U.S. agency okays Scana nuclear units in South Carolina TON (Reuters) - The U.S. Nuclear Regulatory Commission on Friday approved a license for Scana Corp to build two reactors at the Virgil Summer nuclear station in South Carolina, the agency's second approval of additional nuclear units to be built in the United States in two months after a 30-year construction hiatus. Scana and its partner, state-owned electric agency Santee Cooper, want to build two AP1000 reactors at the Summer site near Jenkinsville, at a projected cost of $9 billion. The 1,100-megawatt units are expected to begin operating in 2017 and 2018. In February, the NRC approved Southern Co's proposed Vogtle reactors in a 4-1 vote. No nuclear power plants have been licensed in the United States since 1979 when the partial meltdown of the reactor core of the Three Mile Island plant in Pennsylvania led to design changes that caused construction costs for nuclear plants to skyrocket and others to be canceled. An expected revival of nuclear construction in the United States has now been tempered by falling natural gas prices and slowing growth in power demand. Friday's NRC action "is a significant event for our company and marks the culmination of an intense review by the NRC," said Kevin Marsh, Scana's chief executive, in a statement. Marsh said the country will be watching Scana and Southern as they move ahead with full construction activity. "It's important that we deliver these plants as designed on schedule and on budget," Marsh told Reuters. That's what people will be watching. As he did last month, NRC chairman Gregory Jaczko cast a lone dissenting vote against the new Summer units, citing a need for the agency to make sure all safety issues raised by Japan's Fukushima nuclear disaster are incorporated into new reactors before they are allowed to operate. Congressman Edward Markey of Massachusetts, a critic of the industry, called the 4-1 vote "another victory for the nuclear industry's effort to avoid implementation of the safety upgrades" in the wake of the Fukushima disaster. SCE&G customers are already paying for certain costs related to the new Summer units under a state law designed to encourage nuclear development. Interest in building new nuclear plants resurfaced a decade ago when natural gas prices soared and experts thought the U.S. Congress would place costly restrictions on emissions of carbon dioxide and other greenhouse gases produced by fossil-fueled power plants. But the case for widespread U.S. nuclear plant construction has since eroded due to abundant gas supplies, slow electricity demand in a weak U.S. economy and uncertainty following the Fukushima disaster. Reporting by Eileen O'Grady; Editing by David Gregorio and Dale Hudson