Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Expansion at Olympic Dam means increased energy inputs (of course).

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Apparently, some people out there are shocked with new projections that expanded operations, proposed to be completed around 2013, at BHP Billiton’s Olympic Dam facility will entail significant expansion of the mine’s electricity consumption – projected to be an average of 690 megawatts per year, or around 40% of South Australia’s total electricity consumption, when the expansion is complete.

Here’s the complete story, from news.com.au.

(As an aside, I’m quite pleased to note, when reading the comments on the above-linked webpage, just how much pro-nuclear-energy sentiment seems to be out there.)

Olympic Dam is a copper mine. When the expanded production reaches full capacity in 2015 or so, 450,000 tons of copper metal will be produced annually.

There is a little bit of uranium, gold, and a couple of other things mixed into the orebody which are valuable too, so they extract them as well when the copper ore is processed.

It’s a homogeneous orebody – the uranium and copper and things are all mixed together, so it is impossible to mine the copper without mining uranium, too.

For that 450,000 tons of copper metal that will be produced, only about 14,000 tons of uranium oxide will be produced. The uranium is only a byproduct.

Remember – without copper being mined out of the ground, no electricity of any kind, clean, green or not, can be generated, distributed or used. Without production of aluminium metal, a popular target of so-called environmentalists, electricity transmission over overhead cables cannot be done.

Even since the stone age or the bronze age, mining has been integral to the existence of our technological civilisation. Even as we move to clean sources of energy to power our technological civilisation, such as geothermal and nuclear energy, mining will always be essential.

Now, the expanded mine will consume 690 megawatts of electrical power, on average.

A typical nuclear power reactor generating 1 gigawatt of electricity requires an amount of uranium fuel corresponding to about 200 tons of natural uranium in the form of uranium oxide per year.

So, Olympic Dam will consume 690 megawatts of electricity – and it will produce enough uranium in one year to generate 70 gigawatts of electricity for one year –
over one hundred times the total power consumption of the mine.

Yes, you might be thinking that this ignores the other energy inputs into the nuclear fuel cycle – but it also assumes an extremely inefficient once-through fuel cycle using low-enriched uranium in current light water reactors, without recycling of fuel.

Of course, one must remember that the vast majority of the energy input at Olympic Dam goes into the extraction and smelting of copper metal – the overall “energy gain” typically associated with actual uranium mining operations are typically much higher than 100.

Another point that anti-mining and anti-nuclear-power activists love to make in Australia is that mines such as Olympic Dam use too much water.

The Olympic Dam mine consumes about 30 megalitres of water a day – 30 million litres, in total, for the township, as well as all mining operations. Is that a lot?

Olympic Dam, at present, produces about 200,000 tons of copper annually, along with a relatively small amount of uranium, about 4300 tons of U3O8.

Now, I’m not an expert on mineral extraction, hydrometallurgy, and mining operations, but I will make the rough assumption that the production of one ton of copper metal consumes the same amount of water as the production of one ton of uranium oxide. Therefore, we infer that uranium production at Olympic Dam consumes 2% of the total amount of water, or 600,000 litres per day, or 140 litres of water per metric ton of uranium oxide produced.

If 200 tons of natural uranium in the form of uranium oxide is sufficient to make up the fuel for a 1 GW nuclear power reactor for one year, and that reactor operates with an 90% capacity factor, then the production of Uranium at Olympic Dam then consumes 3550 litres of water per TWh of electricity that can be produced from that uranium.

For comparison, the mining of coal consumes about 200 litres of fresh water per ton of coal produced. Given that a typical coal-fired power station consumes about 0.5 metric tons of coal to produce 1 MWh of electricity, the mining of coal for electricity generation consumes 100 million litres of water per TWh of electricity production.

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