Palo Verde Nuclear Generating Station
Encyclopedia
The Palo Verde Nuclear Generating Station is a nuclear power plant
located in Wintersburg, Arizona
, about 45 miles (80 km) west of central Phoenix
. It is the largest nuclear generation facility in the United States, averaging over 3.3 gigawatts (GW) of electrical power production in 2008 to serve approximately 4 million people. Arizona Public Service
(APS) owns 29.1% of the station 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%).
Located in the Arizona desert, Palo Verde is the only nuclear generating facility in the world that is not situated adjacent to a large body of above-ground water. The facility evaporates water from the treated sewage of several nearby municipalities to meet its cooling needs.
pressurized water reactor
s, each with an original capacity of 1.27 gigawatts electrical, current (2007) maximum capacity of 1.24 gigawatts electrical, and typical operating capacity 70%–95% of this. The plant is a major source of power for Phoenix and Southern California, capable of serving about 4 million people. The plant provides about 35% of the electricity generated in Arizona each year. The plant was fully operational by 1988, taking twelve years to build and costing $5.9 billion, eventually employing 2,386 people. The plant employs 2,055 full-time on-site workers.
It supplies electricity at an operating cost
(including fuel and maintenance) of 1.33 U.S. cents per kilowatt-hour. This is cheaper than coal (2.26 cents/kW·h) or natural gas (4.54 cents/kW·h) in the region at the same time (2002), but more expensive than hydro (0.63 cents/kW·h). Assuming a 60-year plant life and 5% long-term cost of capital, the depreciation and capital costs not included in the previous marginal cost for Palo Verde are approximately another 1.4 cents per kilowatt-hour. In 2002, the wholesale value of the electricity produced was 2.5 cents/kW·h. By 2007, the wholesale value of electricity at the Palo Verde hub was 6.33 cents/kW·h.
According to APS, power generation operations to date at Palo Verde have offset the emission of almost 484 million tonnes of carbon dioxide (the equivalent of taking up to 84 million cars off the road); more than 253,000 tonnes of sulphur dioxide; and 618,000 tonnes of nitrogen oxide. The company noted, "If Palo Verde were to cease operation at the end of the original licence, replacement cost of natural gas generation - the least expensive alternative - would total $36 billion over the 20-year licence renewal period."
Due to its location in the Arizona desert, Palo Verde is the only nuclear generating facility in the world that is not located adjacent to a large body of above-ground water. The facility evaporates water from the treated sewage of several nearby municipalities to meet its cooling needs. 20 billion US gallons (76,000,000 m³) of treated water are evaporated each year. This water represents about 25% of the annual overdraft of the Arizona Department of Water Resources Phoenix Active Management Area. At the nuclear plant site, the wastewater is further treated and stored in an 80 acre (324,000 m²) reservoir for use in the plant's cooling towers.
The nuclear steam supply for each unit was designed and supplied by Combustion Engineering, designated the System 80
standard design–a predecessor of the newer standard System 80+ design. Each primary system originally supplied 3.817 GW of thermal power to the secondary (steam) side of each plant. The design is a so-called 2 × 4, with each of four main reactor coolant pumps circulating more than 111,000 gallons per minute of primary-side water through 2 large steam generators.
The main turbine generators were supplied by General Electric
and when installed were the largest in the world, capable of generating 1.447 GW of electricity each. They remain the largest 60 Hz turbine generators.
Bechtel Power Corporation
was the Architect/Engineer/Constructor for the facility initially under the direction of the Arizona Nuclear Power Project (a joint APS/SRP endeavor), later managed exclusively by Arizona Public Service. Edwin E. Van Brunt was the key APS executive in charge of engineering, construction, and early operations of the plant. William E. Bingham was the Bechtel Chief Engineer for the project. Arthur von Boennighausen was one of the Owner's Representatives for Arizona Public Service.
Unlike most multi-unit nuclear power plants, each unit at Palo Verde is an independent power plant, sharing only a few minor systems. The reactor containment buildings are some of the largest in the world at about 2.6 Mcuft enclosed. The three containment domes over the reactors are made of 4 feet (1.2 m) thick concrete.
