Monday, July 29, 2013

“What Happens When the Oil Runs Out?”

Summary of a lecture by Professor Chris Rhodes to the Conway Hall Ethical Society, Conway Hall, Red Lion Square, London. 11.00 am, Sunday July 28th, 2013.

The world supply of crude oil isn’t going to run out any time soon, and we will be producing oil for decades to come. However, what we won’t be doing is producing crude oil – petroleum – at the present rate of around 30 billion barrels per year. For a global civilization that is based almost entirely on a plentiful supply of cheap, crude oil, this is going to present some considerable challenges. If we look over a 40 year period, from 1965 to 2005, we see that by the end of it, humanity was using two and a half times as much oil, twice as much coal and three times as much natural gas, as at the start, and overall, around three times as much energy: this for a population that had “only” doubled. Hence our individual average carbon footprint had increased substantially – not, of course, that this increase in the use of energy, and all else, was by any means equally distributed across the globe.

From the latest document that I can find – the B.P. Statistical Review – we see that the majority form of energy used by humans on earth is crude oil, accounting for 33% of our total, closely followed by coal at 30%: a figure that is rapidly catching up with oil, as coal is the principal and increasing source of energy in developing nations such as China and India. Natural gas follows in a close third place, at 24%; nuclear and hydroelectric power at 5-6% each; and the tiny fraction of our overall energy that comes from “renewables”, is just 1.6%. Thus, we are dependent on the fossil fuels for 87% of our energy. Now, such a comparison is almost misleading and naïve, because it tacitly presumes that if our oil supply becomes compromised, we can make a simple substitution for it using some other energy source.

However, this is not so readily done in practice, because oil is a particular and unique substance, having both a high energy content, and that it is readily refined into liquid fuels – effectively by distillation – to provide the petrol and diesel that runs practically all of the world’s transportation. Moreover, everything we depend upon - literally everything: food, materials, clothes, computers, mobile phones, pharmaceuticals etc. – for our daily existence is underpinned by a plentiful supply of cheap crude oil. So, the loss of this provision is going to have a profound, and shattering effect on human civilization.

In the “good old days”, e.g. the Humphrey Jones “Giant Gusher” drilled in Texas in 1922, it was necessary only to drill a hole in the ground to get oil. An oil well contains not only oil, but gas at high pressure, meaning that once the cap-rock that holds it all in place is broken, the oil is forced out in that familiar jet of black gold. The good old days indeed, because then it was necessary only to expend an amount of energy equal to that contained in one barrel of oil to recover a hundred barrels, which is like investing a pound and getting a return of a hundred pounds – a very good net profit. In 2013, the return is maybe twenty pounds or just three for extra-heavy oil, or for “oil” derived from tar sands, once it has been upgraded into liquid fuel.

Of greatest concern is how much oil is remaining. As noted, we currently use 30 billion barrels a year – 84 million barrels a day, or a thousand barrels every second. When it is trumpeted about some new and huge find of oil, e.g. the Tupi field off Brazil, thought to contain 8 billion barrels, in reality this is only enough to run the world for three months. Context should not be lost in these matters. The quality of the oil is also at issue. For example, much of the remaining oil is of the “heavy”, “sour” kind, meaning that it is not necessarily liquid at all, but bitumen, and contains relatively high levels of sulphur, necessitating complex and energy-intensive processing to get the sulphur out – which would otherwise be corrosive toward the steel used in the refinery – and to crack the heavier material into lighter fractions that can be used as fuel, or as feedstocks for industry.

So, it’s not just that we have got through much of our original bestowal of oil, but that what remains is of poorer quality – in other words, we have used-up most of the “good stuff”! Oil shale does not contain oil at all, but a material called “kerogen” which is a solid and needs to be heated to five hundred degrees Centigrade to break it down into a liquid form that in any way resembles what we normally think of as “oil”. So, when it is claimed that there are “three trillion barrels” of oil under America, really this is only to encourage voters and investors, because the actual Energy return on Energy Invested (EROEI) is so poor that there has been no serious commercial exploitation of oil shale to date, and probably there never will be.

Not only are we entirely dependent on crude oil for all our fuel and materials, but without cheap crude oil, and natural gas to make nitrogen fertilizers, we would be unable to maintain our present system of industrialised agriculture. If we look at a field of soya beans being harvested in Brazil, we see a number of features. For one, those beans are not consumed at source, but are transported around Brazil and around the world. So, oil-derived fuels are necessary not only to run the tractors and combine harvesters, but the trucks, ships and planes to move the crop onto the world markets. In addition, we see the vast clouds of dust being thrown up behind the marching array of mighty machines – combine harvesters – which represents the loss of top-soil.

Even if we could solve all our energy problems, we are consuming the living and fragile portion of the earth’s surface that is our soil, and upon which we are utterly dependent to grow any food at all. We have “lost” around one third of our soil in the past half century - much of this through unsound and unsustainable agricultural practices - which does not bode well for the survival of a burgeoning human population. Another feature is that this land was once rain forest, which has been cleared to use the land for farming.

