Calvert Cliffs Nuclear Power Plant

The Calvert Cliffs Nuclear Power Plant (CCNPP) is a nuclear power plant located on the western shore of the Chesapeake Bay near Lusby, Calvert County, Maryland.

The Calvert Cliffs Nuclear Power Plant is owned and operated by EDF, has two 2700 megawatt thermal (MWth) Combustion Engineering Generation II, two loop pressurized water reactors. Each generating plant (CCNPP 1&2) produces approximately 850 megawatt electrical (MWe) net or 900 MWe gross. Each plant's electrical load consumes approximately 50 MWe. These are saturated steam plants (non-superheated) and are approximately 33% efficient (ratio of 900 MWe gross/2700 MWth core). Only the exhaust of the single High Pressure Main Turbine is slightly superheated by a two stage reheater before delivering the superheated steam in parallel to the three Low Pressure Turbines. Unit 1 uses a General Electric designed main turbine and generator, while Unit 2 uses a Westinghouse designed main turbine and generator. The heat produced by the reactor is returned to the bay, which operates as a cooling heat-sink for the plant.

Unit 1 went into commercial service in 1975 and Unit 2 in 1977. The total cost of the two units was approximately 766 million USD.

Unit 1 had its two steam generators replaced in 2002 and its reactor vessel closure head replaced in 2006, while unit 2 had its two steam generators replaced in 2003, and its vessel closure head replaced in 2007.

The water around the plant (see lower-right-center of photograph) is a very popular place for anglers. Unit 1 & 2 each takes in bay water (from the fenced-in area) to cool its steam driven turbine condensers plus other bay water cooled primary and secondary system heat exchangers. The bay water is pumped out at a nominal flow rate of 1.2 million gallons per minute (75,000 L/s) per unit (Unit 1 and 2) for each steam turbine condenser. The water is returned to the bay no more than 12 °F (6.7 °C) warmer than the bay water. Unlike many other nuclear power plants, Calvert Cliffs did not have to utilize water cooling towers to return the hot water to its original temperature. As the water comes out very quickly and creates a sort of artificial rip current, it can be a dangerous place to fish. CCNPP 3 will only need about 10% of the bay cooling water volume needed for Unit 1 and 2 combined. The increase in fish and shellfish impingement and entrainment will be less than 3.5% over Unit 1 and 2 existing conditions.]

In February 2009, Calvert Cliffs set a world record for Pressurized Water Reactors (PWRs) by operating 692 days non-stop. (US-EPR), Generation III+ In addition, Unit 2's capacity factor in 2008 was a world-record high of 101.37 percent.

November 2010, a deal to transfer Constellation Energy Group's stake in a nuclear development company to its French partner, EDF Group, closed, according to the SEC. A month prior, Constellation agreed to sell its 50 percent stake in Unistar Nuclear Energy to EDF for $140 million, giving EDF sole ownership of the joint venture and its plans to develop a third unit at Calvert Cliffs in Southern Maryland. The deal called for EDF to transfer 3.5 million shares it owns, valued around $110 million, to Constellation and give up its seat on the Constellation board. EDF designee Samuel Minzberg resigned.


The population within 50 miles of Calvert Cliffs was 2,890,702, according to 2010 U.S. Census data analyzed for, a decrease of 2.0 percent in a decade. The 2010 population within 10 miles is 48,798 (increase of 86.4 percent). Cities within 50 miles include Washington, D.C., (45 miles to city center).

2000 renewal of operating license

In 2000, the Nuclear Regulatory Commission extended the license of the plant for 20 additional years, making Calvert Cliffs the first nuclear plant in the United States to receive such an extension. President George W. Bush visited the plant in June 2005, the first time a president had visited a nuclear power plant in nearly two decades.

Proposal to add a third reactor

UniStar Nuclear Energy announced it will probably build a new advanced U.S. Evolutionary Power Reactor (US-EPR) at this site. UniStar Nuclear Energy, a Delaware limited liability company, is jointly owned by Constellation Energy (CEG) and Électricité de France (EdF), a builder and supplier of nuclear power plants in Europe. This proposed single nuclear unit will produce approximately twice the energy of each individual existing plant. See Nuclear Power 2010 Program.

