Operations Site Works, which is worth up to £160m over four years, covers engineering support services for asset care and maintenance.
The new framework replaces the multi-discipline site works and the site wide asset care frameworks.
Amec Foster Wheeler has worked on various Sellafield projects over the years, in various partnerships, including as part of the Axiom alliance and the joint venture behind the £600m box encapsulation plant.
Interserve has worked with Sellafield for 17 years, supporting it during major projects such as the opening of the Evaporator D facility, expanding capacity for processing nuclear waste.
Interserve managing director for infrastructure and industrial, Guy Bruce, said: “Having worked in the nuclear sector for more than 65 years, we're extremely well equipped to deal with the challenges that operating in such an environment presents. Our team of experts carry out their day-to-day responsibilities with the level of precision and care required at a reprocessing plant, using their skills and knowledge to manage customer projects in a safe and efficient way.
“The nature of work at Sellafield also requires flexibility to scale up activity to deliver complex multidisciplinary projects. Our longstanding relationship with Sellafield has given us an in-depth understanding of its unique needs, allowing us to work with our partners Amec Foster Wheeler to tailor the service we provide."
Clive White, president of Amec Foster Wheeler Clean Energy, added: “Winning the Operations Site Works framework reflects our strategy to extend the range of services we provide to Sellafield Limited.
"We welcome the opportunity of taking a greater role in the full project lifecycle, focusing on delivering safe, efficient and predictable outcomes and supporting Sellafield Limited in its cost-efficiency objectives, while also having a positive social impact on communities, skills and growth in Cumbria.
"The combination of Amec Foster Wheeler and Interserve creates a highly capable vehicle that will work to bring international best practice and value-driven solutions to the Sellafield mission."