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A startup energy company, called Marathon Fusion, may soon be living out the dream of alchemists from the Middle Ages. In a recently released posted to the arXiv preprint server, the company outlines a method to turn an isotope of mercury, ¹⁹⁸Hg, into ¹⁹⁷Au, the most stable form of gold.

They say this can be done while also creating an abundance of clean energy via nuclear fusion in a tokamak reactor. Maybe even more impressive is the amount of gold they say this process will create—2 metric tons of gold per gigawatt of thermal power per year, according to their simulations.

Chrysopoeia—the process of transmuting base metals, like mercury, into gold—has been demonstrated at small scales using particle accelerators and neutron capture in the past, but never in an economically viable way. Marathon Fusion's idea is to make both gold production and energy production economically viable through this new method. They believe this will help facilitate the deployment of fusion energy at scale and, ultimately, to achieve enough energy abundance to make an impact on climate change.

They say, "Implementation of this concept allows fusion power plants to double the revenue generated by the system, dramatically enhancing the economic viability of fusion energy."

The method involves incorporating mercury in the reactor's breeding blanket—a layer surrounding the plasma chamber—which is usually made from lithium. This new mercury/lithium alloy blanket is designed to maximize (n, 2n) reactions, which absorb one neutron and release two. The result is optimized tritium fuel production and gold production. When the fast neutrons created by this process bombard the ¹⁹⁸Hg, the ¹⁹⁸Hg is converted into unstable ¹⁹⁷Hg, which then decays into stable ¹⁹⁷Au.

The half-life of ¹⁹⁷Hg is only about 64 hours, so the decay into gold is relatively fast. However, small amounts of other radioactive isotopes are also created in the process, requiring a "cooling time" before the end product can be released to the public. A general, but conservative, rule is that the radioactivity must be less than that of a banana, and for this particular gold product, that comes out to a cooling time of about 17.7 years.

The study authors don't seem to be deterred by this impediment though. They say, "In practice, given that much of all gold is used to store value and is not actively in use, we do not expect the need to store it for 7–17 years to be a major impediment; at worst, it means that the product will initially have somewhat less value than pure ¹⁹⁷Au, and so some discount should be applied to the value of freshly produced gold."

Still, the implementation of this energy-creating alchemy machine may be several years away, as the study has only implemented this idea in simulations. While the simulations are promising, there are still some other hurdles to overcome, like finding the initial inventory of enriched mercury and reactor materials that can handle the process.

If it does pan out, however, this method would be a boon for environmental preservation—not only creating clean energy, but also reducing harmful gold mining activity.

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