The facility's design incorporates many features to enhance safety by addressing issues identified earlier in the operation of commercial nuclear reactors. The design is also one of the most spacious internally, providing exceptional room for the conduct of operations and maintenance by the operating staff.
The Palo Verde 500 kV switchyard is a key point in the western states power grid, and is used as a reference point in the pricing of electricity across the southwest United States. Many 500 kV power line
s from companies like Southern California Edison
and San Diego Gas & Electric
send power generated at the plant to Los Angeles
and San Diego
via Path 46
, respectively. In addition, due to both the strategic interconnections of the substation and the large size of the generating station, the Western Electricity Coordinating Council
considers a simultaneous loss of 2 of the 3 units the worst case contingency for system stability.
The site was granted a construction permit for two additional units in the late 1970s, however these units were canceled in the mid-1980s for economical risk reasons. Contrary to popular belief, the two additional units would not have been on the same arc as the three existing units — they would have been arranged south of Unit 3 on a north-south axis. As originally conceived they would have used dry cooling tower
s rather than the forced-draft wet cooling towers used in the existing design.
were documented by the former Soviet Union
as target locations in the event of nuclear conflict during the Cold War
. In March 2003, National Guard troops were dispatched to protect the site during the launch of the Iraq war amidst fears of a terrorist
attack.
The site team and nearby town of Wintersburg remain a key focus of work in regard to homeland security, ranking in importance along with Arizona's major cities, military bases, ports of entry, and tourist sites.
Security guards working for the utility are armed with semi-automatic weapons. They check identification and search vehicles entering the plant. Other security measures protect the reactors, including X-ray machines, explosive "sniffers", and heavy guarded turnstiles that require special identification to open. Armed guards, security checkpoints with machines, and bomb sensors are standard at every nuclear power plant in the US.
On 2 November, 2007, a pipe with gun powder residue was found in the bed of a contract worker's pickup truck during normal screening of vehicles. It was then confirmed to contain explosives by local police. APS then initiated a seven hour security lock-down of the plant, allowing no one to enter or exit the plant. The site also declared a Notification of Unusual Event, which is the lowest of four Emergency Plan event classifications.
"Our Security personnel acted cautiously and appropriately, demonstrating that our security process and procedures work as designed," said Randy Edington, APS Executive Vice President and Chief Nuclear Officer. "These actions are clearly in line with our goal of ensuring the health and safety of the public and our employees."
The finding came as the "final straw" for the NRC, after Palo Verde had several citations over safety concerns and violations over the preceding years, starting with the finding of a 'dry pipe' in the plant's emergency core-cooling system in 2004.
During a March 24, 2009, public meeting, the NRC announced that it cleared the Confirmatory Action Letter (CAL) and has returned Palo Verde to Column 1 on the NRC Action Matrix. The commission's letter stated that "The U.S. Nuclear Regulatory Commission has determined that the Palo Verde Nuclear Generating Station has made sufficient performance improvement that it can reduce its level of inspection oversight." “Performance at Palo Verde has improved substantially and we are adjusting our oversight accordingly,” said Elmo E. Collins, NRC’s Region IV Administrator. “But we will closely monitor the plant. We are reducing our oversight, but not our vigilance.”
On November 18, 2005, the U.S. Nuclear Regulatory Commission announced approval of uprates at two of Palo Verde's reactors. According to the NRC press release, "The power uprates at each unit, located near Phoenix, Arizona, increases the net generating capacity of the reactors from 1,270 to 1,313 and 1,317 megawatts electric, respectively, for Units 1 and 3. The licensee intends to implement the uprate by the end of December for Unit 1, and by the end of 2007 for Unit 3."
On April 21, 2011, the NRC renewed the operating licenses for Palo Verde's three reactors, extending their service lives from forty to sixty years.
defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of 10 miles (16.1 km), concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about 50 miles (80.5 km), concerned primarily with ingestion of food and liquid contaminated by radioactivity.
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
located in Wintersburg, Arizona
Wintersburg, Arizona
Wintersburg is a census-designated place in Maricopa County, Arizona, United States, located about 50 miles west of Phoenix, and 15 miles west of Buckeye along Interstate 10....
