About 80 jobs are said to be going at Ballylumford power station in County Antrim, according to the trade union Unite.
It said 60 additional contractor positions are also at risk.
The union has issued a statement ahead of an announcement expected shortly on the future of the plant in Islandmagee by owners AES.
However, there is speculation it will be reprieved.
The future of the stations has been uncertain for months, after Kilroot failed to win a generation contract to supply the all-island Single Electricity Market (SEM).
In January, AES said it intended shutting the power station with the loss of up to 240 jobs.
Deliberations involving the utility regulator have been taking place since then.