MELBOURNE (Reuters) - Global miner BHP Billiton <BHP.AX> <BLT.L> said it was assessing the impact of an ongoing outage at its Olympic dam copper smelter in South Australia, as it released its annual results on Tuesday.
The outage followed the failure of several boiler tubes at the acid plant, it said without offering an expected timeline for operations to resume.
"Remediation and mitigation activities are underway, and underground mining operations continue as normal," it said in its full-year earnings release.
Olympic Dam's copper production was expected to increase to between 200,000 tonnes and 220,000 tonnes in the 2019 financial year, reflecting improved operational stability and higher ore grades from the Southern Mine Area, BHP said in its operational report on July 18.
The mine produced some produced 137,000 tonnes of copper last financial year due to major planned smelter maintenance.
Olympic Dam was now the "only part of our business which is not delivering an acceptable return on capital," Chief Executive Andrew Mackenzie said in a results briefing on Tuesday.
"I accept that we have a lot to do to continue to build confidence in Olympic dam... We have seen considerable improvement in our development rates... in the southern mine area and that has put our growth plans back on track."
(Reporting by Melanie Burton; editing by Richard Pullin)