On July 13, 2007, UniStar Nuclear Energy filed a partial application to the Nuclear Regulatory Commission to review its plans to build a new nuclear power plant, Calvert Cliffs Nuclear Power Plant 3 (CCNPP 3) based on the AREVA U.S. Evolutionary Power Reactor (US-EPR), Generation III+, four loop pressurized water reactor. The remainder of the license application was submitted to the NRC in March 2008. The NRC confirmed its acceptance for technical review in June 2008. The CCNPP 3 reactor will be rated at 4590 MW thermal/1710 MW electrical gross. Plant loads will be approximately 110 Mwe, thus the net generation is 1600 MWe. Plant thermal efficiency will be approximately 36% (ratio of 1710 MWe to 4590 MWth). A final decision by Constellation to start construction had been expected by the end of 2009, paving the way for pre-construction activities.

This third reactor will help address the need for more baseload, generating power in the Mid-Atlantic region. The plant will be located south of the existing CCNPP 1&2 and will be set back from the shoreline. Although only a single unit, its power plant footprint will be almost 2 times the size of the twin units CCNPP 1&2. It will have a closed-loop cooling system using a single hybrid mechanical draft cooling tower. It will incorporate plume abatement (no visible water vapor plume). Units 1&2 use an open-cycle heat dissipation system (no cooling towers). Two thirds of the heat produced by the Unit 3 reactor will be released to the atmosphere via the cooling tower. This also is a saturated steam plant with a Main Steam Turbine (one high pressure turbine in tandem with three low pressure turbines) and a Main Generator design similar to Unit 1 & 2. ALSTOM will supply the Main Steam Turbine and Main Generator.

Units 1 and 2 and their support facilities use a well water system for their potable water supply. It consists of five wells that pump water from the second highest aquifer, the Aquia Aquifer, at the minus 400–500 foot below sea level elevation. The State of Maryland limits daily usage for these five wells to 450,000 gallons per day (gpd). Actual daily usage averages 225,000 gpd. Unlike units 1 and 2, Unit 3 will have a desalination plant to produce potable water using reverse osmosis. The desalination plant will produce up to 1,250,000 gallon of potable water per day for Unit 3 and supporting facilities with total dissolved solids (TDS) less than 400 parts per million (ppm). The source for the desalination plant will be the brackish bay water from the makeup supply to the circulating water system. The TDS for the brackish bay water runs 10,000-15,000 ppm. The potable water will be distributed as makeup water for the demineralized water system, miscellaneous potable water services, fire protection and source water for the four ultimate heatsink cooling towers used during normal shutdown and power operation.

On November 13, 2007, UniStar Nuclear Energy filed an application for a certificate of public convenience and necessity with the Maryland Public Service Commission for authority to construct CCNPP 3. This application is being considered in Case Number 9127.

Opponents and supporters of the proposed third reactor at Calvert Cliffs have been involved in a series of public hearings before officials of the U.S. Nuclear Regulatory Commission. In March 2009, Bill Peil of southern Calvert County asked the Nuclear Regulatory Commission to deny an emissions permit for the reactor due to health and safety concerns he maintains the plant poses to the community. UniStar Nuclear Energy President and CEO George Vanderheyden urged the NRC to approve the air permit application.

In October 2010, Constellation Energy said that it had reached an impasse in negotiations for a federal loan guarantee to build the proposed third nuclear reactor at Calvert Cliffs. The government was seeking a fee of $880 million on a guarantee of about $7.6 billion, to compensate taxpayers for the risk of default. However, Constellation Energy has said that fee would doom the project, “or the economics of any nuclear project, for that matter”.

In April 2011, the Nuclear Regulatory Commission (NRC) stated that UniStar is not eligible to build a third reactor, as it is not a U.S. owned company since Constellation pulled out of the partnership in 2010. The NRC would continue to process the application, but a license would not be issued until the ownership requirements were met. The reactor is now estimated to cost $9.6 billion.


