Mining uranium in cornfields and pastures. How exactly does China mine its uranium ore?

Guess what these things that look like extra-large McChicken nuggets in my hand are?

Its common name is yellowcake. This isn't the kind of cake you can eat, but an important raw material in the nuclear industry —— sodium diuranate.

After a series of processing, it can be made into fuel rods, and finally converted into the electricity we use in our daily lives.

Today, let's take a look at the very beginning of nuclear fuel —— what exactly does uranium ore look like.

Where does uranium ore come from? What does it look like?

Where does uranium come from?

Uranium, with an atomic number of 92, was born in supernova explosions and neutron star collisions.

4.6 billion years ago, it was accreted onto the Earth along with the primordial matter of the solar system, forming compounds with elements such as oxygen and fluorine. These minerals formed uranium ore during subsequent geological evolution.

Actually, there is a bit more uranium than we think. Its average abundance in the Earth's crust is about 2.7 ppm, which means there are 2.7 grams of uranium per ton of crustal material, similar to metals like cobalt, nickel, and lead. In contrast, the average abundance of gold in the Earth's crust is only 0.004 ppm.

However, for uranium mined by traditional methods, the general industrial grade is 0.05%, which means 500 grams of uranium per ton of ore. That is, it needs to be 185 times higher than the average abundance to be worth mining. So, although it seems abundant, it is actually too dispersed and difficult to mine.

Uranium is also an element with relatively active chemical properties. There is almost no "pure uranium" underground; it all exists in the form of compounds.

Common combinations include pitchblende, uraninite, coffinite, autunite, and so on.

Uranium is distributed from the south to the north of China. In Hunan, Guangdong, and Jiangxi, the main types are granite - type and volcanic - type uranium ore. In Xinjiang and Inner Mongolia, the main type is sandstone - type uranium ore. Uranium ore resources have also been discovered in the Northeast and even in regions like Yunnan, Guizhou, and Sichuan.

The uranium ore we are looking at this time is in the place with the most grasslands in China, which is also the place with the most uranium resources —— Inner Mongolia.

What does uranium ore look like?

I'm now at the Nalinggou Uranium Deposit in Nagebei Town, Dalate Banner, Ordos City, Inner Mongolia. This is the largest natural uranium production capacity project in China —— the "Guoyou No. 1" demonstration project of China National Nuclear Corporation. The yellowcake you saw earlier comes from this grassland.

But if I don't tell you that there is mining going on here, you definitely won't be able to tell. Because the mine here is completely different from what we imagine. There are no mine shafts to be seen, and no miners either. The only thing you can see is many yellow, green, and blue boxes placed on the grassland.

Let's take a look together at how "Guoyou No. 1" extracts uranium from underground.

These yellow, green, and blue boxes are actually the "mine shafts" of "Guoyou No. 1".

The green boxes represent injection wells, which are responsible for injecting the leaching solution into the sandstone - type uranium ore layer;

The blue boxes represent extraction wells, which are responsible for pumping out the liquid with dissolved uranium elements;

The yellow boxes are responsible for monitoring the groundwater environment.

They are arranged in a honeycomb pattern of six injection wells and one extraction well, with a well spacing of about 30 meters.

Each mining area has a centralized control room, which is responsible for switching and monitoring the flow of the injected and extracted liquid. There are also two evaporation ponds on the periphery, where a small amount of excess water after treatment will evaporate into the atmosphere.

Not far away, you can see a busy drilling rig drilling wells in a new mining area.

This is the "Guoyou No. 1" that adopts the "carbon dioxide + oxygen" in - situ leaching process. It is completely different from the traditional mining mode of mines. You can mine without seeing the mine.

What we just talked about is the mining work that can be seen on the surface. Next, let's take a look at what happens to uranium in the places underground that we can't see ——

How can in - situ leaching of uranium achieve mining without seeing the mine?

How many steps are there in total to turn uranium into yellowcake?

First, the well will go about 400 meters underground to reach the uranium ore layer. Here, there is not only sandstone but also a large amount of groundwater.

The injection well will inject carbon dioxide (CO₂) and oxygen (O₂) dissolved in water as a leaching agent underground.

After carbon dioxide dissolves in groundwater, it forms a weak acid, which can lower the pH value of groundwater and enhance the solubility of uranium minerals.

Oxygen will promote the oxidation of uranium, converting the low - oxidation - state tetravalent uranium (U⁴⁺) in sandstone - type uranium ore into high - oxidation - state hexavalent uranium (U⁶⁺).

At this time, uranium ions will gradually dissolve into the leaching solution, and then be pumped out through the extraction well, summarized in the liquid collection tank through the centralized control room, and then sent to the hydrometallurgical plant along the pipeline.

Here, the uranium solution will pass through an adsorption tower, and the uranium - containing ions will be adsorbed by the resin in the adsorption tower. The uranium - containing resin will then be transferred to the elution tower and eluted by the eluent to obtain a qualified solution.

Hydrochloric acid will be added to these qualified solutions to remove unfavorable ions, and then sodium hydroxide will be added to the stirring tank. Sodium hydroxide provides hydroxide ions (OH - ), which react with uranyl ions to form a sodium diuranate precipitate.

Since these precipitates are generally yellow solids and look like cakes after being pressed, that's why people call it yellowcake.

Inside the nuclear industry, its real code is "111". This is the final product produced in the mining area.

Currently, the international price of natural uranium (U₃O₈) is about $70 per pound, which is equivalent to one million RMB per ton.

The uranium content of sodium diuranate is about 70%. Since it is uranium, it definitely has radiation, but the radiation of natural uranium is negligible. One - jin of natural uranium ore releases 0.02 millisieverts (mSv) of radiation per day, which is about the same as wearing a luminous watch.

At first, I was also worried about radiation. The engineer in the mining area told me that as long as you don't really eat it like a McChicken nugget and wash your hands carefully after touching it, there will basically be no impact.

How to turn uranium into electricity?

Next, these yellowcakes will be sent to a purification and conversion plant, where sodium diuranate will be converted into uranium hexafluoride (UF₆).

Then, they will go to a uranium enrichment plant and a fuel element factory to be made into nuclear fuel rods for use in nuclear reactors.

These fuel rods are loaded into a nuclear reactor. By initiating a fission reaction, a large amount of heat energy is released. The heated water turns into steam, and the steam then drives a steam turbine, which in turn drives a generator to produce electricity.

Finally, it is transmitted to our homes