Uranium miner Energy Resources of Australia Ltd (ERA) has suffered a 31 per cent drop in quarterly production because of limited access to the open pit at its Ranger mine in the Northern Territory.

ERA, the producer of a tenth of the world's uranium, produced 1,030 tonnes of uranium oxide in the June quarter of calendar 2008 from the Ranger operation.

This compares with 1,490 tonnes in the previous corresponding quarter.

ERA said there was still restricted access to higher grade ore, which was predominantly in the bottom of the pit, at the end of the wet season even though water levels in the pit were substantially lower than at the same time in 2007.

ERA said it was able to access the higher grade ore in the last two weeks of June and lift the mill head grade from 0.22 per cent uranium oxide to 0.31 per cent.

Output during the six months to June 30 was six per cent lower than the previous corresponding period, at 2,357 tonnes of uranium oxide.

ERA is spending $57 million to expand the open pit and extend mining at the Ranger operation to 2012 to capitalise on the greater demand for uranium expected from the construction of new reactors.

Deutsche Bank said in a note to clients that the "world is on the verge of a uranium renaissance" and that the "financial markets continue to underestimate the potential for a rapid increase in uranium demand".

UBS said in a client note that the outlook for uranium was positive amid "strong energy values globally over the longer term in addition to mounting environmental pressures".

Shares in the ERA gained 39 cents to $24.35 by 1346 AEST.

ERA is 68.4 per cent owned by Rio Tinto Ltd and the the Ranger operation is about 250 kilometres east of Darwin