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

Posts Tagged ‘uranium

Western Australia lifts uranium mining ban.

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Western Australia has lifted the previous Labor government’s effective ban on uranium mining, with immediate effect. The Government’s decision, which has been fully expected ever since the change of government in WA, makes way for the potential exploitation of dozens of uranium deposits across the state.

“It is now open to the mining industry in this state, if they wish to proceed with plans to develop the uranium industry,” Premier Colin Barnett said today.

“It’s significant that Australia has the largest reserves of uranium of any country in the world and is second only to Canada as the major producer and exporter.”

The move would not require legislation because Labor’s previous ban on uranium mining was only administrative, he said. “Both Geoff Gallop and Alan Carpenter talked about a ban on uranium and the like but never introduced any legislation to do it”.

“They simply put in place that administrative caveat on a mining lease; now we are removing that.

“The one practical difficulty we face is that 1475 mining leases have been issued since June 2002 which exclude uranium mining, so the department is now seeking some legal advice.”

Uranium prices have fluctuated over recent years, with a spot price of $US135.00 per pound in June 2007 to $US46 last Friday.

Australia produced and exported just 20 per cent of the world market and demand would continue to rise strongly, Mr Barnett said.

West Australian Mines and Petroleum Minister Norman Moore said he had met with uranium producers since the state election but would not say which companies had shown an interest in mining.

He said proper processes needed to be put in place first.

“The department (of minerals and energy) has met with … counterparts from South Australia and the Northern Territory and the commonwealth and we will put in place quickly the regulatory regime for the mining and transport of uranium,” Mr Moore said.

“There’s a lot of benefits to be had for Western Australia if we have a uranium industry and I’d like to see it happen sooner rather than later.”

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Written by Luke Weston

November 17, 2008 at 12:24 pm

Uranium chemistry, and some interesting blogs to check out.

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Special Nuclear Material is a great blog containing lots of interesting stuff. (Though it’s not really energy and nuclear energy related.)
It was this post on uranium chemistry that I found the blog via, and which I found really interesting.

Incredibly interesting, informative stuff. I’m impressed that he’s done all that inorganically, with no solvent extraction, and got good uranium selectivity, at least as far as you can tell from looking at pictures of the stuff.

Some people out there in the public might be alarmed by the fact that you can actually pull this off, all the way to UF4, in your basement. I’m not alarmed at all, I think it’s really impressive.

What alarms me a little more is that they actually sell moderately concentrated hydrofluoric acid to any idiot who walks into a store, in the US. (No disrespect to US citizens, in general, is intended or implied in the slightest here, of course.) I’m surprised that CPSC doesn’t absolutely freak out. (Maybe they will, if they find out that terrorists could use the stuff for dreaded nooklear purposes, though…)
God forbid if you actually want to buy psuedoephedrine cold pills or lye or something, though.

The portable BGO probe made from a subdivided part of a PET scanner – one of the PMTs and one corresponding small part of the array of BGO crystals – is very nice, too.

Whilst on the subject of blogs, I’m happy to give a shout out to Pro Nuclear Democrats as well. As they say, energy, energy security and the environment are not partisan issues.

Written by Luke Weston

October 17, 2008 at 8:33 am

Thermodynamics, stars, uranium, life and everything: Part II

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The amount of time necessary to exhaust nuclear energy provided by existing uranium deposits, unused energy in current reserves of used radioactive “waste”, heat produced by the radioactive decay of uranium, thorium and potassium deep inside the Earth (in other words, geothermal energy), and uranium in seawater could indeed last billions of years – approaching the evolution of the sun off the main sequence, and with that, the end of life on this world.

If the energy from the Sun is “renewable”, so too is nuclear energy equally every bit as renewable.

The concentration of uranium in seawater in the world ocean is about 3.3 parts per billion. The total mass of Earth’s hydrosphere is about 1.4×1021 kilograms, therefore putting the total mass of uranium in the world ocean at 4.62 billion tonnes.

Current total world demand for electricity stands at 16,330 TWh per year. Let’s conservatively suppose that, over the millennia to come, the average total world demand for electricity is four times what it is at present, or 65,320 TWh. Conventional LEU fueled light-water reactors and inefficient once-through fuel use in these reactors consume about 200 tonnes of uranium mined per gigawatt-year of electric power generation.

Hence, if we make the assumption that all the nuclear energy generation over these coming millenia is performed with this inefficient once-though LEU fuel chain and no recycling or reprocessing of nuclear fuels is performed, then the world demand for uranium can be expected to be 1.49 million tonnes per year.