This is done either simply by setting fire to the forest, or by more exquisite means, such as taking a ship’s anchor chain, four hundred feet long - and if it is two inches in diameter, weighing five tonnes – then stringing it between two one hundred tonne tractors and simply driving over the terrain, so that the chain rips through everything that is there, tearing the trees out by their roots and destroying the structure of the soil in the process. The upshot is that the soil becomes unproductive within only a few years and so it is necessary to move on and do the same thing elsewhere.

In Britain we import about 40% of what we eat, and we use around 7 million tonnes of crude oil each year to fuel our food-chain. It can be said that we literally “eat oil”.

The concept of “Peak Oil” is due to Marion King Hubbert, a petroleum geologist working for the Shell Development Company in Texas, who predicted that oil production in America would peak in 1970. At that time, Texas was “awash” with oil – America being the world’s major oil-exporting nation then - and so no one took him seriously: but when in 1970, he was proved correct, Hubbert’s Peak entered the realm both of hard science and folklore. According to Hubbert, there is a 40 year lag between the year of peak discovery and that of peak production. If we apply this to the world situation, where global oil discovery peaked in 1965, we expect a global production in 2005. Indeed world production of oil has been on a flat line since 2005, and it is thought that we are at the production limit.

The price of oil has quadrupled in the past 10 years, reflecting the more strenuous efforts that are necessary to maintain production: deepwater drilling, fracking, tar sands, all of which have much lower energy returns than for conventional crude oil. Indeed, oil that is recovered from fracking costs about $105 a barrel to produce which until recently was more than it could be sold for. However, the price of oil is creeping up, and the industry is prepared to bear the loss for now, because it knows that the price of a barrel of oil will shortly rocket, and having cornered this “new” portion of the industry, will make big profits. Oil companies are not charities, after all. I emphasise the word “new” because fracking – properly called hydraulic fracturing – has been around since 1947: what is new is the combination of this technique with horizontal drilling, meaning that porous but impermeable rocks can be drilled-out laterally, then “fracked” to break them open thus releasing the oil or gas that they contain.

Fracking is a controversial matter, and there are grave concerns about groundwater contamination from the process. It is not only the fear that the chemicals that were originally present in the fracking fluid might migrate upward into the water table, but that other toxic materials, e.g. radon, that were confined safely within the natural prevailing geology, might be exhumed too. The Royal Society (U.K. equivalent of a national academy of sciences) has concluded that the procedure is safe, so long as it is strictly regulated, but how can this be guaranteed, when profits are the order of the day, and if the technology is to be employed across the world?

What too will become of the millions of gallons of contaminated water, injected under great pressure into the wells to fracture the rock, that remains? Will this be disposed of safely or simply left behind, potentially to leak into and contaminate the groundwater and the soil? This would be a tragic and cruel legacy for future generations.

Analyses made by both the Energy Information Administration (EIA; effectively part of the U.S. Department of Energy) and its counterpart organisation, the Paris-based International Energy Agency (IEA), concur that we will have lost around half our production of conventional crude oil by 2030. This is equivalent to four times the present output of Saudi Arabia, and it seems highly unlikely that this gap in supply can be filled from unconventional sources. Since we are entirely dependent on crude oil to fuel the world’s transportation, and looking at the amount of oil we are likely to be left with, we may conclude that it will be necessary to curb transportation by about 70% over the next 20 years.

This means the loss mainly of personalised transport and it is unfeasible that there will be 34 million electric cars in the U.K. (the current number of oil-fuelled cars) any time soon, and in reality, never. The only sensible means to move people around using electric power is by light rail and tramways, i.e. mass-transit systems.

If we can’t address the problem from the supply side we have to curb our demand. In the absence of cheap and widely accessible transport we will need to produce far more of our food and materials at the local level. Such a metamorphosis of human civilization from the global to the local, will be underpinned by building strong, resilient communities in which people share their skills and knowledge, to provide as much as possible at the local, grass-roots level. This is the underpinning philosophy of the growing network of Transition Towns. Frightening though all of this may appear, we may evolve into a happier and more fulfilling state of living than the percieved status quo, but which in truth is all too rapidly slipping through our fingers.

Friday, July 26, 2013

A Halt on Polish Shale Gas and Leaky Tar Sands.

I saw a screening of "Drill Baby Drill", a film by Lech Kowalski, at the Reading International Solidarity Centre (RISC) recently. There is much to remark upon about both of these creations: the latter has a forest garden actually growing on its roof, in just a foot of soil (including a large cherry tree!), while the film portrays a resistance by a group of Polish farmers to the mighty oil/gas industry who wanted to drill for shale gas in their town of Żurawlów. They held out for 48 days, and finally drove the big boys away. The theme is an inspirational one, not only in a David and Goliath way, but that the group, who are not scientifically educated, manage to accumulate sufficient information via the internet to realise that what they had thought to be of great local and national benefit, carries a lot of hidden and unsavoury baggage with it.

They are patriotic people, and strongly in support of the promise that shale gas will drive and elevate the economy of Poland, to the benefit everyone, but I am left with the footage of interviews of those in the U.S. who have experienced fracking (hydraulic fracturing) first hand, and the suggestion that the millions of gallons of contaminated water in the shale gas wells will simply be left behind to percolate upwards, potentially leaking into the groundwater and contaminating the soil, rather than being carefully pumped out and disposed of safely. If this proves to be the case, it will be a rather grim legacy for the children and the grandchildren: a real "sins of the fathers" scenario.

