Ionizing radiation

Signal of radiation risk in transport.

Ionizing radiation is radiation with sufficient energy to ionize matter, extracting electrons from their states bound to the atom.

Radiation and types of radiation

Electromagnetic spectra in diagram that illustrates that ionizing radiation appears in frequencies above 3⋅ ⋅ 1015{displaystyle 3cdot 10^{15}} Hz.

There are other energy emission processes, such as that due to a lamp, a heater (called a radiator precisely because it radiates heat or infrared radiation), or the emission of radio waves in broadcasting, which receive the generic name of radiation.

Ionizing radiation can come from radioactive substances, which emit such radiation spontaneously, or from artificial generators, such as X-ray generators and particle accelerators.

Those coming from sources of ionizing radiation found naturally in the earth's crust can be classified as composed of alpha, beta, gamma-ray or X-ray particles. Ionizing photons can also be produced when a charged particle that has a Given kinetic energy, it is accelerated (either positively or negatively), producing braking radiation, also called bremsstrahlung, or synchrotron radiation, for example (making accelerated electrons impinge on a dense medium such as tungsten, lead or iron is the usual mechanism for producing X-rays). Other natural ionizing radiations can be neutrons or muons.

Ionizing radiation interacts with living matter, producing various effects. Radiobiology is responsible for the study of this interaction and its effects.

Since its discovery by Wilhelm Conrad Roentgen in 1895, they have been used in medicine and industry. The best known application is X-ray devices, or the use of radiation sources in the medical field, both in diagnosis (gammagraphy) and in treatment (radiotherapy in oncology, for example) through the use of sources (eg cobalt therapy) or particle accelerators.

Classification of ionizing radiation

Simple representation of the penetration power of different types of ionizing radiation. An alpha particle does not penetrate a sheet of paper, a beta does not penetrate a sheet of metal and a gamma photon penetrates even large thicknesses of metal or concrete.

Depending on whether they are photons or particles

• Electromagnetic radiation: This type of radiation is made up of photons with enough energy to ionize matter (i.e., more than a few dozen electronvolts). According to their origin and energy they are classified into x-rays and gamma rays.
• Corporal radiation: includes Alpha particles (helio cores), beta (high-energy electrons and positrons), protons, neutrons and other particles that are produced only by cosmic rays or very high-energy accelerators, such as pions or muons.

Depending on the ionization produced

• Direct ionizing radiation: It usually understands the corpuscular radiations formed by charged particles that interact directly with electrons and the nucleus of the atoms of white or target molecules such as oxygen and water. They usually own a high-energy linear transfer.
• Indirectly ionizing radiation: It is made up of unloaded particles such as photons, neutrinos or neutrons, which when passing matter interact with it producing charged particles, these being those that ionize other atoms. They usually have a low linear energy transfer.

Depending on the source of ionizing radiation

• Natural radiation: originate from radioisotopes present in the air (such as ²²²Rn or the ¹⁴C), the human body (e.g. ¹⁴C or ²³⁵U), food (e.g. ²⁴Na or ²³⁸U), the earth's crust (and therefore the rocks and building materials obtained from them, such as the ⁴⁰K), or space (cosmic radiation). They are radiations not produced by man. More than 80% of the exposure to ionizing radiation on average to which the population is exposed comes from natural sources.

• The different artificial radiations: They are produced by certain devices or methods developed by the human being, such as the apparatus used in radiology, some used in radiation therapy, by radioactive materials that do not exist in nature but that the human being is capable of synthesizing in nuclear reactors or particle accelerators, or by materials that exist in nature but which are chemically concentrated to use their radioactive properties. The physical nature of artificial radiation is identical to that of natural ones. For example, natural X-rays and artificial X-rays are both X-rays (fotons or electromagnetic waves that come from the disexcitation of atomic electrons). Examples of artificial sources of radiation are X-ray, medical or industrial applications, particle accelerators of medical, research or industrial applications, or materials obtained through nuclear techniques such as cyclotrons or nuclear power plants.

The remains of the bomb explosions in World War II, in the atomic tests carried out in the atmosphere by the nuclear powers during the beginning of the Cold War, or those due to the Chernobyl accident give rise to a presence ubiquitous man-made radioisotopes from fission (mainly ¹³⁷Cs). Isotopes with the longest half-period will be detectable for tens of years over the entire Earth's surface.

