The nuclear industry is abuzz with talk of an avant-garde next-generation nuclear concept, pundits are chattering and governments are starting to show interest; advocacy for thorium is gaining traction and LFTRs are stealing the show. Some, such as fervid thorium exponent Kirk Sorensen, are proclaiming this technology to be the innovation that revolutionises our approach to energy and invigorates our fight against climate change.[i] So, what is thorium? Naturally-occurring and frequently accommodated in amalgams of rare-earth metals, thorium is typically present in the single isotopic form Thorium-232.[ii] It was uncovered in 1828 by Swedish chemist Jons Jakob Berzelius, who, rather imaginatively, named it after the Norse God of Thunder, Thor. Experimentation into the utility of thorium as a nuclear fuel has been relatively unsystematic and underfunded over the past 60 years. Noteworthy examples include investigation into the efficacy of thorium based fuels in Pressurised Heavy Water Reactor 'Candu' units at Canada's AECL Chalk River Laboratories; designs for a thorium fuelled Advanced Heavy Water Reactor in India — construction of which is envisaged for 2022 — and the intermittent operation of a High-Temperature Gas-Cooled 'Dragon' Reactor in the UK, between 1964 and 1973, for a total of 741 full power days. However, it is a series of projects conducted throughout the 1960s at the Oak Ridge National Laboratory in the USA that appeal most strongly to the contemporary imagination.[iii]

The ORNL erected a 7.4 megawatt — a megawatt is equivalent to 1 million watts — prototype Molten Salt Reactor, utilising U-233 as its principal fissile driver; Molten Salt Reactors that utilise fissile thorium are known as Liquid Fluoride Thorium Reactors (pronounced 'lifter' in acronymic form, LFTRs are the most exciting thorium concept and as such shall be the focus of this essay). To elucidate the basic mechanics, LFTRs are bifurcated into two compartments: the reactor core and surrounding thorium 'blanket'. Within the core, isotopic uranium U-233 fissions to expel neutrons, which then exit the core and fuse with fissile Th-233 in the 'blanket'. The fusion with neutrons results in Th-233 transmuting to U-233, which is then transported into the core and fissions to propagate the process — LFTRs 'breed' fuel because of the neutron-dependent transmutation that occurs.

The technical superiority of LFTRs, relative to conventional nuclear, is conferred by numerous structural refinements. Amongst these, automatic temperature regulation nullifies any requisite for control rods or an active cooling system, as in conventional reactors. To be precise: the molten salt is expanded by heat generated through fission in the core, thus retarding the rate of fission. Conversely, if more power is demanded from the reactor, more heat energy is extricated from the saline and the returning cooler salt augments the rate of fission. Overheating is only conceivable if the flow of molten salt is disrupted and heat energy is agglomerated in the core; yet even this hypothetical is liable to a self-checking mechanism: surfeit heat will melt a solid salt freeze plug, allowing the liquid fuel to safely decant into a drain tank.

The reactor is sustained at atmospheric pressure throughout operation; fluoride salts boil at approximately 1400°C, so needn't be pressurised to retain their liquid state. In a conventional Light Water Reactor, water undergoes intense pressurisation to inhibit extrication into a gaseous state — a consequence of which is the requisite to construct highly pressurised containment facilities. LFTRs obviate this bloated hindrance: reducing size, danger and enhancing aesthetics. The fuel in a Molten Salt Reactor is, obviously, molten, so cannot melt-down in the same way that solid fuel in a LWR can. In the rare eventuality that a LFTR is the object of military/terrorist hostility, the liquid fuel would only contaminate the immediate vicinity, leaving the environment largely unscathed. The products of fission would remain in the saline as stable fluorides, and the construction of a rudimentary protective encampment around the plant would inhibit soil leaching.[iv]

