Palo Verde Nuclear Generating Station
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The Palo Verde Nuclear Generating Station, commonly referred to as Palo Verde Power Plant is a nuclear power plant located in Wintersburg, Arizona, about 45 miles (80 km) west of central Phoenix, and is currently the largest nuclear generation facility in the United States, averaging over 3.2 gigawatts (GW) of electrical power production in 2003[1] to serve approximately 4 million people. Arizona Public Service owns the largest portion (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%).[2]
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[edit] Description
The facility is on 4,000 acres (16 km²) of land and consists of three Combustion Engineering pressurized water reactors, each with an original capacity of 1.27 gigawatts electrical, current (2007) maximum capacity of 1.24 gigawatts electrical,[3] 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[4], eventually employing 2,386[5] people. The plant employs 2,055 full-time on-site workers.
It supplies electricity at a production cost (including fuel, maintenance and operation) of 1.33 U.S. cents per kilowatt-hour[5]. This is cheaper than coal (2.26 cents/kWh) or natural gas (4.54 cents/kWh) in the region at the same time (2002), but more expensive than hydro (0.63 cents/kWh). 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/kWh. By 2007, the wholesale value of electricity at the Palo Verde hub was 6.33 cents/kWh[6]. Nuclear power generators are very profitable when fossil fuel prices are high.
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 water. Instead, it uses treated sewage from several nearby municipalities to meet its cooling water needs, recycling 20 billion US gallons (76,000,000 m³) of wastewater each year. 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 x 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.
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.
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 million cubic feet (74,000 m³) enclosed. The three containment domes over the reactors are made of 4-foot (1.2 m) thick concrete designed to withstand a commercial airplane crash.[7]
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 lines 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 1970's, however these units were cancelled 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 towers rather than the forced-draft wet cooling towers used in the existing design.
[edit] Security
Palo Verde was of such strategic importance, due to a variety of its features, that it and Phoenix 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 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.[7]
[edit] 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 the most monitored nuclear power plant 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 of 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.[7]
[edit] History
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Palo Verde's selection was questionable. The land selected was not the primary site, because it was in the middle of nowhere, had no water supply, and put the Phoenix-Metro area into jeopardy in the event of even a minor accident, because of the prevailing easterly winds, would endanger the capital. However, the site did have one major attraction. The owner of the land was 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.[8]
[edit] Incidents
On November 2, 2007, a contract worker, 61-year-old Roger Hurd, was stopped at a security checkpoint when his truck was found to have what authorities initially classified as a small pipe bomb. However, upon subsequent testing, the pipe segment was found not to have any explosive material. Further, the pipe segment was so small that, had it been a pipe bomb, it would not have destroyed the truck, let alone the facility. The plant was put on lockdown until the afternoon, but was otherwise operating as usual. Hurd fully cooperated with authorities and when his Phoenix-area apartment was searched, nothing was found to link him to the production of the pipe bomb.[9][10]
[edit] References
- ^ Palo Verde performance figures for 2003. Retrieved on 2007-11-13. from the Energy Information Administration, showing ~90% usage of the 3.7 GW available capacity.
- ^ PNM Resources formerly Public Service of New Mexico
- ^ Current theoretical maximum output of Palo Verde. Retrieved on 2007-11-13. of 3.7 GW from SRP electricity, Pheonix.
- ^ Winning a Prudence Audit. Retrieved on 2008-03-25.
- ^ a b Economic Benefits of Palo Verde Nuclear Generation Station. Retrieved on 2008-03-08.
- ^ Energy Markets Report. Retrieved on 2008-03-08.
- ^ a b c Detained worker: Had no idea pipe bomb was in truck. Retrieved on 2007-11-13.
- ^ Mark Siegel (1988). The Arizona Project. ISBN 0-945165-02-1.
- ^ Official: Nuclear plant contractor had pipe bomb. Retrieved on 2007-11-13.
- ^ Nuclear plant employee stopped with explosive device. Retrieved on 2007-11-13.
