Thorium energy has the potential to revolutionise our entire civilisation.
If we look back at previous leaps forward in human technology- the development of the light-bulb, the internal combustion engine and the internet- all of these dramatically reconfigured how we behave as a society. These developments relied on the continued and insatiable demand of the human race for energy, something that is already limiting the further development of many countries and potentially poses the largest threat to world peace. The developing world continues to carve up the remaining oil, natural gas and coal reserves to protect their own interests, but what if human’s next bright idea not only addressed all of these problems and ensured continued global development, but also came from work pioneered by physicist Alvin M. Weinberg 50 years ago….
Nuclear fission, the energy released from splitting the atoms of nuclear fuels, is the most awesomely powerful reaction we can generate on earth. On the other hand, the huge yield of energy produced by nuclear reactions are sadly a cause of fear in our current society as a result of the decision to utilise this power for the generation of plutonium, the fissionable element produced as a bi-product of conventional nuclear reactors and ingredient number 1 in nuclear bombs.
So where does this energy come from?
Well the famous equation e = mc2 states that energy (e) is equivalent to mass (m) multiplied by the speed of light squared (c2). I’d be quite surprised if you hadn’t already heard of this but when we actually consider what it means- it tells us that matter, every atom within the universe, contains a huge amount of energy just waiting to happen and that matter and energy are equivalent and just different forms of the same thing.
Since c2 is such a unimaginably vast number (the speed of light is 299,792,458 metres per second which is then multiplied by itself and the mass of the object) the equation is saying there is a truly enormous amount of energy held in all matter. The average sized human contains 7 x 1018 joules of potential energy which is enough to explode with the force of 30 hydrogen bombs. Fortunately for everyone all of this energy cannot be liberated, and even the most efficient nuclear reactors only use about 2% of the fissionable material which they’re fed thanks to the outstanding stability of the atom and a poor decision by the Nixon administration, which we’ll hear more about now.
Both nuclear fission, the splitting of atomic nuclei, and fusion of atomic nuclei liberate vast quantities of energy. It seems impossible that both formation and destruction of an atoms nucleus could yield energy, but this is dependent on the type of nuclei used and there inherent stability. The most stable nuclei in nature are of moderate size, such as iron, hence fission of larger nuclei such as uranium-235 used in fission reactors into smaller more stable nuclei (closer to iron, Fe-55), whereas fusion uses smaller nuclei (hydrogen and helium) to make larger ones.
In nuclear fission, the atomic nuclei of uranium-235 is split by bombarding the positively charged nucleus with neutrons causing the formation of unstable isotopes that split releasing energy and further high energy neutrons. These then collide with adjacent atomic nuclei inducing a chain reaction that produces several fission products including plutonium-239.
If you could annihilate the nuclei of atoms with sufficient force, fission could be possible with numerous elements, unfortunately our choices are extremely limited to the two main “fissile” elements: Uranium-235 (which accounts for less than 1% of all uranium) and Uranium-238 (an alternate isotope that is less fissile but much more abundant) and Thorium-232 (at last!) that is technically “fertile”. This means it can be converted to fissile uranium through neutron absorption within the reactor and subsequent nuclei conversion, meaning thorium can be used in “breeder” reactors that allow the conversion to fissile uranium within the core, a highly efficient method that allows 99% of the Thorium-232 to be used in the reaction.
Unfortunately the advent of this technology coincided with a wartime scenario and nuclear proliferation during the cold-war and subsequently uranium-235 (the least abundant, most inefficient choice) was chosen as a source for both nuclear power and plutonium for nuclear bombs.
It is only now that the world is waking up to the benefit of thorium-232 as a nuclear fuel.
Mining 800,000 tonnes of uranium ore yields only 250 of fissionable uranium, only 2% of which is actually used during the nuclear reaction. This is because the likelihood of splitting the uranium nucleus is reduced due to the large size of the uranium atom, furthermore uranium is often stabilised within ceramic plates within nuclear reactors – this reduces the accessibility of the fuel and increases the chances of uranium instead decaying to Xenon-119 rather than splitting and releasing energy. Xe-119 is a major “neutron poison” as is absorbs neutrons and decreases both yield and efficiency of the reaction.