LFTRs can be compact, permitting effective operation in inaccessible locations (country towns, military bases, research camps etc). It's even possible to construct Small Modular Reactors at a central site and then assemble them at the desired location — or, to amalgamate them into a more potent productive unit. Unlike conventional LWRs, LFTRs do not require water to be supplied throughout operation, thus negating the requisite for supplementary infrastructure. As such, it becomes viable to locate them in more densely populated areas. Conventional nuclear produces large quantities of radioactive waste, but LFTRs allow you to siphon-off waste products and reprocess transuranics — all the thorium can be fissioned.[v] Although it's true that LFTRs produce radioactive fission products, only 17% of these have long half-lives — approximately 300 years — and LFTRs are spectacularly more efficient than LWRs: utilising 98% of fuel rather than the traditional 2%. Not even the waste products go to waste, because they accommodate a wealth of valuable industrial compounds. Plutonium is not produced, making it exceptionally challenging to construct nuclear weapons. Even superfluous heat energy needn't go to waste: if redirected, it can feed industrial processes like water desalinisation and hydrogen production.[vi]

The structural superiority of the LFTR is compounded by diverse economic advantages. Thorium is three times more abundant in the Earth's crust than uranium, with the largest known deposits in Australia, India, Norway and the USA. Remarkably, the energy in 5000 tons of Thorium would satiate world energy demand for an entire year — and there are 44 million tons of Thorium in the world! A LFTR produces the same quantity of energy from 1 ton of thorium as a LWR does from 250 tons of uranium; and LFTRs, being substantially safer than conventional nuclear, would be capable of jettisoning much of the burdensome regulatory stipulations imposed upon contemporary plants.[vii] According to www.thorium.tv: 'you might be able to go as low as $220 million or below, if 80% of reactor costs truly are attributable to expensive anti-meltdown measures'. By ameliorating the often painful start-up costs, LFTRs could act as a beacon for international capital, allowing for the rapid establishment of a multitude of plants and swift absorption of market share.

Following commercialisation, annual operating costs would nosedive, further incentivising ownership and construction: 'Current operating costs, ignoring fuel costs, for a 1-gigawatt plant are about $50 million/year. With greater automation and simplicity in Generation IV plants, in addition to more reasonable safety and security regulations, this cost will be decreased to $5 million/year' — even fuel will be cheaper: 'Fuelling a 1-gigawatt uranium plant today costs $30 million/year. Fuelling a 1-gigawatt thorium plant will cost only $1 million/year'. Plant ownership would be highly proficuous, and energy consumption more affordable: 'over a 60-year operating lifetime, both plants produce 60 gigawatt-years of power. The total cost for the uranium plant is $4.9 billion, at a rate of $81.6 million per gigawatt-year. The total cost for the thorium plant is $490 million, at a rate of $8.16 million per gigawatt-year. Thorium power makes nuclear power ten times cheaper than it used to be, right off the bat'. Unfettered by the requisite for water transferral and protective encasement, and with fewer transuranic disposal costs, LFTRs are highly economical.[viii]

Besides the aforementioned benefits, the greatest potential of LFTRs lies in the low-emission sourcing of energy. We need to be pragmatic about the transition to clean energy: renewable is promising but inchoate, and nuclear has the industrial horsepower to effect serious change.

With public support and private ingenuity, the 35% of British energy provided by nuclear and renewable could usurp the 37% share of oil, and eventually the remaining third of market share held by natural gas.[ix] Yet, it's important not to become myopic in focusing exclusively on hypothetical environmental benefits, for this risks overshadowing broader implications. Much global conflict is fought over finite energy resources, so, it's imaginable that a superabundance of affordable and sustainable energy would precipitate an age of heightened stability, energy independence and national security — there would be less war and more prosperity. The inextricable correlation between abundant energy and higher living standards means that a stable energy supply is a requisite of future economic growth; modernisation on this scale would widely extend the reach of capitalism in raising people from perdition in the depths of penury. On a symbolic level, it would transform our relationship with the planet, heralding a shift towards a more symbiotic future.

