Palo Verde Nuclear Generating Station

Palo Verde Generating Station
Company type	Nuclear power plant
Industry	Energy
Founded	1988; 38 years ago
Headquarters	Tonopah, United States
Area served	Southern Arizona, Southern California, Central New Mexico
Key people	Arizona Public Service (operator and 29.1% owner)
Products	Electricity generation (nuclear power)
Number of employees	2055
Parent	Arizona Public Service and partners

The Palo Verde Generating Station is a nuclear power plant situated near Tonopah, Arizona, approximately west of central Phoenix. It holds the distinction of producing the highest annual electricity output among all U.S. power plants and was the largest by net generation as of 2021. Ranking third in terms of rated capacity nationwide, it generates nearly 32 million megawatt-hours each year.

With an average production near 3.3 gigawatts (GW), the facility supplies electricity to an estimated four million residents. Ownership is led by Arizona Public Service (APS), which holds a 29.1% stake and oversees operations. Additional partners include Salt River Project (20.2%), El Paso Electric Company (15.8%), Southern California Edison (15.8%), PNM Resources (7.5%), Southern California Public Power Authority (5.9%), and the Los Angeles Department of Water and Power (5.7%). APS has secured a 20-year license extension for all three units, allowing operation through 2045–2047, with opportunities for further renewals.

Positioned within the Northeastern Sonoran Desert, Palo Verde is distinctive as the sole large-scale nuclear facility worldwide that is not located near a significant water body. Instead, it relies on treated sewage effluent from nearby communities for reactor cooling.

Description

Spanning , the Palo Verde Generating Station consists of three pressurized water reactors, initially rated at 1.27 GW electric power each, later uprated to 1.4 GW. The plant typically operates between 70 and 95 percent of its full capacity and serves as a key electricity provider for regions including Southern Arizona, Southern California, and Central New Mexico. Major urban centers receiving power include Phoenix, Tucson, Albuquerque, Las Vegas, Los Angeles, and San Diego.

Palo Verde contributes roughly 35% of Arizona’s total electricity supply. The facility was completed in 1988 after a construction period lasting 12 years, with a total investment near $5.9 billion, and currently employs about 2,055 full-time personnel.

In 2015, operating expenses averaged 4.3 cents per kilowatt-hour. Back in 2002, costs stood at 1.33 cents per kWh—more economical than regional coal at 2.26 cents or natural gas at 4.54 cents but higher than hydroelectric power at 0.63 cents per kWh. Wholesale electricity prices increased from 2.5 cents per kWh in 2002 to 6.33 cents by 2007.

During its license renewal in 2011, Arizona Public Service emphasized that Palo Verde’s operation had prevented nearly 484 million metric tons of CO₂ emissions—comparable to removing 84 million cars from the road annually—as well as significantly cutting sulfur dioxide and nitrogen oxide emissions. APS projected that substituting this output with natural gas generation would entail costs around $36 billion over two decades.

Bechtel Power Corporation acted as Architect/Engineer/Constructor under the Arizona Nuclear Power Project—a joint venture between APS and SRP—before APS assumed full management responsibility. Prominent contributors included APS executive Edwin E. Van Brunt and Bechtel Chief Engineer William G. Bingham.

Uniquely sited in a desert environment without access to large surface water sources, Palo Verde utilizes treated municipal wastewater for cooling purposes—evaporating up to 26 billion gallons annually—which accounts for about one-quarter of the Phoenix area’s water overdraft. This wastewater undergoes additional onsite treatment and is stored in reservoirs to supply water for the plant’s wet cooling towers.

Each unit’s steam system was designed by Combustion Engineering following the System 80 blueprint, delivering thermal power of 3.817 GW per unit with four reactor coolant pumps circulating over 60,000 gallons per minute through two steam generators each.

General Electric provided the main turbine generators, which were the world’s largest at installation with capacities of 1.447 GW each and continue to be the largest operating generators at a frequency of 60 Hz.