Hence, consuming 1.49 million tonnes of uranium per year to supply all the world’s electricity, the 4.62 billion tonnes of uranium presently dissolved in the ocean will supply the world’s electricity for 3100 years.

\mathrm{\frac{4.62 \times 10^{9}\ tonnes}{(200\ tonnes\ per\ GW\cdot year) \cdot (65320\ TWh/year)}\ =\ 3100\ years}

Here we have assumed that no use is made of efficient, advanced reactors or breeder reactors and no use is made of the excess “depleted” uranium-238 or natural thorium, no deuterium is used for nuclear fusion, and no uranium is mined on land. Such assumptions are of course ridiculous, but let’s just be as conservative as possible, for argument’s sake for the purposes of this baseline, worst-case scenario.

If we considered a truly efficient efficient use of nuclear fuel, we may consider an efficient, advanced reactor such as a molten-salt reactor, efficiently transmuting uranium-238 into plutonium-239 in situ to generate energy. We may assume that 200 MeV of energy is released per fission event, and that the efficiency of the 238U transmutation and liberation of useful energy output from these nuclear processes within the reactor is, say, 75% overall. If we assume that this thermal energy is converted in a Brayton-cycle power plant with a thermodynamic efficiency of 50%, then hence we know the amount of natural uranium required to fuel the reactor.

\mathrm{\frac{1\ GW\ \cdot\ 1\ year\ \cdot\ 238\ u\ \cdot\ 1.66 \times 10^{-24}\ grams/u}{200\ MeV\ \cdot\ 75\% \cdot\ 50\%}\ =\ 1.04\ tonnes}

Just over one tonne of natural uranium is required, to generate one gigawatt-year of energy. (That number is basically the same if we’re looking at efficiently burning thorium in a MSR, incidentally, also.) If we utilised nuclear energy efficiently, like this, then the 4.62 billion tonnes of uranium presently dissolved in the ocean would supply the energy we discussed above, 65,320 TWh, for (just under) an astonishing 600,000 years!

\mathrm{\frac{4.62 \times 10^{9}\ tonnes}{(1.038\ tonnes\ per\ GW\cdot year) \cdot (65320\ TWh/year)}\ =\ 597,558\ years}

However, we are not finished yet. Elution of the uranium in the Earth’s crust into the ocean occurs on an ongoing basis, adding 3.24×104 tonnes of uranium to the ocean annually.

It was motivated by Cohen* that we could recover uranium from seawater at perhaps half of that rate; 16,000 tonnes of uranium from seawater per year. This quantity of uranium would supply 15.4 TW of electric power, if used efficiently as outlined above. In order to supply 65,320 TWh of electricity per year, four times the current worldwide demand for electricity, we only require 7750 tonnes of uranium per year, less than half that figure of 16,000 tonnes.

[* Many of you will be familiar with Cohen’s work, but if you are not, that book is highly recommended.]

Cohen argues that given the geophysical cycles of erosion, subduction and uplift, the uranium elution into the oceans would last for five billion years, at a rate of withdrawal of 6500 tonnes per year. At a rate of consumption of 7750 tonnes per year, in the absence of the use of any uranium and thorium mined on the crust, or the use of deuterium for nuclear fusion, the uranium from the oceans alone can be expected to meet world demand for electricity, at 65,320 TWh of electricity per year, for 4.2 billion years. Over a timeframe on the order of 109 years, of course, some non-trivial fraction will be lost, simply due to radioactive decay – however, at the same time, we have not even begun to consider the use of uranium and thorium reserves in the crust, or the use of the vast supply of deuterium as an energy source.

Clearly nuclear energy remains a viable resource on the Earth for a time scale of approximately five billion years – these nuclear fuels will not be consumed or depleted over a timeframe comparable to the life of the sun on the main sequence. Just as the finite hydrogen within the core of the Sun is a “renewable” energy resource, so too is the finite resource of terrestrial nuclear energy an equally renewable energy resource.

However, there is one final point we have overlooked. Even during its life in the main sequence, the Sun is evolving, as with all such stars. The Sun is gradually increasing in luminosity, by about 10% every one billion years, and its surface temperature is correspondingly slowly rising. This increase in the luminosity of the sun is such that in about one billion years, the surface temperature of the Earth will permanently have become too high for liquid water to exist, the oceans will evaporate and a catastrophe of the most immense proportions imaginable will overtake our planet. The Aztecs foretold a time `when the Earth has become tired… when the seed of Earth has ended’. All life on Earth will be extinguished, billions of years before all the nuclear fuels will be depleted.

