Prairie Island Nuclear Generating Plant

Operator: Xcel Energy/Northern States Power Company - Minnesota
Location: 40 miles southeast of Minneapolis-St. Paul, Minn.
Address:
Prairie Island Nuclear Generating Plant
1717 Wakonade Drive East
Welch, MN 55089-9642
Operating License Unit 1: Issued – April 05, 1974, Expires – August 09, 2033
Operating License Unit 2: Issued – October 29, 1974, Expires – October 29, 2034
Reactor Type: Pressurized Water Reactor (PWR)
Electrical Output Unit 1: 551 Megawatts Electrical (MWe)
Electrical Output Unit 2: 545 Megawatts Electrical (MWe)
Prairie Island's two pressurized water reactors generate about 20 percent of the electricity used by Xcel Energy's customers in the Upper Midwest. The plant is located on a 520-acre site about 40 miles southeast of Minneapolis-St. Paul and about five miles north of Red Wing, Minn. Under 40-year operating licenses granted by the federal Nuclear Regulatory Commission, Unit 1 began commercial operation in December 1972 and Unit 2 began commercial operation a year later. On June 27, 2011, the NRC renewed for 20 years the plant's original operating licenses, authorizing the Prairie Island units to continue generating electricity until 2033 and 2034. Each Prairie Island reactor can generate about 550 megawatts of electricity, for a total plant output of about 1,100 megawatts. That's enough to power about 1 million homes.

  • In a pressurized water reactor, water is highly pressurized so it does not boil as it flows through the reactor and picks up heat released by the fission of uranium atoms. From the reactor, the water in the primary system flows through a steam generator where heat is transferred to water in the secondary system, boiling it to steam. The water in the primary system goes back to the reactor and the steam produced in the secondary system is directed to the turbine-generator to produce electricity.
  • Each reactor core holds 121 fuel assemblies. Each assembly is about 13 feet long and is a square array (about 7.75 inches by 7.75 inches in cross-section) of individual fuel rods each about the diameter of a finger.
  • Each unit is shut down for refueling and maintenance about once every 18 months, and approximately one-third of the fuel assemblies are replaced.


Prairie Island is among Xcel Energy's lowest-cost sources of generation on a per megawatt-hour basis. It is a carbon-free power source and does not produce any greenhouse gas emissions.

  • The plant runs essentially 24 hours a day, seven days per week, except during refueling outages, which occur approximately every 18 months and last about four to six weeks. The plant is very reliable, with a fouryear average capacity factor of 88 percent from 2010 – 2013. (Capacity factor is the ratio of a power plant's actual output over a period of time and its output had it operated a full capacity the entire time.)
  • In 2013, Prairie Island generated nearly 8 million megawatt-hours of electricity. Prairie Island constructed a dry cask storage facility in 1995. The facility, which is needed to support current plant operations as well as operations during the 20-year license extension period, is licensed by the federal Nuclear Regulatory Commission. The Minnesota Public Utilities Commission also has approved the use of up to 64 casks and other equipment needed for dry storage.
  • Thirty-five casks now are filled and in the dry storage facility. Others will be loaded as needed. In Fall 2013, Prairie Island replaced two steam generators in Unit 2 during the site's planned refueling outage. These generators had completed nearly 40 years of operation — an industry-first occurrence. A high standard of engineering, maintenance of chemistry, effective monitoring and preventive maintenance allowed for the event-free operation of these steam generators for the extent of the Unit's original license. Prairie Island's Unit 1 steam generators were replaced in 2004.
  • The $280 million project demonstrates Xcel Energy's commitment to investing in significant capital and human resources to ensure continued operations at Prairie Island and exemplifies the company's commitment to providing safe, reliable, emission-free energy at a reasonable cost to customers.
  • The steam generator is a key component of a pressurized-water reactor type nuclear power plant. Steam generators are heat exchangers used to convert water into steam from heat produced in the nuclear reactor core.
  • AREVA was contracted to fabricate and manufacture the replacement steam generators. Manufactured in Chalon St. Marcel, France, the generators are approximately 70 feet tall and weigh 330 tons each. The generators were transported from France by ocean vessel to New Orleans, where they were off-loaded onto a barge for their journey up the Mississippi River to the station.
  • With the new steam generators in place, arrangements were made to remove the old steam generator components from the site. The upper halves of the two generators were shipped in November 2013 to facilities in Memphis, Tenn., for recycling. The lower halves were shipped in December 2013 to a licensed disposal facility in Clive, Utah.
  • The new steam generators were declared "in-service" on Dec. 16, 2013. Unit 2 was brought back on-line on Dec. 31, 2013, marking the completion of the refueling outage and the steam generator project. To request a speaker on nuclear power issues, go to www.xcelenergy.com and click on Speakers Bureau in the Company/Community section.
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