The first steps to restart some of the highest priority of work at Sellafield have begun.

But Sellafield Limited said its initial work was "cautious" to restart projects.

Work at the Sellafield site in West Cumbria nuclear complex was paused, including reprocessing and construction work on major projects so the firm could focus on keeping the site safe and secure.

A statement released by Sellafield said: "The business has built confidence in its ability for key workers to begin some of the most important high hazard and risk reduction work again."

While reprocessing is still paused, but a small amount of construction at a new facility to accept waste for a high hazard legacy waste silo will begin.

Due to the coronavirus pandemic escalating, the number of people working on the Sellafield site was slashed to around 1,500.

The cautious restart will add around 120 people to the number on site, with around 120 people starting to attend off-site offices mainly in Warrington to access specialist equipment and software.

The statement added: "It will be a cautious, limited, phased restart of work over the coming weeks using ‘lead and learn’ principles on specific work packages to build understanding on helping people safely return to work.

"Detailed risk assessments have determined how many people can safely work in every location being used, taking into account factors such as social distancing, PPE requirements, operational procedures and a huge range of other considerations around people being able to get to work safely and stay safe and comfortable once there.

"All of the work can also all be stopped quickly if necessary, for example if a second wave of Covid-19 impacts on the availability of key workers.

"The decision has been taken to begin phasing in new work while the national lockdown continues because on the balance of risk, it’s the safest thing to do. Thousands of other Sellafield Ltd employees will continue with their existing arrangements of working remotely where possible."

Martin Chown, Sellafield Ltd chief executive, said: “We have always said we will only progressively restart certain operations when safe to do so. The excellent preparation and risk analysis work we have done so far has given us the confidence to be able to restart the most important work which is of national interest. Safety is in our DNA. If any organisation can work safely around Covid-19, we can.

“We’ve thought long and hard about the questions ‘Can we? Should we? Will we?’ before restarting any piece of work. But we also have to be aware of the risks involved in not restarting more work - every day of delay caused by the pandemic is another day further in the future where a nuclear incident could in theory happen.

“I am incredibly proud of every single individual in our organisation and our supply chain, who has kept the site safe and secure through this crisis. Our key workers are doing a vital job and it’s a major step forward to be able to start cautiously building up the number of people delivering our critical mission.”