Nuclear fission uses radioactive material to produce energy, a process that produces very little CO₂ emissions. So, we had to ask: What is the carbon footprint of nuclear fission?

Nuclear fission has the third-lowest carbon footprint of all energy types. Per kWh produced, nuclear fission emits 12 grams of CO₂ on a life-cycle basis. It combats climate change and has various environmental benefits, but comes with the threat of nuclear waste products.

Keep reading to learn about the overall carbon footprint of nuclear fission and its carbon footprint throughout its life cycle. 

How is Nuclear Fission Defined

Nuclear fission is the generation of energy produced when splitting apart the nucleus of an atom. It is one of two ways to produce nuclear energy. 

“Nuclear fission: a nuclear reaction in which a heavy nucleus splits spontaneously or on impact with another particle, with the release of energy.”

Cambridge Dictionary

When a neutron strikes the nucleus of an atom, the atomic center can break apart into pieces, starting a chain reaction and releasing energy in the form of radiation and heat. 

What is the Carbon Footprint of Nuclear Fission 

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the greenhouse gas (GHG) emissions associated with consumption, but also includes other emissions such as methane, nitrous oxide, and chlorofluorocarbons.

“Carbon footprint: the amount of greenhouse gasses and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home or driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills). 

What Is the Overall Carbon Footprint of Nuclear Fission

On a life-cycle basis, nuclear fission emits 12 grams of CO₂ equivalent per kilowatt-hour (kWh) of electricity produced, which is tied for the third-lowest out of all energy types.

All operating nuclear power plants today utilize the process of nuclear fission. Because of this, nuclear fission is commonly referred to as ‘nuclear energy’ in the data and literature. 

Nuclear energy accounted for roughly 10% of global electricity generation in 2022, generating approximately 2,500 TWh of electricity from approximately 413 GW of installed capacity.

Some countries rely heavily on nuclear energy whilst others have not yet tapped into the resource. For example, nuclear energy provides roughly 60% of France, Slovakia, and Ukraine’s electricity, but South America and Africa get virtually no energy from nuclear. The top 5 countries represent roughly 70% of the world’s nuclear energy generation.

To understand the carbon footprint of nuclear fission, we must assess its lifecycle and each stage’s carbon footprint. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials. Over the years, companies have strategically used LCA to research and create more sustainable products. So, let’s have a look at the LCA of nuclear fission!

The total carbon footprint of nuclear fission would equal the carbon footprint from building + the carbon footprint from operating + the carbon footprint from building back. 

What Is the Carbon Footprint of Building Nuclear Fission

The carbon footprint of building nuclear fission includes constructing the power plant, mining and processing the uranium, and transporting the processed nuclear fuel to the power plant.

• Construction: A nuclear fission power plant has many components, and building these components requires machinery that emits CO₂. The containment building, reactor vessel, steam lines, pumps, turbines, generators, transformers, and cooling towers are all components with a carbon footprint. 

• Mining: This includes open pit, underground, and in situ leach (ISL) mining. Uranium is mined in the same manner as coal, meaning it also comes with CO₂ emissions. The mining industry generates between 1.9 billion and 5.1 billion tons of CO₂ annually, with an additional 400 million tons coming from power consumption. 

• Milling: Extraction of the uranium from the ore (or leachate) by crushing the ore and leaching it in sulfuric acid.

• Conversion and enrichment: Increasing the concentration of U-235 to between 3.5% and 5% by centrifuging the milled uranium until the two isotopes (U-238 and U-235) separate. 

• Fuel Fabrication: Ceramic pellets of reactor fuel are formed from pressed uranium oxide which is baked at high temperatures and encased in metal tubes to form fuel rods. A 1,000 MWe reactor requires roughly 27 tonnes (29.7 tons) of fuel each year. 

• Transportation: Nuclear fuel is typically transported from fabrication sites to power plants by road, rail, or sea, all of which run on diesel fuel. Burning one gallon of diesel fuel produces 22.38 pounds of CO₂.

CO₂ emissions at this stage occur when constructing the power plant, mining and processing the uranium, and transporting the processed nuclear fuel to the power plant.

What Is the Carbon Footprint of Operating Nuclear Fission

Nuclear fission reactors do not produce any CO₂ emissions in the operating phase because there is no burning of fossil fuels or combustion byproducts.

Nuclear fission power plants operate in the following manner:

• The reactor starts and Uranium-235 atoms in the reactor core split (fission), releasing heat and neutrons.
• Neutrons fission other nuclei in the reactor core in a chain reaction, generating more heat and more neutrons.
• Control rods contain materials that absorb some of the neutrons, helping to contain the chain reaction.
• The heat generated turns water that surrounds the immersed reactor into steam.
• The steam spins a turbine which drives a generator to produce electricity.

Nuclear fuel is extremely dense, so you don’t need a lot of it to create a lot of energy. One U-235 pellet 1 inch tall is the equivalent of 1 ton of coal. Since 1 ton of coal creates 2.086 tons (4,172 lbs) of CO₂ when it is burned, a 1-inch U-235 pellet directly avoids the emission of over 2 tons of CO₂ from our atmosphere. 

What Is the Carbon Footprint of Building Back Nuclear Fission

The organizations tasked with deregulating and decommissioning nuclear fission power plants vary from country-to country. For example, the U.S. Nuclear Regulatory Commission is responsible for overseeing the decommissioning of nuclear fission power plants in the US. 

In general, the process of shutting down nuclear fission plants is expensive, labor-intensive, time-consuming, and comes with health and safety risks. The entire process can take up to 60 years. 

