# Duane Arnold Energy Center

The Duane Arnold Energy Center (DAEC) was Iowa's only nuclear power plant. It is located on a 500-acre (200 ha) site on the west bank of the Cedar River, two miles (3.2 km) north-northeast of Palo, Iowa, USA, or eight miles (13 km) northwest of Cedar Rapids.
DAEC entered operation in February 1975. On August 10, 2020, the plant cooling towers were damaged during a derecho, and repairs were deemed uneconomical, as the plant had already been scheduled for decommissioning in October 2020.
The operator and majority owner is NextEra Energy Resources (70%). The Central Iowa Power Cooperative owns 20% and the Corn Belt Power Cooperative owns 10%.

## Electricity Production

During last full year of operation in 2019, Duane Arnold generated 5,235 GWh of electricity.
Generation (MWh) of Duane Arnold Energy Center :
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual (Total) |
| 2001 | 382,045 | 355,555 | 392,652 | 140,468 | 25,150 | 334,683 | 371,033 | 346,686 | 387,653 | 299,934 | 385,585 | 431,278 | 3,852,722 |
| 2002 | 419,086 | 389,255 | 341,087 | 415,917 | 362,672 | 413,091 | 420,340 | 297,088 | 256,177 | 415,893 | 414,668 | 428,684 | 4,573,958 |
| 2003 | 426,122 | 174,819 | 315,195 | 129,836 | 428,226 | 412,413 | 421,188 | 419,019 | 414,515 | 428,839 | 47,782 | 369,703 | 3,987,657 |
| 2004 | 436,867 | 406,472 | 435,372 | 348,679 | 430,021 | 412,259 | 425,362 | 424,868 | 410,790 | 358,931 | 405,590 | 433,737 | 4,928,948 |
| 2005 | 435,019 | 389,371 | 335,065 | -3,758 | 350,046 | 417,219 | 430,679 | 436,209 | 424,708 | 440,751 | 433,268 | 449,736 | 4,538,313 |
| 2006 | 447,826 | 404,283 | 446,131 | 408,722 | 440,321 | 422,145 | 428,371 | 430,874 | 406,505 | 442,826 | 364,834 | 452,604 | 5,095,442 |
| 2007 | 447,618 | 39,080 | 112,431 | 389,138 | 450,516 | 424,532 | 446,502 | 442,377 | 429,795 | 445,362 | 437,740 | 453,784 | 4,518,875 |
| 2008 | 457,143 | 427,569 | 452,124 | 440,067 | 450,927 | 425,093 | 440,375 | 430,578 | 431,845 | 451,846 | 438,708 | 435,927 | 5,282,202 |
| 2009 | 394,244 | 5,357 | 360,881 | 399,821 | 452,957 | 433,616 | 452,271 | 451,155 | 430,826 | 400,789 | 444,369 | 452,645 | 4,678,931 |
| 2010 | 448,384 | 416,381 | 451,812 | 365,407 | 410,842 | 428,419 | 444,885 | 442,437 | 417,963 | 323,312 | -3,723 | 304,521 | 4,450,640 |
| 2011 | 459,664 | 413,726 | 452,839 | 442,326 | 453,393 | 429,706 | 443,408 | 327,685 | 439,116 | 454,320 | 437,920 | 461,126 | 5,215,229 |
| 2012 | 460,908 | 423,779 | 454,876 | 440,969 | 446,229 | 431,359 | 439,675 | 429,765 | 395,535 | 57,036 | 29,454 | 337,410 | 4,346,995 |
| 2013 | 455,731 | 409,782 | 458,752 | 441,980 | 452,246 | 431,369 | 447,624 | 447,147 | 430,065 | 449,169 | 439,814 | 457,106 | 5,320,785 |
| 2014 | 455,018 | 406,629 | 454,318 | 437,773 | 440,692 | 427,081 | 428,435 | 417,752 | 389,557 | 31,449 | 32,761 | 231,003 | 4,152,468 |
| 2015 | 418,537 | 414,738 | 453,805 | 438,786 | 434,472 | 431,512 | 434,796 | 444,377 | 430,791 | 446,190 | 439,209 | 456,233 | 5,243,446 |
| 2016 | 451,835 | 427,035 | 453,576 | 437,215 | 442,094 | 329,420 | 433,422 | 427,221 | 402,800 | 20,861 | 417,958 | 459,228 | 4,702,665 |
| 2017 | 458,665 | 411,012 | 456,960 | 438,264 | 446,374 | 430,857 | 427,637 | 440,204 | 428,408 | 382,121 | 439,912 | 453,095 | 5,213,509 |
| 2018 | 454,361 | 410,060 | 450,580 | 435,050 | 437,412 | 421,904 | 426,623 | 411,903 | 137,946 | 409,884 | 442,856 | 456,820 | 4,895,399 |
| 2019 | 448,846 | 411,424 | 453,075 | 376,139 | 450,708 | 432,612 | 441,330 | 445,597 | 429,336 | 451,258 | 439,593 | 455,798 | 5,235,716 |
| 2020 | 456,363 | 425,228 | 452,682 | 419,860 | 392,817 | 289,107 | 358,850 | 109,956 | 0 | -- | -- | -- | 2,904,863 |

