The 4.8 billion dollar mixed oxide, or MOX, plant at Savannah River Site is designed to get rid of weapons grade plutonium by turning it into fuel for commercial nuclear reactors.
The National Nuclear Security Administration oversees the construction.
This week the agency said last year more than 15 percent of the engineers and technicians working at the site left for jobs in the commercial nuclear industry.
That includes places like Plant Vogtle near Augusta where the highly trained workers make about 25 percent more money.
Tom Clements is with environmental group Friends of the Earth. He says recent efforts to expand nuclear power in the U.S. means those highly trained workers are in demand.
"The MOX plant at Savannah River has to compete for qualified personnel," says Clements. "If they don’t pay as much then they’re not going to get those personnel."
NNSA officials say replacing the workers is difficult.
In many cases, they say, under qualified workers have to be hired and trained, which is a slow and expensive process.
The MOX plant is scheduled to go online in 2016.