The intermediate level waste was produced at the site during its operations and is safely stored inside a self-shielded cast iron container.
According to Magnox, the ISF is with a footprint the size of a football pitch and can hold around 850 packages of nuclear waste.
Berkeley site director Steve McNally said, "This is a huge achievement for the site and a fitting end to a successful year.
"It’s a great reward for the effort and dedication the team has shown and provides momentum for a new year of safe delivery."
Berkeley decommissioning programme is under way and each box of waste that is retrieved and stored in the ISF is a step closer to care and maintenance, which is expected in 2021.
Magnox is management and operations contractor responsible for safely managing ten nuclear sites.
