A nuclear power plant near Hartsville has been identified as one of 38 across the country at risk of being mothballed because of age and expense, a national study shows.

The H.B. Robinson reactor, built in 1970, is listed in a report by an economic analyst as in danger of being closed mainly because it has been running nine years longer than its original federal license limit, which expired in 2004. The plant, operated by Duke Energy, was given an operating license extension to 2030.

Robinson is the only one of South Carolina’s nine reactors on the at-risk list. Duke Energy spokesman Charles Ellison said the company is committed to upgrading the plant and keeping it in operation through 2030.

The list was created as part of an economic analysis of costs involved in operating, maintaining and upgrading the nation’s aging nuclear plants. The study identified at-risk reactors in 23 states.

The study was conducted by Mark Cooper, senior fellow for economic analysis at Vermont Law School’s Institute for Energy and Environment. He has testified as an expert witness for environmental groups in numerous nuclear power related cases, including one pending before the South Carolina Supreme Court to halt construction of two new reactors near Jenkinsville, 25 miles north of Columbia.

The two new reactors are among only four currently being built in the nation. They were launched as part of what was thought just a few years ago to be the beginning of a nuclear renaissance. Until construction began on the four reactors, no new ones had been licensed and started since 1979 when the Three Mile Island nuclear disaster turned the nation against atomic power.

In a press call Wednesday to release the study, Cooper said he conducted the analysis to help state and federal policy makers. He said they need to realize that they must come up with a plan to find effective and economical ways to replace electricity capacity as the old reactors are forced to shut down because of excessive costs. The U.S. currently has 104 reactors in operation at 65 plants.

Cooper pointed out that four nuclear reactors have recently been scheduled for early retirement because of excessive repair and other costs. And, he said, cheaper low-carbon fuels, especially natural gas, have made nuclear even more uneconomical than before.

The cost of oil and natural gas has decreased so much in recent years because of a drilling technique called “fracking.” It uses liquid and pressure to crack underground rock layers to free vast amounts of fuels.

Nuclear power plants simply cost too much to build and operate, Cooper has said. The two new reactors South Carolina Electric & Gas currently has under construction at its V.C. Summer site are projected to cost more than $10 billion, three times the cost of an equivalent natural gas-fired plant.

SCE&G has said the reactors ultimately will save ratepayers billions of dollars because nuclear fuel costs almost nothing compared to fossil fuels. Cooper has argued in court papers that it would be cheaper for ratepayers to stop construction and mothball the plants.

Environmental groups contend that SCE&G should temporarily use natural gas while improving efficiency and aggressively expanding solar, wind and other renewable energy sources.

Reach Doug Pardue at dpardue@postandcourier.com or 937-5558.