Duane Arnold Energy Center
The Duane Arnold Energy Center (DAEC) is located on a 500-acre (2.0 km 2) site on the west bank of the Cedar River, two miles (3 km) north-northeast of Palo, Iowa, USA, or eight miles (13 km) northwest of Cedar Rapids. It is Iowa's only nuclear power plant. DAEC entered operation in June 1974. It currently generates a net power output of approximately 615 megawatts using a single General Electric Mark I boiling water reactor. The majority owner and operator is NextEra Energy Resources (70%). The Central Iowa Power Cooperative owns 20% and the Corn Belt Power Cooperative owns 10%.

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. 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 would allow the DAEC to achieve this power level. Currently, the power level is limited to 1,880 MWt (about 615 MWe) and final modifications should be completed during the 2009 refueling outage. On 27 January 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.

In December 2010, the Nuclear Regulatory Commission granted Duane Arnold a 20-year extension license lasting until 2034, taking the plant well beyond the life of its original 40-year operating permit.

Plant equipment
DAEC has a single GE BWR-4 reactor with a Mark I containment. Twenty-four forced-draft cooling towers utilize 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 lake. Facilities exist on site for dry storage of spent fuel with capacity for the entire life of the plant (including license renewal). This reactor is fueled by uranium.

Known problems
Duane Arnold's primary containment shell was undersized in the original design.. The "torus direct vent bypass system" retrofit was installed in all 18 Mark I reactors in the late 1980s and is operated by a butterfly valve at the operators' control, after a zero leakage rupture diaphragm breaks prior to reaching the primary containment max design pressure. Operators now have the controls necessary to protect against a rupture of primary containment, however remote.. The reactor has been shutdown in unplanned scrams eleven times since the year 2000, as indicated in NRC performance indicator reports.

Community impact
DAEC employs more than 500 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 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.