Is thorium renewable

Thorium: green nuclear energy?

The story takes place in Norway. An ecological government comes to power and causes a stir. The Prime Minister announces the final phase-out of the utilization of fossil fuels in favor of green nuclear energy: thorium. This scenario from the hit Norwegian television series Occupied could soon no longer be fiction. In view of its enormous potential, the mineral is increasingly becoming the focus of interest. But can this long-awaited wonder resource really solve all of our pollution problems?

A metal with a divine name

Thorium is anything but a new discovery. It has been known for almost two centuries. To be precise, it was discovered in Norway on the island of Løvøy and sent in 1829 to the Swedish scientist Jöns Jakob Berzelius (1779–1848) for research. He determined that it was a new element and named it after Thor, the god of thunder in Norse mythology. Interestingly, the metal remained unused until 1885, when the gas incandescent body was invented. It was used until the incandescent lamp market collapsed at the end of World War I. In 1898 the German chemist Gerhard Carl Schmidt (1865–1949) and two months later the famous physicist Marie Curie (1867–1934) discovered the radioactivity of thorium. Thorium experimental reactors were built in the 1950s, but research was quickly stopped in favor of uranium.

Much has changed since then. Uranium-235 is a non-renewable raw material. The recoverable deposits are expected to be exhausted by 2040, and many countries such as China, India, Japan and Norway are increasingly shifting their focus to the thorium industry.

A mineral with many benefits

It should be noted that thorium has many advantages over uranium. Since its half-life is very long (about three times the age of the earth), it is abundant in the earth's crust and is present in the form of a single isotope, thorium-232. Large deposits are found all over the world, and thorium is found underground in almost every country in the world. It is slightly radioactive and only dangerous if inhaled or ingested in large quantities. It is powerful and has a high overall efficiency. It can be used 100% and does not need to be enriched. In comparison: only a small percentage of uranium can be recycled. The nuclear fuel cycle when using thorium reduces waste. The majority of radioactive waste therefore has a half-life of less than 50 years!

The only problem lies in the realization of these thorium power plants. In contrast to uranium-235, which is used in modern nuclear power plants, thorium is not fissile but can only be incubated. Direct energy generation through nuclear fission is not possible. It must first be converted into uranium-233 - a cleaner fissile material than the fuels currently in use - but to do this, plutonium-239 must be added, which is, however, made in today's nuclear reactors. As paradoxical as it may sound, the thorium cycle does not function independently at the beginning and must first go through the uranium cycle. Over time, plutonium is no longer required in the production of uranium-233 and the reactors that are operated with the uranium cycle can be saved. However, according to some experts, this transition period should last at least a hundred years.

Fewer accidents ... on paper

Harnessing energy from thorium also requires the development of very innovative reactors. So far, however, these have only existed on paper. Various approaches have been proposed and the most promising is the utilization of thorium in molten salt reactors. The nuclear fuel is in liquid form dissolved in molten salt (600 to 900 ° C). This simultaneously acts as a moderator, carrier medium (which transports the heat between two or more temperature sources) and as a shielding barrier.

Finally, the question of security arises. Although molten salt reactors should not get out of control as in the case of Chernobyl or Three Mile Island, they do not protect against malfunctions in the cooling system (scenario as in Fukushima). A nuclear power plant generates residual heat even after it has been shut down properly. This heat must be dissipated, otherwise the temperature will rise inexorably and the system will be destroyed. Molten salt reactors are no exception. Also, one must not forget that nature is much more resourceful than humans when it comes to disasters ...