If you were to mine 1 cubic meter of bedrock an extract the thorium from this rock you would get about 12g of the element, which is enough to power every single electrical appliance you will use for the next 15 years. But it gets better, 83% of the fission products produced in thorium reactors is safe after 10 years, and the remaining matter is safe after 300 years.
What’s the half-life of uranium fission products? Well anywhere from 23,000 to 704,000,000 years depending on the product, which at the moment we seal in concrete and bury forever – a messy, expensive and ridiculous solution to a problem that shouldn’t exist.
Liquid fluoride thorium reactors (LHFR):
Thorium reactors are entirely different from conventional light water reactors (LWR), as they are known. A thorium reactor converts Thorium-232 into fissile Uranium-233. The entire reaction is carried out at approximately 14000C compared to the puny 3000C of conventional reactors. This is because thorium reactors use soluble fuel, with the thorium fuel dissolved into a highly concentrated fluoride, lithium, beryllium salt solution. These are extremely thermo-stable solutions and allow the reactor to both operate with, and be cooled by, this mixture. Convention light water reactions use highly pressurised water to keep it liquid at 300oC to cool the core. This feature dictates the entire conventional reactor design, and a failure in coolant is actually what lead to the Chernobyl disaster in Ukraine in 1983 as pressurised water at 300oC when released expands to roughly 300x its size, damaging the reactor and preventing coolant reaching continuing chain reaction within the core.
In a thorium reactor a “cold” blanket of fertile material surrounds the reactor core – this thorium-fluoride salt is yet to be bred into radioactive uranium-233 and insulates the core at the extremely high reaction temperatures. Ingeniously this design of reactor also naturally “saves itself” following a loss of power to the reactor (as occurred in the Fukishima meltdown) or a leak in the coolant blanket. Should this occur the coolant will simply drain into a reservoir tank and as this coolant is also the fertile (but not fissile) fuel crucial for the reaction – the reaction stops itself. It’s a nuclear reactor you can just switch off, and more amazingly, cannot have a meltdown!
I am sorry to keep ramming this down your throats – but this type of reactor is also capable of safely destroying current nuclear waste, and actually produce energy at the same time, and thorium-232 itself is a lightly radioactive highly abundant element that American current has 5000 tonnes of this buried as a bi-product of mining operations – enough to meet the entire countries energy needs for a year.
Want even more good news!!?
Due to the extremely high reaction temperatures of these reactors, they could also be used to drive the combination of atmospheric CO2 and H2O into hydrocarbons usable as fuel. That’s right, carbon neutral petrol! We could also use this waste heat from the reactors to:
- Desalinate water in areas that have low freshwater
- Split water to generate H+ for fuel cells that producer no CO2 – without the need for energy hungry electrolysis…..
The list goes on and on.
So there you have it. Thorium energy has awesome potential – and we’ve had the technology to do this for 50 years, making the transition to a new energy source even more feasible.
You may be interested to know that Princeling Jiang Mianheng, son of former leader of china Jiang Zemin purchased the blueprints for LFTRs in 2011 from the Oak Ridge laboratories where the technology was pioneered in the 1960s. Mr Jiang is spearheading a project to utilise thorium power to meet the countries insatiable energy needs and will have 750 staff working towards this goal by 2015, most of them PhD students in applied nuclear physics. Unfortunately the UK isn’t taking a stance on thorium energy – but once the technology becomes widespread it will be impossible not to yield to it benefits, and with the promise of sustainable, safe energy reserves capable of lasting us for the next 20,000 years how the hell are you going to explain why you chose not to 100 years in the future when the oil runs out……
If you would like to read more on the subject, this is a nice follow on article: http://www.inlec.com/blog/2014/06/the-big-debate-could-thorium-save-the-world-from-global-warming/
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Peter McIntyre, Akhdiyor Sattarov (2010). Accelerator-driven thorium-cycle fission: Green nuclear power for the new millenium Beyond the standard models of particle physics, cosmology and astrophysics DOI: 10.1142/9789814340861_0011