Monticello Nuclear Generating Plant
| Company type | Nuclear power plant |
|---|---|
| Industry | Energy |
| Founded | 1971 |
| Fate | Operational |
| Headquarters | Monticello , United States |
Area served | Minnesota, United States |
| Products | Electricity generation (671 MWe) |
| Owner | Xcel Energy |
| Parent | Northern States Power (operator) |
The Monticello Nuclear Generating Plant is a nuclear energy facility located in Monticello, Minnesota, positioned adjacent to the Mississippi River. Since commencing operations in 1971, it has operated a single boiling water reactor based on the General Electric BWR-3 model, with an output capacity of 671 MWe. Ownership lies with Xcel Energy, while its regional branch, Northern States Power, manages daily operations.
Initially authorized to operate until 2010, the plant's license was extended in 2006 to allow activity through September 8, 2030. In January 2023, Northern States Power submitted an application seeking another 20-year extension. The license was subsequently renewed until 2050, ensuring continued operation for decades to come.
Regulatory history
The Monticello facility began producing power in 1971 using a single boiling water reactor of the General Electric BWR-3 type, generating 671 MWe. Its original operating license was valid until 2010; however, a renewal granted in 2006 extended this authorization until September 8, 2030.
In early 2023, Northern States Power Company requested an additional two-decade license extension beyond the existing expiration date.
Geography, seismic risk and surrounding population
The Nuclear Regulatory Commission (NRC) defines two distinct emergency planning zones around nuclear sites: a 10-mile plume exposure pathway zone focused on airborne radioactive hazards and a broader 50-mile ingestion pathway zone addressing risks from contaminated food and liquids. According to a 2010 NRC seismic risk assessment, the annual probability of an earthquake causing core damage at Monticello is estimated at 1 in 52,632.
Data from the 2010 U.S. Census indicated that within a 10-mile radius of Monticello, the population numbered 62,976—a growth of 36.5% over ten years. Within a 50-mile radius, nearly three million people reside, including the metropolitan areas of Minneapolis (38 miles away) and St. Paul (45 miles distant).
Notably, the segment of the Mississippi River near Monticello remains ice-free during winter months, attracting hundreds of trumpeter swans, largely due to warm water discharged by the plant.
Incidents and updates
In November 1971, approximately 50,000 gallons of "low-level" radioactive water were released into the Mississippi River to facilitate maintenance activities.
On December 20 and again on December 29 of that year, maintenance procedures involved discharging a combined total of 13,500 gallons of water contaminated with cesium-137.
An accidental release of about 1,300 gallons of radioactive water occurred on May 5, 1982; authorities assessed that this posed no danger to public health.
21st century
In January 2007, an unexpected shutdown was triggered after a control box weighing thirteen tons shifted slightly. Investigations attributed this event to substandard welds and fatigue from prolonged vibration exposure throughout the plant’s operational history.
Construction began in June 2007 on an independent spent fuel storage installation (ISFSI) pad located onsite, with completion aimed for December that year. This facility was designed to accommodate twelve horizontal storage modules (HSMs), each capable of holding sixty-one spent fuel assemblies.
On September 11, 2008, a transformer cable fault caused loss of off-site power supply and initiated an automatic shutdown.
A week later, on September 18, an equipment rental worker suffered electrocution after coming into contact with a 115-kV power line outside the inactive plant area due to insufficient situational awareness.
In February 2011, plant management identified a safety concern involving four control rod blades; replacement was scheduled for March.
Proposals made by Xcel Energy in 2006 aimed at upgrading the plant included increasing power output and extending operational life by two decades. The Nuclear Regulatory Commission approved a license amendment in December 2013 raising capacity from 600 MWe to 671 MWe. However, project expenses ultimately exceeded estimates by more than $400 million. In response, the Minnesota Public Utilities Commission in 2015 denied full cost recovery and disallowed returns on these excess expenditures. Consequently, Xcel reported losses exceeding $100 million during Q1 of that year and recovered $27 million less than anticipated.