Scientists at Johns Hopkins University became concerned that the discharge of heated cooling water from the plant would be detrimental to a crucial element of the Chesapeake Bay ecosystem, the bay's famed blue crabs. In the late 1960s, litigation borne of Congress's National Environmental Policy Act eventually spawned one of the most celebrated environmental cases in American history, Calvert Cliffs Coordinating Council v. Atomic Energy Commission, forcing the Atomic Agency Commission to consider the environmental impact of building and maintaining such an atomic energy plant.
Calvert Cliffs Nuclear Power Plant
Country United States
Locale Calvert County, near Lusby, Maryland
Status Operational
Commission date Unit 1: 1975
Unit 2: 1977
Licence expiration Unit 1: 2034
Unit 2: 2036
Owner(s) Électricité de France
Operator(s) Électricité de France
Architect(s) Bechtel
Constructor(s) Bechtel

Reactor information
Reactor type(s) PWR
Reactor supplier(s) Combustion Engineering

Power station information
Generation units Unit 1: General Electric
Unit 2: Westinghouse

Power generation information
Installed capacity Unit 1: 873 MW
Unit 2: 863
Annual generation Unit 1: 8,104 GW-h
Unit 2: 6,807

Prairie Island Nuclear Power Plant

The Prairie Island Nuclear Power Plant is an electricity-generating facility located in Red Wing, Minnesota along the Mississippi River, adjacent to the Prairie Island Indian Community reservation. The nuclear power plant, which first began operating in 1973, has two nuclear reactors (pressurized water reactors) made by Westinghouse that produce a total 1,076 megawatts of power. They are licensed to operate through 2013 and 2014.

The Prairie Island Nuclear Power Plant is owned by Northern States Power Company (NSP), today a subsidiary of Xcel Energy, and is operated by Xcel Energy and no longer operated by the Nuclear Management Company (NMC).

It is one of two active nuclear facilities in Minnesota and has proven to be the most controversial due to the storage of nuclear waste in large steel casks on-site, an area which is a floodplain of the Mississippi.

In April 2008, Xcel requested that the U.S. Nuclear Regulatory Commission (NRC) renew the licenses of both reactors, extending them for an additional twenty years. The license renewals are not expected until June 2011.

The company has also requested the use of a similar storage system at its Monticello plant, which is currently licensed through 2030.

In May 2006 repair workers at the plant were exposed to very low levels of radiation due to inhalation of radioactive iodine-131 (131I) gas. The gas leaked from the steam generators, which were opened for inspection. 131I gas is normally removed by means of a carbon-based filter; in this case the filter had developed a small leak. The NRC deemed this event to be of very low safety significance and notes that it did not result in any overdose.

The population within 50 miles of Prairie Island was 2,945,237, according to 2010 U.S. Census data analyzed for, an increase of 7.8 percent in a decade. The 2010 population within 10 miles is 27,996 (increase of 4.6 percent). Cities within 50 miles include Minneapolis (39 miles to city center) and St. Paul (32 miles to city center).

NSP had initially intended to send radioactive waste to a storage facility operated by the United States federal government, but no such site is yet open for use (the Yucca Mountain nuclear waste repository is under construction, but following heavy opposition is no longer considered an option by the Obama Administration). In 1991, the company requested permission from the Minnesota Public Utilities Commission to eventually store waste in 48 dry casks on the site. Opposition by environmentalists and the neighboring Prairie Island tribe led the Minnesota Legislature to decrease the number of allowed casks to 17, enough to keep the plant operating through approximately 2003.

Eventually, those casks filled, and Xcel Energy requested that the limit be expanded beyond 17 casks. The legislature granted the request, but required the company to make greater use of renewable energy such as wind power and to pay the local Indian community up to $2.25 million per year to help with evacuation improvements and the acquisition and development of new land and to help pay for a health study and emergency management activities.

Prairie Island Nuclear Power Plant
Country United States
Locale Red Wing, Minnesota
Status Operational
Commission date Unit 1: December 16, 1973
Unit 2: December 21, 1974
Licence expiration Unit 1: August 9, 2013
Unit 2: October 29, 2014
Owner(s) Xcel Energy
Architect(s) Fluor Pioneer

Reactor information
Reactors operational 2 x 548 MW
Reactor type(s) pressurized water reactor

Power generation information
Annual generation 8,914 GW·h

Diablo Canyon Nuclear Power Plant

Diablo Canyon Nuclear Power Plant is an electricity-generating nuclear power plant at Avila Beach in San Luis Obispo County, California. It was built directly over a geological fault line, and is located near a second fault. The plant has two Westinghouse-designed 4-loop pressurized-water nuclear reactors operated by Pacific Gas & Electric. The facility is located on about 750 acres (300 ha) in Avila Beach, California. Together, the twin 1,100 MWe reactors produce about 18,000 GW·h of electricity annually, supplying the electrical needs of more than 2.2 million people, sent along the Path 15 500-kV lines that connect to this plant.

