Electricity and natural gas firm Xcel Energy resumed power generation at its Monticello nuclear generating plant in Minnessota, US.
Operators have returned the plant, which has a capacity of 600MW, to full power on 3 August 2013, after completing refueling and maintenance outage works.
Work during the outage, which started on 2 March 2013, included the installation of two new feed water heaters and two new transformers.
The company also completed work on projects that will allow the plant to increase its generation capacity by 71MW.
Around 3,000 contract workers joined the plant's 500 employees to complete the work and ensure safe and reliable operations through 2030.
Xcel Energy is in the process of obtaining approval from the US Nuclear Regulatory Commission to operate the plant at the higher capacity level.
The Monticello plant, which is about 40 miles northwest of Minneapolis, produces adequate electricity to power nearly 450,000 homes.