It is this kind of prospect that often causes even those initially in favour of fracking, to change their hearts in rejection and opposition of it, especially in their own back yard. In "Drill, Baby Drill", although the farmers managed to prevent fracking taking place in their own town, "Big Oil/Gas" simply began drilling in another town just down the road, and so the battle may have been won but the war continues. In view of the volume of shale gas recovered in the United States, the strategy has been dubbed as a "bonanza" and even a "miracle", since shale gas now accounts for 40% of total U.S. gas production

For comparison, shale-oil (tight oil) production amounts to 30% of total U.S. home oil production. Clearly fracking in the big business, but it is debatable how much can be recovered and exactly how miraculous this will be: i.e. a long term saviour or a flash in the pan. Rather than the widely trumpeted "100 years worth of gas", the actually proven reserves are nearer 11 years worth, and hence the case might be somewhat overstated

Now, the geology is different in the U.S. than in Europe, and so we should not take the success of our transatlantic cousins as any kind of guarantee that we will be bestowed with a similar bounty. I am unsure about the environmental hazards associated with fracking, and I note that a scene in the film "Gasland", which purportedly shows a man going into his kitchen and lighting the water from the tap - allegedly, because it was so heavily contaminated with methane from fracking - has been confessed as bogus, or more generously put, that "its narrative is flawed" A film called "Truthland" ensued in which a "mom" interviewed industry and academic experts, which led to a retraction of some of the claims in the original film, Gasland.  The Royal Society (the British equivalent of a national academy of sciences) has investigated the risks of fracking, and concluded that so long as it is "strongly regulated" the procedure is safe

But will there be adequate control, when rapid profits are the order of the day, and can this really be guaranteed in all nations? One thinks of those children and grandchildren again. When corners are cut, fracked wells can become "leaky" with the risk of emitting methane into the atmosphere, and this is a far more potent greenhouse gas than is generally understood. Rather than the oft cited value that methane is twenty times worse than carbon dioxide, as a greenhouse gas, the heat trapping efficiency (radiative forcing factor) of CH4 is actually nearer to 100 times greater than that of CO and so this is another potentially unwelcome component of our energy legacy. Agreed that methane is oxidised in the troposphere on a roughly 12 year time-scale, but while it is around it is trapping heat very effectively, and its oxidation product is our old friend, CO2, with its accepted longevity in the atmosphere, and warming potential.

All, however, is not well with the shale gas industry in Poland. I had heard before that from 9 exploratory wells drilled in Poland came a gas so heavily contaminated with nitrogen (N2) that it wouldn't burn Now this is an important issue, since the quality of the gas is not known, irrespective of estimates of how much of it there may be to be extracted, until the material is actually recovered and analysed. As already noted, the rocks are different in the U.S. from those in Europe which includes Poland.  ExxonMobil moved out of Poland in June 2012 after drilling only two wells, while in May 2013, Canada’s Talisman and Marathon Oil, an American firm, also abandoned drilling for shale gas in Poland because the results were disappointing

Thus, we might not be so "lucky" over here in the rest of Europe or in other continents as in the U.S., although the U.K. government has given the go-ahead for drilling, but having removed the rights of local authorities to make decisions independent of central Government energy policy This led to a protest in Sussex, one of England's leafier corners Very likely, the resistance that was possible in Żurawlów in Poland, will not prove comparably tenable in the U.K.

Another point is that shale (oil or gas) wells tend to decline in their output relatively rapidly, maybe to half in the first year and to 20% by the end of the second year. "Drill Baby Drill" indeed, because to maintain output it will be necessary to drill well after well, year on year, in a compensatory capacity. It should be noted that fracking is nothing new, and the first such well was drilled in 1947. What is new is the combination of this technology with horizontal drilling, so that the well can be extended laterally, thousands of feet into the shale, and similar wells can be drilled by "rotating" the horizontal bore, in effect around the 360 degree circumference of the circle, thus extracting gas over an area of several square miles.

When a "mature field" is referred to, it really means an area that has been thoroughly pulverised! This is more reasonable to do in the U.S., which has been referred to as "MAMBA-land", meaning "Miles And Miles of Bugger All", where no one lives, whereas in the U.K. certainly, along with much of Europe, it will be necessary to drill under some quite densely populated conurbations, if widescale fracking does go ahead. But given the desperation to grab unconventional energy sources, I have no doubt that it will.

Speaking of desperation, I note that the Canadian oil sands (more properly called tar-sands because they contain bitumen, not petroleum) are leaking, and no one quite knows why The leak is reckoned to have been active for 9 weeks (at least?), and it seems to be from a tar sands extraction facility at Cold Lake, Alberta. Because it is so visible, most attention has been attracted by the surface mining operations there, but the latest piece of news refers to the underground side of the story.

Some 80% of the bitumen that is extracted in Alberta comes not from the surface but from further below, and superheated steam is injected downward, into the tar sands, in a process called "cyclic steam stimulation" or CSS, which melts the bitumen and allows it to flow to the surface. Sitting on top of the leaky spot are some 30 acres of swampy forest where apparently dozens of animals have been killed. So far, 60,000 pounds of contaminated vegetation and 26,000 barrels of "watery tar" have been removed from the area.

