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Radioactivity: types, radioactive elements, applications

The unstable core of a radioactive element undergoes decay and the emission of radioactivity until it reaches its energy stability. Radioactive emissions have a high energy content, which confers a high ionizing power that affects the substances that are exposed to them.

Geiger radioactivity counter

Radioactivity was discovered by Antoine Becquerel in 1896 while experimenting with the fluorescence of uranium. Later, Ernest Rutherford discovered the existence of two types of nuclear radiation, which he called α and β. This experimental finding was published in 1899.

Natural radioactivity is that which is found in nature without the intervention of man; while artificial radioactivity is that produced by human intervention. The first is detected in natural radioisotopes, and the second in artificial radioisotopes and supermassive elements.

Although radioactivity has numerous applications that benefit man, such as the production of energy, it also has harmful effects that lead to its death. For example, if the radiation dose is high, the chances of developing undesirable mutations or cancer are disproportionately increased.

Natural radiation

Highly enriched uranium

Natural radioactivity is made up of a set of elements with unstable nuclei that exist in nature and that spontaneously disintegrate with the emission of radioactivity. That is, the intervention of man is not necessary for this to occur.

It is represented by radioactive elements from the earth’s crust, the atmosphere and that from cosmic space. Among them we can mention: uranium-238, uranium-235, carbon-14, uranium-235 and radon-222.

Artificial radiation

Artificial radiation made up of a group of radioactive elements created in research laboratories. How? By bombarding non-radioactive elements with nuclei, helium atoms or other types of radiation, to convert them into radioactive isotopes.

The 30 P 15 is a radioactive atom decays spontaneously to the emission of a radiation type β, transforming nickel ( 30 Ni 14 ). Cobalt-60, a radioactive isotope used in the treatment of cancer, is a man-made radioactive element.

Radioactive elements found deep within the earth’s crust, and which have been brought to the earth’s surface by mining and oil extraction, are also considered as part of artificial radioactivity.

Likewise, artificial radiation is due to supermassive and synthetic elements, whose nuclei immediately decompose to give rise to other elements.

Types of radioactivity

Radioactive clover, symbol used to represent radioactivity

– Radiation type alpha (α)

It is a particle emitted by an unstable nucleus. It is made up of two protons and two neutrons, and therefore α radiation is considered to be a naked helium ( 4 He 2 ) atom , without electrons. Due to the presence of two protons, the alpha particle is endowed with a positive charge.

Radiation α is not very penetrating and is stopped by a sheet of paper, having little range in the air. Examples of emitters of α radiation are uranium-238 and radium-226.

When an α particle is emitted, the atom produced has its atomic number reduced by 2 units and its atomic weight and atomic weight by 4 units, as can be seen in the following example:

238 U 92  →  4 He 2     +     234 Th 90

The α-type radiation, although it does not pass through the skin, when ingested is the most harmful type of radioactive particle, due to its size giving it great ionizing power.

– β radiation

Β-type radiation is ionizing radiation that has a range of approximately one meter in air. It can be stopped by a sheet of aluminum foil. During the radioactive decay phase, the emission of an electron or a positron occurs, both of nuclear origin.

Therefore, there are two types of β radioactive emissions: β  and β + .

Radiation β 

This type of radiation is due to the emission of an electron of nuclear origin and a neutron that transforms into a proton. The atomic weight does not change, but the atomic number increases by one unit.

n → p + e          + electron antineutrino

Example:   32 P 15   →  32 S 16      + e         + antineutrino electron

Β + radiation

In this type of radiation, the emission of an electron of nuclear origin with a positive charge (positron) occurs. The unstable nucleus is stabilized by transforming a proton into a neutron, so the atomic weight does not change, but the atomic number is reduced by one unit.

p → n + e +       + 1 electron neutrino

Example: 23 Mg 12  →  23 Na 11      + e +      + 1 electron neutrino

– Gamma radiation (γ)

This radiation is electromagnetic in nature, that is, it is a powerful and penetrating wave, being stopped by blocks of lead. This high penetration of γ radiation allows its use in the form of cobalt-60 in the treatment of cancer at deep body sites.

– Neutron emission

It occurs when neutrons are emitted at high speed. This radiation is non-ionizing and is stopped by water and concrete. The importance of neutron radiation is that it can transform non-radioactive elements into radioactive ones.

