DARWIN City Council is worried about plans to export 1.6 million tonnes of uranium oxide from East Arm Wharf.

But BHP Billiton said the radioactivity from the ore would barely be distinguished from that naturally occurring.

Lord Mayor Graeme Sawyer said there was a danger of leakage during cyclones and tidal storm surges.

He said BHP would have to give assurances that the oxide was not at the "high end" of dangerous.

The mining giant has applied to the Federal Government to expand Olympic Dam in South Australia.

About 1200 tonnes of uranium oxide each year is already shipped out of Darwin from the mine.

This would be increased 1333-fold.

The ore would be freighted nearly 2500km north to Darwin on daily trains.

BHP said a new "fully enclosed" storage, handling and loading base would be built at East Arm.

The number of shipping containers carrying uranium from Darwin would rise from 200 a year to 900 and up to 90,000 tonnes of concentrate in the form of black powder would be stored at the wharf at any one time.

Oxide already exported from Darwin has radiation levels of 990,000 parts per million. The black powder would have levels of only 2000 parts per million.

Radiation that low would be indistinguishable from background levels beyond 10m, BHP said.

Mr Sawyer said he was also concerned everyone "from Inpex, to Olympic Dam, across to Mount Isa", was looking to ship resources without proper planning.

"It's starting to look like we will ship anything in that area through Darwin," he said.

"We are just not ready for it and I don't know if we can get ready for it on our own."