The term CSS is slightly reminiscent of CCS - (carbon capture and storage), a strategy that is proposed to lead the way to "clean coal" - and it has been said that it is more eco-friendly than surface mining. However, CSS releases the most carbon that is incurred by the two procedures, because of the large amount of energy needed to turn water into steam One fifth of Canada's gas consumption is taken by its production of tar sands and it has been suggested that nuclear reactors should be installed on-site to provide the energy instead

So: on May 21st (2013) springs of a watery bitumen-emulsion began to seep out of the earth from cracks that suddenly appeared in the ground (I wonder if there is a crack in the rock somewhere lower down - since what normally comes up to the surface is a a mixture of water and bitumen - and having escaped, this fluid has found a natural "conduit"). What is the cause exactly, and what might the longer term consequences be? Will it enter the groundwater? Most of all, what can be done about it... if anything?

Monday, July 08, 2013

Thorium Based Nuclear Power: A Current Commentary

The following was published in the journal Science Progress, of which I am an Editor and where I write a regular "Current Commentary" column, in this issue with the view to giving some publicity to the prospects and potential advantages of deriving energy from thorium. The final article (containing figures, schemes etc.) can be downloaded from this link

Thorium instead of Uranium?
It may well turn out that thorium is a better nuclear fuel than uranium, since it offers the advantages that: (1) it has around four times the abundance of uranium on Earth, overall; (2) practically 100% of it can be bred into the fissile nuclear fuel 233U; (3) smaller amounts of plutonium and other transuranic elements are produced than is the case from uranium fuel; (4) the thorium fuel cycle might be used to consume plutonium, thus reducing the nuclear stockpile, while converting it into useful energy. There was a conference held in Chicago, in May 2013, on “5th Thorium Energy Alliance – Future of Thorium, Energy and Rare Earths.”

Thorium1 is a naturally occurring radioactive element, with the chemical symbol Th and an atomic number of 90. The mineral, now known as thorite, was discovered in 1828 by the Norwegian priest and mineralogist, Morten Thrane Esmark. In that same year, the element, thorium, was identified in the material by the Swedish chemist, Jöns Jakob Berzelius, who named it after Thor, the Norse god of thunder. Thorium is found in soils at an average concentration of 6 parts per million (p.p.m.), and in most rocks. In higher concentrations, thorium occurs in several kinds of mineral, of which the most common is the rare earth phosphate mineral, monazite, which contains up to about 12% thorium phosphate, but 6-7% as an average. World monazite resources are estimated to be of the order of 12 million tonnes, two-thirds of which are in heavy mineral sands deposits on the south coast and east coast of India. The world total of economically extractable thorium is estimated at around 2.61 million tonnes (Table 1)2, and Australia and the United States top the list with 489,000 and 400,000 tonnes of it, respectively. Norway has 132,000 tonnes of thorium, which adds to the large energy reserves of this country in terms of gas, oil and coal, not to mention hydropower, from which 99% of its electricity is generated. Other than negligible amounts of a few highly radioactive isotopes, thorium occurs exclusively as 232Th. Although 232Th is not fissile in itself, it can be converted to a fissile fuel in the form of 233U, via the absorption of slow neutrons. Hence, as is the case for 238U, 232Th is "fertile" and may be bred into a nuclear fuel, which in the former case is 239Pu. Kirk Sorensen, a major proponent for the development of thorium power, in particular in conjunction with the Liquid fluoride reactor, LFR (also called the molten salt reactor, MSR) has offered the following3, in regard to the essential differences between the two elements 232Th and 239Pu, as pertaining to their use in nuclear weapons or “dirty bombs”:

“There are several reasons why U-233 is unattractive for nuclear weapons. One is that it doesn't produce as many neutrons in fast fission as Pu-239. Another is that its properties in very fast fission (such as a nuclear detonation) are poorly understood.

But the biggest deterrent is that U-233 is inevitably contaminated with U-232 during its formation. It is highly impractical to separate them. And U-232 has a short half-life (~80 years) and a decay chain that includes the strong gamma emitter Tl-208. A few months after the U-233 is isolated from parent materials, the decay chain of U-232 begins to set up and the strong 2.3 MeV gammas of Tl-208 would irradiate the weapon, its electronics, as well as providing an easily-detected alert to the world that U-233 was present in a location.

In contrast, the alpha decay of U-235 and Pu-239 are rather easily shielded, making clandestine transport of these weapons much easier, and well as allowing long-term storage with relatively little damage to the electronics of the device. With all these drawbacks, it is not surprising that U-233 has not been utilized in operational nuclear weapons. This inherent physical resistance to proliferation is a powerful argument for the adoption of thorium as a basic nuclear energy source.”

