Friday is here, and the weekly 'A Taste of Science for the Weekend' column is back — number 60 💫
And this time — about nuclear fusion, mercury, and how to combine them to produce... gold!
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The dream of producing gold and growing ever richer has accompanied humanity since the alchemists of the Middle Ages.
Their attempts always ended in disappointment, but an American startup called Marathon Fusion claims it has succeeded in turning mercury into gold.
The process has yet to be conclusively proven, but the scientific explanation behind it sounds remarkably plausible.
How does it work?
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Nuclear fusion is a process in which two atoms merge into one, releasing an enormous amount of energy.
It is a technology still under development, and if it does reach commercial use, it will provide nearly unlimited energy and change the world entirely.
A nuclear fusion reactor is based on the fusion of deuterium and tritium.
Unlike deuterium, which can be readily extracted from seawater, tritium is an extremely rare material, and must therefore be produced within the fusion reactor itself.
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To produce tritium, the reactor walls are coated with lithium.
When a neutron strikes lithium, it is absorbed and converts the lithium into an unstable isotope that decays into tritium and helium.
The tritium produced is then used to sustain the ongoing fusion process.
In addition to lithium, the coating also contains another element — such as beryllium or lead — whose role is to absorb one neutron and emit two in return, thereby supplying the neutrons needed to convert lithium into tritium.
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The lead can be replaced with mercury, and that is where the magic happens.
Like every element, mercury has various isotopes.
An element is defined by the number of protons and neutrons that make it up, while its isotopes are distinguished by the number of neutrons they contain.
Mercury-198 is an isotope of mercury containing 198 particles in its nucleus (118 neutrons and 80 protons), and in nature it accounts for only about 10% of all mercury.
When mercury-198 is added to the reactor walls, it absorbs one neutron and emits two, thereby becoming mercury-197.
Mercury-197 is an unstable radioactive isotope — it radiates energy into its surroundings and decays within a matter of days into gold-197.
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A future 1-gigawatt fusion reactor could produce between 2 and 5 tonnes of gold per year as a valuable by-product.
The drawbacks are the need to refine mercury-198 to the purity required for the process, and the fact that a commercial nuclear reactor does not yet exist — it may be decades before we see one.
On top of all that, the gold produced is radioactive and must be stored in complete isolation for 18 years before it becomes safe to use.
And yet, gold is a strategic asset stockpiled by governments for the long term, and the prospect of easily gaining tonnes of it is one more compelling reason to invest in nuclear fusion.
Shabbat Shalom 😊
In the video: New Zealand's largest gold mine, from the YouTube channel Earthmovers Media
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