Radioactive activity

It is the way in which the amount of radiation is expressed. It is related to the number of decays per second (dps) experienced by the radioactive material present. The unit of radioactive activity of the International System of Units (SI) is the Becquerel, which is equivalent to 1 dps.

However, the oldest unit, and the one that is still used today, is the curie, which is equivalent to 3.7 · 10 10 dps. That is, one curie is equal to 3.7 · 10 10 becquerel.

Radioactive elements

Radioactive rods

Radioactive elements are those that have unstable nuclei that reach their stable condition by emitting energy in the form of radioactivity.

Several non-radioactive elements possess radioactive isotopes. For example, the element carbon possesses non-radioactive atoms and radioactive isotopes, such as carbon-12 and carbon-14, respectively.

This is a list of elements whose isotopes are all radioactive. The list is made up of the name of the element and its most stable radioactive isotope.

-Tecnetius, Tc-91

-Prometio, Pm-145

-Polonio, Po-209

-Astato, At-210

-Francio, Fr-223

-Radio, Ra-226

-Actinium, Ac-227

-Torium, Th-229

-Uranium, U-236

-Americio, Am-243

-Curio, Cm-247

-Californium, Cf-251

-Nobelio, No-259

-Dubnio, Db-268

-Roentgenio, Rg-281

-Moscovio, Mo-288

Gamma radiation emitters

Some radioisotopes that emit gamma radiation are:

-Cobalt-60

-Barium-133

-Zinc-65

-Potassium-40

-Manganese-54

-Cesio-137

-Sodium-22

Beta radiation emitters

-Strontium-90

-Sulfur-35

-Carbon-14

-Tritium ( 3 H 1 )

Alpha radiation emitters

-Uranium-238

-Polonio-210

Applications of radioactivity

Spherical nuclear reactor surrounded by cooling towers. Source: Avda / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Medicinal

Radioactive isotopes are used in medicine for diagnostic and therapeutic purposes. Some radioactive isotopes serve as tracers for the diagnosis of diseases, since they have the same characteristics as the atoms of non-radioactive elements.

Iodine-131 is used in medicine for the determination of cardiac output and plasma volume . But the most important application of iodine-131 is to measure the activity of the thyroid gland, since the thyroid hormones carry iodine.

Phosphorous-32 is used in the determination of the presence of malignant tumors, since cancer cells tend to absorb more phosphate than normal cells. Technetium-99 is used in determining the anatomical structure of organs.

Cobalt-60 and cesium-137 are highly penetrating gamma emitters used to kill cancer cells, with minimal damage to neighboring cells.

Scientific and academic activities

Radioactivity is used to determine the requirements of plants that must be supplied by soils. Radioactive materials are also used to determine, through the use of gas chromatography, the components of oil and smoke.

In archaeological studies, carbon-14 activity is used to determine the age of certain fossils. This isotope occurs naturally in the atmosphere and is only incorporated by living things.

Irradiation of plants is used to induce mutations and make them more resistant to environmental conditions.

Industry

Radioactivity is used to sterilize medical materials. It is also used in the sterilization of food and the containers that contain it.

In addition, radioactivity is used in the processing of fabrics, prior to a treatment that makes them resistant to wrinkles.

Cookware with non-stick properties are treated with radioactivity to prevent food from sticking to the metal surface. Radioactive tracers are used to determine the efficiency of motor oils in automobile engine cylinders.

Radioactivity is used in the removal of toxic gases, such as sulfur dioxide and nitrogen oxides from the environment. The radioactive material is used to measure the thickness of the eggshells, and also to remove the fragile eggs before proceeding to their packaging.

The polyethylene material used as the wrapper is also subjected to radioactivity. The radioactive treatment allows the polyethylene to be heated and make it adhere properly to the food it covers.

In addition, radioactivity is used to determine fluid levels in oil and chemical tanks, as well as the moisture and density of soils and materials at construction sites. It is also used to determine imperfections in metal castings and welds.

Nuclear reactors

They are a facility capable of producing prolonged chain reactions. They are used for: the production of heat used in the generation of electricity for the different uses of the population. They are also used to manufacture materials for maritime nuclear propulsion, artificial satellites and rockets.

They allow the transmutation of chemical elements to create radioactive isotopes; for example, americium, used in smoke detectors, and cobalt-60 for medical use. And finally, these reactors produce plutonium for nuclear weapons and fuel for other reactors.

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