Spherical nuclear fuel in a vacuum

'Wind energy, solar energy, nuclear energy' - I thought. 'The wind is blowing, the sun is shining ... Stop, and what is the core?' It would be interesting to know ...

Ab uranus

Now the basis of nuclear fuel is uranium. The most common types of uranium in nature are the isotope with a mass of 238 and the isotope 235. In natural uranium, they are contained in a ratio of approximately 99.3% and 0.72%. Uranium is a metal, so you have to dig it. But first, we need to know something. “Uranium is not inherently radioactive.” However, this is the exclusive opinion of Rosatom . Everyone else, of course, knows that uranium is radioactive.. However, not much. Alpha radiation (helium-4 nuclei), although most characteristic of uranium, is delayed by the skin and, in the case of external exposure, is not dangerous. Beta radiation (electrons / positrons) is also there, but it is well delayed by a simple cloth. Gamma radiation (photons), although penetrating, but in our case, due to its low intensity, contributes on a par with beta radiation. As a result, despite the fact that uranium ore is not only uranium, let’s say right away, it will not shine too much.

Take a look at the decay products of uranium. They have radon , and this is bad news . As we are told around:

The decay of the nuclei of radon and its daughter isotopes in the lung tissue causes microburn.

Polonium isotopes resulting from the decay of radon are a significant source of _internal_ alpha radiation.

The relative harmfulness of radon daughter products is greater than the harmfulness of radon itself. Once in the human body, it contributes to the processes leading to cancer (bones, blood, lungs, thousands of them ...), anemia, leukemia.

Remember, radon is an important factor when working with uranium ore.

And finally, uranium itself is highly toxic . Getting it into the body by any means in excess of the permissible norm is extremely undesirable.

When it enters the body, uranium acts on all organs, being a general cell poison. The molecular mechanism of action of uranium is associated with its ability to inhibit the activity of enzymes. First of all, the kidneys are affected (protein and sugar appear in the urine, oliguria). In chronic intoxication, hematopoiesis and nervous system disorders are possible.

It is often indicated that when working with uranium, it itself delivers no worse than radon, but which effects are caused by the presence of the first, and which by the second, it is sometimes difficult to make out, so no one really says. We will not try our luck and suppose the worst option. Although, Kurchatov simply wiped his hands on a handkerchief. True story.

Uranium reserves

Uranium dioxide Already a cake?

Before you dig, you need to find out where. Australia is a significant leader in uranium reserves - 1780 kt (30% of the global volume). Take a look at the top five (and the percentage of global production in 2017 ):

1. Australia - 30% (10%)
2. Kazakhstan - 14% (39%)
3. Canada - 8% (22%)
4. Russia - 8% (5%)
5. Namibia - 7% (7%)

If everything is correct, then the uranium on earth will last us for about a hundred years. Not so much, but there is at least thorium .

Mining methods

“How much curie does it take to light a bulb?” - an old French joke.

First option . If uranium is shallow (up to 500 m), the quarry method can be used. Excavators and trucks. Cheap and cheerful, minimum radiation. Open air helps a little from radon and uranium dust. Thus, such a career will give us no more than a couple of militia per year. This is considered absolutely safe. The problem arises when mining waste appears. But more about that later.

Second option. It is designed for cases when the ore lies a little deeper and you have to dig a mine. As a rule, they do not dig more than two kilometers, otherwise it is already ineffective in price. When mining deep, radon enters into an active game. It needs to be constantly monitored, caught, pumped out and fed to the hamsters in the mines with fresh air. We don’t forget about dust either. Tightening safety procedures and a sophisticated production mechanism increase the cost of this method compared to the first. The waste problem persists.

Third method. Underground Leaching Method (MPV). Significantly different from the first two. First, a well is drilled to the uranium deposit (no deeper than 600 m). Then, a solution of sulfuric acid begins to be fed into it, which binds uranium particles (leaching). The resulting solution is pumped to the surface and is already extracted from it, after which it is processed, uranium. The advantages of this method are a significant simplification of the organization of the process. Accordingly, the price is reduced. Hamsters with shovels are no longer needed. So the method can be used in severe climatic conditions. Radon and dust cease to bother us. The pumped solution also contains a minimum of excess components, which greatly simplifies the issue of radioactive contamination. In general, this method is considered promising, but so far it has been used somewhere in 15% of deposits.

Environmental impact

A sad example. The Rio Tinto River The

first sadness regarding any mining is AMD aka sewage. The bottom line is that many sulfides are found in mining waste, which, in the presence of water and oxygen, give us sulfuric acid. In the case of abandoned underground mines, a change in water flows makes this process inevitable. Moreover, toxic metals (copper, aluminum, arsenic, mercury) are also found among sulfides. If all this joy gets into the river, drinking and living in it is no longer recommended. All this is compounded by the fact that in especially neglected cases the situation will not be corrected already 'never'.

Second sadness. After uranium is extracted from the ore, we still have a bunch of unnecessary garbage (in solid and liquid form). It includes both radioactive elements (thorium, radium) that are not mined by us, and unassembled uranium. The level of radioactivity of such waste can reach 85% of the level of initially mined ore. If all this is simply dumped together, then, as we already know, gamma radiation and constantly emitted radon (which, generally speaking, is formed from radium) can cause serious harm to the environment.

Third sadnessconcerns the method of underground leaching. Using this method, we almost do not receive garbage, and do not pollute the air. But the process inevitably causes groundwater pollution. Possible leaks of the working solution (i.e. sulfuric acid) can lead to significant changes in the geological structure, which are not always easy to predict. A major challenge here is to protect water sources.

Again in a bottle

One of the tailings in Canada

As we understand it, the waste must be put in one place. It is called the tailing dump (from the English. 'Tailings' - waste). It can simply be a mountain of garbage, a dam or a lake. Our primary goal is isolation from the surrounding natural hydraulic system. Those. it is important for us that the storage does not leak and does not overflow. For the first, we need reliable fencing along the edges. The second requires the installation of decantation systems, plus it is desirable to take into account the amount of precipitation / evaporation in the design. After stopping the collection of waste, it is necessary to install a dome - protection against radon. As additional measures, - drainage of the storage, protection against soil erosion. Next is constant observation. Service life - from a minimum of 200 years to a desirable of 1000 years. With the help of which mother you can stand so much, science does not dare to answer.

Forecasts for periods from 175 to 975 years are complicated by a high degree of uncertainty due to the lack of sufficient practical data.

Accordingly, future maintenance costs are also difficult to assess. There is evidence of primary costs when decommissioning mines . Amounts range from several tens of millions to a couple of billion dollars. Also there is interesting data from UMTRA about how many deaths they prevented by their activities and how it came about. For a hundred years, it has turned out ~ 1.3k lives, one million dollars in total. In general, it is clear that the task requires attention, time and money. Any significant damage to the tailings can lead to sad consequences .

Useful materials

Uranium Mining and Milling Wastes: An Introduction
Uranium Mining in Virginia (2012)

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