UPDATE 1-Five U.S. nuclear plants make DOE loan short-list

(Adds fourth name on short-list and cost estimate for Calvert Cliffs, paragraphs 3-6, 11)

By Eileen O'Grady

HOUSTON, Feb 18 (Reuters) - The field of U.S. companies competing for $18.5 billion in government-backed loans to build new nuclear plants has narrowed to five from about 14 last year, company sources said.

Officials with two projects in Texas, one in Maryland and one in South Carolina confirmed they were still in the running for a piece of U.S. Energy Department loan backing, which could be crucial to spurring the first round of nuclear plant building in more than 30 years.

Comanche Peak Nuclear Power Co. NRG Energy's (NRG.N) South Texas Project, both in Texas; Unistar Nuclear's Calvert Cliffs 3 reactor in Maryland; and SCANA Corp/Santee Cooper's two-unit expansion at the Summer station in South Carolina are among five projects still under DOE consideration, officials said.

George Vanderheyden, president of Unistar Nuclear Energy, a joint venture of Constellation Energy (CEG.N) and EDF Group (EDF.PA) of France, said the DOE notified the company this month that it was one of five projects in the running.

"We were quite excited to reach that next step," Vanderheyden said.

A spokesman for Comanche Peak Nuclear, a joint venture of Dallas-based Luminant, part of Energy Future Holdings, and Mitsubishi Heavy Industries, confirmed that the company is also on the short-list. The venture is considering two new reactors at Luminant's existing Comanche Peak site in north Texas.

Last year, developers of 14 new nuclear plants requested DOE guarantees totaling $122 billion, far exceeding the program's budget, the agency said. Several companies dropped out of the running in December, leaving at least 10 projects seeking federal support.