The economics of oofle dust
by Chris Shaw, The Feral Metallurgist
AUSTRALIA - The prime minister has asked for a robust debate on uranium mining. So be it. In the matter of Australia's role in the global nuclear industry, there is no substitute for general knowledge. Acceding to the desires of political or economic ideologues is not an option.
Most of us see the gathering of energy as being analogous to taking the trusty chainsaw out into the forest. We pay brave souls to cut coal from the ground, or pump oil from a windswept platform far out to sea. Others process and refine coal, oil and gas to produce the distributable energy and goods of our everyday lives. No mystery there.
Nuclear energy requires us to think again. This is not "business as usual". There is no trusty woodsman gathering fuel for the nuclear hearth in the way that we usually think of it.
Uranium begins its journey
From the orebody to the reactor, uranium begins its journey conventionally enough. Like other metallic mining operations, the wanted mineral is carefully separated from the natural matrix. When the separation has been achieved to the level of purity that is practicable in an outback processing plant, the uranium oxide "yellowcake" is now concentrated enough to be conveniently transported away. Radiation levels of yellowcake are tolerable with respect to its relatively small quantity. Steel containers provide adequate short-term shielding.
The opposite might be true of the plant tailings, which although weaker in radioactive mineral, are now cast upon the surface of the land in very large amounts. Here I yield to the wisdom of the environmental scientist to inform us what is or is not tolerable.
Only a pinch of oofle dust remains
Only a small portion of natural uranium has the ability to detonate the process that generates uranium heat energy. Seven atoms in every thousand are subtly different to their brothers. In my naive way, I will tell you that those seven atoms have the potential to release some of the energy that went into the creation of the heavier elements, in old stars, so long ago.
In that distant past, unstable transitory atoms were far more plentiful. By gathering remnant transitory atoms together in greater abundance, we can re-create those energetic times once again, if only for a brief while, in the heart of a reactor.
Hunt the oofle dust
There is no chemical difference between the scarce uranium atoms (U235) and the plentiful (U238), so common chemical processes will not serve to separate them. They are isotopes.
U235 atoms are one per cent lighter than U238. This subtle difference is how we differentiate between the two. Imagine searching for a tablespoon of flour in a crate of talcum powder, grain by grain - then multiply the problem a million fold, because we are forced to deal with nature's smallest building blocks.
In order to separate all the atoms first, we must turn the uranium into a vapour. The heat required to do this is so great that it would rob a very significant amount of our nuclear energy output - and remember, we are in the business of making an energy profit.
Externalising the problems
Like any good corporate pirate, we must maximise profit and externalise the costs. This is why nuclear power generates really bad karma. This is the principle that is hushed up by nuclear profiteers. This is the rub. This is the bit that we all have to learn and understand. Read on ...
Liberating the oofle dust
In order to vaporise uranium "cheaply" at a low temperature, it is first necessary to combine it with fluorine. The combination of 6 fluorine atoms with each single uranium atom, gives the only compound (UF6) that will become a gas when moderately heated.
Yellowcake is refined, and then dissolved in concentrated hydrofluoric acid to give an intermediate compound with 4 fluorine atoms (UF4). Further treatment with fluorine gas attaches two more atoms to give uranium hexafluoride (UF6).
Uranium hexafluoride is not found in nature because it is unstable. By making the uranium so easy to manipulate, we have also made it so easy to blend into the surrounding environment; into water, air, soil and our bodies. In other words, the genie is out of the bottle. UF6 must be treated with kid gloves.
Concentrating the oofle dust
So subtle is the weight difference between U235 and U238, that separation and concentration becomes a very onerous task. Batteries of high-speed precision centrifuges are coupled together in their thousands in order to achieve commercial throughput. All must be gas tight and maintained at the correct temperature, so that UF6 does not condense back into fluid. All must be made from materials that will not react or combine with UF6. A centrifuge plant is a very considerable capital cost. The total energy investment is significant.
Mass-balancing oofle dust
To stoke a nuclear fire, we require a concentration of 35 (U235) atoms in every thousand. This means that for every tonne of nuclear fuel produced, there MUST be 9 tonnes of depleted uranium hexafluoride (dUF6) to be disposed of. There is no way out of this simple mass-balance: dUF6 still retains 3 atoms of U235 per thousand.
Commercial-in-confidence, shhhhh!
The US alone has in excess of 720,000 tonnes of depleted uranium hexafluoride in storage in enormous "parking lots". It is contained in large, thick-walled special steel containers, which must be re-painted and tested for leaks continuously. The containers hold almost all of the dUF6 that was created since 1946.
Laughingly, the US DoE describes this intractable mess as "a future resource", but there is no way out. The energy and capital cost of changing this poison into something benign makes the nuclear option a loser. Ask yourself, if there was a buck to be made, would that "resource" still be there after six decades?
The true cost of value-adding
For every tonne of reactor-grade UF6 produced, Australia must keep 9 tonnes of dUF6 as a gift to future generations. Yet a steel cylinder does not a time-machine make.
Can the economists of McBank, McMine or McTreasury even hope to guess at a price for our uranium exports, which takes this into account? Will they even bother to try?
Far better to "externalise" the problem. That's how we have always done business, isn't it?
Try this thought-experiment
You are a match-tester. Your job is to strike every match on the production line in order to see which ones don't work.
The fact that your boss has shares in a cigarette lighter factory makes you feel a little uneasy. But he pays a handsome salary, so you put your thoughts behind you, buy a good suit and convince yourself and your wife that your efforts are somehow a noble contribution to the progress of mankind.
By the current rules of the corporate-nuclear game, you would be right.
The bottom line
The getting of wisdom is not too hard. Although we have only touched upon the initial stages of the nuclear chain, many of the in-principle designs and blueprints for nuclear power are freely available on the Web. Rube Goldberg is particularly recommended. Google him.
Over to you.
~~~~~~~~~~~~~~~ Editorial Notes ~~~~~~~~~~~~~~~~~~~
This looks like another time to mention David Fleming's important document WHY NUCLEAR POWER CANNOT BE A MAJOR ENERGY SOURCE.
Check out the archives for some other great and idiosyncratically styled articles by Chris Shaw, the Feral Metallurgist.
Chris's Online Opinion bio states:
Chris Shaw was a mining metallurgist, until retreating to care for his beloved partner. Mining metallurgists are trained to appreciate the laws of natural abundance. Mining is where the wishful thinking of economists meets the reality of nature. Chris sometimes operates under the pseudonym "Feral Metallurgist", so that he can enjoy an air of mystique which he doesn't actually deserve.
Published on 29 May 2006 by Online Opinion. Archived on 31 May 2006.
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