Tech UPTechnology20 questions about nuclear energy

# 20 questions about nuclear energy

## 1. Before we begin, what is energy?

Energy is a property of matter that is governed by conservation principles; that is, it remains unchanged. In the universe, we observe that energy remains constant in the homogeneity of space-time, and there are four fundamental forces that govern interactions between particles: gravity, electromagnetism, weak nuclear energy, and strong nuclear energy. In this article, we are going to focus on the latter.

## 2. What is nuclear energy?

Nuclear energy is responsible for holding subatomic particles together, and giving them stability. The atom, which is the basic unit of which all matter is made, is in turn composed of smaller particles. The protons and neutrons, in its nucleus ; and the electrons, which surround it.

When we measure the mass of the nucleus of an atom of any element, for example, gold, we can calculate its mass by adding these protons and neutrons. But, when we obtain its mass experimentally, we observe that it is slightly less than what we had calculated. Why? There is something that we were not taking into account in our sum. Part of the mass of this nucleus exists in the form of energy, which serves to hold subatomic particles together and preserve their stability.

The force that holds together protons and neutrons in the nucleus of an atom is what we know as nuclear energy , and it is the same force that is released during a process of fusion or fission.

This notion, that mass is related to energy, was provided to us by the most famous equation of the 20th century, developed by Albert Einstein: E = mc2 ; that is, energy equals mass times the speed of light squared.

## 3. What is the difference between fission and fusion?

Surely you have heard of both terms, and it is common that they are confused or that their differences are not clear. Both are physical processes that release this nuclear energy , but differ in the process by which it is achieved. We explain each of these processes below.

## 4. How is nuclear energy obtained?

Fission (separation, disintegration, division) of an atomic nucleus occurs by bombardment with other neutrons. This results in the core ‘breaking’ into two or more smaller cores. Neutrons are also released in this split, which in turn can bombard more nearby atomic nuclei and repeat the process. The latter is what is known as a chain reaction .

For its part, fusion (union, annexation) is the more or less opposite process: at very high temperatures, the union of two or more light nuclei is carried out to give rise to heavier atoms. This reaction is what occurs in our Sun, which fuses hydrogen atoms continuously to produce helium; the energy unleashed in the process is what reaches us on Earth in the form of light and heat.

## 5. Why don’t we use nuclear fusion?

Nuclear fusion, as we mentioned, is only possible if we heat the atomic nuclei to temperatures almost impossible to achieve on Earth, equivalent to those inside the Sun, where fusion occurs: hundreds of millions of degrees Celsius.

A nuclear plant emitting water vapor into the atmosphere. / IStock

## 6. What are nuclear power plants?

Nuclear power plants are large complexes where nuclear reactors are located, inside which this physical reaction takes place that gives rise to nuclear energy.

Although there are several ways to trigger a nuclear reaction, the one that occurs inside most nuclear reactors is to heat water. In order for nuclear energy to experience its greatest moment of expansion as an energy source, in the 70s , intense research was carried out to find the most efficient way to obtain controlled nuclear reactions. The most popular was the light water reactor.

## 7. How does a nuclear reactor work?

In a light water reactor, water is heated using a nuclear chain reaction (and most importantly, controlled), by fission. This reaction heats the water, which is in a separate chamber without contact with the secondary chamber. Here we find steam generators, turbines … and other elements that transport energy. In the end, this is directed to an alternator and, later, to a transformer, which achieves the necessary voltage to generate electrical energy.

## 8. How many types of reactors are there?

Nuclear reactors are classified according to the speed of the neutrons that produce fission reactions. The most common are light water, pressurized water, boiling water, and graphite-gas reactors; the latter uses graphite as a moderator and CO2 as a refrigerant.

## 9. How many nuclear power plants are there in the world?

According to Foro Nuclear, there are currently 448 reactors operating in the world, which produce around 11.5% of the world’s electricity.

Specifically in Spain there are 7 operational nuclear reactors : Almaraz I and II (Cáceres), Ascó I and II (Tarragona), Cofrentes (Valencia), Trillo (Guadalajara) and Vandellós II (Tarragona), a nuclear fuel factory in Juzbado (Salamanca) ) and a radioactive waste storage center in El Cabril (Córdoba).

In addition, according to the most recent data from the United Nations International Atomic Energy Agency: China, India, Russia, South Korea, Finland and France are under construction of another 58 nuclear plants.

In Europe, France is the country that is most committed to nuclear energy, since 73% of the electricity it produces is already of nuclear origin.

Illustration of a nuclear reactor. The primary chamber, where the fission takes place, in orange./iStock

## 10. What are nuclear fuels?

Nuclear energy produces several million times more energy than any other physical reaction. But, to produce this vast amount of energy, we need very heavy elements, such as uranium 235. The heavier and more unstable an element is, the greater the energy released.

The most widely used nuclear fuels are uranium and plutonium. On the other hand, the isotopes (simple nuclei) used to bombard the uranium and plutonium nuclei during the fission process are thyrite (very toxic and very expensive) and deuterium (present in water).

## 11. Is nuclear energy clean energy?

In the middle of the 20th century, the idea of using nuclear energy as a source of renewable, cheap and efficient energy excited both the scientific community and countries and large power plants. However, not all are advantages. The big problem with nuclear energy is waste and how to store it.

## 12. What is nuclear waste and why is it dangerous?

When nuclear fission occurs, the smallest nuclei into which our uranium or plutonium atom has disintegrated are rendered useless. There are ways to reuse these nuclei to re-produce nuclear reactions in them, in a process known as reprocessing; But this would require a different type of nuclear reactor, and at the moment we do not have this technology. These remaining nuclei are what we know as nuclear waste.

