Energy Resources Australia (ERA), a Rio Tinto-owned company, received federal and Northern Territory approval to restart the Ranger mine from Thursday.
But green campaigners said the decision was "extraordinary" because it came before the release of a report into the collapse of a leach tank at the mine last December which resulted in the leak of about one million litres of radioactive and acidic slurry.
ERA has said no environmental damage was caused, but processing operations have been suspended ever since.
ERA's chief executive Andrea Sutton said the spill was a serious incident that damaged community confidence in its operations.
"We recognise that an important aspect of the recovery from this incident will be restoration of that confidence in our processing operations," Ms Sutton said.
ERA expects the processing plant to return to normal production levels during the third quarter of this year, with the company's 2014 production of uranium oxide expected to be between 1,100 tonnes and 1,500 tonnes.
ERA said findings into the cause of the failure of the leach tank and the integrity and maintenance of the Ranger processing plant had formed the basis of the company's restart plan which was approved by its board last month.
The company said Northern Territory and Commonwealth regulators had both investigated the integrity of the Ranger processing plant and related maintenance and safety systems.
ERA has said no environmental damage was caused but the Mirarr traditional owners have complained that the leak may not be properly cleaned up despite ERA’s plans to expand the site.
"It's extraordinary that ERA are getting a green light when the long-promised report that led to the suspension hasn't even seen daylight," the Australian Conservation Foundation's spokesman Dave Sweeney told AAP.
"If the government is confident in their process, then put the whole thing in the public domain and stop this approach of piecemeal assessment that happens behind closed doors."
However, the Gundjeihmi Aboriginal Corporation, which acts on behalf of the Mirarr traditional owners, said it accepts the restart for the time being.
"We're comfortable with this start-up, but in order for us to not all be back here in several years' time, we need a major culture shift at the mine," CEO Justin O'Brien said.
He said he was confident both levels of government would review the regulation of the mine to simplify it and bring it into line with broader industry practice on process safety codes.
"This is as much a failure on the part of the regulatory system as it is on the part of the mining company," Mr O'Brien said.
ERA wants to open a new mine alongside Ranger called Ranger 3 Deeps. The underground uranium deposit contains around 34,000 tonnes of uranium oxide, making it one of the world’s biggest recent uranium discoveries.
The company on Thursday downgraded its earnings forecast due the suspension of processing operations.
"ERA's first half earnings will be impacted by the additional costs associated with the suspension of processing operations and the company today provided earnings guidance of a loss of between $120 million and $140 million for the first half of 2014," ERA said in a statement.
ERA shares fell 1.5 cents to $1.30.