Global prices of copper and uranium are likely to go down in the coming years as is expected from the oversupply that will be boosted by the planned expansion of Australia's Olympic Dam by global mining company BHP Billiton Ltd.

On Monday, the Federal and South Australian governments gave BHP the environmental approval to proceed with its $30 billion plan to expand and develop the Olympic Dam mine which is seen to yield copper and uranium oxide production by more than quadruple to about 750,000 tonnes and about 19,000 tonnes, respectively, every year.

But analysts are critical of the project's value, saying that in as much as investor reception is positive to the BHP-Olympic Dam project and that it will boost global production of the mineral resources, the resulting oversupply will pull down the prices of copper and uranium prices in the long run.

Term uranium prices slid initially after the Fukushima disaster but for many weeks prices have remained stable, until last week. Term uranium prices fell US$1.00 to US$55.00/lb, according to Industry consultant TradeTech's mid-term price indicator. While TradeTechs' long-term price indicator also fell US$2.00 to US$63.00/lb.

Meanwhile, copper prices remained below the $7,000 per metric ton level. Bank of America Merrill Lynch projected a price below $5,500 in the months ahead.

"It's a very risky undertaking for BHP Billiton because it is such a long period of time before there is payback, and at the same time, you're bringing new product to ... a thin market where exceptional margins are being made at the moment because it is so tight," Morningstar senior research analyst Mark Taylor told AAP.

Uranium was "a super small market, so there's going to be large swings and roundabouts without too much push and shove. It's a healthy byproduct for BHP Billiton ... but do they want to be pressuring uranium markets?" Taylor added.

Located north of Adelaide, the Olympic Dam mine is the world's fourth-largest copper and gold deposit and the largest known uranium deposit. More than 13,000 jobs are expected once works begin and it is expected to contribute to Australia's cash coffers an estimated $45 billion annually over the next 40 years.

BHP's board of directors will make a final decision early on 2012 if it will push through with its expansion plans of Olympic Dam, as it has to meet the 250 environmental conditions contained in the environmental approval given by federal and state governments, which includes impact on air quality, local communities, groundwater supplies, and wildlife and the marine environment around a future desalination plant on Eyre Peninsula.

During its projected 40-year life, the mine will grow to be more than 4km long, 3.5 kilometres wide and 1km deep.

The global miner, though, hopes to accomplish all regulatory requirements before this year ends. It still needs to obtain a new operating license from South Australia before expansion works begin.

BHP Billiton shares climbed 5.1% to $75.18 on Monday.

The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27% was mined in Kazakhstan. Kazakhstan, Canada, and Australia are the top three producers and together account for 63% of world uranium production. Other important uranium producing countries in excess of 1000 tonnes per year are Namibia, Russia, Niger, Uzbekistan, and the U.S.

Uranium is most prominently used as fuel for nuclear power plants.