Decommissioning a nuclear fission power plant involves the following steps: 

• Removing and storing spent nuclear fuel rods in spent fuel pools
• Decontaminating the plant
• Reducing residual radioactivity at the plant
• Dismantling plant structures
• Transferring contaminated materials to disposal facilities
• Clearing the site with the NRC for other uses 

CO₂ emissions at this final stage occur when transporting used fuel and radioactive material and deconstructing the plant.

What Role Does Nuclear Fission Play in Combating Climate Change

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 33 billion tons (bt) of CO₂ are emitted from burning fossil fuels. The carbon found in fossil fuels reacts with oxygen in the air to produce CO₂. This warms the earth by acting as a heating blanket, and a warmer earth comes with a host of negative side effects. 

Using nuclear fission to produce energy instead of fossil fuel energy helps mitigate the following negative effects of climate change:

• Increasing temperatures: Earth’s atmosphere has warmed 1.5°C since 1880. This may not seem like a lot, but these degrees create regional and seasonal temperature extremes, reduce sea ice, intensify rainfall and drought severity, and change habitat ranges for plants and animals.

• Rising sea levels: Global sea levels have increased approximately 8-9 inches since 1880, displacing people living along coastlines and destroying coastal habitats. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, and landfills remain at risk if sea level rise goes unchecked. 

• Melting of sea ice: Since 1979, arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 

• Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.

• Ocean acidification: The ocean absorbs 30% of the CO₂ released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expels the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

The more we reduce CO₂ emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

To help keep global temperature rise below 1.5°C, as outlined in the Paris Agreement, we must shift at least 80% of our electricity generation to low-carbon sources. Over 140 countries have stated a net-zero target, covering roughly 88% of the world’s emissions. However, under current conditions, global emissions are projected to increase by 9% by 2030 instead of the 45% reduction in emissions that is needed.

How Environmentally Friendly Is Nuclear Fission

The overall environmental friendliness of nuclear fission is a controversial topic. Although the process of nuclear fission produces zero CO₂ emissions, the handling and disposal of nuclear waste is a serious issue. 

“Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

Nuclear fission can reduce the effects of global warming by limiting global emissions, but uranium mining and nuclear waste are drawbacks that must be taken into consideration.

What Are the Environmental Benefits of Nuclear Fission 

Nuclear fission is expected to continue to play a key role in the clean energy movement. This is because nuclear fission:

• Has a low carbon footprint: Nuclear energy has an average life-cycle CO₂ equivalent emission value that is much less than coal, 12g of CO₂ equivalent per kWh compared to 820g of CO₂ equivalent per kWh, respectively.

• Has a minimal land use impact: Nuclear energy produces more electricity on less land than any other clean-air source. A standard, 1,000-megawatt nuclear fission facility requires only a little more than 1 square mile to operate, a number that is 360 and 75 times less than what is required for wind farms and solar power plants, respectively. 

• Is energy dense: Nuclear fuel is extremely dense, so you don’t need a lot of it to create a lot of energy. One U-235 pellet 1 inch tall is the equivalent of 1 ton of coal. Since 1 ton of coal creates 2.086 tons (4,172 lbs) of CO₂ when it is burned, a 1-inch U-235 pellet directly avoids the emission of over 2 tons of CO₂ from our atmosphere. 

• Generates very little waste: A typical 1,000-megawatt nuclear fission facility produces only three cubic meters of nuclear waste. In comparison, the average coal-fired power plant produces roughly 300,000 tons of coal ash and more than 6 million tons of CO₂ every year.

• Promotes energy security: Nuclear energy contributes to energy security by increasing the stability of our power grids. Unlike renewable energy, which faces variations in supply and demand, nuclear energy can provide a reliable and consistent source of clean energy. 

• Promotes energy independence: Being able to produce your own electricity without the aid of foreign countries is an important step in becoming self-sufficient. For example, former President George W. Bush signed the Energy Independence and Security Act of 2007 to reduce U.S. dependence on oil, expand the production of renewable fuels (and confront global climate change).

• Creates jobs: In the US alone, the nuclear industry employs 100,000 people directly and 475,000 jobs secondarily. Because there are 60 reactors under construction currently and 110 more are being planned, the number of jobs is expected to continue to increase globally.

What Are the Environmental Drawbacks of Nuclear Fission 

Nuclear fission does come with some drawbacks that, if handled properly, can be mitigated. The main environmental drawbacks associated with nuclear fission are uranium mining and nuclear waste.

• Uranium mining: This process contaminates the environment with radioactive dust, radon gas, water-borne toxins, and increased levels of background radiation. Exploratory drilling and mining also heavily increase the risk of water contamination. 

• Nuclear waste: Although nuclear fission produces minimal waste, the waste that it does produce is radioactive and can remain hazardous for many thousands of years. These radioactive waste products include uranium mill tailings, spent (used) reactor fuel, and other radioactive wastes. If these were to leach into the environment it could contaminate the soil and water. 

Ways to minimize negative environmental impacts include the proper handling, transportation, storage, and disposal of radioactive waste to ensure that it does not leach into the environment. 

Final Thoughts

Nuclear fission is an incredibly efficient energy source that uses heat acquired from splitting the nuclei of atoms to create electricity. On a life-cycle basis, nuclear fission only emits 12 grams of CO₂ equivalent per kilowatt-hour (kWh) of electricity produced, which is tied for the third-lowest out of all energy types.

Nuclear fission benefits the environment by mitigating climate change, creating jobs, promoting energy independence, and protecting air quality. Environmental drawbacks including mining and nuclear waste can be mitigated with proper handling and disposal methods. 

Stay impactful,

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