Nuclear (Energia de Fissão)

by Sérgio Granato de Araújo

  

Nuclear reactors harness nuclear fission (splitting heavy atoms, such as Uranium‑235) to heat water and produce turbine-steam.  Unlike many REN energy sources, power from nuclear energy can be generated around the clock and isn’t dependent on the weather conditions, like wind & solar power [NG, 2023].

  

Energy production & ICAP

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Today, nuclear power is the second-largest source of low-carbon electricity globally (after hydropower), supplying around 9–10% of the world’s electricity from 416 operating reactors, with a total IC of about 376.3 GWe ("e": useful electrical power), as of Nov/2025, across around 30 countries.  In 2024, 421 operating reactors, with a total IC of 377.0 GWe, generated around 2,617 TWh of electricity [IAEA, 2026].  Annual uranium demand is estimated at ~70,000 tons in 2025, rising to just over 150,000 tons by 2040, driven by NPP expansion and performance improvements [WNA, 2025].

  

The U.S. operates the world’s largest nuclear fleet, with 94 reactors and a total IC of 97 GW.  China follows with 57 reactors, totaling 57–60 GW, and currently represents the fastest-growing nuclear market, with the largest number of reactors under construction.  France ranks third, operating 57 reactors with an IC of 61–63 GW, and continues to maintain the highest share of nuclear power in its national electricity mix (67,3%) among major economies [IAEA, 2026].

    

Across the European Union, approximately 100 reactors are currently in operation in 13 member states, accounting for about 23–24% of total electricity generation.  With limited domestic fossil fuel resources, France remains the most nuclear-dependent country in the EU, with nuclear energy supplying roughly 60–65% of national electricity production.  However, the aging French nuclear fleet has required intensive maintenance, constraining availability in recent years.  In 2024, performance rebounded sharply, significantly improving reliability & output.

  

Uranium: reserves & production

 

Uranium is naturally found in rock or mineral deposits.  Quite abundant, it is 40 times more common than silver and 500 times more common than gold.  Australia's Uranium reserves are the world's largest, with around 30% of global resources, followed by Kazakhstan (15%), Canada (9%), and Namibia (8%).  In 2024, Kazakhstan, however, produced the largest share of Uranium from mines (39%), followed by Canada (24%), Namibia (12%), and Australia (8%) [WNA, 2025].

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Uranium enrichment

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Enrichment process increases the Uranium-235 concentration from 0.7% to 3%-5%, which is the level used in most reactors.  Before enrichment, Uranium oxide is converted to Uranium hexafluoride (UF6), a gas at relatively low temperatures.  The enrichment process is carried out using a centrifuge that separates heavier atoms (U-238) from lighter ones (U-235) [NCR, 2020].

  

The enriched Uranium is then converted to Uranium Dioxide (UO2) powder, which is then pressed to form small fuel pellets and heated, making a hard ceramic material.  These pellets are subsequently inserted into thin tubes known as fuel rods, which are grouped together to form fuel assemblies, each with around 90 to well over 200 fuel rods [WNA, 2023].  Figure 1 shows nuclear fuel in its powder & pellet form.

  

It is worth noting that uranium‑235 in reactors (3–5%) is far less concentrated than bomb-grade uranium (≥90%), making reactors safe while bombs enable explosive chain reactions.

  

Density, lifecycle & capacity factor

  

1 kg of Uranium equals 2.7 million kg of coal.  Some new-generation nuclear power stations are now certified for 80 years of operation, far longer than a gas- & coal-fired power stations (45 & 35 years) and unconventional renewable installations (solar & wind: 25 & 20 years).  Also, nuclear has the highest capacity factor of any other energy source, producing reliable, carbon-free power more than 92% of the time in 2021, nearly twice as much as coal (49.3%) or natural gas (54.4%) plant, and almost three times more often than wind (34.6%) & solar PV (24.6%) plants [EG, 2022].

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Origin of Nuclear Power

  

First developed in the 1940s, and during the WWII research initially focused on producing bombs, in the 1950s attention turned to the peaceful use of nuclear fission, for power generation [WNA, 2023].  In 1954, the world's first NPP to generate electricity for a power grid, Obninsk NPP, began operations in Obninsk, Soviet Union.  The world's first full scale power station, Calder Hall in the U.K., opened on Oct/1956.

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CO2 emissions, waste & recycling​

  

In an emissions sense, nuclear power is considered to be clean.  Nuclear fuels, such as the element Uranium, are not considered renewable as they are a finite material mined from the ground and can only be found in certain locations.  Moreover, there are concerns around what to do with spent fuel from reactors, as there’s still no definitive way to dispose of it indefinitely without risk: high-level waste (HLW) must be stored isolated from the biosphere with sufficient shielding so as to limit radiation exposure.

  

Nuclear waste generally is over 90% Uranium.  Thus, the spent fuel (waste) still contains 90% usable fuel.  It can be chemically processed and placed in other reactors to close the fuel cycle: a closed fuel cycle means much less nuclear waste and much more energy extracted from the raw ore [WIN, 2023].  The U.S. does not currently recycle spent nuclear fuel, but France does [EG, 2023].

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NPP (nuclear power plants)

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NPP designs can be classified into generations.  The first commercial nuclear reactors built in the late 1950s & 1960s are classified as 1G.  2G systems include commercial reactors built from 1970 to 1990. 3G reactors incorporate evolutionary improvements over 2G systems [EE, 2022].  4G NPP describe a set of advanced reactor designs, including i) liquid metal (sodium, lead) cooled fast reactors, ii) advanced high temperature, and iii) gas cooled reactors, reactors that use non-conventional burning (CANDLE & Molten Salt reactors), and direct conversion.  Sodium cooled fast reactors (SFR) could allow use both fissile material & spent fuel from current reactors to produce electricity [EG, 2023].

  

A boiling water reactor (BWR) is a type of light water nuclear reactor (LWR) used for the generation of electrical power (unlike a PWR, water boils directly in the reactor core).  LWR, as opposed to heavy water, whose H atoms are all deuterium, uses normal water as both its coolant & neutron moderator. BWR is the 2nd most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), which is also a type of light water nuclear reactor [WNA, 2023].  Figure 2 shows Palo Verde, the largest NPP in the U.S. (PWR-type reactor).

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Global NPP leaders

  

The Russian state-owned corporation Rosatom holds the world’s largest portfolio of NPP construction projects abroad, reinforcing its dominant position in the global nuclear industry.  In contrast, Électricité de France (EDF) remains a leading nuclear operator & reactor developer in Europe, with strong expertise in large-scale projects such as the EPR (European Pressurized Reactor), while Westinghouse continues to play a pivotal role as a global reactor tech provider, particularly through its advanced PWR designs, but with a smaller number of full-scale overseas construction projects.