“You can run a civilisation on thorium for hundreds of thousands of years, and it’s essentially free,” says Kirk Sorensen, former NASA engineer and one of today's forward looking nuclear technologists. This week we look at the progress that has been made in developing thorium-based nuclear reactors, global stores, and why China and India believe this ‘miracle metal’ could be the next best thing.
By Heba Hashem, Middle East Correspondent
Thorium versus Uranium
A tonne of thorium - the slow-decaying, slightly radioactive metal - produces as much energy as 200 tonnes of uranium, or 3,500,000 tonnes of coal. Besides being much cheaper, thorium is three times more abundant than uranium, so much that miners treat it as a nuisance, being a radioactive by-product when digging up rare earth metal.
Unlike uranium, thorium is a low-carbon metal, and although not fissionable, it can be used as a nuclear fuel through breeding to fissile uranium-233 (U-233). Thorium decays its own hazardous waste and can expel the plutonium left by uranium reactors. Also, thorium cannot melt down and does not produce reliable fuel for bombs.
Both uranium and thorium are mined as ore and then detached from the rock, but thorium is four times more prevalent in Earth's crust than uranium.
“Thorium has the potential to be the backbone of our energy future, and we need to move quickly towards it,” says Kirk Sorensen, a former NASA rocket engineer and now chief nuclear technologist at Teledyne Brown Engineering.
Typical nuclear power stations use uranium as their fuel source, but thorium reactors can offer greater safety, vastly reduced waste and much higher fuel efficiency. While only 0.7% of uranium’s energy is extractable, energy from thorium is 100% extractable.
“Once you start looking more closely, it blows your mind away. You can run a civilisation on thorium for hundreds of thousands of years, and it’s essentially free. You don’t have to deal with uranium cartels,” says Sorensen.
What if thorium was used to power nuclear reactors?
To replace coal we must consider material inputs, and for the renewables they are high –approximately 5 times the steel and concrete required per megawatt generated.
Thorium energy can be used to replace petroleum fuels, desalinate water, and provide heating. Although not fissile itself, Th-232 will absorb slow neutrons to produce the fissile and long-lived U-233.
According to the World Nuclear Association (WNA), the irradiated fuel can be unloaded from the reactor, the U-233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle.
Alternatively, U-233 can be bred from thorium in a blanket, the U-233 separated, and then fed into the core.
When it comes to the process of converting thorium to energy, the Liquid-Fluoride Thorium Reactor (LFTR) would prove ideal.
This is because the LFTR uses liquid fluoride fuel to carry the uranium and thorium in a two-fluid arrangement designed to follow thorium’s natural conversion to protactinium, uranium, and then to energy.
On the other hand, the more modern version of LFTR would couple the fluoride reactor to a closed-cycle gas turbine, and enable the extraction of energy from thorium at efficiency roughly 300 times greater than we currently get from uranium in existing reactors.
“This radical improvement in efficiency means that the world energy needs would be supplied with about 6000 tonnes of thorium rather than the 65,000 tonnes of uranium, 5 billion tonnes of coal, 32 billion barrels of oil, and 3 trillion cubic meters of gas we use today”, explains Sorensen.
While there are development and construction costs are not yet estimated; hypothetically speaking the underlying costs could be significantly less than current ones as the low-pressure operation and compact size would result in much cheaper construction costs.
Moreover, small modular thorium reactors can be built as “drop-in” replacements for coal plants, minimizing the cost of transition.
Economy leaders race to thorium
The idea of using thorium in nuclear reactors was conceived in the fifties and was last researched in US in the early seventies at the Oak Ridge National Laboratory in Tennessee.
More than three decades (in 2010) the Department of Energy approved $200,000 funding at Oak Ridge for analytical studies of the Molten Salt Reactor (MSR) using thorium and uranium.
In Asia, both India and China are progressing towards achieving thorium-based nuclear energy.
"They have tons of thorium and almost no uranium resources," Dan Ingersoll, senior program manager for nuclear technology programs at Oak Ridge National Laboratory points out.
In February this year, the Chinese Academy of Sciences announced it will finance a programme to develop a Thorium Fuelled Molten Salt Reactor (TFMSR).
The Academy stated that the goal was to develop a new generation of nuclear energy systems and to achieve commercial use in 20 years or so.
“We intend to complete the technological research needed for this system and to assert intellectual property rights to this technology,” an academy statement read, in regards to its Chinese TFMSR programme, headed by Dr Jiang Mianheng.
Meanwhile, India's ambitious three-stage energy security plan will be exploiting the country's vast reserves of thorium- which could make India a leading global exporter of the more efficient alternative nuclear technology.
Stage two in particular will involve using reprocessed plutonium to fuel “fast reactors” that breed more U-233 and plutonium from thorium and uranium.
This will be followed by stage three, in which advanced heavy-water reactors will burn U-233 while converting India’s thorium reserves into further uranium within a sustainable “closed” cycle.
The United Kingdom is also jumping on India’s thorium bandwagon, with five nuclear-research proposals being jointly funded by the U.K.’s Engineering and Physical Sciences Research Council (EPSRC) and by India’s Department of Atomic Energy of which EPSRC is investing £1.2m.
It is worth noting that the most common source of thorium is monazite, a rare earth phosphate mineral found in igneous and other rocks, although the richest concentrations are in placer deposits, concentrated by wave and current action with other heavy minerals.
World monazite resources are estimated to be about 12 million tonnes, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India.
Locating the world’s thorium reserves
Thorium resources are plentiful everywhere, but Australia and the US are said to have the largest deposits.
A single thorium site in Idaho could provide nearly all the world’s yearly demand for thorium, with its large vein deposit of thorium and rare earth metals.
“But long before we even need that, there’s 3200 tonnes of thorium sitting in the desert of Nevada, neatly separated for us, that the US would probably give to the UK for free–if they paid the cost of shipping”, Sorensen points out.
The 2009 IAEA-NEA "Red Book" states a figure of 3.6 million tonnes of total known thorium resources.
According to 2007 figures, Australia alone had 489,000 tonnes of thorium resources; accounting for 19% of the world’s total, while the US had 400,000 tonnes. Next came Turkey, with 344,000 tonnes, followed by India - 319,000, Brazil- 302,000, and Venezuela- 300,000.
In addition to India, the Czech Republic is also exploring LFTR similar to the reactors tested at Oak Ridge.
"You don't have to be a superpower to do this," Sorensen said. "You could be a state to do this. If the state legislature of Ohio said, 'We want to become the thorium state,' it could. "A handful of engineers in the '50s did it”.
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