## History

In the late 1960s, Iowa Electric Light & Power Co. (now Alliant Energy – West), Central Iowa Power Cooperative and Corn Belt Power Cooperative applied for a nuclear plant license with the Atomic Energy Commission (AEC). On June 17, 1970 a construction permit was granted and work began. The original plan was to complete construction in 40 months at an estimated cost of $250 million.
The energy center was named after Duane Arnold who grew up in Sanborn, Iowa. Arnold was educated at Grinnell College and went to work for Iowa Electric Light and Power Company in 1946. At the time of his death in 1983, at the age of 65, he was chairman of the board and CEO of that company, marrying along the way the daughter, Henrietta, of the previous chairman Sutherland Dows. Arnold was very committed to nuclear energy despite the controversy surrounding that source of energy, and oversaw the construction and opening in 1974 of the plant that bears his name. “In my opinion, nuclear power is the most beneficial method of anything we could possibly do to provide energy to our customers in the future,” Mr. Arnold stated in a 1979 interview with the Des Moines Register, about a month after the Three Mile Island accident.
Construction was completed and the reactor reached initial criticality on March 23, 1974. The cost was $50 million over budget. Commercial operations began on February 1, 1975. The plant was licensed for 1,658 MWt. However, power operations were restricted to 1593MWt (about 535 MWe) until plant modifications were completed in 1985 to utilize the full licensed capacity.
In May 2000, the NRC granted a license transfer of the DAEC to Nuclear Management Company LLC (NMC). Ownership of the plant remained with Alliant, Central Iowa Power Cooperative and Corn Belt Power Cooperative, but NMC would manage the operation of the plant.
In 2001, a power uprate was approved by the NRC to 1,912 MWt. Scheduled outages since that time have added modifications to the plant that have allowed this power level to be sustained without restrictions or challenges to nuclear or industrial safety.
On January 27, 2006, FPL Energy (a subsidiary of FPL Group) closed the sale transaction of 70 percent ownership from Alliant Energy-Interstate Power and Light. FPL Energy (now NextEra Energy Resources) also took control of the operations of the plant from NMC.
DAEC remained online during the 2008 Iowa Flood, when other power plants along the Cedar River shut down. Practice drills for radiological emergencies from the plant allowed the Linn County Emergency Management Agency to better respond to the flooding.
In December 2010, the Nuclear Regulatory Commission granted Duane Arnold a 20-year extension license lasting until 2034, taking the plant beyond the life of its original 40-year operating permit.
In January 2018, NextEra Energy announced that it was unlikely that DAEC would operate beyond 2025. The plant was given a 20-year license extension to 2034 but considered closing after Alliant Energy, which contracts for 70% of the plant's electricity, announced it would instead be buying electricity generated by wind and natural gas. In July 2018 the expected closure date was amended to October 2020. In July 2018, NextEra and Alliant Energy agreed to shorten their power purchase agreement by five years in return for a $110 million buyout payment from Alliant, making the expected closure date 2020.
The unit permanently ceased making power on 10 August 2020, due to storm damage from the August 2020 Midwest derecho. An NRC report of the incident stated that "the vacuum drawn in secondary containment by the standby gas treatment system was slightly below the technical specification (TS) limit", indicating that the secondary containment system might not have been fully effective had it been challenged. Thus the incident was considered by nuclear safety experts to be "a close call".
As of September 2024, John Ketchum, NextEra’s chief executive officer said that, under certain conditions, they’re willing to revive the plant, as several data centers were interested.

