Nuclear energy comes from the energy stored in the nucleus (core) of an atom. This energy is released through fission (splitting atoms) or fusion (merging of atoms to form a larger atom). The energy released can be used to generate electricity.

Fossil fuels—which mainly include coal, oil and natural gas—fill the majority of energy needs around the globe. Generation of electricity is one of the predominant uses of fossil fuels. But this resource is limited.

Nuclear energy can be released by splitting a uranium atom. The nucleus of an atom is made of protons and neutrons. When the nucleus splits, it releases energy in the form of heat. Some neutrons are also released in the split. These neutrons might split other nuclei, releasing more heat and neutrons. This chain reaction is called nuclear fission.

Fossil fuels were formed from the organic remains of prehistoric plants and animals. These remains, which are millions of years old, were converted by heat and pressure in the earth's crust into carbon-containing fuels.

Both nuclear and fossil fuel power plants produce electricity the same way. The heat generated in these plants is used to generate steam. This steam drives a turbine, which powers a generator that converts mechanical energy to electrical energy.

Nuclear energy is cleaner while generating electricity. Nuclear fission provides energy without releasing greenhouse gases such as carbon dioxide. However, nuclear power plants generate radioactive waste, a critical factor when doing a fossil fuel to nuclear power pollution comparison.

In a nuclear power vs coal power comparison, however, consider that combustion of fossil fuels releases carbon dioxide into the atmosphere. In fact, 90 percent of the carbon emissions from electricity generation in the United States come from coal-fired power plants. They emit pollutants such as sulfur dioxide, toxic metals, arsenic, cadmium and mercury.

A pellet of nuclear fuel weighs approximately 0.1 ounce (6 grams). However, that single pellet yields the amount of energy equivalent to that generated by a ton of coal, 120 gallons of oil or 17,000 cubic feet of natural gas, making nuclear fuel much more efficient than fossil fuels.

In addition, nuclear power plants operate more reliably than other power generation facilities. In 2017, nuclear plants worked at full capacity 92% of the time. For comparison, consider the operating times for other energy-generating sources: coal plants (54%), natural gas plants (55%), wind generators (37%) and solar plants (27%).

Uranium is one of the most abundant energy sources on Earth. Uranium can be reprocessed and used again, one of the advantages of nuclear energy over fossil fuels. Fossil fuels, on the other hand, are non-renewable. There has been a steep decline in the energy reserves because of people’s dependence on fossil fuels.

Cost is important when considering the pros and cons of nuclear energy vs fossil fuels. While the operating costs for nuclear power plants exceeds the cost of other electricity-generating power sources, the total cost is less than most. The average total cost of electricity generation includes operations, maintenance and fuels. Costs are reported in mills per kilowatt-hour where one mill equals $0.001 or one-tenth of a U.S. cent.

Average total costs in mills per kilowatt-hour reported for 2017 are, in order of increasing cost, 10.29 for hydroelectric power (including both conventional hydroelectric and pumped storage hydroelectric plants), 24.38 for nuclear power, 31.76 for gas turbine and small scale (defined as gas turbine, internal combustion, photovoltaic or solar and wind plants) and 35.41 for fossil steam plants.

Fossil fuel sources are gradually declining, leading to a potential global scarcity of energy. Nuclear power plants already provide energy in thirty states. With two new plants approved and about 18 applications to build new plants under consideration by the U.S. Nuclear Regulatory Commission in 2018, nuclear power plants may fill that energy need in the United States.