Table 1. World sources of thorium (2007)2.
% of total
South Africa
Other countries
World total

Since 100% of naturally occurring thorium can be converted into nuclear fuel (233U), compared with the mere 0.7% of natural uranium that is fissile, i.e. 235U, which is enriched by centrifugation or gaseous diffusion of uranium hexafluoride (UF6), there is an obvious advantage4. Fuel for fuel, the advantage factor is around 30, in favour of thorium - since that from uranium is enriched to around 3% in 235U - but this is counterbalanced by a depletion of this isotope in the remaining material, which is generally referred to as “depleted uranium” and sometimes used in armaments and missiles. Roughly 1/3 of the power from a U-fuelled fission reactor is due to the fissioning of 239Pu, generated in situ from 238U, and so we can ascribe an overall advantage factor of ca 100 for thorium over uranium, though a value of 250 is claimed, when enrichment “losses” for 235U/238U and higher efficiencies for thorium reactors are included It might be argued that the rest (234U has an abundance of only about 0.0055%) of the 100% of the uranium (238U) can be converted to plutonium in a similarly effective manner, but this requires fast neutrons in a fast breeder reactor: a technology with certain disadvantages, including the need to handle plutonium – a very toxic material, although there are as yet no reported casualties from it - and fears over its proliferation. Often cited too, is the potential fire hazard of pyrophoric liquid sodium, which is often used as a coolant, although helium, lead or a lead-bismuth alloy have all been proposed as alternatives. Thus, if the latter method is to be avoided, considerably more energy might be extracted from thorium than from an equivalent quantity of uranium. Even on the basis of the "known" 2.61 million tonne reserve of thorium (Table 1), a simple sum indicates that it could provide nuclear power for: [2.61 million (tonnes of thorium)/4.02 million (tonnes of uranium)] x 100 (enhancement factor in favour of Th over U) x 62 years (i.e. the current estimate based on uranium5) = ca 4,000 years. Even if we made all our electricity from thorium (currently, 13.5% of world electricity is from nuclear power), there would still be around 500 years worth, and so if governments are intent on nuclear expansion to obviate global warming, thorium may well prove advantageous.

             Ralph W. Moir and Edward Teller (dubbed6 as the “father of the ‘H’ bomb” and the real “Dr Strangelove”), made a study of thorium-based nuclear power from which they concluded that research should be reinitiated after being abandoned for more than three decades7. There is a comprehensive review published by the International Atomic Energy Agency (IAEA) on the subject of thorium-based nuclear power8.
The Thorium Age Waits in the Wings.
There are different ways in which energy might be extracted from thorium, one of which is the accelerator-driven system (ADS)9. Such accelerators need massive amounts of electricity to run them, as all particle accelerators do. As noted below, an alternative means to use thorium as a fuel is in a liquid fluoride reactor (LFR), also termed a molten salt reactor, which avoids the use of solid oxide nuclear fuels. Indeed, China has made the decision to develop an LFR-based thorium-power programme, to be active by 2020. However, the matter of thorium reactors is not straightforward. Neutrons may be produced from heavy elements by spallation, using high-current, high-energy accelerators or cyclotrons. In this process, a beam of high-energy protons (> 500 MeV) is directed at a high-atomic number target (e.g. tungsten, tantalum, depleted uranium, thorium, zirconium, lead, lead-bismuth, mercury) by which means up to one neutron can be produced per 25 MeV of the proton beam energy. A 1000 MeV beam will create 20-30 spallation neutrons per proton, to be compared with 200-210 MeV released in the fission of one nucleus of 235U or 239Pu. If the spallation target is surrounded by a blanket assembly of nuclear fuel, containing e.g. 235U or 239Pu (or 232Th which can breed to 233U), a fission reaction may be sustained, which is an ADS. Here, the spallation-neutrons cause fission in the fuel, and the process is assisted by further fission-neutrons. Since an ADS burns fuel which lacks a sufficiently large fission-to-capture ratio for neutrons to maintain a fission chain reaction, the whole assembly may be instantly turned-off, merely by shutting-off the proton beam, in contrast to inserting control rods to absorb neutrons and make the fuel assembly subcritical, as is necessary in conventional fission-reactors. The latter is often stressed as a key safety feature of an ADS, and while it is true that fission could be stopped almost instantly in an emergency, the substantially greater threat from decay heat would remain, as at Fukushima.
Thorium utilisation
To breed 232Th to 233U, a driver fuel is needed – either plutonium or enriched uranium – otherwise there are insufficient neutrons generated to keep the process going. As is the case for uranium, in order to use all of the thorium as a fuel, fast neutron reactors are required in the system. The concept9 of using an ADS, based on the 232Th—233U fuel cycle, is due to Professor Carlo Rubbia, in which the core would be mostly thorium, and located near the bottom of a tank 25 metres high, and containing around 8,000 tonnes of molten lead or lead-bismuth at a high temperature – this is the “primary coolant”, which circulates by convection around the core. A beam of high-energy protons from the accelerator, would be focussed along a beam-pipe to the spallation target, inside the core, where the spallation-neutrons enter the fuel and transmute the thorium into protactinium, the decay of which forms the fissile 233U. The neutrons also induce fission in uranium, plutonium and possibly any transuranic elements that are present, with an according release of energy. Thus, a 10 MW proton beam might produce 1500 MW of heat. This would accord with a generation of 600 MWe of electricity – allowing for the usual Carnot Cycle energy losses - some 30 MWe of which would be needed to drive the accelerator. However, existing accelerator technology can only produce a proton beam with an energy of 1 MW. A reactor of this kind is sometimes referred to as an energy amplifier. There is a U.K.-Swiss design for an accelerator-driven thorium reactor (ADTR) which has advanced to the stage of a feasibility study, and involves a 600 MWe lead-cooled fast reactor. The proposal is for a ten-year self-sustained thorium fuel cycle, using plutonium as a fission starter, with both the spallation target and the coolant being provided by molten lead. For actual power production, the accelerators would need to be increased in power by an order of magnitude, and massively in terms of reliability (so, I am told). In 2008, a study was made in Norway which compared the advantages and disadvantages of an ADS fuelled by thorium - relative to a conventional nuclear power reactor - from which it was concluded that such a system would be unlikely to be operating in the next 30 years9. I note, however, that experiments are being undertaken in Norway to evaluate the properties of a mixed thorium-uranium solid fuel