Ionizing radiation and health

Exposure to ionizing radiation in humans.

As already mentioned, living beings are exposed to low levels of ionizing radiation from the sun, rocks, soil, natural sources within the body itself, radioactive residues from past nuclear tests, certain consumer products and from radioactive materials released from hospitals and associated nuclear and coal power plants.

Workers exposed to the greatest amount of radiation are astronauts (due to cosmic radiation), medical or X-ray personnel, researchers, and those who work in a radioactive or nuclear facility. In addition, additional exposure is received with each X-ray and nuclear medicine exam, and the amount depends on the type and number of scans.

Exposure to low levels of ambient ionizing radiation has not been shown to affect human health. In fact, there are studies that affirm that they could be beneficial (the hormesis hypothesis).
However, the organizations dedicated to radiological protection officially use the conservative hypothesis that even at moderate doses, and even very low ones, ionizing radiation increases the probability of contracting cancer, and that this probability increases with the dose received (Linear model no threshold). The effects produced at these low doses are often called probabilistic, statistical, or stochastic effects.

Exposure to high doses of ionizing radiation can cause skin burns, hair loss, nausea, illness, and death. The effects will depend on the amount of ionizing radiation received and the duration of the irradiation, and on personal factors such as gender, age at which you were exposed, and your state of health and nutrition. Increasing the dose produces more serious effects.

A dose of 3 to 4 Sv has been shown to cause death in 50% of cases. Effects produced at high doses are called deterministic or non-stochastic as opposed to stochastic.

Usefulness of ionizing radiation

Ionizing radiation has very important applications in science, industry and medicine. In industry, ionizing radiation can be useful for energy production, for food sterilization, for knowing the internal composition of various materials, and for detecting manufacturing and assembly errors. In the field of medicine, ionizing radiation also has numerous beneficial applications for humans. A wide variety of diagnostic studies (nuclear medicine and radiology) and treatments (nuclear medicine and radiotherapy) can be performed with them.

Interaction of radiation with matter

Charged particles, such as electrons, positrons, muons, protons, ions or others, interact directly with the electronic shell of atoms, due to the electromagnetic force.

Gamma rays interact with the atoms of matter with three different mechanisms:

• Photoelectric Absorption: is an interaction in which the gamma incident photon disappears. Instead, a photoelectron is produced from one of the electronic layers of the absorbing material with a kinetic energy from the incident photon energy, less the ligature energy of the electron in its original layer.
• Compton effect: is an elastic collision between a linked electron and an incidental photon, being the division of energy between both dependent on the scatter angle.
• Production of pairs: the process occurs in the field of a core of the absorbing material and corresponds to the creation of an electron pair - positron at the point where the gamma photon disappears. Because the positron is a form of antimatter, once its kinetic energy becomes despicable it will be combined with an electron of the absorbing material, annihilating and producing a couple of photons.

Neutrons interact with the nuclei of matter through the following effects:

• Activation: is a completely inelastic interaction of neutrons with nuclei, through which neutron is absorbed, producing a different isotope. It is the basis of transmutation produced in the ADS's^{[chuckles]required]}.
• Fission: through this interaction neutrons join a heavy core (such as uranium-235) by exciting it in such a way that it causes its instability and subsequent disintegration into two lighter nuclei and other particles. It is the basis of the nuclear fission reactors.
• Inelastic collision: in this interaction the neutron collides with the core by ceding a part of its energy, so the result is a neutron and an excited nucleus that normally emits gamma, ionizing radiations, later.

Units of measurement of ionizing radiation

Human beings do not possess any sense that perceives ionizing radiation. There are various types of instruments that can capture and measure the amount of ionizing radiation that matter absorbs. (See as an example Geiger counters, gaseous ionization detectors, scintillators or certain semiconductors)

There are several units of measurement of ionizing radiation, some traditional and others of the International System of Units (SI).

• Traditional units: It's Röntgen, Rad, REM.
• Units of the international system: The most commonly used are Culombio/kg, Gray (Gy) and Sievert (Sv).