The Sizewell B nuclear power station in the United Kingdom is generating electricity again after being offline nearly four months for planning refueling and maintenance upgrades.

Owner EDF Energy said Sizewell B is reconnected to the grid after the work which began in mid-April. Contracts and EDF crew replenished one-third of nuclear fuel in the plant and performed thousands of maintenance tasks during the scheduled event.

The planned outage was delayed and the project scope reduced due to the COVID-19 pandemic. EDF is continuing to build pressurized water reactor projects but decommissioning numerous advanced gas-cooled reactors by 2030.

“It is the completion of maintenance work and refuelling that ensures we can keep the lights on for another eighteen months,” Robert Gunn, Sizewell B station director, said in a statement. “I am particularly grateful to the Sizewell B team, including our excellent contract partners, for their commitment to a first-class job and the local community for their support during this time.”

Significant work completed included replacing 15 thermal sleeves under the reactor pressure vessel head, maintenance of the steam turbines and generators, and routine servicing of valves, pumps, and motors, together with a full suite of testing for another operating cycle.

The Sizewell nuclear power station is located in Suffolk, England. Sizewell A, which was commissioned in the 1960s, is being retired.

Sizewell B started generating carbon-free electricity in the mid 1990s. The 1.25GW plant powers off of a Westinghouse-supplied pressurized water reactor.

EDF is proposing construction of the Sizewell C nuclear unit expansion project. The French-owned EDF Energy is also developing the Hinkley Point C nuclear power expansion in the UK. Construction on the $25 billion Hinckey Point C is underway with the first unit expected to be completed by 2025.