Distinct from most multi-unit facilities, each Palo Verde reactor functions independently with minimal shared systems between units. The containment structures rank among the largest globally at approximately , featuring domes constructed from thick concrete layers measuring .

The design incorporates advanced safety mechanisms that address challenges identified in earlier nuclear operations and provides spacious interiors that facilitate efficient maintenance and operational activities.

The Palo Verde 500 kV switchyard serves as a vital hub within the western U.S. electrical grid and acts as a pricing benchmark throughout the Southwest region. Transmission lines operated by companies such as Southern California Edison and San Diego Gas & Electric carry power to Los Angeles and San Diego via Path 46. The Western Electricity Coordinating Council regards simultaneous loss of two units as its most severe contingency scenario for grid stability.

Plans initiated in the late 1970s to add two more units south of Unit 3 along a north–south alignment were abandoned before permits were granted due to economic uncertainties.

Among U.S. commercial reactors, Palo Verde’s units are unique in being designed to operate using cores fueled entirely by MOX fuel; however, they have consistently used fresh UOX fuel because domestic nuclear fuel reprocessing has not been implemented.

Electricity generation

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Output (MWh) from Palo Verde Nuclear Generating Station
Year	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Annual (Sum)
2001	2,733,255	2,186,021	2,753,990	1,837,828	2,266,571	2,723,830	2,700,619	2,656,410	2,616,290	1,200,058	2,262,870	2,786,334	28,724,076
2002	2,844,319	2,566,694	2,343,806	2,169,710	2,819,293	2,717,774	2,792,098	2,793,709	2,615,410	1,879,761	2,506,794	2,812,543	30,861,911
2003	2,819,428	2,545,411	2,560,167	1,801,122	2,742,138	2,499,445	2,603,529	2,485,784	2,574,447	1,849,173	1,808,579	2,291,830	28,581,053
2004	2,887,529	2,155,261	2,338,518	1,945,079	2,470,274	1,975,115	2,654,962</ small >	< small > 2 ,777 ,407 < / small >	< small > 2 ,691 ,530 < / small >	< small > 1 ,892 ,961 < / small >	< small > 1 ,804 ,086 < / small >	< small > 2 ,519 ,887 < / small >	28 ,112 ,609	-	2005	< small > 2 ,818 ,173 < / small >	< small > 2 ,193 ,542 < / small >	< small > 2 ,709 ,934 < / small >	< small > 1 ,788 ,261 < / small >	< small > 1 ,790 ,087 < / small >	< small > 1 ,985 ,957 < / small >	< small > 2 ,549 ,613 < / small >	< small > 2 ,114 ,828 < / small >	< small > 2 ,712 ,381 < / small >	< small > 1 ,317 ,335 < / small >	< small > 1 ,860 ,601 < / small >	< small > 1 ,966 ,734 < / small >	25 ,807 ,446	-	2006	< small > 2 ,102 ,482 < / small >	< small > 1 ,891 ,323 < / small >	< small > 1 ,917 ,006 < / small >	< small > 779 ,151 < / small >	< small > 1 ,498 ,282 < / small >	< small > 1 ,837 ,766 < / small >	< small > 2 ,357 ,606 < / small >	< small > 2 ,848 ,844 < / small >	< small > 2 ,361 ,135 < / small >	< small > 1 ,209 ,288 < / small >	< small > 2 ,299 ,443 < / small >	< small > 2 ,909 ,905 < / small >	24 ,012 ,231	-	2007	< small > 2 ,750 ,069 < / small >	< small > 2 ,266 ,482 < / small >	< small > 2 ,884 ,634 < / small >	< small > 2 ,224 ,318 < / small >	< small > 2 ,333 ,073 < / small >	< small > 1 ,785 ,424 < / small >	< small > 2 ,115 ,062 < / small >	< small > 2 ，842 ，093 </小＞	＜小＞２，６６５，８１１＜／小＞｜＜小＞１，３９０，７０７＜／小＞｜＜小＞１，５６６，４８３＜／小＞｜＜小＞１，９５８，２３５＜／小＞！２６，７８２，３９１

(Note: To streamline the dataset for analytical purposes in business contexts and reduce length by roughly ten percent while retaining essential monthly figures and yearly totals.)

