The atom is the smallest part of each element found in nature which preserves its chemical properties; for a long time, it was considered to be indivisible (from the Greek word ατομος, atomos, that which cannot be cut). In reality, it is made up of a nucleus (formed by protons and neutrons) surrounded by electrons able to promote chemical reactions that can produce energy.
Use of nuclear energy stems from the possibility of using the considerable energy present in the atom’s nucleus, much greater than the energy obtained from chemical reactions where the atom’s nucleus is not involved. Nuclear power can be produced both by nuclear fission (separation of the nuclei of heavy radioactive materials) and by fusion (combination of the nuclei of lighter elements). Of the two reactions, fission is the only one that can be achieved and controlled by humans, using the necessary technical precautions linked to prevention of incidents and management of radioactive waste.
On the contrary, it is not yet possible to use fusion for sufficiently long times for continuous production of energy. Indeed, as yet there is no device able to contain hydrogen and keep it “trapped” for long enough at sufficiently high temperature to make aggregation of the nuclei possible.
What it is for
The heat generated during the transformation of nuclear energy into thermal energy, regardless of it being obtained from uranium or plutonium, can be used to obtain mechanic energy, i.e. to move a machine (e.g. a turbine).
Where it is
As for the other non-renewable sources of energy, such as coal, petroleum and natural gas, we must estimate how much nuclear combustible is available on the Earth and at what price. In nature an enormous quantity of natural uranium is present. The oceans, for example, contain approximately one billion cubic kilometres.
A bit of history
It is difficult to find a scientific discovery that has had a greater impact on the population and on world politics than that of nuclear energy. Humanity became aware of this new form of energy on 6 August 1945, when the dramatic news of the explosion of a nuclear bomb on the Japanese city of Hiroshima spread around the world.
Radioactivity is indeed a physical phenomenon in which unstable nuclei are transformed into nuclei of other elements or isotopes (identical atom nuclei from the chemical viewpoint but with different mass, owing to the different number of neutrons) of the starting nuclei, by emitting nuclear radiation. The core, before decaying to a lower energy level, can remain in a radioactive state for a period of time ranging from a fraction of a second to 100 million years.
Radioactivity is naturally present in the Earth’s environment, it has biological effects on human beings due to its ionizing characteristics. These effects are exploited in medical diagnostics (X-rays, scintigraphy/body scans, Computer Assisted Tomography, Positron Emission Tomography etc.) and in anti-tumour therapies (radiotherapy, boron neutron capture therapy, particle or hadron therapy) but they can be harmful if they are not administered carefully. In fact, over a certain limit, radiation can become very dangerous for human health, also in relation to the time of exposure. Radioactivity is dangerous specially if the radioactive elements have a very long “half-time” (transformation into other nuclei) that can last millennia, and they become fixed permanently in the human body or in other living creatures. Radioactivity is also used for sterilization, and to examine the properties and defects of construction materials.
The production of nuclear waste, generating radiotoxic elements, is extremely important and delicate in the nuclear power production cycle and great attention must be paid so that no situation arises in which radioactive elements come into contact with human beings.
Fission is the breaking of the nucleus into two fragments through the action of neutrons on very heavy nuclei, i.e. uranium 235, thorium 232, plutonium 239, etc.
Nuclear fusion is the process that since ancient times has used solar and star energy to activate fusion reactions between hydrogen nuclei. Fusion reaction starts from very light nuclei that aggregate.