, about 45 miles (80 km) west of central Phoenix
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
. It is the largest nuclear generation facility in the United States, averaging over 3.3 gigawatts (GW) of electrical power production in 2008 to serve approximately 4 million people. Arizona Public Service
Arizona Public Service
Arizona Public Service Company is the largest electric utility in Arizona and the principal subsidiary of publicly-traded S&P 500 member Pinnacle West Capital Corporation , which in turn had been formerly named AZP Group, when Arizona Public Service reorganized as that holding company in 1985.With...
(APS) owns 29.1% of the station and operates the facility. Other owners include Salt River Project
Salt River Project
The Salt River Project is the umbrella name for two separate entities: the Salt River Project Agricultural Improvement and Power District, an agency of the state of Arizona that serves as an electrical utility for the Phoenix metropolitan area, and the Salt River Valley Water Users' Association, a...
(17.5%), El Paso Electric Co.
El Paso Electric
El Paso Electric is an Electric utility that provides electricity to western Texas and southern New Mexico. Its service area covers an area from Van Horn, Texas in the east and goes west to Luna, New Mexico and from the United States-Mexico border north to Holloman Air Force Base...
(15.8%), Southern California Edison
Southern California Edison
Southern California Edison , the largest subsidiary of Edison International , is the primary electricity supply company for much of Southern California, USA. It provides 14 million people with electricity...
(15.8%), PNM Resources (10.2%), Southern California Public Power Authority
Southern California Public Power Authority
The Southern California Public Power Authority is a joint powers authority, or a collective of 10 municipal utilities and one irrigation district. SCPPA was created in 1980 to help finance the acquisition of generation and transmission resources for its members. SCPPA is the 26th largest power...
(5.9%), and the Los Angeles Dept. of Water & Power
Los Angeles Department of Water and Power
The Los Angeles Department of Water and Power is the largest municipal utility in the United States, serving over four million residents. It was founded in 1902 to supply water and electricity to residents and businesses in Los Angeles and surrounding communities...
(5.7%).
Located in the Arizona desert, Palo Verde is the only nuclear generating facility in the world that is not situated adjacent to a large body of above-ground water. The facility evaporates water from the treated sewage of several nearby municipalities to meet its cooling needs.
Description
The facility is on 4000 acre (16.2 km²) of land and consists of three Combustion EngineeringCombustion Engineering
Combustion Engineering was an American engineering firm and leading firm in the development of power systems in the United States with approximately 30,000 employees in about a dozen states at its peak. Headquartered in Stamford, Connecticut, C-E owned over two dozen other companies including...
pressurized water reactor
Pressurized water reactor
Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...
s, each with an original capacity of 1.27 gigawatts electrical, current (2007) maximum capacity of 1.24 gigawatts electrical, and typical operating capacity 70%–95% of this. The plant is a major source of power for Phoenix and Southern California, capable of serving about 4 million people. The plant provides about 35% of the electricity generated in Arizona each year. The plant was fully operational by 1988, taking twelve years to build and costing $5.9 billion, eventually employing 2,386 people. The plant employs 2,055 full-time on-site workers.
It supplies electricity at an operating cost
Operating cost
Operating costs can be described as the expenses which are related to the operation of a business, or to the operation of a device, component, piece of equipment or facility.-Business operating costs:...
(including fuel and maintenance) of 1.33 U.S. cents per kilowatt-hour. This is cheaper than coal (2.26 cents/kW·h) or natural gas (4.54 cents/kW·h) in the region at the same time (2002), but more expensive than hydro (0.63 cents/kW·h). Assuming a 60-year plant life and 5% long-term cost of capital, the depreciation and capital costs not included in the previous marginal cost for Palo Verde are approximately another 1.4 cents per kilowatt-hour. In 2002, the wholesale value of the electricity produced was 2.5 cents/kW·h. By 2007, the wholesale value of electricity at the Palo Verde hub was 6.33 cents/kW·h.
According to APS, power generation operations to date at Palo Verde have offset the emission of almost 484 million tonnes of carbon dioxide (the equivalent of taking up to 84 million cars off the road); more than 253,000 tonnes of sulphur dioxide; and 618,000 tonnes of nitrogen oxide. The company noted, "If Palo Verde were to cease operation at the end of the original licence, replacement cost of natural gas generation - the least expensive alternative - would total $36 billion over the 20-year licence renewal period."
