Nuclear Regulatory Commission (NRC) for its Dresden nuclear power station in Illinois that could see the facility remain in operation until 2051.

Constellation, which operates 21 nuclear plants at 14 sites, said the move is another in a series of investments the company is making to add clean, firm energy to the grid.

The filing begins a comprehensive, multi-year review by the NRC to renew the licence for Dresden, which has two boiling water reactor units. The facility’s licence was first renewed by the NRC in 2004.