During refueling in March 2013, original equipment was replaced to support enhanced output capacity. This outage temporarily expanded workforce numbers significantly.
Tritium leak: In November 2022, contaminated water escaped from piping between two buildings onsite. Initial volume estimates were approximately 400,000 gallons but were later revised upward to between 750,000 and 900,000 gallons. By March 16, 2023, only about one-quarter of the tritium released had been recovered. A secondary leak resulting from a temporary repair was detected later that month.
Xcel Energy announced a plant shutdown on March 24, 2023, to address repairs on a leaking pipe dating back fifty years. Company officials acknowledged ongoing risks associated with further tritium contamination seeping into groundwater supplies.
In December of the same year, Xcel Energy faced a $14,000 fine imposed by the Minnesota Pollution Control Agency for discharging contaminated groundwater into temporary holding tanks without obtaining proper permits.
Updated assessments confirm that approximately 829,000 gallons of contaminated water were released during the November leak. This figure appears in documentation provided by both Xcel Energy and the Nuclear Regulatory Commission related to the NRC-approved license extension through an additional twenty years.
Electricity generation
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Total Annual Output | ||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2001 | 440,695 | 340,547 | -4,261 | 369,313 | 431,818 | 417,928 | 422,760 | 415,031 | 411,801 | 396,154 | 21,897 | 212,639 | 3,876,322 | ||||||||||||||||||||||||||||||||||||||||||||||||
| 2002 | 349,057 | 396,128 | 438,866 | 423,484 | 438,208 | 409,953 | 421,673 | 423,789 | 416,914 | 434,384 | 424,937 | 438,164 | 5,015,557 | ||||||||||||||||||||||||||||||||||||||||||||||||
| 2003 | 436,483 | 393,223 | 437,856 | 345,599 | 50,496 | 369,107 | 424,318 | 420,302 | 416,377 | 436,020 | 424,869 | 421,860 | 4,576,510 | ||||||||||||||||||||||||||||||||||||||||||||||||
| 2004 | 433,230 | 408,757 | 440,422 | 424,219 | 423,616 | 350,104 | 420,318 | 425,000 | 412,488 | 436,433 | 423,677</ small > | < small >436 , 618 </ small > | 5 , 034 , 882 | - | 2005 | < small >436 , 233 </ small > | < small >363 , 285 </ small > | < small >42 , 698 </ small > | < small >228 , 534 </ small > | < small >436 , 029 </ small > | < small >413 , 038 </ small > | < small >420 , 637 </ small > | < small >421 , 445 </ small > | < small >414 , 350 </ small > | < small >437 , 081 </ small > | < small >423 , 304 </ small > | < small >438 , 284 </ small > | 4 , 474 , 918 | - | 2006 | < small >437 , 266 </ small > | < small >393 , 609 </ small > | < small >437 , 954 </ small > | < small >421 , 222 </ small > | < small >433 , 091 </ small > | < small >407 , 403 </ small > | < small >411 , 732 </ small > | < small >419 , 876 </ small > | < small >414 , 853 </ small > | < small >437 , 102 </ small > | < small >423 , 707 </ small > | < small >434 , 736 </ small > | 5 , 072 , 551 | - | 2007 | < small >232 , 813 </ small > | < small >391 , 535 </ small > | < small >173 , 046 </ small > | < small >6 , 240 </ small > | < small >420 , 460 </ small > | < small >414 , 784 </ small > | < small >424 , 641 </ small > | < small >425 , 406 </ small > | < small >420 , 682 </ small > | < small >439 , 692 </ small > | < small >407 , 935 </ small > | < small >435 , 035 </ small > | 4 , 192 , 269 | - | 2008 | <小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小><小>< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< 小 >< Small >
(Truncated for brevity) See alsoExternal links |