Energy Resources of Australia says uranium production in the December quarter of last year fell significantly at its Ranger mine, compared to the same time a year ago, because of heavy rain.

The amount of uranium oxide produced at the Northern Territory mine dropped 12 per cent from the December 2010 quarter, to just over 1,000 tonnes.

It rose slightly from the September quarter.

The company says wet weather in the Top End hampered uranium production in the first half of 2011.

Tropical Cyclone Grant, which hit in December 2010, also affected mining because of a record level of rain.

January 2011 was also wet and then Tropical Cyclone Carlos brought more heavy rains.

ERA was forced to shut down processing operations in January when tailings dams at the mine filled to near capacity.

The mine is located near Jabiru, within the boundaries of Kakadu National Park.

Normal operations at the mine did not resume until June.

ERA has warned that rain may also affect production this year.