Thorium can be found quite easily around the world – it is four times more abundant than Uranium – which is the preferred choice for power generation from nuclear energy. We have always had this choice between Uranium and Thorium, but just before the Second World War, politicians chose Uranium because of the useful weapon by-product, plutonium which can be used for making the biggest of all bombs! And depleted Uranium, too is very useful – it can be used for tips on ammunition as it is very hard and toxic! So, clean, safe, cheap and plentiful Thorium was neglected.
Luckily, experimental Thorium power was first developed by the US Navy for submarines. The principle of power generation using Thorium had been proven, so later, the idea was taken further by the Oak Ridge National Laboratory in Tennessee, who successfully built a Thorium “Molten Salt Research Reactor” that ran for five years producing power in the 1960’s.
Generally speaking Thorium reactors are scalable, they can be made large or small and compact to suit their application. The Oak Ridge reactor was quite small, the biggest part was the reactor chamber column, it being some 18 feet tall and at its largest diameter, six feet wide. A Thorium plant is not intricate or complicated like a modern aircraft or even a car, having few moving parts! Because it works at around 7- 800o C it is very heat efficient, and can drive an energy turbine which is quite small, too – as small as a desk! But they can give off enormous heat and energy all derived from an easily obtained fuel!
The Next Great Energy Market
Because of environment issues, energy from Thorium reactors has become a very interesting business proposition to many countries around the world, China and India in particular. Many countries see Thorium power plants as the answer to the world’s energy problems and are racing to research, develop and market various designs for sale all around the world.
There is a quiet race on, to get it market- able. It is small, and can be manufactured in modules or units, and a new Thorium power plant is expected to be cheaper than a coal or uranium power plant. An added bonus is that it can also produce useful, marketable chemicals and gases as by-products. These machines can be located almost anywhere where needed as they require no cooling water. The demand promises to be very great – it is sure to be a ‘hot seller’ once it is developed and has the necessary safety approvals. Thorium reactors can produce vast quantities of electricity burning up its fuel almost entirely, leaving a small residue to be stored safely (for up to 300 years.) And of course .. .. .. .. each unit naturally creates high quality employment.
Research and development has to continue for the present. There are no corrosion problems say its supporters, with the latest development of nickel super stainless steel but they admit to problems keeping valves serviceable at those high temperatures.
There is no pressure containment problems as Thorium, FLIBE, reactors run at atmospheric pressure. They have “walk away” safety: they have to be stimulated to keep going, quite the opposite to ‘continuous upper threshold limit’ of Uranium power generation. Storage of feed Thorium prior to its use presents no problems as it can be just piled high in bins or storage areas – it is earth, after all. It can’t react by itself, but needs to be triggered by a neutron source.
Low radiation
Thorium is a low-level Alpha transmitter with a 12.5 Billion year half – life. Therefore, the sodium in bananas emits more radiation and can be said to be more dangerous. The ash from coal fired generation is more radioactive and so, more dangerous. Thorium is not water soluable and cannot be metabolized – absorbed by the human body. It has 6 million times more energy than coal per unit. This mineral is a by-product of other mining operations: it is usually mined and dug out along with other minerals. In Sri Lanka and India there are large deposits of rare earth mineral sands which can easily be scooped up. But, if necessary, Sri Lanka can negotiate to buy prepared Thorium feed from India.
It would be a very useful research activity if Sri Lanka employs chemists to discover ways of purifying their own feed material in order to get pure Thorium – JOBS for Sri Lankans! Being dependent on imports comes with a risk – of uncertainty concerning delivery time, quality and cost.
Chemical Thorium – a Metal with a half-life of the Universe!
It is the chemical element with symbol ‘Th’ and atomic number 90. It is a radioactive actinide metal. Thorium is one of only two or three significantly radioactive elements that still occur in nature in large quantities as a primordial element – chiefly, Uranium.
A Thorium atom has 90 protons and therefore 90 electrons, of which 4 are valent electrons. Thorium is a silvery metal which tarnishes to black when exposed to air, forming the di-oxide. Thorium is weakly radioactive and all its known isotopes are unstable. Thorium has a half-life of 14.o5 Bn years, or about that of the age of the Universe: it naturally decays slowly.
It is refined chiefly from Monazite sands, as a by-product of extracting ores or rare-earth metals. At room temperatures Thorium has a face-centred cubic crystal structure – and the usual major impurity is Thorium Di-oxide. The melting point is 17500C – above Actinium (12270C) and Protactinium (15600C)
Thorium can form alloys with many other metals and is known to improve the strength of weak Magnesium.
Types of Thorium -based Reactors
According to the World Nuclear Association there are seven types of reactors that can be designed to use Thorium as a nuclear fuel. The first five listed have entered operational service at some time in the recent past:
1) Heavy Water Reactors (PHWRs)
2) Hi Temperature Gas-cooled reactors
3) Boiling (light) water reactors (BWRs)
4) Pressure (light) water reactors (PWRs)
5) Fast Neutron reactors (FNRs)
6) Molten Salt Reactor (MSR, LFTRs)
– Oak Ridge National Laboratory demonstrated MSR from 1965 -69.
7) Accelerator Driven Reactor (ADRs)
8) Aqueous Homogeneous Reactors have also been built and seven are in operation as research reactors.
Unlike natural Uranium, natural Thorium contains only trace elements of fissionable material (such as 231Th) which are insufficient to initiate a nuclear chain reaction, so additional fissile material or a neutron source is necessary to initiate the fuel cycle.
The Future
Progressive intellectuals think Thorium is extremely important for the next step for clean, safer nuclear power generation. Georgia Institute of Technology in the US, say Thorium-based power can mean a 1000 years’ solution or a high quality way of reaching a truly sustainable energy future, solving a huge portion of mankind’s problem of negative environmental damage. They say, small prototype plants should be built.
China, India, Norway, Israel and Russia (where Sri Lanka??) are building Liquid Fluoride Thorium reactors (LFTRs) – molten salt reactors and doing research. India has the largest supplies of Thorium in the world. The Bhabha Atomic Research Centre (BARC) plans to make India Energy independent by 2050.
Last October (2021) the Russian ambassador kindly offered to help Sri Lanka in this field. The offer was not taken up.
In 2016 it was first proposed that Sri Lanka should have its own qualified, trained specialists to study this important area of energy from Thorium. The time opportunity cost, loss must be considered as substantial.
PH., 27/2/2022 -RESUBMITTED BY R.O.S