ACF, the Sydney Environment Institute, the Mineral Policy Institute and the Environment Centre NT have voiced their concerns with the 2020 Ranger Mine Closure Plan in a joint report released today.

This comes after a parliamentary inquiry recently labelled Rio's decision to blow up ancient rock shelters in WA's Juukan Gorge 'inexcusable'.

Energy Resources of Australia, in which Rio Tinto holds a majority stake, operated the uranium mine for decades and are responsible for rehabilitating the land.

"This is a real potential, significant and forever threat to Kakadu if it's not done well," ACF national nuclear campaigner Dave Sweeney said.

Mr Sweeney said a poor rehab process would damage the cultural and environmental value of Kakadu.

"Degradation of water sources ... increased risk of radiation exposure to people and animals ... poor revegetation outcomes.

"There would be cultural damage as traditional owners would not be able to have routine access to their country."

The Ranger uranium mine, which neighbours Kakadu, closes in January 2021, with the former mine site set to be incorporated in to Australia's largest national park in 2026.

Mr Sweeney said there are serious concerns Rio Tinto and ERA will not meet their rehab responsibilities.

"(The plan) lacks really specific issues on some key issues," he said.

"We absolutely want them to be able to deliver on this but we are not at all convinced that they have taken enough detailed steps to do so."

Mr Sweeney said the five year time frame is not long enough, there is no certainty the process will be funded properly and he worries toxic mine waste will leak in to the national park.

Rio has already pledged $750 million dollars for the rehab process, according to Mr Sweeney.

He said more than five years is needed because common obstacles like a heavy wet season can slow the rehab process.

"You lose a few months in the wet season.

"If they have a heavy wet, that blows everything out."

Mr Sweeney said ERA and Rio are too focused on a quick fix.

"Rehabilitation planning is being driven by what is possible in a five year time frame, rather than what is optimal," he said.

"There's not enough space for slippage."

Mr Sweeney said Rio Tinto has a poor track record when it comes to preserving environmental and cultural heritage.

He pointed to two previous mine rehabilitations at Rum Jungle near Batchelor and Mary Kathleen in Queensland, as well as the destruction at Juukan Gorge as examples.

"They've had two previous uranium mining attempts, their rehabilitation has been incomplete and ineffective," he said.

"They have walked away and shifted the cost from both of those from themselves to the Australian taxpayer."

In a statement, an Energy Resources of Australia spokesman said they are committed to rehabilitating the mine site.

The statement said rehabilitation has been ongoing for 25 years at a cost of $642 million since 2012.

The spokesman said ERA is committed to working with Traditional owners, the NT and Federal governments on the mine's closure.

He said Federal government scientists has reported no detrimental impacts to the surrounding environment from the Ranger mine so far.

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