The head of Rio-Tinto owned Energy Resources of Australia (ERA) has quit as the uranium miner posted a slightly improved half year loss.

Chief executive Rob Atkinson has resigned after nearly five years in the job and will move to a role within Rio Tinto, it was announced on Wednesday.

The company also warned that in the short term, the outlook for the uranium market was negative due to continued weak demand.

The situation dates back to the near complete shutdown of Japan's nuclear power industry following the 2011 disaster at the Fukushima plant.

The spot price for uranium oxide hit a seven-and-a-half year low last month when it fell slightly below $US40 a pound.

The record high was $US135 in 2007.

"Long term prices remain in the mid-$US50s per pound ... an oversupply of material in the short term is expected to maintain this trend," ERA said in a statement.

It stuck to its previous positive long-term outlook, saying the present bad news about prices would at least prevent new uranium miners coming onboard.

The company posted a $53.5 million net loss for the six months to June 30, compared to a $59.9 million loss for the same period last year.

It did not pay a dividend after also not doing so previously.

The loss can be partly attributed to high spending, including $64 million on capital expenditure.

And it is partly through $120 million investment preparing to drill at a new Ranger 3 Deeps underground mine it hopes will replace the open pit mine that it closed last year.

It is still producing uranium from stockpiles and has forecast production and sales of 2,700 tonnes to 3,300 tonnes.

The company's shares improved four cents to $2.81.