ENERGY Resources of Australia expects uranium production to fall by 15 per cent in the second quarter.

The reduction is the result of flooding at its main pit that has restricted access to higher grade ore, said ERA, which produces 10 per cent of the world’s uranium.

Shares in ERA (ASX: ERA: quote) fell 1.7 per cent to $19.96 this afternoon, after the miner said average grade of uranium oxide was expected to be between 0.2 per cent and 0.25 per cent.

It compares with a 0.32 per cent grade in the three months to March, Darwin-based ERA said today.

ERA, a Rio Tinto subsidiary, said access to the bottom of the pit at the Ranger Mine in the Northern Territory had been restricted, even though water levels were substantially lower than at the same time last year, when exceptionally heavy rainfall had caused production delays.

Full access should be re-established towards the end of the second quarter and the mill will process stockpiled ore in the mean time.

ERA produced 1327 tonnes of uranium oxide in the March quarter, a 32 per cent increase on the corresponding period in 2007, which was largely the result of better weather. But production fell 15 per cent compared with the December quarter because of a decline in the ore grade.

ERA mined 812,448 tonnes of ore in the three months to March, 6 per cent more than in the corresponding period last year.

The miner milled 479,539 tonnes in the first quarter, a 20 per cent gain on the previous year, but 1 per cent lower than the December quarter.

Rio Tinto, which owns 68.4 per cent of ERA, is the world's second biggest uranium producer, according to the World Nuclear Association.