An alternative technology to the ADS, is the "Liquid Fluoride Reactor" (LFR), which is described and discussed in considerable detail at, and reading this site has convinced me that the LFR may provide the best means to achieve our future nuclear energy programme. Thorium exists naturally as 232Th, which is not of itself a viable nuclear fuel. However, by absorption of relatively low energy "slow" neutrons, it is converted to protactinium10 (233Pa). The latter either decays further to 233U or captures another neutron, which converts it to the non-fissile 234U. 233Pa has a relatively long half-life of 27 days and a high cross section for neutron capture (the so-called "neutron poison"), hence, instead of undergoing a simple and fast decay to 233U, a significant fraction of the 233Pa consumes neutrons which convert it to non-fissile isotopes, so attenuating the reactor efficiency. To avoid this, the 233Pa must be extracted from the active zone of the thorium LFR, so that it may be allowed mainly to decay to 233U. In one scenario, this may be achieved by using columns of molten bismuth, with lithium dissolved in it, that are several metres high. The function of the lithium is to selectively reduce protactinium salts to metallic protactinium, which is then extracted from the molten-salt cycle, the bismuth acting mainly as a carrier (solvent). Bismuth has a low melting point (271 °C), a low vapour pressure, lithium and actinides are quite soluble in it, and it is immiscible with molten halides10. The "breeding" cycle can be initiated using plutonium, say, to provide the initial supply of neutrons, and indeed the LFR could provide an efficient way of disposing of weapons-grade plutonium and heavily-enriched uranium from the world's stockpiles, producing useful energy in the process.
The LFR makes in-situ reprocessing possible, and much more easily than is the case for solid-fuel based reactors. To date, there have been two working LFR's built11, and if implemented, the technology would avoid using uranium-plutonium fast breeder reactors, which need high energy "fast" neutrons to convert 238U, which is not fissile, to 239Pu which is. The design of the LFR is inherently safer and does not require liquid sodium as a coolant, while it also avoids the risk of plutonium getting into the hands of terrorists. I maintain my reservations about how long other resources, e.g. oil and gas will last, with which to mine and process either uranium or thorium, but if the latter appears viable in the longer run, I suggest that molten salt (liquid fluoride) reactors might provide a more viable approach than the far more complex (and as yet untested) accelerator-driven systems.

More thorium would doubtless be found if it were looked for hard enough, and so the basic raw material is not at issue. Being more abundant in most deposits than uranium, its extraction would place less pressure on other fossil fuel resources used for mining and extracting it. Indeed, thorium-generated electricity could be piped-in for that purpose. Despite these apparently impressive advantages, the new build of infrastructure would be massive, to switch over entirely to thorium, as it would be to convert to any other new technology, on the grand scale, including hydrogen and biofuels, with attendant costs of materials, energy, labour and other resources. Indeed, this provides the mass of resistance that is to be expected over the implementation of all kinds of new technology. My belief is that, once the “liquid fuels crisis” occurs, which will be the major, and most immediate, consequence of a decline in world conventional crude oil production, “peak oil”, we may be able to produce liquid fuels from coal, possibly using electricity produced from thorium. The problem of nuclear waste is expected to be lessened through the use of thorium, since fewer actinides result from its fuel cycle compared with that from uranium. It is not clear how the development of thorium energy in Europe will be funded, if at all, since much of the Euratom budget is being spent on the ITER nuclear fusion project, and the remainder on uranium-based fission programmes12.

Oak Ridge National Laboratory (ORNL) molten salt breeder reactor.
232Th, 235U and 238U are radionuclides that predate the formation of the Earth some 4.5 billion years ago, and were created in the cores of dying stars through the r-process being dispersed galactically by supernovas. Around half13 the internal heat of the Earth is produced from the decay of these radioactive elements, along with 40K, and it is this effect, unknown at the time of Lord Kelvin, that led him to conclude this planet to be much younger than it actually is, at between 20 million and 400 million years, rather than the currently accepted value of 4.54 (± 0.05) billion years14. As a result of both historical and technical factors, each of the above type of nuclide tends to be associated with different kinds of reactor: across the world, the principal nuclear fuel is 235U, as it has been since the dawn of the nuclear age, and this is usually used in light water reactors; 238U/239Pu has been used mainly in, liquid sodium cooled, fast breeder reactors and CANDU Reactors; 232Th/233U is thought best suited to fuel molten salt reactors (MSR)11.

