The Wylfa nuclear power plant in North Wales is up and running again after a five-month closure.
Reactor 1 was shut down in January for its last scheduled maintenance but the discovery of further problems delayed its restart.
The 43-year-old facility, which is expected to close later this year, finished the 2013/14 financial year with a total output of 2.81 terrawatt hours (TWh) of electricity – enough to power around 70 million smart phones.
It also generated around £140 million of revenue for the Nuclear Decommissioning Authority (NDA), which owns the site.
Dr Brian Burnett, NDA Head of Programmes said: “Wylfa’s return to service is good news for the taxpayer, for Anglesey and for the site workforce.”
A second reactor at Wylfa was shut down in April 2012.