It might strike you as being rather bizarre that governments are only just apperceiving the benefits of green nuclear, but a miserable, stultifying confection of radiophobic media bias, wincingly high research costs and Big Nuclear's vested discouragement — LFTRs would render all exorbitantly pricey uranium plants — in which corporations have large sunk costs — superannuated and obsolete — have made investment impolitic until now. Despite all this, we probably would have had functioning MSRs operating around the world by now if the Nixon Administration hadn't jettisoned the thorium project at ORNL in the 1960s; ironically, it was one of the benefits of thorium, the conspicuous absence of plutonium production, that the administration perceived to be a weakness — the DoD was seeking to use nuclear power to foster its domestic nuclear armaments programme.[x] Political expediency has since resigned any aspiration of resuscitating the research programme to destitution in the graveyard that is the government archives. Only in the USA — and more recently China — have government research budgets had the available funds to finance a serious thorium research programme; so, to put it simply, no one has been willing to foot the bill — it's a classic case of short-terminism triumphing over prudence. What about private firms? Only established energy companies would be able to raise the capital, and every energy company interested in nuclear is already a stakeholder in conventional uranium reactors[xi]: what's the point of sinking money into research for a decade, only to have the eventual conclusion of that research invalidate your principal market assets? Energy companies need to sell the nuclear energy produced — technically converted from chemical to electrical energy, 'produced' may invoke the erroneous notion of energy being generated ex nihilo — by current reactors to justify the massive capital costs associated with establishing those reactors: for firms with a vested interest in conventional nuclear the development of thorium is unneeded and may actually pose an existential threat to their market share (smaller firms have tried, but the fiscal horsepower is lacking). Disparate incidents — Castle Bravo, Chernobyl and Fukushima being the most memorable — have caused the public and media to perceive nuclear with gratuitous cynicism. Less than 40% of people in the UK and US are supportive of nuclear power — in countries like Germany that dips as low as 7% — and this is as much the product of sensationalist journalism as it is general ignorance.[xii] Contrary to popular belief, nuclear power actually obviated an average of over 1.8 million net deaths worldwide between 1971-2009, due to the preclusion of burning fossil fuels to supply this energy and the decreased air pollution and green house gas emissions that ensued[xiii] (that's just conventional nuclear, imagine what thorium would do). A sad series of unfortunate coincidences have culminated to relegate this visionary technology to the slideshows of conference power-points — until now.

Despite an ambitious grassroots campaign in the USA to promulgate awareness, much of the intrigue surrounding thorium has been engendered by the Chinese government. The ravenous Chinese industrial economy demands fuel, lots of it, so their government is frenetically sinking billions into exploring a diversity of conceptual energy sources. Their home-grown thorium research initiative has been expedited, with the aspiration to construct a 2MWt pilot plant (Thorium-Breeding Molten Salt Reactor - Liquid Fuel) by 2018, a 10MWt experimental reactor by 2025 and a 100MWt demonstration plant by 2035. 750 staff will be employed by the project by 2015 — which is a lot as research projects go — so it's fair to say there's no deficiency of enthusiasm for it. In nuclear-averse Norway the opportunity has proved too good to pass up, and private research is underway at the Halden Reactor Project. Having withheld its signature on the Treaty on the Non-proliferation of Nuclear Weapons, India has faced difficulty in importing uranium to fuel their current fleet of nuclear reactors, so aims to construct a Heavy Water Reactor capable of utilising their extensive domestic thorium reserves. It's reasonable to posit that the USA will eventually join in: forecasts reveal that domestic coal production will decline over the next decade, and LFTRs would be an intelligent substitute. So, the future of energy is at a crossroads: we either turn a blind eye to pioneering green nuclear technology and go it alone with renewable, or, we adopt a mixed, pragmatic approach, and permanently refashion mankind's relationship with the planet.

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[i] http://www.forbes.com/sites/kirksorensen/ [ii] http://www.ncpa.org/pub/ib149 [iii] http://www.world-nuclear.org/info/current-and-future-generation/thorium/ [iv] http://www.the-weinberg-foundation.org/wp-content/uploads/2013/06/Thorium-Fuelled-Molten-Salt-Reactors-Weinberg-Foundation.pdf [v] http://www2.hmc.edu/~evans/LamThorium.pdf [vi] http://thoriummsr.com/intro/pros-and-cons-list/ [vii] http://en.wikipedia.org/wiki/Thorium [viii] http://www2.hmc.edu/~evans/LamThorium.pdf [ix] http://www.eia.gov/countries/country-data.cfm [x] http://thedigitalfirehose.blogspot.co.uk/2013/09/why-are-we-using-uranium-instead-of.html [xi] http://en.wikipedia.org/wiki/List_of_companies_in_the_nuclear_sector [xii] http://www.bbc.co.uk/news/science-environment-15864806 [xiii] Pubs.GISS: Kharecha and Hansen 2013: Prevented mortality and greenhouse gas emissions from historical... (nasa.gov)