Nuclear power plants generate electricity by using controlled nuclear fission chain reactions (i.e., splitting atoms) to heat water and produce steam to power turbines. Nuclear is often labeled a “clean” energy source because no greenhouse gases (GHGs) or other air emissions are released from the power plant. As the U.S. and other nations search for low-emission energy sources, the benefits of nuclear power must be weighed against the operational risks and the challenges of storing spent nuclear fuel and radioactive waste.
Nuclear Energy Use and Potential
• Nuclear energy provides about 20% of U.S. electricity, and this share has remained stable since around 1990. Nuclear power plants had a capacity factor of 93% in 2018.
• The first U.S. nuclear power plant was completed in 1957.2 During the 1970s, more than 50 nuclear reactors went online.1 Presently, 30 states have at least one nuclear plant and more than half have multiple reactors.2,3 Since 1995, U.S. nuclear electricity generation has grown despite no new reactors and 11 shutdowns, due to higher capacity and utilization of existing plants.
• 667 reactors have been built worldwide since the first was built in 1954 in Obninsk, Russia, though currently, there are less than 450 in operation, 98 of which are in the U.S. As of June 2019, 56 reactors are under construction, including 4 in the U.S. and 13 in China.
• In 2016, the U.S. generated nearly a third of the world’s nuclear electricity. The next largest generators of nuclear electricity were France, China, and Russia.
• Pressurized Water Reactors (PWR) and Boiling Water Reactors (BWR) are the most common technologies in use.7 Two-thirds of U.S. reactors are PWRs.
• Levelized cost of energy (LCOE) includes the expected costs of building, operating & maintaining, and fueling a power plant. Estimated LCOE for plants built in the near future are: combined cycle natural gas: 5.01 ¢/kWh; coal with 30% carbon capture and sequestration: 13.01 ¢/kWh; nuclear: 9.26 ¢/kWh; and biomass: 9.53 ¢/kWh.9
Nuclear Fuel
• Most nuclear reactors use “enriched” uranium, meaning the fuel has a higher concentration of uranium-235 (U235) isotopes, which are easier to split to produce energy. When it is mined, uranium ore averages less than 1% U235.
• Milling and enrichment processes crush the ore and use solvents to extract uranium oxide (U3O8, i.e., yellowcake), chemically convert this to uranium hexafluoride (UF6), this is enriched to increase the U-235 concentration in the fuel, finally a fuel fabricator converts UF6 into UO2 powder which is pressed into pellets with 3%-5% U235 concentrations.
• Uranium can be enriched by gaseous diffusion or gas centrifuge. Both concentrate the slightly lighter U235 molecules from a gas containing mostly U238 the former with membrane filters and the latter by spinning. Other technologies are currently in development, with laser enrichment processes closest to commercial viability.
• In 2018, 721,000 pounds of U3O8 were extracted from 7 mines in the U.S.13 The highest grade ore in the U.S. average less than 1% uranium, some Canadian ore is more than 15% uranium.
• 1% of uranium available at reasonable cost is found in the U.S. The largest deposits are in Australia (30%), Kazakhstan (14%), Canada (8%), and Russia (8%).15 U.S. nuclear plants purchased 40 million pounds of uranium in 2018.16 10% of the fuel originated in the U.S.; the remainder was imported mostly from Canada (24%), Kazakhstan (20%). Australia (18%), and Russia (13%).
• Globally, nuclear power reactors required 65,014 metric tons of uranium in 2017.
Energy and Environmental Impacts
The nuclear fuel cycle is the entire process of producing, using, and disposing of uranium fuel. Powering a one-gigawatt nuclear plant for a year can require mining of about 20,000-400,000 metric tons (mt) of ore, processing it into 27.6 mt of uranium fuel [FACT CHECK - ? that would be 55 billion pounds of U3O8 (yellowcake)?], and disposing of 27.6 mt of highly radioactive spent fuel [FACT CHECK - has open-pit mining overburden been included in this waste number?] and 200-350 m3 of low- and intermediate-level radioactive waste. U.S. plants currently use “once-through” fuel cycles with no reprocessing.
• A uranium fuel pellet (1/2 in. height and diameter) contains the energy equivalent of one ton of coal or 3 barrels of oil. Typical reactors hold 18 million pellets.
• Each kWh of nuclear electricity requires 0.1-0.3 kWh of life cycle energy inputs.
• Although nuclear electricity generation itself produces no GHG emissions, other fuel cycle activities do release emissions.
• The life cycle GHG intensity of nuclear power is estimated to be 34-60 g CO2e/kWh—far below baseload sources such as coal (1,001 gCO2e/kWh).
• Uranium is mostly extracted by open pit mining (13.7%), underground mining (31.9%) and in-situ leaching (ISL) (48.1%). ISL/ISR, the injection of acidic/alkaline solutions [now mostly CO2 and O2] underground to dissolve and pump uranium to the surface, eliminates ore tailings associated with other mining but raises aquifer protection concerns.
• ISR standards were initially instituted in 1983, and have been multiple times since, most recently in 1995. Though recent attempts (2015/2017) by the EPA have been made to add more groundwater and monitoring standards, neither have been finalized [because they were unnecessary and unreasonable].
• Nuclear power plants consume 270-670 gallons of cooling water/MWh, depending on operating efficiency and site conditions, [mostly taken from lakes or rivers and then returned at a slightly higher temperatures.]
[Read on, but watch for exaggerations that the numbers are not explained properly, e.g., waste volumes.]
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