The firm said the work is expected to take ten years to complete and it would reduce its annual costs by $35m and result in the layoffs of 265 people.

The power plant owner Exelon handed over keys and $800m trust fund paid into by ratepayers to EnergySolutions to handle the decommissioning, according to Chicago Tribune.

EnergySolutions spokesman Mark Walker was quoted by the newspaper as saying that the job cuts are not expected to affect the Zion project.

"What we’re doing with other portions of the company will not have an impact on the work we are doing at Zion," Walker said.

Zion Nuclear Power Station, which sits on the shores of Lake Michigan, has been closed since 1998.

About 60% of EnergySolutions’ revenue comes from a $1bn-per-year contract with UK-based nuclear operator Magnox to decommission 20 reactors and operate two others.