The US Duane Arnold nuclear plant in Linn County, Iowa, will be decommissioned early as a result of damage by the recent derecho (violent storm).
The 601MWe boiling water reactor, which began commercial operation in 1975, was previously set to be decommissioned at the end of October.
NextEra Energy Resources said on 24 August that "After conducting a complete assessment of the damage caused by recent severe weather, NextEra Energy Resources has made the decision not to restart the reactor at Duane Arnold Energy Centre (DAEC).
"The strong storms that hit the area on 10 August caused extensive damage to Duane Arnold’s cooling towers, and our evaluation found that replacing those towers before the site’s previously-scheduled decommissioning on 30 October 2020, was not feasible,” it added.
There was also damage to the outside of the building but none of it impacted safety systems or critical components.
Duane Arnold is licensed with the Nuclear Regulatory Commission (NRC) to operate until February 2034, but NextEra announced in July 2018 that it had agreed to with Alliant Energy shorten a power purchase agreement the company had, which would allow it to close the station by the end of 2020.
NextEra has been working with employees to begin the transition process, offering early retirements, transfers to other jobs within the company, or the opportunity to stay to assist with decommissioning. Those options remain intact, a spokesman Peter Robbins told local reporters.
During the storm, wind speeds of up to 126mph were recorded in eastern Iowa. More than 95% of residents in, Iowa, lost power due to infrastructure damage.
DAEC declared an “Unusual Event” on 10 August due to a loss of offsite power, which resulted in an automatic scram. The unit was operating at 82% power at the time. Operators submitted a report to the NRC, noting damage on site, but stating the reactor building was intact.
The plant was operating both of its standby diesel generators and no problems that would affect reactor safety were reported. NextEra plans to decommission the plant using the SAFSTOR method in which it will be made safe and subsequently decontaminated (deferred decontamination). The company will have up to 60 years to complete the decommissioning process.
Photo: Duane Arnold Energy Center in Winter (Credit: AsNuke - Own work CC BY-SA 4.0)