Uranium miner Energy Resources of Australia (ERA) Ltd expects reduced production in the second quarter because rain water pooled in the bottom of their main pit has restricted access to higher grade ore.

The average grade of uranium oxide during the second quarter is expected to be between 0.2 and 0.25 per cent.

That compares with the grade of 0.32 per cent in the three months to March, ERA said in a statement.

The Rio Tinto subsidiary said water levels in the pit at the Ranger Mine in the Northern Territory are substantially lower than the corresponding point in 2007.

But there still is restricted access to higher grade ore mostly at the bottom of the pit, which should be re-established towards the end of the second quarter.

The mill will process stockpiled ore in the mean time.

ERA produced 1,327 tonnes of uranium oxide in the first quarter, a 32 per cent increase on the corresponding period in 2007 because the weather was better.

Production fell 15 per cent compared with the three months to December because the ore grade declined.

ERA mined 812,448 tonnes or ore in the three months to March, six per cent more than in the corresponding period last year and in the fourth quarter 2007.

ERA milled 479,539 tonnes in the first quarter, a 20 per cent gain on the corresponding period in 2007 and one per cent lower than in the three months to December.

ERA spent $3.8 million during the year to March on exploratory drilling and uranium mineralisation is known to extend to the east and below the current pit.

The Darwin-Headquartered company plans to conduct further drilling east of the pit.