In the meantime, our descendants will have evolved into something quite different, as far divergent from us in evolutionary terms as we are from the simplest one-celled organisms to have existed on the Earth. If they still inhabit the Earth, our descendants will leave, perhaps to Mars, or to the moons of the gas giants, Europa, perhaps, rich in water and perhaps not dissimilar to Earth if warmed up a little, or perhaps to a younger, more distant world, orbiting a younger star, around which their civilization will flourish once more.

Written by Luke Weston

October 12, 2008 at 1:12 pm

Thermodynamics, stars, uranium, life and everything: Part I

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We hear a lot about this phrase “renewable energy” these days. But what exactly is “renewable energy”?

Why are certain energy systems considered “renewable”, whilst others are not? What makes, say, solar power “renewable” energy, but nuclear power not, supposedly, “renewable energy”? These questions bear thinking about.

Now, uranium is technically a finite mineral resource, just like the bauxite used to construct wind turbines is a finite resource and the silica used to construct silicon photovoltaic devices is a finite mineral resource from the Earth.

Five billion or so years from now, the hydrogen within the Sun’s interior will be exhausted, and it will begin to use that in its less dense upper layers. It will expand to eighty times its current diameter, about 7.5 billion years from now, to become a red giant, cooled and dulled as a result of its vastly increased surface area. As the Sun expands, it will swallow up the planet Mercury. However, Earth and Venus can be expected to survive, since the Sun will lose about 28 percent of its mass, and its lower gravity will send them into higher orbits. The Earth will be left scorched, its land surface reduced to the consistency of hot clay by a flux of solar heat a thousand times more powerful than that today, and our atmosphere will be stripped away into space by a now-ferocious solar wind. Not one living cell on this planet will remain alive.

Eventually, the helium produced in hydrogen fusion in the Sun’s outer regions will fall back into the core, increasing the density until it reaches the levels needed to fuse helium into carbon. A “helium flash” will then occur; the Sun will shrink abruptly to slightly larger than its original radius, as its energy source has fallen back to its core. Due to the increase in the reaction rates, due to the increased temperature and pressure at the stellar core, and the smaller amount of helium compared to hydrogen, the complete helium-burning stage will last only 100 million years. Eventually it will have to again resort to its reserves in its outer layers, and will again attain a red giant form. This phase lasts a further 100 million years, after which, over the course of a further 100,000 years, the Sun’s outer layers will fall away, ejecting a vast stream of matter into space and forming a planetary nebula.

Eventually, all that will remain of the Sun is a white dwarf, a hot, dim and extraordinarily dense object; half its original mass but only the size of the Earth. Were it viewed from Earth’s surface, it would be a point of light the size of Venus with 100 times its current apparent luminosity. Eventually, after trillions of years, it will fade and die, finally ceasing to shine altogether.

Why is geothermal energy produced by the \mathrm{\alpha -decay} of uranium in the ground considered as “renewable” when that produced by fissioning those same atoms in a reactor is not?

The answer, of course, is that that’s not the point. The point is that “renewable”, as we hear the term used in society today, doesn’t have any rigorous physical meaning. Loosely, the popular definition of “renewable” means “not fossil fuels and not nuclear energy”, and fossil fuels do not meet the above definition when used at today’s consumption rates (if oil use were cut by a factor of 100,000, it would also be renewable). More correctly, “renewable” energy has come to refer to anything that the Green lobby hasn’t chosen to oppose – anything except fossil fuels or nuclear reactor-derived energy. (Nuclear geothermal energy seems to be OK, though.)

When something does meet the definition that the environmentalist lobby doesn’t like, they amend the mysterious unwritten non-scientific definition to exclude it.

For example, whale oil could produced by farming whales, constituting “renewable biofuel”, in exactly the same way that sugarcane-derived ethanol is in principle a “renewable” fuel. I can’t see the capital-G Green lobby being too keen about the idea, though.

Now, it seems reasonable to argue that, for example, wind energy or solar energy are not in fact consuming any significant finite resources at all during their ongoing operation, the raw materials such as aluminium, silicon or concrete used in the construction of their infrastructure not withstanding.

Opponents of nuclear energy often seem keen to point out that nuclear fuels are what they often describe as “finite, nonrenewable” resources. However, there’s no such thing as a source of energy that we can use without consuming any finite resource, because the energy that we can extract from any isolated system is in itself a finite resource. When the free energy of the universe is expended, the “heat death” of the entire universe is the result. This is the end of all that is, all that was, and all that ever will be, and this is going to happen.

There’s no such thing as “renewable energy”.

The free energy of any isolated system, for any reasonably literal, sensible definition of the word renewable, is not “renewable”.

“Renewable energy” does not exist. That’s the second law of thermodynamics.

Written by Luke Weston

October 12, 2008 at 12:58 pm

Uranium-232, thorium… oh, and The Bulletin.

