Plant Background

An introduction to Nuclear USA.

Basic Plant Stats, courtesy of the NRC:

Location: Monticello, MN (35 miles NW of Minneapolis, MN) in Region III 
Owner: Xcel Energy. Operator: Northern States Power Company
Operating License: AEC Prov. Lic Issued – 09/08/1970, NRC Facil Op Lic (OL) Issued 01/09/1981
Renewed License: Issued – 11/08/2006 
License Expires: 09/08/2030
Docket Number: 05000263

Reactor Type: Boiling Water Reactor (same type as Fukushima)
Electrical Output: 579 MWe (Operating at 106.3% of Original Design)
Reactor Vendor/Type: General Electric Type 3
Containment Type: Wet, Mark I

Within 10-mile Evacuation Zone: 91,000 People (2010 Total Population), 21 Public Schools, 8 Hospitals.

Within 50-mile Potential Contamination Zone: 3,127,000 People (2010 Total Population), 1418 Public Schools, 202 Hospitals

Background In Detail:

The Monticello Nuclear Generating Plant is a boiling water reactor with a nominal venerating capacity of 600 MWe. It is located on the Mississippi River in Wright County, Minnesota, owned by Xcel Energy Corporation and operated by Northern States Power Co.—Minnesota.  More than 500 people are employed full time at Monticello. Xcel Energy also owns the Prairie Island Nuclear Generating Plant near Red Wing, Minnesota. 

Initial criticality was achieved on December 10, 1970. Full power was achieved March 5th, 1971 and commercial operation began on June 30th, 1971.

Operation Details:

  • The plant received a 40-year operating license from the federal Nuclear Regulatory Commission in 1970, and it began commercial operation in 1971. In 2006, the NRC renewed the Monticello plant’s license for 20 years, which will allow operations until 2030.
  • The plant runs essentially 24 hours a day, seven days per week, except during refueling outages, which occur approximately every 24 months and last about four to six weeks. The plant is highly reliable with a five-year average capacity factor of 89 percent from 2005 – 2009. (Capacity factor is the ratio of a power plant’s actual output over a period of time and its output if it had operated at full capacity the entire time.)
  • In 2006, Monticello generated slightly more than 5 million megawatt-hours of electricity, eclipsing its prior record set in 2004.
  • In January 2007, Monticello reached 637 consecutive days of operation, the longest run in plant history.
  • Plans are under way to increase the power output from the Monticello plant by approximately 70 megawatts (see below, “Current Capacity”). 

Boiling Water Reactor:

  • In a boiling water reactor, water flows through the reactor and picks up heat released by the fissioning of uranium atoms. The water boils to steam, which then is directed to the turbine-generator to produce electricity.
  • The reactor core holds 484 fuel assemblies. Each assembly is about 14 feet long and is a square array of individual fuel rods about the diameter of a finger.
  • About every 22 months, the plant is shut down and one-third of the used fuel assemblies are removed from the core and replaced with new ones. The term “cycle” refers to the 22-month period of operation between refuelings.
NRC image of a Boiling Water Reactor

NRC image of a Boiling Water Reactor

Spent Fuel Storage:

  • When used fuel is moved from the reactor, it is stored in a pool inside the plant. In the 1980s, Monticello shipped 1,058 spent fuel assemblies to a General Electric facility in Illinois.  Monticello safely built a dry cask storage facility in 2007 – 2008. Ten canisters, each holding 61 fuel assemblies, were safely transferred to the concrete storage bunkers in the fall of 2008.
  • In fall 2004, the Xcel Energy’s board of directors authorized pursuing license renewal for up to 20 years for the Monticello and Prairie Island plants. The NRC renewed Monticello’s operating license in late 2006, allowing that plant to operate for an additional 20 years to 2030. Xcel Energy submitted the application to renew Prairie Island’s operating licenses in April 2008. A decision on that application is expected in  2011.

Current Capacity–Extended Power Uprate (EPU):

  • Xcel has been making moves to boost the generating capacity of the 600-megawatt Monticello plant by 71 megawatts, or 11.8 percent, as part of a plant “uprate” approved in 2009 by the Minnesota Public Utilities Commission. (Federal regulators allow a maximum of 18 percent generation capacity during uprates).
  • Upon completion of the Extended Power Uprate (EPU), the output of Monticello’s reactor will be 684 MW.
  • General Electric (GE) was awarded the EPU contract in January 2007 (although the uprate wasn’t approved until 2009).
  • EPUs typically require modifications and a modernization of major pieces of plant equipment including the high-pressure turbine, reactor feedwater and condensate pumps and motors, main generator and/or transformers. According to Viktoria Mitlyng, senior public affairs officer for the NRC, increasing generation capacity, “will create more vibration and wear and tear on equipment.”
  • During a nine-week shutdown in 2011, Xcel built a $12.5 million “security access facility” in order to meet U.S. Nuclear Regulatory Commission regulations and spent nearly $8 million to install wiring and equipment to meet federal fire-protection regulations.
  • Contractors hired by Xcel also will tie two 345-kilovolt transmission lines to the plant as part of the CapX2020 transmission line project between Fargo, N.D., and Monticello.
  • Both of Minnesota’s Nuclear power plants (Monticello and Praire Island) were designed for a 40-year window of operation. There are worries that current, increased operating levels align Monticello and Praire Island with equipment, durability and design needed for plants with a 100-year life expectancy.

From a letter from the NRC to Mr. Dan P. Stinnett (Field Supervisor, US Fish and Wildlife Services), 3 June 2005:

RE: Request for list of Protected Species within the area under evaluation for the Monticello Nuclear Generating Plant License Renewal (TAC No. MC6441).

The site consists of 2,150 acres with roughly two miles of frontage on both banks of the Mississippi River in Wright and Sherburne Counties. The majority of the acreage is located on the southern side of the river with approximately 450 acres on the northern side of the River. Approximately 50 acres are occupied by the plant and its supporting facilities. The remaining acres are underdeveloped with approximately 174 acres leased by local farmers and 144 acres are under lease for recreational use. 

The circulating water system utilizes both open and closed cycle operating modes, as well as a combination of the two. Cooling water is drawn and discharged to the Mississippi River through and approach channel and discharge canal. Monticello is also equipped with two mechanical draft cooling towers enabling complete or partial recirculation of cooling water when required by the special permit (NPDES) condition. The circulating water system components include the intake structure, circulating water pumps, main condenser, discharge structure, cooling tower pumps, two induced-draft cooling towers, and discharge canal.

Currently there are seven transmission lines emerging from the Monticello Substation. The transmission lines in the scope of the environmental review for license renewal are those that were constructed for the specific purpose of connecting the plant to the transmission system. Transmission lines installed as a result of the construction and operation of Monticello are the Monticello-Coon Creek 345kV line and the Monticello-Parkers Lake 345kV line totaling about 60…[Appendix E cuts off]


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