Nuclear waste is dangerous because it is highly radioactive. Although at low doses radioactivity should not be dangerous , exposure to high levels, and also prolonged, is associated with genetic mutations (alterations in DNA, the information that our cells contain).

All the matter that surrounds us emits radiation , even ourselves; in fact, radiation of natural origin is responsible for 87% of the total dose that humans receive. However, we are still not sure how high doses of radioactivity affect living things.

Furthermore, nuclear waste can cause environmental damage, for example groundwater contamination.

Nuclear waste drums./iStock

## 13. How is nuclear waste stored?

Nuclear waste loses its harmfulness over the years … too many. A nuclear waste can remain toxic for several thousand years.

Therefore, the waste is shielded and stored in safe places: large pools, in which the water cools the waste; or in drums, which are placed in armored warehouses, with concrete, and buried under layers of earth. But warehouses are not forgotten, they have a surveillance time that can last from 60 to 300 years. Furthermore, storage in these structures is often very expensive.

## 14. Why don’t we send nuclear waste into space?

Faced with the problem of waste storage, many people have offered original and alternative ideas, and one of them is a solution that, a priori, seems logical: Why don’t we send nuclear waste away from Earth in space vehicles?

The answer is simple: for responsibility and safety. The complex handling of these unstable waste, combined with the use of rockets, would increase the risk of a nuclear accident with dire consequences for the planet.

## 15. Why do nuclear accidents occur?

The most serious nuclear accidents in history occurred in 1957, at a Russian storage plant near Kyshtym; and in 1986, at the Chernobyl plant.

When accidents of this type have occurred, they have been caused by a loss of control of the fission process, which can lead to hydrogen explosions and radioactivity leaks. For this reason, it is essential to carry out good maintenance of the plant, and to follow strict safety regulations.

A release of radioactivity can leave an entire area hundreds of kilometers around unfit for life.

Another nuclear accident, listed as such by the International Atomic Energy Agency, occurred in 2011 in Fukushima. This time, it was caused by natural causes, due to a tsunami that affected the nuclear power plant. Although the causes were not human, the incident produced a significant release of radioactive material into the environment.

## 16. Is nuclear energy efficient?

Approximately 10% of the energy that humans use to carry out their activities comes from nuclear fission.

Although we have talked about pollution, its advantages over other types of energy sources is that what is produced with nuclear energy is energy that is no longer produced by fuels that are much more harmful to the planet, and to human health.

Although nuclear waste is highly toxic, it is stored in the safest places possible. Instead, the pollution derived from the burning of fossil fuels is released directly into the atmosphere, contributing to a progressive acceleration of climate change, in addition to being the cause of a major public health problem.

In 2018, a study in the European Heart Journal revealed that in Europe alone 800,000 people die prematurely due to air pollution.

Furthermore, another 2013 study by the NASA Goddard Institute for Space Studies and the Earth Institute at Columbia University revealed that global nuclear energy has prevented an average of 1.84 million deaths related to air pollution. air; in addition to avoiding 64 gigatons of greenhouse gas emissions that would have resulted from the burning of fossil fuels.

## 17. What are the uses of nuclear energy?

The discovery of the powerful physical reactions of nuclear energy had very unflattering beginnings. This technology was used to make the atomic bomb , the most powerful and destructive weapon known.

After the two colossal bombs were dropped in the summer of 1945 on the towns of Hiroshima and Nagasaki, an international treaty was agreed that limited the military use of nuclear energy , and its incredible power was considered to have a peaceful potential; that is, to generate energy efficiently and cheaply.

The science of nuclear energy, moreover, developed with much more profitable uses, for example, in medicine, as a method of radiodiagnosis, research, and even therapy.

## 18. What advantages does fusion have over fission?

Fusion is a nuclear process that generates much less radioactive waste than fission. Also, in the event of a runaway reaction or leak, the plasma would expand and cool over time, thus not causing a dangerous explosion.

## 19. When will we be able to have energy by fusion?

Nuclear fusion occurs naturally and uninterruptedly inside our Sun. Could we build a small, artificial star on Earth in order to emulate this energy source, efficient and with minimal waste? To do this, we would need reactors capable of reaching temperatures as high as that of our Sun.

There are already reactors capable of generating enormous temperatures, such as the REIT (International Thermonuclear Experimental Reactor), in France. Another type of reactor capable of achieving this is the inertial confinement, which uses pulses from super-powerful lasers. However, these types of reactors are still experimental and the technology is still too expensive.

## 20. What is energy transformation?

Fossil fuels (coal and oil) are the result of organic matter pressed and chemically modified for millions of years, conserved underground, and that today we use to generate energy through more chemical processes than its burning.

However, in addition to the vast pollution produced by the atmosphere and its deadly consequences, fossil fuels are limited. That is, they are not renewable energy, since the amount of reserves on the planet is finite.

The clearest alternative is energy sources such as wind or solar ; however, these still have limitations, especially since they are not efficient enough to cover a considerable supply rate.

Due to the obvious problems of fossil fuels, the energy transformation is a gradual substitution of these energy sources for cleaner, renewable and efficient ones.

Nuclear energy is a highly efficient source of energy, but it still has drawbacks, mainly derived from the storage of its resources, which must be addressed. However, as we have seen, nuclear fusion energy seems the ideal alternative to these problems, despite the fact that its achievement is still very expensive, and it would still produce radioactive waste, although on a smaller scale.

For many, encouraging countries to expand supplies through fission nuclear sources momentarily solves the problem of fossil fuels, and also that of efficiency; but we still have the serious handicap of nuclear waste.

There are several alternatives: stopping the advance of nuclear energy until investigating new ways of storing much more efficient waste; or assume the risk in favor of a reduction of greenhouse gases, at least for a limited period, until the efficient development of energy by fusion, in which the storage of its waste is acceptable for the planet.

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