Energy Resources of Australia Ltd (ERA) says it will temporarily suspend processing operations at its Ranger mine in the Northern Territory and also reported an 83 per cent plunge in calendar year net profit.

Shares in ERA fell $1.35, or 11.37 per cent, to $10.52 by 1410 AEDT.

The Rio Tinto Ltd-controlled company on Friday reported a 2010 net profit of $47 million, down sharply from $272.6 million in 2009.

ERA said mining operations were severely affected by the prolonged 2009/10 wet season, an early start to the 2010/11 wet season and geotechnical issues.

The stronger Australian dollar and lower average realised uranium sales price adversely affected earnings, while increasingly complex geology in the bottom of Pit 3 led to lower than anticipated mined ore grade.

The miner said its processing plant suspension was to ensure tailings storage facility (TSF) levels weren't too high throughout the rest of the wet season.

The suspension would last for 12 weeks and was a precautionary measure because the La Nina weather pattern had brought significantly higher than average rainfall to Ranger since October.

"Water levels in the TSF aree currently higher than our predictions for this time of year," the company said in a statement.

"Further, the Bureanu of Meteorology has forecast that the region will experience above average rainfall for the remainder of the 2010/11 wet season.

"The decision to temporarily suspend plant processing operations will significantly reduce inflows into the TSF and therefore will provide extra capacity to manage unexpcted extreme rain events in the coming months."

Normal wet season mining operations will continue as planned while the plant downtime will be used for maintanance and improvement initiatives, ERA said.

For the full 2010 year, uranium oxide sales were down nine per cent at 5,026 tonnes or 11.08 million pounds.