the world.” 

ITER’s tokamak will have one million components and ten million parts. 35 nations are involved in the ITER project, whose ultimate aim is to produce net energy (i.e. more energy output from fusion reactions than the energy input required to generate it in the first place). As ITER’s website notes, it “will not capture the energy it produces as electricity, but—as first of all fusion experiments in history to produce net energy gain—it will prepare the way for the machine that can.”

ITER is the most ambitious and grand effort to produce commercially scalable and carbon-free nuclear energy. The project is a testament to the potential of human cooperation and reflects the volume of public and private interest in (and innovation on) nuclear fusion.   

All in all, the trajectory of nuclear fusion is hard to predict. But the possibility of a grid with widespread nuclear fusion is as realistic as it has ever been.

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Conclusion - A Decarbonized Energy Future Will Include Nuclear But It’s Complicated

Many of the vexing challenges imposed upon human civilization by the climate crisis lack easy answers. Without question, the debate over nuclear power is one of the most complex and carries massive implications. It strikes at the heart of how we have constructed our modern society and how we may coexist in a world ravaged by self-inflicted destabilizing forces.

It is likely that for a very long time, renewable energy alone will be unable to meet all of humanity’s energy needs. Like some other carbon-free sources of energy (such as large hydropower), nuclear energy is nonrenewable but provides a steady supply of power no matter the weather. It requires a relatively small land footprint and is more aligned with existing grid infrastructure than renewables. And continued innovation could make nuclear more cheap, reliable, and nimble as an energy source.

These benefits must be balanced by the real risks associated with nuclear power. Nuclear power plants take years to build and require complex management and coordination that quite literally carries deadly consequences if not done properly on a continuous basis. The construction of a nuclear plant ensures the existence of highly radioactive nuclear waste for many thousands of years. 

In certain areas with the requisite conditions and overall stability needed to support nuclear power, it might make sense to keep nuclear plants operating, retrofit fossil fuel plants for nuclear, and/or build new nuclear plants. In other areas, it might make sense to rely more heavily on renewables, namely solar and wind.

A decarbonized energy future at the speed needed to avert the worst case scenarios of the climate crisis will likely necessitate more nuclear power generation. But the decisions we make today about how to power our world will linger for thousands of years, perhaps hundreds of thousands of years.

Do these long-term risks of nuclear power outweigh the societal damage from fossil fuels that nuclear power can undo? And will nuclear power innovation coalesce at the speed needed to build a civilization-wide decarbonized grid? I’d say the answer to both is probably yes but tremendous uncertainty complicates the picture.

Key Takeaways:
  1. Measured on a deaths per terawatt-hour basis (equivalent to the annual electricity consumption of 150,000 European Union citizens), nuclear energy is similarly dangerous to wind and solar energy, causing about 0.03 deaths per terawatt-hour. Oil produces about 18.4 deaths per terawatt-hour while coal produces 24.6 deaths per terawatt-hour. 
  2. Whereas other clean energy sources - solar, wind, and hydropower in particular - require a lot of land per unit of electricity generated, nuclear does not. And since nuclear material is so power-dense, nuclear power demands far less transmission infrastructure than its clean competition.
  3. Building a new conventional plant takes about 10 years on average and nuclear energy is materially more expensive than solar and wind power.
  4. Small modular reactors counteract many of the downsides of large nuclear reactors, which are cumbersome and ill-adapted to a more resilient and decentralized energy future. But the cold reality is that nuclear power, no matter how big or small, must be carefully managed to prevent catastrophic damage to surrounding communities.