The Department of Energy is preparing this week to announce a major breakthrough in nuclear energy that may pave the way for a clean power revolution. The agency is expected to disclose Tuesday that American scientists at the federally run Lawrence Livermore National Laboratory in California have successfully produced a fusion reaction that resulted in a net energy gain, according to The Washington Post, a process which replicates the way energy is created on the sun. The development has long been considered a “holy grail” of the country’s green power ambitions—leading to totally renewable, unlimited energy. Billions of dollars in both public and private funds have been plowed into similar projects. Scientists, however, are quick to predict that the commercial technology is at least a decade away.