The team cleaning up the prototype fast reactor (PFR) have notched up seven years of safety.
They have worked for just over two million man hours without accidents that cause time off work of three days or more.
The achievement comes at a time when work is going on to remove large items of redundant equipment from the redundant reactor building.
Since 2005, a world record 1,500 tonnes of radioactive liquid metal coolant has been drained from the reactor and destroyed.
Three thousand tonnes of steelwork has already been stripped out of the redundant facility, and one thousand tonnes of radioactive pond water has been cleaned up and disposed of.
Reactor decommissioning manager Mike Brown praised his team of DSRL and contractor staff.
“Decommissioning PFR is a challenging undertaking, but nothing is more important than the safety of our workforce,” he said.
“During these seven years there has been extensive heavy lifting, working at height, confined space entries and handling of volatile alkali metals, all completed without serious accident.
“We have also managed to maintain general safety awareness to prevent the slips, trips and falls that can catch any of us out in our day to day working life by making safety awareness part of our culture.
“The whole team looks out for each other. They do not turn a blind eye to unsafe practices and our healthy ‘tap on the shoulder’ attitude has helped us meet this amazing achievement.
“I can’t commend them enough for applying a workable safety improvement programme which is clearly valuable given this remarkable achievement.”