The decision by the Nuclear Regulatory Commission means the proposed $7.9 billion merger has two remaining regulatory hurdles to clear. The Maryland Public Service Commission is expected to issue a decision Friday, while the Federal Energy Regulatory Commission also needs to rule on the deal, which would create the largest competitive energy company in the United States.
Operating licenses for five nuclear plants in New York and Maryland would be transferred to Exelon.
Constellation Energy and French utility EDF own the plants under a joint venture called Constellation Energy Nuclear Group. After the merger, the joint venture would continue to own and operate the nuclear fleet.
"We are pleased that the NRC has approved the license transfer, which is a key step toward completing our merger," Exelon President and Chief Operating Officer Christopher M. Crane said in a statement.