The 31-page report released last month also found that one of the mistakes at the site near the South Carolina-Georgia border could have resulted in a spill of high-level radioactive waste.
The safety issues involved a facility that is being built to convert weapons-grade plutonium into fuel for commercial nuclear reactors.
According to the report, three structural components obtained and installed by the prime contractor at SRS during construction of the mixed oxide fuel fabrication, or MOX, facility did not meet safety specifications.
"These substandard items necessitated costly and time consuming remedial action to, among other things, ensure that nonconforming materials and equipment would function within safety margins," the report said.
The report said installing the components resulted in cost increases. As of October, the report said, the MOX facility had run up costs of more than $680,000 resulting from problems associated with nonconforming safety-class reinforcing steel. The faulty steel was discovered after a piece of it broke during construction.
Weaknesses in internal control, according to the report, could have led to the installation of critical components that didn't meet standards and could have injured workers and the public.
A message left seeking comment from Savannah River Site spokesman Jim Gaver was not immediately returned.