Due to its location in the Arizona desert, Palo Verde is the only nuclear generating facility in the world that is not located adjacent to a large body of above-ground water. The facility evaporates water from the treated sewage of several nearby municipalities to meet its cooling needs. 20 billion US gallons (76,000,000 m³) of treated water are evaporated each year. This water represents about 25% of the annual overdraft of the Arizona Department of Water Resources Phoenix Active Management Area. At the nuclear plant site, the wastewater is further treated and stored in an 80 acre (324,000 m²) reservoir for use in the plant's cooling towers.
The nuclear steam supply for each unit was designed and supplied by Combustion Engineering, designated the System 80
System 80
System 80 is a pressurized water reactor design by Combustion Engineering . Three System 80 reactors were built at Palo Verde power plant....
standard design–a predecessor of the newer standard System 80+ design. Each primary system originally supplied 3.817 GW of thermal power to the secondary (steam) side of each plant. The design is a so-called 2 × 4, with each of four main reactor coolant pumps circulating more than 111,000 gallons per minute of primary-side water through 2 large steam generators.
The main turbine generators were supplied by General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
and when installed were the largest in the world, capable of generating 1.447 GW of electricity each. They remain the largest 60 Hz turbine generators.
Bechtel Power Corporation
Bechtel
Bechtel Corporation is the largest engineering company in the United States, ranking as the 5th-largest privately owned company in the U.S...
was the Architect/Engineer/Constructor for the facility initially under the direction of the Arizona Nuclear Power Project (a joint APS/SRP endeavor), later managed exclusively by Arizona Public Service. Edwin E. Van Brunt was the key APS executive in charge of engineering, construction, and early operations of the plant. William E. Bingham was the Bechtel Chief Engineer for the project. Arthur von Boennighausen was one of the Owner's Representatives for Arizona Public Service.
Unlike most multi-unit nuclear power plants, each unit at Palo Verde is an independent power plant, sharing only a few minor systems. The reactor containment buildings are some of the largest in the world at about 2.6 Mcuft enclosed. The three containment domes over the reactors are made of 4 feet (1.2 m) thick concrete.
The facility's design incorporates many features to enhance safety by addressing issues identified earlier in the operation of commercial nuclear reactors. The design is also one of the most spacious internally, providing exceptional room for the conduct of operations and maintenance by the operating staff.
The Palo Verde 500 kV switchyard is a key point in the western states power grid, and is used as a reference point in the pricing of electricity across the southwest United States. Many 500 kV power line
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
s from companies like Southern California Edison
Southern California Edison
Southern California Edison , the largest subsidiary of Edison International , is the primary electricity supply company for much of Southern California, USA. It provides 14 million people with electricity...
and San Diego Gas & Electric
San Diego Gas & Electric
San Diego Gas & Electric is the utility that provides natural gas and electricity to San Diego County and southern Orange County in southwestern California, United States...
send power generated at the plant to Los Angeles
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...
and San Diego
San Diego, California
San Diego is the eighth-largest city in the United States and second-largest city in California. The city is located on the coast of the Pacific Ocean in Southern California, immediately adjacent to the Mexican border. The birthplace of California, San Diego is known for its mild year-round...
via Path 46
Path 46
Path 46, also called West of Colorado River, Arizona-California West-of-the-River Path , is a set of many alternating current high-voltage transmission lines that are located in southeast California and Nevada up to the Colorado River...
, respectively. In addition, due to both the strategic interconnections of the substation and the large size of the generating station, the Western Electricity Coordinating Council
Western Electricity Coordinating Council
The Western Electricity Coordinating Council was formed on April 18, 2002, from the merger of the Western Systems Coordinating Council which itself was formed on August 14, 1967, the Southwest Regional Transmission Association , and Western Regional Transmission Association...
considers a simultaneous loss of 2 of the 3 units the worst case contingency for system stability.
The site was granted a construction permit for two additional units in the late 1970s, however these units were canceled in the mid-1980s for economical risk reasons. Contrary to popular belief, the two additional units would not have been on the same arc as the three existing units — they would have been arranged south of Unit 3 on a north-south axis. As originally conceived they would have used dry cooling tower
Cooling tower
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or in the case of closed circuit dry cooling towers rely...
s rather than the forced-draft wet cooling towers used in the existing design.
