The first chief executive of Sellafield Limited will leave the company next year.

Paul Foster has announced he will step down in January.

Mr Foster has been a senior executive at the Sellafield site since 2000 and became managing director then the first chief executive of Sellafield Ltd in 2016.

He has overseen major projects at the site, including removing the majority of spent fuel from the world’s oldest nuclear fuel pond; creating access routes in to the world’s oldest nuclear fuel store and the start of the removal of materials from some of the world’s most hazardous nuclear facilities.

A Sellafield Ltd spokesman said: "In the process, Paul established Sellafield Ltd as a business that delivers more value for money than ever before. Sellafield Ltd is on target to deliver £1.4bn in efficiencies by 2020 and has pledged a further £1bn to £1.4bn to government by 2029."

Mr Foster said: “It has been an incredible privilege to serve as the first chief executive of Sellafield Ltd. I have had the pleasure to work alongside some remarkable people on a mission of acute national importance and together, we have ensured that more progress than ever before is being made at Sellafield.

“As a new business, Sellafield Ltd is providing more value for the taxpayer than at any point previously. We are making Sellafield safer, sooner, investing in the local community and changing the business to ensure future success for the taxpayer, government, NDA, our workforce and our local communities.

“Five years is a significant amount of time to spend as chief executive in any organization and is longer than I originally intended to serve.

"It is the right time to seek a new challenge and I know that the Sellafield workforce will continue to be successful in the future.”

Mr Foster oversaw the introduction of new terms and conditions across Sellafield Ltd and managed the completion of nuclear fuel reprocessing at Thorp, while ensuring that every person working at the plant remained in employment.

The firm said he has also identified and started to tackle issues with regard to equality, diversity and inclusion, including taking personal action to address bullying and harassment.

In recent months, he has overseen the creation of a new 20-year, multi-billion-pound partnership contract between Sellafield Ltd and the supply chain partners, PPP, that will enable more progress to be made at Sellafield.

The company said: "As the first chief executive of Sellafield Ltd, Paul has established a new approach towards how the company acts as a responsible corporate citizen.

"Under Paul’s leadership, Sellafield Ltd has recruited record numbers of apprentices, and our new approach towards the social impact of Sellafield’s operations has seen Sellafield Ltd invest over £40m in projects of benefit to the communities closest to the site since 2015."

They include a £10m investment in the new Campus Whitehaven; £1.75m in the new WELL Project designed to lift educational attainment levels in every West Cumbrian classroom; £3.6m into new economic growth and diversification projects in Whitehaven and the creation of a new community apprenticeships scheme providing apprenticeships for 50 people.

Lorraine Baldry, Sellafield Ltd chairman, said: “Paul has delivered unprecedented progress across the Sellafield site and business and his achievements will be lasting.

"Five years is a considerable amount of time to serve in such a challenging role and I’m grateful for everything that Paul has achieved. I wish him every future success.”

David Peattie, chief executive of the Nuclear Decommissioning Authority, said: “I’d like to thank Paul for his five years leading the organisation and for his support in building a stronger NDA group.

"His legacy of cleaning-up the UK’s largest and most complex nuclear site is one of national importance.

“Sellafield Ltd today is a stronger organisation because of Paul’s leadership, progressing hazard and risk reduction on the site and supporting the goals of the UK nuclear decommissioning programme.”

It is not known who will replace Mr Foster in the role.

John Grainger, executive director of Britain's Energy Coast Business Cluster, said: "For all of the 21st century, Paul has held prominent positions rising to director level and culminating with his appointment as chief executive.

"He has been a constant in a period of continuous change and indeed differing ownership. He has been an outstanding manager and leader and will certainly be a hard act to follow.

"As the transition from large Sellafield to a smaller Sellafield with a larger supply chain he has laid down a challenge that will be testament to his intuition and foresight. His legacy will be one of success with greater productivity alongside cost reduction without a trimming of the core workforce.

"He has had an almost unique empathy with the community having West Cumbrian roots, and we are grateful for that. His departure coincides with the end of reprocessing at Sellafield and his successor will assume control of a site concentrating on environmental remediation. “

Mike Starkie, Copeland mayor, also paid tribute to Mr Foster.

He said: “Paul’s commitment to our industry and site mission has been matched by his absolute vision for Sellafield as part of a transformed West Cumbrian economy.

“Paul has faced some huge challenges at Sellafield Ltd head on, and with my absolute confidence in his ability and leadership, and I am saddened that he is leaving.

“The relationship between Sellafield Ltd and Copeland Council has never been stronger than it has been on Paul’s watch. He is deeply committed to the place, as well as the site, and that is highly valued by many, but none more so than me.

“Paul has set Sellafield Ltd on a new path and lead the workforce through huge changes, and I very much hope that his successor will progress our mutual and agreed ambitions. These are big shoes to fill.

“I know these sentiments reflect the position of my executive, chief executive and leadership team.

“On a personal level, he is someone I hold in the highest regard and have the utmost respect. I wish Paul nothing but success in his future.”