Nuclear energy in simple words

EFN answers student's questions


"Hello, I am doing a project for science, which requires me to interview someone who is an expert on nuclear power. Can you give me information on nuclear power and why it is a clean energy if it is well managed? Thanks."

EFN often receives questions from students, from school to university, preparing reports on nuclear energy and requesting information. This document is intended to answer student's most frequently asked questions, and to help them prepare their reports about nuclear energy.


1. How were nuclear power plants discovered?

The first existing natural reactor was located at OKLO in Africa, long ago, almost 2 billion years ago. It was a natural reactor in Gabon, Africa. A nuclear reaction happened there naturally, and continued for thousands of years, with a nuclear chain reaction : the natural fission of uranium. Fifteen similar natural reactors have been found in Africa. Probably, there have been more such natural reactors in other areas of the world, which have not yet been discovered. This natural nuclear reaction was possible 2 billion years ago, but would not be possible today anymore because the proportion of uranium 235 in nature, which generates the natural fission, slowly decreases with time. The amount of natural radioactivity today is much smaller than it was when life first appeared on the planet, because natural radioactivity slowly decreases.

--> See answer to next question as concerns man-made nuclear reactions and power plants


2. Who were major contributors to nuclear power ?

- 1896 Henri Becquerel discovers radioactivity

- 1898 Pierre and Marie Curie discover uranium ore

- 1905 Einstein formulates the equivalence of mass and energy

- 1932 Chadwick discovers neutrons

- 1934 Irene and Frédéric Joliot-Curie discover artificial radioactivity

- 1934 Zsilard takes the first license on nuclear energy production

- 1938 Lise Meitner, Hahn and Strassmann show evidence of uranium fission

- 1939 Halban, Joliot-Curie and Kowarski take a French patent on nuclear energy production

- 1942 construction and start-up of the first critical assembly, by Robert Moon and Enrico Fermi (power 0.5 Watt)


3. What different kinds of nuclear reactors are there?

Actually and essentially (about 80% of the world nuclear electricity production) :

- PWR (Pressurized Water Reactor)

- BWR (Boiling Water Reactor)

- CANDU (heavy water moderated, light water cooled reactor)

- Research reactors (more highly enriched fuel, pond reactor)

Other technologies such as sodium fast neutron reactors (example : Monju in Japan, BN300 and BN600 in Russia, Phenix and Superphenix in France), lead reactors, helium reactors, graphite reactors (such as RBMK in former USSR), high temperature reactors (such as the PBMR being constructed in South Africa, the HTTR in Japan, and the GT-MHR being developed), and reactors operating with plutonium or thorium instead of uranium, have been used in the past, or are being developed for the future. The nuclear technology is now quite mature, especially for the water reactors, and is also constantly evolving and improving. Adding up the total number of years that nuclear reactor have been operating, gives more than 10 000 cumulated years of experience : quite a long experience of many of the basic types of reactors has now been accumulated.


4. What are the advantages of nuclear power?

It is a form of energy which :

- respects the environment (no contribution to the green-house effect)

- is highly dense (a small quantity of material produces a very large quantity of energy), therefore it uses only very small amounts of uranium or thorium which are very abundant in nature, in the Earth, and even in the ocean

- it produces very small quantity of wastes, which are confined, not rejected in nature like exhaust fumes of cars, and these waste decay with time, they are very radioactive only in the beginning, and afterwards, their radioactivity is quickly reduced as time passes

- has reserves of fuel for a long time and will be able to produce energy for long period (reserves of oil are only of a few decades) even with mass production, especially if fast neutron reactors are developed. Taking into account the amount of energy required by populations for a decent lifestyle, so called alternatives sources (wind and solar) are not at all able to produce the quantities needed, and in addition, at comparable cost (they are much more expensive and unfortunately too diluted).


5. What are some disadvantages of nuclear power?

If mis-handled some accidents, such as Chernobyl, may occur. However, Chernobyl was a major accident, but not the catastrophe related by the media.

Just some figures concerning release of radioactivity to atmosphere :

- military tests (USSR, US, ...) Curies

- Mayak accidents (USSR) 120.000.000 Curies (medias never talk about it)

- Chernobyl (USSR) 65.000.000 Curies (42 died, but almost all of them were firemen having received very high doses without adequate protection INSIDE the building shortly after the accident)

- TMI (US, with better plants) 8 Curies (no one was injured nor died in this accident)

- Tokai Mura (Japan). 2 workers who made a major mistake received very high doses and died (and a third standing nearby in the same room was badly burnt), but no radioactive particles were released outside the site.

- France : no major accident in 40 years, 80% of its electricity is nuclear


6. What are some interesting facts about nuclear power ?

Essentially, I would mention two subjects :

- we are citizens of the world and we have to think about the future of the developing countries. If we assume that the future need of energy in these countries would be satisfied with fossil fuel (oil or coal), the atmosphere of our planet would be rapidly polluted to a non acceptable point for the future of humanity. From another hand, it is impossible to refuse the development to those countries : so, we have to develop small and safe nuclear reactors for the equipment of third world countries.

- in the 1960's, radioprotection authorities decided to take into account the LNT theory (Linear No Threshold theory) for the development of radioprotection rules. This theory, based on the existing knowledge at that time, and by precaution, assumed that there is no radiation at all without harmful effect, and that even very small doses of radiation can affect our health, but proportionnally less. This decision leads to theoretical calculations about the effects of low doses of radiations, and to the possibility of frightening peoples even about very small doses of radiation, although such small levels of radiations have never been proved harmful (under 100 mSv received one-shot). Today, there are more and more scientists to say that, at natural levels that were already in nature before humans and any industry ever existed, radiations are not harmful. As an example, peoples living in Kerala (India), where natural radiation are over 30 to 50 times more than the average in the world, have an average life-time longer than other people in India (see the Kerala document in the "documents in english" section of EFN's web site). An increasing amount of evidence even suggests that reasonably small natural doses of radiation could even be useful and necessary for our health. This phenomenon is called hormesis and is explained by the fact that our species has always in an environment of constant natural radiations and that our body's chemistry has therefore adapted over millions of years to these radiations. Recent research suggests that natural amounts of radiation may be especially useful for the stimulation of our immune defenses and cell-repair mechanisms (see the LNT document in the "documents in english" section of EFN's web site). However, this does not mean that we should be careless about nuclear energy, because very high doses of radiation are of course dangerous, can even be lethal, and should therefore be avoided.

I hope to have answered, briefly but correctly, your questions. Would you need more precisions, don't hesitate to refer to the other documents available on our web site :

My name is Michel Noraz, I live in the beautiful French countryside near the sea in Normandy. I am retired. I want to leave a clean planet for the future generations, and I am very proud that my country has safely contributed to lower the pollution for the entire planet. Without nuclear energy, France would consume almost twice as much oil, coal and gas, and pollute much more the atmosphere, as is the case in many other countries with less nuclear energy. Other countries should also develop safe nuclear energy. If it is well handled, it can be very respectful of the environment.

Best regards.

Michel Noraz

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