## Plant equipment

DAEC has a single GE BWR-4 reactor with a Mark I containment. Twenty-four mechanical draft cooling towers utilized water from the Cedar River as a heat sink. Facilities exist to process all contaminated water onsite and the DAEC operates with a "zero release" policy to not discharge any contaminated water back to the Cedar River. Facilities exist on site for dry storage of spent fuel with capacity for the entire life of the plant (including license renewal).
The site is scheduled for a 200 MW label capacity solar park with a 75 MW / 300 MWh (4-hour) battery by 2024. Lazard estimates that the wholesale price of replacement electricity will be $0.04/kWh, but a more realistic estimate that takes account of the 11.4% cost of capital reported by NextEra puts the wholesale price at $0.21/kWh, not including operating and decommissioning costs.

## Known problems

The Mark I containment was undersized in the original design; the Nuclear Regulatory Commission's Harold Denton estimated a 90% probability of explosive failure if the pressure containment system were ever needed in a severe accident. This design flaw may have been the reason that the tsunami in 2011 led to explosions and fire in Fukushima Daiichi nuclear disaster.

## Accident analysis

In 2010, the Nuclear Regulatory Commission estimated that the risk of an earthquake causing core damage to the reactor at Duane Arnold was 1 in 31,250 each year.
In 2013, in response to the Fukushima Daiichi nuclear disaster, the Nuclear Regulatory Commission ordered Duane Arnold "to install a reliable hardened venting capability for pre-core damage and under severe accident conditions, including those involving a breach of the reactor vessel by molten core debris" due to the similarity in reactor design.

## Community impact

DAEC employed hundreds of people in the Cedar Rapids area. Some of these workers are represented by the International Brotherhood of Electrical Workers, others by Security, Police and Fire Professionals of America.
Emergency warning towers are maintained by DAEC and provide a means for tornado warnings as well as plant emergencies. The Emergency Planning organization at DAEC works with local, county, and state officials to maintain an emergency plan. The emergency plan can be found in the front of area phonebooks. Drills are conducted on a regular basis in accordance with requirements from the Nuclear Regulatory Commission (NRC) and the Federal Emergency Management Agency (FEMA).
Tax revenues from DAEC amount to about 1% of the total revenues for Linn County, Iowa. Pleasant Creek Reservoir, a 410-acre (1.7 km$^2$) lake, was developed by Alliant Energy and the Iowa Conservation Commission to provide a recreation area and act as a source of cooling water during times of low flow in the Cedar River.
While the DAEC site covers 500 acres (2.0 km$^2$), only a portion of that is used for power production. The remainder is leased to farmers for crop production or is left in its natural habitat.
In 2014, the Nuclear Energy Institute released a study showing the positive impact of DAEC on the economy and environment. Key findings are listed below.
* DAEC employs nearly 600 full-time workers that earn more than double the average pay of workers in Benton County and approximately 55 percent more than those in Linn County
* DAEC contributes $246 million of economic activity locally and contributes approximately $255 million to Iowa's economy each year
* For every dollar DAEC spent, the Iowa economy produced $1.27
* DAEC produces more than 1,100 direct and secondary jobs
* DAEC's operation helps avoid the emission of nearly 4 million tons of carbon dioxide annually, which is the equivalent of taking almost 800,000 cars off the road

## Surrounding population

The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of 10 miles (16 km), concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about 50 miles (80 km), concerned primarily with ingestion of food and liquid contaminated by radioactivity.
The 2010 U.S. population within 10 miles (16 km) of Duane Arnold was 107,880, an increase of 8.2 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within 50 miles (80 km) was 658,634, an increase of 7.1 percent since 2000. Cities within 50 miles include Cedar Rapids (10 miles to city center).

## Proposed Restart

In early 2025, NextEra Energy Duane Arnold, LLC (NextEra), the licensee for DAEC expressed an interest in returning the plant to an operational status and resuming commercial operation.
To restart DAEC, NextEra would need to gain NRC approval to restore the licensing basis of the plant to an operational status, return plant components to a status that supports safe operation, and make any upgrades necessary to meet the proposed operational licensing basis.
NRC staff will carefully review the regulatory and licensing documents for the plant, inspect new and restored components necessary to operate safely, and continue ongoing oversight to ensure sufficiency of all plant systems and programs.
The NRC will engage in several pre-submittal interactions with the DAEC staff on various topics related to the potential for restart, and will continue to host public meetings related to the potential for the DAEC to resume power operations throughout the project.