Traditional owners in Kakadu National Park have been rocked by a second security breach in two weeks at the Ranger uranium mine, and say the site's radiation control measures are failing.
Four uranium storage barrels were discovered in bushland outside of Darwin on Monday, outraging the Gundjeihmi Aboriginal Corporation (GAC), which acts on behalf of the Mirarr people.
The weathered and fire-damaged drums had apparently been there for some time, and a preliminary inspection by the Northern Territory Department of Health and mine operators Energy Resources of Australia (ERA) shows no radioactive material was detected.
But the incident follows another two weeks ago when a controlled vehicle was driven off the site, allegedly through a long-standing hole in a fence, before being stopped down the highway by Ranger security personnel.
GAC CEO Justin O'Brien said Ranger's radiation management plan is failing, in breach of the industry code.
This may also be a breach of ERA's mining authorisation, in which case the Rio Tinto subsidiary should be prosecuted, he said.
"To us it's a no-brainer," Mr O'Brien told AAP on Wednesday.
"If you can steal a controlled vehicle coming from a contaminated part of the mine through a hole in the fence, if you can remove drums of the type used to store (uranium oxide) and store them in a public area outside Darwin, and both of these things occur under the nose and without the knowledge of the mining company, then you've got a problem,"
ERA is exploring a potential underground mining operation on the Ranger site, called Ranger 3 Deeps, but has undertaken not to begin any work without the permission of the Mirarr people.
"It's profoundly disappointing that this comes at a time when we have on the table proposals for further mining at Ranger," Mr O'Brien said.
"Our relationship with the mining company generally has been improving in recent years... And yet this sort of Keystone Cops regulation about a major uranium operation keeps recurring.
"It doesn't augur well for our consideration of further mining."
GAC is calling on federal Industry Minister Ian Macfarlane to honour the social contract the government entered into in the 1970s with the community, leading to the mine's creation.
"In recognition of public safety... the Australian government (should) play a strong regulatory investigative role, and by default some sort of mediation role between us and the company," Mr O'Brien said.