A COMMUNITY park has been closed after being found to be radioactive. 

The Rum Jungle South Recreation Reserve, near Batchelor, 100km south of Darwin, which is used as a picnic and swimming spot, is an old uranium mine. 

Resources Department chief executive Richard Galton said an "extensive assessment"' of the park would be carried out following low-level radioactivity being detected at a waste rock pile. 

The tests are likely to keep the park closed until the end of next dry season. 

"There is no evidence that any visitors to the reserve have been exposed to a health risk," Mr Galton said. "Tests of the water in the lake have shown it to be safe to swim in, but because the readings at a few isolated locations on top of the waste rock pile were elevated, further comprehensive tests will be undertaken. 

"The radiation levels detected were so low that a person would have to stand on an affected spot for over 70 hours to exceed the maximum annual public dose."

The site operated as a uranium mine in the early 1960s and was rehabilitated in 1991 before being transferred to the Coomalie Community Government Council in 1998. 

"It is nearly 20 years since the site was rehabilitated and given that standards have evolved, as well as the potential impacts of erosion and weathering on the waste rock pile, a precautionary approach is appropriate," Mr Galton said. 

"A thorough assessment of the site is warranted to accurately measure the potential impact of any long-term radiological exposure."

Coomalie council chief executive John Hughes said people swam in the lake, which is the old mine pit. He said camping was not allowed at the small reserve.