The MSR at Oak Ridge National Laboratory was pioneered by Alvin M. Weinberg, where two prototype molten salt reactors were successfully designed, constructed and operated. These were the Aircraft Reactor Experiment in 1954 and Molten-Salt Reactor Experiment which ran between 1965 and 1969, and in both cases, liquid fluoride fuel salts were used. Fuelling with 233U and 235U was demonstrated during separate test runs. A proposed molten salt breeder reactor (MSBR) was designed at ORNL, during the period 1970-1976, with LiF-BeF2-ThF4-UF4 (in the relative proportion: 72:16:12:0.4) as its fuel, and with a graphite moderator, to be replaced every four years, with NaF-NaBF4 as the secondary coolant, and a peak operating temperature of 705 °C. However, the MSR program was closed in the early 1970s, in favour of the liquid metal fast-breeder reactor (LMFBR). Research into MSRs then lapsed in the United States, and as of 2011, the ARE and the MSRE remained the only molten-salt reactors ever operated. The MSBR project received funding until 1976, equivalent to $38.9 million from 1968 to 1976 (compensated for inflation to the monetary $ value in 1991)11.

Rare Earth Elements and Thorium Power.
Thorium is present in the ores of rare earth elements, and indeed, there is more thorium available from this source than the world demand for it15. As a consequence of its radioactive nature of thorium, a hazard is posed from its content in waste produced by the processing of rare earth oxides. However, as we have noted, thorium could be bred into a nuclear fuel and most simply used in a liquid fluoride reactor (LFR), rather than burying it underground in concrete. 97% of world market supplies of rare earth elements (REEs) come from China and look to become insecure in regard to meeting "green" energy targets, since supplies of REEs are scheduled to be retained for Chinese home energy projects. REEs are essential raw materials for the fabrication of high-performance magnets in hybrid cars and wind-turbines. The REE distribution in monazite sands is around 45 - 48 % cerium, 24% lanthanum, 17% neodymium, 5% praseodymium, along with minor quantities of samarium, gadolinium and yttrium. Europium concentrations tend to be low, in the region of 0.05%, and very low concentrations of the heaviest lanthanides in monazite accord with the term "rare" earth for these elements, with correspondingly high prices. The thorium content16 of monazite is variable and can be as high as 20 - 30 %, although commercial monazite sands typically contain 6 - 12% thorium oxide.

In January, 2013, a controversial REE processing plant was commissioned by the Australian based mining company Lynas in Malaysia17, where it is argued that environmental protection laws are less rigorous than in Australia. The plant is predicted to produce one third of global demand for REEs, hence breaking the Chinese monopoly. 

Thorium-based power: positive and negative features.
Positive aspects4.
Although precise knowledge of the true amount of reserves, globally, is limited, thorium is estimated to be about 3-4 times more abundant than uranium in the Earth's crust. Very likely, further sources of the material would be found, if they were sought with sufficient assiduousness, noting that the EROEI would fall with the decreasing grade (thorium content) of particular ores. Current demand for thorium (mostly not for power generation) has been satisfied as a by-product of rare-earth extraction from monazite sands, but demand for the metal is relatively low in comparison with that for REEs, so that the thorium ends-up as radioactive waste from processing this mineral. Since thorium consists of a single isotope (232Th), it can be employed in thermal reactors without requiring isotope separation, unlike natural uranium, from which the fissile 235U must be separated and enriched for use as a nuclear fuel in fission-reactors.

Relative to uranium-based fuels, thorium offers a number of appealing features: the thermal neutron absorption cross section (σa) is about three times, and the resonance integral (average of neutron cross sections over intermediate neutron energies) about one third for 232Th of the respective values for 238U, meaning that the conversion of thorium is more efficient in a thermal reactor. Although the thermal neutron fission cross section (σf) of the resulting 233U is comparable to 235U and 239Pu, it has a much lower capture cross section (σγ) than the latter two fissile isotopes, providing fewer non-fissile neutron absorptions and a better neutron economy. Finally, the ratio of neutrons released per neutron absorbed (η) in 233U is > 2, and over a wide range of energies, which covers the thermal spectrum, meaning that thorium-based fuels might be used in a thermal breeder reactor.

Because the 233U produced in thorium fuels is always contaminated with 232U, thorium-based nuclear fuel has an inherent proliferation resistance. 232U cannot be separated from 233U by chemical means, and it has several decay products which emit high energy gamma radiation, alerting to the presence of such materials, e.g. “a bomb in a suitcase”. 233U can be denatured by mixing it with natural or depleted uranium, meaning that before it could be used in nuclear weapons, isotopic separation would be necessary.

On a timescale, roughly of 103 to 106 years, the radiological hazard of conventional uranium-based used nuclear fuel is dominated by plutonium and other minor actinides, but once these have decayed, long-lived fission products once more make a significant contribution. A single neutron capture in 238U is sufficient to produce transuranic elements, whereas six such captures are generally necessary to so convert 232Th. 98–99% of the nuclei in the thorium-cycle fuel would fission either at the 233U or 235U stage, thus resulting in fewer long-lived transuranics. As a result, in mixed oxide (MOX) fuels, thorium offers an advantage over uranium, in minimising the generation of transuranics while maximising the destruction of plutonium.

The advantages of thorium in nuclear waste management, while noting that it produces far less in the way of transuranics, are mitigated by the production of 231Pa. also an α-emitting actinide, with a half-life of 3.3 x 104 years, along with the full range of fission products. It is the presence of the latter, more than their amounts, this is the problem. Indeed, the chemical intractability of thorium oxide makes it a good waste form in its own right, although it does almost preclude volume reduction by separating the few percent of genuine waste from unused material. That said, direct disposal eliminates the plant and secondary waste production incurred in such separation, which naturally is equally available for uranium.

