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Nuclear Energy

Tonopah, Arizona hosts the Palo Verde Nuclear Generating Station.

Palo Verde Nuclear Generating Station is not just the largest nuclear plant in the U.S. The 4,000 acre plant, boasting three combustion engineering pressurized water reactors, has been the nation’s largest energy plant since 1992.

Palo Verde can produce up to 4000 mW of electricity, powering the homes of four million people across four states. Located approximately 50 miles west of Phoenix, it supplies about 35% of the electricity generated in Arizona each year. This single plant employs about 2,500 workers and has a 1.8 billion dollar economic impact on Arizona. Arizona Public Service (APS), owns 29.1% of the plant and operates the facility. Other owners include Salt River Project (17.5%), El Paso Electric Co. (15.8%), Southern California Edison (15.8%), PNM Resources (10.2%), Southern California Public Power Authority (5.9%), and the Los Angeles Dept. of Water & Power (5.7%). Power is distributed to shareholders in New Mexico, Southern California, and Texas.

Recycling and Sustainability

Tonopah, Arizona hosts the Palo Verde Nuclear Generating Station.

Palo Verde is the only nuclear power plant in the world not located next to a large source of water. Instead, an innovative program cools used cores in treated wastewater. In 2010, the plant signed a 40-year contract with five cities in the Phoenix area to buy 26 billion gallons of treated wastewater a year. This productive use of treated wastewater is considered a win-win situation by the power plant, which gets essential water for a reasonable cost, and for the cities, which receive revenue and can upgrade their wastewater processing facilities.

A nuclear plant produces zero carbon emissions. According to APS, operation of Palo Verde has offset close to 484 million tons of carbon dioxide since the plant opened in 1988—the equivalent of taking up to 84 million cars off the road.

Uranium in Arizona

Open the mineral districts map to explore all of Arizona’s mineral resources.

Uranium is the primary radioactive fuel for nuclear power and one of Arizona’s mined resources, occurring in several types of formations. Intermittent mining operations of stratiform deposits started in 1918 in areas of the Navajo Nation, including Monument Valley. Poor execution of early mining endeavors has led to consequences in environmental quality and health of Navajo Nation residents, resulting in a nationally authorized cleanup of contaminated areas.

Entirely different in geologic structure, substantial uranium deposits appear in breccia pipes on the Colorado Plateau. Breccia pipes are vertical or near vertical caverns of broken rock resulting from solution collapse of Redwall Limestone. Breccia pipes can be thought of as geologic catchalls. About 225 million years ago, dissolution and collapse of the Redwall Limestone and overlying strata provided a conduit for mineralized geothermal and groundwater, resulting in precipitation of a variety of minerals that eventually fill the pipes with geologic potpourri. Approximately fifteen percent of these formations are thought to contain high-grade uranium ore occurring as uraninite.

Breccia pipes

Despite uranium-rich breccia pipes surrounding the Grand Canyon, mining has been intermittent for economic, environmental, and cultural reasons. Secretary of the Interior, Ken Salazar, approved a twenty year ban on new mining claims around the Grand Canyon in 2012, protecting approximately 1 million acres surrounding Grand Canyon National Park. Two breccia pipe uranium mines north of the park, Pine Nut and Arizona One, are currently in operation. 

Find images of nuclear reactors, cooling pools, and more equipment from this 4,000 acre facility.

How Does Nuclear Energy Work?

Nuclear power plants use controlled nuclear fission to generate electricity.

Nuclear fission is the process of splitting atoms. When an element is radioactive, its atoms are not stable. A nuclear power plant uses a nuclear reactor to split (fission) the atom of a radioactive element such as uranium by bombarding an atomic nucleus with free neutrons. Splitting an atom releases neutrons, which strike other nearby nuclei leading to a chain reaction, very much like a cue ball splits a rack of balls in a game of pool.

This reaction releases immense amounts of heat. The heat is used to convert water to steam; the steam spins turbines; the turbines provide mechanical energy to an electrical generator, which converts mechanical energy into electricity. Steam heated turbines also produce electricity in geothermal plants, petroleum, natural gas and coal-burning power plants, and biomass plants. The difference is the heat source.

When an atom cannot be split any more, the spent cores become nuclear waste. Nuclear waste is still emitting high-energy particles, therefore is very dangerous. In the U.S., waste is stored in special containers surrounded by cooling ponds to absorb energy and keep the cores cool.