Power utility EDF has begun a major overhaul of the Sizewell B nuclear power station in southeast England with work set to cost £75m (€65m, $71m) and take around two months.

During the outage teams at Sizewell B – which is due to close in 2035, but could operate until 2055 – will carry out work that includes replacing a high-pressure rotor and three low pressure rotors in one of the station’s turbine generators and replacing about a third of the fuel assemblies in the reactor.

EDF said workers will carry out detailed inspections of reactor systems and examine high pressure pipework across the reactor system.

Every 18 months teams at Sizewell B take the site’s nuclear reactor offline for refuelling and other works designed to improve the efficiency of the plant’s operations. During the outage EDF will bring in more than 1,000 extra staff to perform more than 12,000 tasks.

The reactor, which every year generates enough zero-carbon electricity to meet the needs of more than 2.5 million homes, was taken offline on 11 October.

Sizewell B is a 1,198 MW pressurised water reactor unit that began commercial operation in September 1995.

EDF acquired the UK nuclear fleet, which has nine units in operation at five sites, in 2009 and, since then, has invested around £1.2bn in Sizewell B to maintain reliability.

Sizewell B is due to generate electricity until 2035, but EDF is considering plans to keep it operational until 2055.

The company said there is no immediate need to make a final investment decision on long-term operation.

“As well as finalising the technical case, we are seeking greater cost certainty and confidence in the long-term commercial case to enable a final investment decision when ready,” a statement said.

EDF has said there is an “obvious case” for extending the life of Sizewell B, but it needs a government framework to enable it to make a decision.