Negative aspects4.
The application of thorium as a nuclear fuel poses a number of problems, particularly for solid fuel reactors. Since natural thorium contains no fissile isotopes, it is necessary to add fissile material 233U, 235U, or plutonium, in order to attain criticality. Along with the high sintering temperature necessary to make thorium-dioxide fuel, this is a complicating factor in fuel fabrication. ORNL experimented11 with thorium tetrafluoride as a fuel component, in their run of a molten salt reactor from 1964–1969, which was far easier both to process and to separate from contaminants, which slow-down or actually halt the chain reaction.

In an open fuel cycle (using 233U in situ), a higher burn-up is necessary to achieve a favourable neutron economy. Although thorium dioxide performed well at burn-ups of 170,000 MWd/t and 150,000 MWd/t at Fort St. Vrain Generating Station  and AVR respectively, achieving this in light water reactors (LWR), which are the vast majority of existing power reactors, worldwide, is a challenge. In a once-through thorium fuel cycle, the residual 233U constitutes long-lived radioactive waste.

The main objection on the part of the nuclear industry to thorium is its radiotoxicity, greater by an order of magnitude than that of uranium, in consequence of the presence of 232U and decay products, therefrom. Thus, a completely new infrastructure would be required, involving more stringent dust control.

The thorium fuel cycle requires a relatively long interval to breed 232Th to 233U. The half-life of 233Pa is about 27 days, which is an order of magnitude longer than the half-life of 239Np, as occurs in breeding from 238U to 239Pu. As a result, substantial quantities of 233Pa, which is an effective absorber of neutrons, build up in thorium-based fuels. Thus, instead of undergoing a simple and fast decay to 233U, a significant fraction of 233Pa consumes neutrons which convert it to non-fissile isotopes, e.g. 234Pa, and this attenuates the reactor efficiency. Therefore, the 233Pa must be extracted from the active zone of the thorium LFR, so that it may be allowed mainly to decay to 233U. Eventually, the 233Pa would breed into fissile 235U, but this process requires overall two more neutron absorptions, and hence occurs at the further expense of the neutron economy. The likelihood of transuranic production is also increased.

Although the presence of 232U would inhibit its use in a nuclear weapon, 233U was once so employed, as part of a bomb core in the MET blast during “Operation Teapot” in 1955, though the energy yield was appreciably less than had been anticipated. 

Current thorium projects18.
Research and development of thorium-based nuclear reactors, primarily the Liquid fluoride thorium reactor (LFTR), MSR design, has been or is currently ongoing18 in the U.S., U.K., Germany, Brazil, India, China, France, the Czech Republic, Japan, Russia, Canada, Israel and the Netherlands.
  • China. Using components produced by the West and Russia, it was reported early in 2012 that China planned to build two prototype thorium molten salt reactors by 2015. A budget for the project was established at $400 million, which will require 400 workers. China has also finalized an agreement with a Canadian nuclear technology company to develop improved CANDU reactors using thorium and uranium as a fuel.
  • India. This is the "only country in the world with a detailed, funded, government-approved plan" to focus on thorium-based nuclear power. In late June, 2012, India announced that their "first commercial fast reactor" was near completion and would rely on thorium for its fuel. The nation plans to develop up to 62, mostly thorium-based reactors, intended to be fully operational by 2025.
  • Norway. In Norway, the privately-owned company, Thor Energy, announced in late 2012, that in collaboration with the government and Westinghouse, it will start a 4-year long trial to employ thorium as a nuclear fuel in one of its existing nuclear reactors.
  • U.S. In its report to the Secretary of Energy, in January 2012, the Blue Ribbon Commission on America's Future notes that a "molten-salt reactor using thorium [has] also been proposed”, while in the same month, it was stated the U.S. Department of Energy is "quietly collaborating with China" on a molten salt reactor using thorium fuel.

  • Japan. In the aftermath of three meltdowns at nuclear power plants in 2011, Japan utility Chubu Electric Power, wrote in June, 2012, that they are considering thorium as “one of future possible energy resources.”
  • Israel. Researchers from Ben-Gurion University in Israel and Brookhaven National Laboratory in New York began, in May 2010, a collaboration to develop self-sustaining thorium reactors, "meaning one that will produce and consume about the same amounts of fuel."
  • U.K. In Britain, a member of the House of Lords, Bryony Worthington, is actively promoting thorium, which she refers to as “the forgotten fuel”. However, the UK’s National Nuclear Laboratory (NNL) has published a paper on the thorium fuel cycle, finding that, "the thorium fuel cycle does not currently have a role to play," in that it is "technically immature," and “would require a significant financial investment and risk without clear benefits," and which are "overstated." The environmental group, Friends of the Earth UK, are of the opinion that research into thorium-based power might be "useful" as a fallback option.
(2) Data taken from Uranium 2007: Resources, Production and Demand, Nuclear Energy Agency (June 2008), NEA#6345 (ISBN 9789264047662). The 2009 figures are largely unchanged. Australian data from Thorium, in Australian Atlas of Minerals Resources, Mines & Processing Centres, Geoscience Australia