How close is nuclear fusion

According to the Financial Times and The Washington Post, the US Department of Energy is anticipated to make the announcement on 

Tuesday that scientists have for the first time successfully achieved a nuclear fusion reaction that resulted in a net energy gain.

The experiment's outcome would be a significant milestone in the long-term goal to release an endless source of

renewable energy that may help end dependence on fossil fuels. 

Nuclear fusion, the process that drives the sun, has been replicated by researchers for decades.