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Something of a question for the readers:

Why is uranium-232, produced via a (n,2n) reaction from U-233 in a thorium breeder reactor, viewed as such a uniquely favorable impediment to diversion of material for weapons proliferation? You would expect a breeder reactor operating on a U-238/Pu-239 fuel cycle to produce some Pu-238 directly via the same (n, 2n) reaction in Pu-239 – the cross sections are about the same for fast neutrons – and Pu-238 is certainly a strong impediment to nuclear weapons use of the plutonium, as much as is U-232.

Does the Th fuel cycle actually offer some real advantage over a U fuel cycle in this regard , where the U fuel cycle does not deliver?

I suppose that the lesson to take home is that the fuels and operating conditions in power plant reactors are uniquely unfavorable for the production of weaponisable fissile materials, irrespective of the exact fuel cycle used, uranium or plutonium.

Also, the Bulletin of the Atomic Scientists seems to get a little more tabloid-like with every issue, to me at least – what’s with that?

It almost seems like every major piece in the current edition is skeptical of, cautious about, pessimistic about, wary of, or simply all out opposed to new expansion of nuclear energy in the United States and the rest of the world.

Written by Luke Weston

October 5, 2008 at 1:39 am

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Funny Numbers.

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This is a chunk extracted from a recent post by Matt in the nuclear energy debate that is currently happening over at TalkClimateChange forums.

Rod Adams has already responded in the debate with his piece – but I was astonished by just how inaccurate these numbers are – so I wanted to have a look at these figures, and remind everyone exactly what the more correct figures are.

“Starting from this: A standard 100mw/eh nuclear reactor requires in the region of 160 tonnes of uranium fuel ā€“ processed from around 16 million tonnes of rock ā€“ each year.”

“100 mw/eh” ? Is that supposed to mean 100 MWe ? A standard nuclear power reactor, in the form in which they’re normally encountered, generates far more than 100 MWe – 1000 MWe is typical, for the standard currently popular designs of nuclear power reactors.

The amount of uranium required to fuel a nuclear power reactor, using currently widespread technology, i.e. LEU fuelled LWR, equates to about 200 metric tons of uranium oxide, before enrichment, per gigawatt-year of energy obtained.

Assuming 0.15% uranium oxide in the ore, that’s 133,300 tons of ore that needs to be processed per GW-yr.


“And knowing that An average [UK] home utilises 4700 kWh per year

The 100MW can provide 876,000,000 kWh. There are 25 million homes in the UK, or 117,500,000,000 kWh demand. Therefore to provide for just the electricity needs of the UK, requires 134 nuclear reactors.

(In reality, electricity demand is not 24/7. Since nuclear has to run continuously, you would need more fuel that the 134 x 160 = 21,440 tonnes of uranium per year.)”

Household electricity demand is estimated at 117.5 TWh. The actual total electricity consumption in the UK was 345.2 TWh as of 2004, according to the World Factbook – but this kind of estimate as made above isn’t too bad – it gives the correct order of magnitude.

Assuming that power reactors generate 1 GWe with a capacity factor of 90%:

345.2 TWh / (1 GW * 90% * 1 year) = 44 reactors needed to supply the UK’s electricity demand.

Obviously, it’s not entirely efficient if you somehow decide you want to use excess nuclear capacity to meet all the peak-load demand.

“(Note that this is also 134 x 16M = 2,144,000,000 or just over 2 billion tonnes of rock that need processing, transporting etc)”

133,300 tons of ore needs to be processed per GW-yr, assuming 0.15% uranium oxide content.

So, that’s 5.25 millon metric tons of uranium ore per year to supply the UK’s electricity.

The coal alternative is 177 million metric tons of coal.

“The McArthur River project is the world’s largest known high-grade uranium deposit. It is presently being developed to allow the start of production in late 1999. Located in northern Saskatchewan, Canada, the deposit is estimated to contain 416 million pounds of U3O8”

416 million pounds = 188 694.426 metric tonnes. Therefore the world’s largest known reserve of uranium has enough fuel to provide electricity to the UK domestic market – ignoring offices, industry, manufacturing and railways – for just under 9 years.”

Supplying the UK’s entire electricity needs from nuclear energy would consume about 8000 metric tons of uranium oxide per year.

That 416 million pounds of uranium oxide has an energy content corresponding to the UK’s total electricity consumption, at current levels, for 24,000 years.

I won’t really hold Matt responsible for such glaring inaccuracies, though – the bad data was taken straight from The Ecologist, here .

Written by Luke Weston

April 6, 2008 at 12:00 pm

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, Iā€™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.