URANIUM producer Energy Resources of Australia (ERA) has delivered its third highest annual production for the Ranger mine as the wet season begins to affect operations.

ERA which produces about a 10 per cent of the world's uranium, from Ranger in the Northern Territory, produced 5339 tonnes of uranium oxide during the year.

This was marginally short of forecast output of 5400 tonnes.

The Ranger operation is about 250 kilometres south-east of Darwin and is often affected by flooding from monsoonal rain.

ERA re-established access to the higher grade ore in the bottom of the Ranger pit after flooding early in 2008, and produced 1634 tonnes of uranium oxide during the three months to December 31.

Output during the quarter was 5 per cent higher than the previous corresponding quarter in 2007 and 21 per cent higher than the third quarter in 2008.

But ERA said that the onset of the wet season during the fourth quarter had affected mining rates, with the amount of material mined during the three months to December 31 nine per cent lower than during the third quarter.

Shares in ERA, 68.4 per cent-owned by Rio Tinto Ltd, gained 17 cents to $18.09 by 10.17am (AEDT).

ERA sold 5272 tonnes of uranium oxide during the 2008 year but could not take full advantage of the spot uranium price due to contractual commitments.

The spot market at the end of December was $US52.50 per pound, while ERA's average realised sale price of uranium oxide for the year was $US32.53 per pound.