June 1 (Reuters) - U.S. regulators plan to finalize a set of new safety rules for operating the nation's nuclear reactors in August, after considering public comment through July. The U.S. Nuclear Regulatory Commission has drafted several guidelines to ensure proper implementation of three orders the agency issued to nuclear power plants in March, in response to lessons learned from the Fukushima Daiichi nuclear accident in March last year. "Public comments on the draft interim staff guidance (ISG) will help the NRC ensure the guidance is as complete as possible," the agency said in a statement dated May 31. The draft represents approaches made by operators of the nation's nuclear reactors to meet the requirements of the three orders before Dec. 31, 2016, the compliance deadline. "The ISGs are not mandatory, but U.S. nuclear power plants would have to seek NRC approval if they wanted to follow a different compliance approach," the NRC said. Nuclear regulators around the world have tightened scrutiny of reactor operations after an earthquake and tsunami damaged the Fukushima reactor. The biggest nuclear power operators in the United States include Exelon Corp, Entergy Corp, Dominion Resources Inc, Duke Energy, Progress Energy , NextEra Energy, Southern and the Tennessee Valley Authority.