Federal officials say Westinghouse Electric Company must fix problems with a new nuclear reactor design before a decision can be made on whether to approve it.
Nuclear Regulatory Commission Chairman Gregory Jaczko said Friday that a review of the design has uncovered questions about the reactor's shield building. Regulators had earlier questioned whether it could protect against severe weather or a jetliner crash.
Southern Company plans to use the AP1000 design for two new reactors at Plant Vogtle.
The NRC said Westinghouse made errors in calculating the possible pressures on the walls of a water cooling tank and within the plant's containment area during an accident.
Westinghouse said none of the issues are "safety significant."
In addition to the reactors at Plant Vogtle, power companies also have proposed using the new reactor design in Alabama, Florida, North Carolina and South Carolina.