Security
Palo Verde was of such strategic importance, due to a variety of its features, that it and PhoenixPhoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
were documented by the former Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
as target locations in the event of nuclear conflict during the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
. In March 2003, National Guard troops were dispatched to protect the site during the launch of the Iraq war amidst fears of a terrorist
Terrorism
Terrorism is the systematic use of terror, especially as a means of coercion. In the international community, however, terrorism has no universally agreed, legally binding, criminal law definition...
attack.
The site team and nearby town of Wintersburg remain a key focus of work in regard to homeland security, ranking in importance along with Arizona's major cities, military bases, ports of entry, and tourist sites.
Security guards working for the utility are armed with semi-automatic weapons. They check identification and search vehicles entering the plant. Other security measures protect the reactors, including X-ray machines, explosive "sniffers", and heavy guarded turnstiles that require special identification to open. Armed guards, security checkpoints with machines, and bomb sensors are standard at every nuclear power plant in the US.
On 2 November, 2007, a pipe with gun powder residue was found in the bed of a contract worker's pickup truck during normal screening of vehicles. It was then confirmed to contain explosives by local police. APS then initiated a seven hour security lock-down of the plant, allowing no one to enter or exit the plant. The site also declared a Notification of Unusual Event, which is the lowest of four Emergency Plan event classifications.
"Our Security personnel acted cautiously and appropriately, demonstrating that our security process and procedures work as designed," said Randy Edington, APS Executive Vice President and Chief Nuclear Officer. "These actions are clearly in line with our goal of ensuring the health and safety of the public and our employees."
Safety concerns
In an Arizona Republic article dated February 22, 2007, it was announced that the Nuclear Regulatory Commission had decided to place Palo Verde into Category 4, making it one of the most closely monitored nuclear power plants in the United States. The decision was made after the NRC discovered that electrical relays in a diesel generator did not function during tests in July and September 2006.The finding came as the "final straw" for the NRC, after Palo Verde had several citations over safety concerns and violations over the preceding years, starting with the finding of a 'dry pipe' in the plant's emergency core-cooling system in 2004.
During a March 24, 2009, public meeting, the NRC announced that it cleared the Confirmatory Action Letter (CAL) and has returned Palo Verde to Column 1 on the NRC Action Matrix. The commission's letter stated that "The U.S. Nuclear Regulatory Commission has determined that the Palo Verde Nuclear Generating Station has made sufficient performance improvement that it can reduce its level of inspection oversight." “Performance at Palo Verde has improved substantially and we are adjusting our oversight accordingly,” said Elmo E. Collins, NRC’s Region IV Administrator. “But we will closely monitor the plant. We are reducing our oversight, but not our vigilance.”
History
The selection of the present site for Palo Verde was controversial. Critics claim that the site was not the first choice because it was in the middle of nowhere, had no water supply, and because of the prevailing westerly winds, put the Phoenix-Metro area into jeopardy in the event of a major accident. Critics claimed that that site was selected over alternatives because it was owned by a relative of Keith Turley, who received almost $2 million for the land. Keith Turley was the president of APS, and a member of the Phoenix 40. Units 1 and 2 went into commercial operation in 1986 and Unit 3 in 1988.On November 18, 2005, the U.S. Nuclear Regulatory Commission announced approval of uprates at two of Palo Verde's reactors. According to the NRC press release, "The power uprates at each unit, located near Phoenix, Arizona, increases the net generating capacity of the reactors from 1,270 to 1,313 and 1,317 megawatts electric, respectively, for Units 1 and 3. The licensee intends to implement the uprate by the end of December for Unit 1, and by the end of 2007 for Unit 3."
On April 21, 2011, the NRC renewed the operating licenses for Palo Verde's three reactors, extending their service lives from forty to sixty years.
Seismic risk
The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Palo Verde was 1 in 26,316, ranking it #18 in the nation according to an NRC study published in August 2010.Surrounding population
The Nuclear Regulatory CommissionNuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of 10 miles (16.1 km), concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about 50 miles (80.5 km), concerned primarily with ingestion of food and liquid contaminated by radioactivity.