Diablo Canyon Nuclear Power Plant was originally designed to withstand a 6.75 magnitude earthquake from four faults, including the nearby San Andreas and Hosgri faults, but was later upgraded to withstand a 7.5 magnitude quake. It has seismic monitoring and safety systems, designed to shut it down promptly in the event of significant ground motion.

The Diablo Canyon Nuclear Power Plant draws cooling water from the Pacific Ocean, and during heavy storms both units are throttled back by 80 percent to prevent kelp from entering the cooling water intake. The cooling water is used once and not recirculated.

The plant is located in Nuclear Regulatory Commission Region IV.

Unit One

Unit One is a 1,122 MWe pressurized water reactor supplied by Westinghouse. It went online on May 7, 1985 and is licensed to operate through November 2, 2024. In 2006, Unit One generated 9,944,983 MW·h of electricity, at a nominal capacity factor of 101.2 percent.

Unit Two

Unit Two is a 1,118 MWe pressurized water reactor supplied by Westinghouse. It went online on March 3, 1986 and is licensed to operate through August 20, 2025. In 2006, Unit Two generated 8,520,000 MW·h of electricity, at a capacity factor of 88.2 percent.


Pacific Gas & Electric Company went through six years of hearings, referenda and litigation to have the Diablo Canyon plant approved. A principal concern about the plant is whether it can be sufficiently earthquake-proof. The site was deemed safe when construction started in 1968.

However, by the time of the plant's completion in 1973, a seismic fault, the Hosgri fault, had been discovered several miles offshore. This fault had a 7.1 magnitude quake 10 miles offshore on November 4, 1927, and thus was capable of generating forces equivalent to approximately 1/16 of those felt in the 1906 San Francisco earthquake. The company updated its plans and added structural supports designed to reinforce stability in case of earthquake. In September 1981, PG&E discovered that a single set of blueprints was used for these structural supports; workers were supposed to have reversed the plans when switching to the second reactor, but did not. According to Charles Perrow, the result of the error was that "many parts were needlessly reinforced, while others, which should have been strengthened, were left untouched." Nonetheless, on March 19, 1982 the Nuclear Regulatory Commission decided not to review its 1978 decision approving the plant's safety, despite these and other design errors.

In response to concern that ground acceleration, or shaking, could cause spillage of submerged fuel rod assemblies which, upon exposure to air, could ignite, PG&E and NRC regulators insist that the foregoing scenario is anticipated and controlled for, and that there is no basis to anticipate spillage. Additional seismic studies are in process, however completion of those studies is not a condition precedent to reissuance of the operating licenses for the two onsite units.

A PG&E request to extend the life of the plant by 20 years has been postponed from April 2011 pending the resolution of the nuclear emergencies in Japan.


The Diablo Canyon Independent Safety Committee (DCISC) was established as a part of a settlement agreement entered into in June 1988 between the Division of Ratepayer Advocates of the California Public Utilities Commission (PUC), the Attorney General for the State of California, and Pacific Gas and Electric Company(“PG&E”).

The DCISC consists of three members, one each appointed by the Governor, the Attorney General and the Chairperson of the California Energy Commission. They serve staggered three-year terms. The committee has no authority to direct PG&E personnel.

Cooling intake event

Starting October 22, 2008, Unit 2 was taken offline for approximately two days due to a rapid influx of jellyfish at the intake.

Diablo Canyon Nuclear Power Plant
Status Operational
Commission date Unit 1: May 7, 1985
Unit 2: March 13, 1986
Licence expiration Unit 1: November 2, 2024
Unit 2: August 20, 2025
Owner(s) Pacific Gas & Electric
Operator(s) Pacific Gas & Electric
Architect(s) Pacific Gas & Electric

Reactor information
Reactors operational 1 x 1118 MW
1 x 1122 MW
Reactor type(s) Pressurized water reactor
Reactor supplier(s) Westinghouse

Power generation information
Annual generation 18,588 GW·h
Net generation 17,091 GW·h