What is Thorium?
Thorium was discovered in 1828 by Jöns Jacob Berzelius. Thorium is referred to by the symbol “Th” in chemistry. The word “thorium” is a word derived from Thor, the god of thunder mentioned in mythological Norse legends.
It has an atomic number of 90, an atomic weight of 232, and a density of 11.7 grcm3. Its melting point is 1750 degrees and its boiling point is 4790 degrees. It is located in the 3-D group of the Periodic table in Chemistry. Color is silvery white, lead color. Thorium, found in the actonides element series, is a radioactive element and constitutes 0.0007% of the earth’s crust.
Nuclear power, which is obtained as a result of the splitting of the nuclei of uranium and plutonium atoms, makes important contributions to the supply of controllable energy for human beings in various countries today. Like uranium, thorium is a nuclear fuel raw material.
Thorium, like uranium, is not found in free form in nature, but is found in about 60 minerals. Of these, only monazite and thorite are used in the production of thorium. These minerals are also often found together with rare earth elements.
Thorium is a nuclear fuel raw material waiting for its turn. The biggest reason for this is the problem of the nuclear fuel cycle. Thorium-232 can be converted to uranium-233 by some processes. Thorium-233 is a fissile material like uranium-235. As a result of this fragmentation, a great amount of energy is released. Due to the fuel cycle problem, there are currently no commercial-scale power plants powered by thorium, although prototypes of these power plants have been trialled for a long time in the UK, Germany and the USA.
Due to the lack of consumption on a commercial scale, the consumption of thorium as an energy raw material is almost non-existent. Apart from its use as an energy raw material, there is still no bed operated solely for thorium, since the amount of thorium consumed in different areas of use is not high and the world production of around 700 tons of ThO2 per year is obtained entirely from monazite as a by-product.
Countries reporting thorium reserves; Egypt, Australia, Brazil, Republic of South Africa, Canada, Argentina, Norway, Thailand and Turkey are the countries that have declared thorium reserves. These countries, which are thought to have a total reserve of around 658,000 tons, constitute a source for thorium.
Today, its consumption as a stagnant raw material is almost negligible. There is still no bed operated solely for Thorium. However, Thorium is the nuclear fuel raw material of the future.
Historical Developments in Thorium
• In 1885, thorium began to be used in gas lamp liners.
• High purity metallic thorium was isolated in 1925 by Dutch chemists Anton Eduard van Arkel and Jan Handrik.
• In the 1960s, thorium nuclear fuel tests began.
• In 1976, thorium began to be used in nuclear power reactors.
• Between 1983-1989, a 300 MW thorium high temperature reactor was tested in Germany.
SEE ALSO: Top 5 Deadliest Elements on Earth
Uses of Thorium
Thorium is an important energy source due to its radioactive property. It is a fuel with a more environmentally friendly identity among nuclear reactors. Compared to uranium, it is less harmful to nature. It produces less plutonium and transuranium elements than uranium in the fuel cycle. Therefore, it can replace uranium as a nuclear fuel.
There are no commercial and economic scale nuclear facilities working with thorium. However, efforts are being made to use it as a nuclear fuel. In case thorium starts to be used in nuclear power plants, the existing reserves gain commercial importance. And its economic value can be determined.
Thorium cannot be used alone as a nuclear fuel in today’s conditions. Th-232, a fertile isotope, must be converted to U-233, a fissionable isotope by swallowing a neutron. As a result of the reaction of Th-232 with low-energy neutrons (neutron absorption), the less stable Th-233 is formed first.
Th-233, on the other hand, transforms into Pa-233 (protactinium) within 23 minutes by emitting a beta particle. Thorium is not a fissile element. Pa-233 transforms into fissile U-233 with a half-life of 163,000 years in 27 days. Th-232 begins its productive cycle with another fissile substance such as U-235 or Pu-239.
Thorium – Uranium mixed fuels produce less plutonium than uranium fuel. It can also work at a high burning rate. This, in turn, contributes to the increase of the plant capacity factor by extending the residence time of the fuel in the reactor, that is, the fuel reloading period.
Thorium has several ways to produce energy.
A plant developed in India uses solid thorium fuel in water-cooled reactors similar to those found in today’s uranium-based power plants.
A completely different approach being explored in China and the United States is the liquid fluoride thorium reactor (LFTR or “lifter”). This technology was developed by the American government in the 1960s for prototyping, but attempts were pushed back because it coincided with weapons production. The researchers argue that its potential is much greater than the water-cooled approach because LFTRs can extract a higher percentage of energy from thorium fuel.
A third possible approach, encouraged by particle physicists such as Nobel laureate Carlo Rubbia, would be to use thorium in critical accelerator-powered reactors. However, this remains in the field of nuclear engineering rather than scientific theory.
World Thorium Reserves
According to IAEA/NEA 2014 data: