The GMB Union has confirmed that Rio Tinto are in talks with a potential buyer for the Alcan powerstation.
Alcan worker Paul Scott said, "The main worry is that the workforce will be fighting for a handful of jobs."
The union has said that despite talks more than 500 people at the smelter are now "highly likely" to be jobless by the end of the year, with most leaving in May.
"It will have an absolutely devastating impact."
Keir Howe from the GMB Union said, "It will have an absolutely devastating impact. I met with hundreds of GMB members over the last few days and they're anxious and angry."