Are nuclear power plants CO₂-free? By Jasper Vis Discussions about nuclear energy regularly concern the question of what its CO₂ emissions are. It is sometimes claimed that nuclear energy has a high carbon footprint. It is true that nuclear energy causes a certain amount of greenhouse gas emissions over its entire life cycle. But extensive studies show that life-cycle greenhouse gas emissions from nuclear power are much lower than electricity from gas or coal. And about as low as wind energy. The CO₂ emissions from nuclear energy are much lower than from fossil sources Nuclear energy, like other energy sources, has both advantages and disadvantages. However, I am surprised that the CO₂ emissions of nuclear energy are sometimes mentioned as one of the disadvantages. Over the entire life cycle of nuclear energy, greenhouse gas emissions are much lower than electricity from fossil sources. And about as low as wind energy. I previously wrote about the CO₂ emissions of wind energy and solar energy and the suggestion by some that they have high CO₂ emissions over their entire life cycle (which is not the case). Given the regularly recurring discussion, I thought it would be good to also write a blog about the CO₂ emissions of nuclear energy. This blog is only about the CO2 emissions of nuclear energy, not about other aspects In this blog I will only address the question of what the greenhouse gas emissions are over the entire life cycle of nuclear energy. Of course, other aspects of nuclear energy are at least relevant, but I will not consider them here. The fact that the carbon footprint of nuclear energy is low does not mean that it is an easy or quick solution to the climate problem. CO₂ emissions from nuclear energy are about as low as from wind energy There is a whole branch of science that deals with calculating the environmental impact of products, the so-called life cycle analysis. The environmental impact of each step is accurately mapped out. Below is a graph from a 2011 IPCC report, which includes dozens of studies on greenhouse gas emissions over the entire life cycle of electricity production from various sources. For each energy source, these studies carefully consider the use of all materials for all steps: from the extraction of the raw materials to the disposal of the installations at the end of their lifespan. The overview shows that over the entire life cycle, the greenhouse gas emissions of nuclear energy (see the orange arrow) are much lower than those of electricity produced from natural gas, oil or coal (the bars to the right of nuclear energy). From all the studies included in the IPCC1 analysis, the median value for nuclear energy is approximately 10 grams of CO₂ equivalent per kilowatt hour (kWh). See the dark blue line. The emissions of nuclear energy over the entire life cycle are therefore many times lower than those of fossil sources such as coal (~1000 grams of CO₂/kWh) or natural gas (~450 grams of CO₂/kWh). And of the same order as the emissions from wind energy (approximately 10 grams of CO₂/kWh). Nuclear energy is therefore not CO₂-free, but according to most studies, the CO2 over the entire life cycle is just as low as wind energy and much lower than fossil electricity. Digging deeper: some studies estimate the carbon footprint of nuclear power to be higher The graph above also shows that the IPCC has included a small number of studies in which the emissions for nuclear energy are estimated to be considerably higher (see the white bar in the graph that shows the highest value). In the scientific article in which the harmonization of studies on nuclear energy is explained, the background of this highest estimate is explained. This is a study in which the most unfavorable assumptions have been made on various aspects. Therefore, according to the article, the result of that study cannot be generalized2. And even at this highest estimate, the emissions of nuclear energy are considerably lower than those of electricity from fossil sources. Uranium extraction and enrichment are also included in the life cycle analyses The IPCC harmonized overview only includes studies that include all relevant processes over the entire life cycle, see the diagram below (derived from the aforementioned scientific article). Naturally, this also includes the extraction of uranium ('mining') and its enrichment ('enrichment'). These are CO₂-intensive processes, but their total CO2 emissions are small compared to the large amount of electricity that can be extracted from the uranium. You could compare it to the steel needed for windmills. Producing steel is a CO₂-intensive process. Yet the amount of CO₂ released during the production of the steel for a wind turbine is small compared to the total electricity production over the lifetime of the wind turbine. Digging deeper: CO2 emissions rise as the uranium ore becomes poorer The CO2 footprint of nuclear energy increases if ores with a lower uranium content have to be used. This can happen if nuclear energy is used on a larger scale worldwide and more uranium has to be extracted. This is a subject to which the Dutchman Jan-Willem Storm van Leeuwen has devoted extensive attention in the past. See this website. CO2 emissions from uranium mining and enrichment will decrease as their energy supply becomes cleaner On the other hand, the CO2 emissions from the extraction and enrichment of uranium strongly depend on the energy sources used. For example, considerable amounts of electricity are used in the enrichment of uranium. For example, the graph below from the annual sustainability report of Urenco (a company that enriches uranium) shows that the vast majority of their greenhouse gas emissions come from indirect emissions (green in the graph below, 'scope 2'). This mainly concerns the emissions associated with the electricity that Urenco uses. If the electricity production in the country where the enrichment takes place comes largely from renewable sources and/or nuclear energy, the (indirect) CO2 emissions from the enrichment will fall. The graph below analyzes the possible effect of the use of poorer uranium ore (scenario A, B and C) on the one hand and the CO2 intensity of the total energy system (low, medium, high carbon) on the other. The graph comes from the aforementioned scientific article. It explains that this scenario analysis resembles the approach described earlier by Jan-Willem Storm van Leeuwen. It strikes me that in the figure below the future CO2 footprint of nuclear energy remains very low if the energy mix has a low CO2 intensity (see the 3 lines with 'low carbon' at the bottom of the graph). Even if the use of uranium increases (scenario C). This suggests that in an energy system with a low CO2 intensity, the carbon footprint of nuclear energy remains low, even if poorer uranium ore has to be used. Recent scientific article paints a similar picture The IPCC overview of life cycle analyzes (LCA) dates from 2011 and is therefore more than 10 years old. That is why I searched the scientific literature for recent articles on the carbon footprint of nuclear energy. In a 2021 article, Pomponi and Hart describe their analysis for a new nuclear power plant of the EPR type. And compare their results with other studies. Using three different LCA methods, Pomponi and Hart arrive at average values ​​of 17, 25 and 28 grams of CO2 equivalent per kWh, respectively. The authors state that this is significantly higher than the IPCC median value of 12 grams of CO2 per kWh and the range of 5-22 grams of CO2 per kWh from a report by the British Committee on Climate Change. That may be so, but even with the values ​​from this article, the CO₂ emissions of nuclear energy are dozens of times lower than those of fossil electricity. Conclusion: CO2 footprint of nuclear energy much lower than fossil energy Many studies have been done on the CO2 emissions of nuclear energy. The results differ, but one conclusion always stands in my opinion: the emission of greenhouse gases over the entire lifespan of nuclear energy is (very) low. And many times lower than fossil energy sources. Read more: https://jaspervis.wordpress.com/2022/01/22/zijn-kerncentrales-niet-co%e2%82%82-vrij/