Security

Due to Palo Verde's critical strategic value, it was identified alongside Phoenix, Arizona, as a potential target in Soviet Cold War military strategies. In March 2003, concerns over terrorist threats related to the Iraq War led to the deployment of National Guard forces to secure the facility.

Palo Verde and the adjacent town of Tonopah are prioritized for homeland security on a level comparable to Arizona’s largest urban centers, military installations, border checkpoints, and popular tourist destinations. Armed security staff conduct thorough identification verifications and vehicle inspections. Additional security protocols include the use of X-ray scanners, explosive detection equipment, and controlled access points with guarded turnstiles requiring specialized identification.

On November 2, 2007, routine screening uncovered a pipe containing explosives in a contract employee’s vehicle. This discovery resulted in a seven-hour lockdown and activation of a Notification of Unusual Event—the lowest tier in emergency classifications. Arizona Public Service (APS) affirmed that this incident validated the effectiveness of their security procedures.

In late September 2019, multiple unauthorized drone flights over Unit 3 prompted investigations by the Nuclear Regulatory Commission, FBI, Department of Homeland Security, FAA, and local law enforcement agencies. The individuals responsible and their motives remain unidentified.

Safety concerns

An article published on February 22, 2007, in the Arizona Republic reported that the Institute of Nuclear Power Operations (INPO) assigned Palo Verde to Category 4, indicating it was among the most rigorously supervised nuclear plants in the United States. This classification followed INPO’s detection of electrical relay failures in a diesel generator during tests conducted in July and September 2006.

This problem was considered the "final straw" after multiple safety citations dating back to 2004, including the identification of a 'dry pipe' within the emergency core-cooling system.

By March 24, 2009, the Nuclear Regulatory Commission lifted the Confirmatory Action Letter (CAL) and moved Palo Verde back to Column 1 on its Action Matrix. The NRC highlighted notable enhancements in plant performance and reduced inspection intensity while continuing diligent oversight.

To improve emergency preparedness, 58 nuclear warning sirens were installed within a 10-mile Emergency Planning Zone (EPZ) surrounding the facility to alert local residents if an incident occurs.

History

The selection of Palo Verde’s site was contentious because of its desert environment, scarce water resources, and prevailing westerly winds that could potentially carry radioactive materials toward the Phoenix-Mesa region during an accident. Critics claimed that the location was chosen due to ownership by a relative of Keith Turley—APS president and member of the "Phoenix 40"—who earned nearly two million dollars from selling the land.

Commercial operation began with Units 1 and 2 in 1986, followed by Unit 3 starting service in 1988.

On November 18, 2005, the NRC authorized power uprates for Units 1 and 3, raising their net electrical output from 1,270 megawatts to approximately 1,313 and 1,317 megawatts respectively.

The NRC extended operating licenses for all three reactors on April 21, 2011, lengthening their operational lifespan from forty years to sixty years.

Seismic risk

According to an August 2010 study by the Nuclear Regulatory Commission, Palo Verde faces an estimated annual probability of core damage due to earthquakes at about one in 26,316 events—ranking it eighteenth nationally for seismic risk.

Surrounding population

The Nuclear Regulatory Commission has established two distinct emergency planning zones around nuclear facilities: a 10-mile radius plume exposure pathway zone, which addresses airborne radioactive hazards, and a 50-mile ingestion pathway zone, focused on the risk of consuming contaminated food and beverages.

As of 2010, the number of residents living within a 10-mile radius of Palo Verde stood at 4,255, marking an increase of 132.9% compared to the previous ten years. The population within a 50-mile range approached 2 million, reflecting a growth of 28.6% since the year 2000. The city of Phoenix is situated roughly 47 miles from the power station.

External links

U.S Nuclear Plants - Palo VerdeEnergy