Is China Gaining an Edge in the Undersea Race?
Uranium is the most common fuel for nuclear power plants, but it is a limited resource on land. It is estimated that the oceans of the Earth contain about 4 billion tons of uranium, which is 1,000 times the amount found on land (extracted from ore). On land, uranium is rare!
However, extracting uranium from seawater is more expensive than mining it from ore. How can this issue be resolved?
The Race for Renewable Nuclear Energy
The United States, Japan, and China are competing to be the first country to produce fully renewable nuclear energy. Specifically, nuclear fuel made from uranium extracted from seawater makes nuclear energy completely renewable.
Forbes cites research from scientists stating that uranium is dissolved in seawater at very low concentrations, only about 3 parts per billion (3 micrograms/liter). However, since the Earth is covered by oceans for 3/4 of its surface, there is a vast amount of seawater—approximately 350 billion trillion gallons. Therefore, there are about 4 billion tons of uranium in seawater at any given time.
Nevertheless, the concentration of uranium in seawater is controlled by chemical reactions in a stable (or pseudo-equilibrium) state between water and rock in the Earth’s crust, both in the ocean and on land. This results in a total of 100 trillion tons of uranium. Thus, whenever uranium is extracted from seawater, more uranium is washed out from the rocks to replace it, maintaining the same concentration.
The amount is so large that humans cannot extract enough uranium in the next billion years to reduce the overall concentration of uranium in seawater, even if nuclear power provides 100% of our energy and humanity exists for a billion years.
In other words, uranium in seawater is truly renewable. It can be renewable like solar energy.
Essentially, uranium in the Earth’s crust is finite. The same goes for the Sun—humans often assume this giant star is an infinite energy source, but it will eventually burn out, though that won’t happen for another 5 billion years. Even the winds on Earth will cease around that time as our atmosphere boils during the initial death of the Sun in the form of a Red Giant.
Thus, this finiteness is so large that it is almost infinite by human standards!
The oceans contain 4 billion tons of rare elements (compared to land), and that is the primary fuel in nuclear power plants.
According to Professor Jason Donev from the University of Calgary (Canada): “Renewable literally means ‘to make new again.’ Any resource that is naturally replenished over time, such as the generation of wind or the growth of biological organisms for biomass or biofuels, can definitely be renewable. Renewable energy means energy that humans harness from nature will continuously be replaced or offset by itself. And now uranium fits this definition.”
Therefore, by any definition, solar energy, wind, hydropower, and nuclear energy can be considered renewable. And this is when the U.S., Japan, and China embarked on the race to produce renewable nuclear energy (specifically, extracting uranium from seawater).
China Awakens the “Giant Treasure”
According to calculations, the 4 billion tons of uranium in seawater is about 1,000 times more than the uranium deposits found on land (in ore form), Xinhuanet reports.
This 4 billion tons of uranium could fuel thousands of 1,000 MW nuclear power plants for 100,000 years.
Even though it exists, the current processes for extracting uranium from seawater are economically inefficient and not competitive with mining uranium ore on land.
That is why researchers around the world have been working tirelessly to develop a range of materials and fibers that can efficiently and cost-effectively extract uranium from seawater.
Recently, a research team from the Institute of Physics and Chemistry Engineering, under the Chinese Academy of Sciences, has developed a new material inspired by the fractal properties of blood vessels that can absorb uranium from seawater more than 20 times compared to previous approaches.
This material is a hierarchical porous membrane with extremely small pores for more effective extraction of uranium from seawater, China Science Daily reports.
This hierarchical porous membrane is inspired by fractal structures in biology, which are found throughout nature, such as the branching tubes of animal and plant blood vessels. Such structures can facilitate mass and fluid transfer with minimal energy consumption.
According to researchers from the Institute of Physics and Chemistry Engineering, this biological tubular membrane allows for rapid diffusion and adsorption of sufficient uranyl ions through the hierarchical porous structure, compared to conventional porous membranes. Tests show that this new membrane can increase adsorption capacity by up to 20 times.
Image caption: a. Hierarchical network of blood vessels in living organisms; b. Model based on branching tubes inspired by the circulatory system of mammals; c. Diagram illustrating the hierarchical porous membrane. It contains pores of three different size scales; d. The working principle of the hierarchical porous membrane used to adsorb uranium. (Image: Institute of Physics and Chemistry Engineering, China)
Enlarged image d. (Image: Institute of Physics and Chemistry Engineering, China)
In natural seawater, one gram of such membrane can extract 9.03 milligrams of uranium—this result was achieved after 4 weeks of testing by Chinese scientists.
[Adsorption is the process that occurs when a gas/liquid is attracted to the surface of a porous solid or the increase in concentration of this substance on the surface of another substance].
The research team behind this method believes it can provide a reliable energy source (uranium from seawater) that could last for thousands of years at the current consumption rate.
