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Beta Radiation (Beta Rays) | Beta-minus and Plus Radio radioactivity

Beta Radiation (Beta Rays) β

Beta radiation is a form of radioactivity in which the nucleus emits electrons and antineutrinos (beta minus radiation) or positrons and neutrinos (beta plus radiation). This process gives rise to another nucleus with one fewer neutron and one more proton than the original nucleus. The work of Wolfgang Pauli, Francis Perrin and Enrico Fermi made it possible to understand in 1932-1934 that beta minus decay is caused by the transmutation of neutrons into protons.

Modern theory of electro-weak interactions describes this process at a basic level as the emission of a W boson by a d quark turning into a u quark, with the W boson manifesting into electrons and antineutrinos. An electron capture reaction in which the nucleus absorbs electrons and emits neutrinos while increasing the number of neutrons and reducing the number of protons by one unit is an inverse beta reaction and the theoretical understanding is similar.

Beta radiation, emitted by radioactive atoms, is a beam of electrons. Beta radiation causes more damage than alpha radiation because it is electrically charged.

How to protect yourself from Beta Radiation?

To protect against beta radiation, a simple sheet of aluminum of a few millimeters will suffice. You can also use a sheet of glass or a one-centimeter plexiglass screen, which can stop most beta particles.

Biological effects of beta rays on health

If the human body is exposed to beta rays from the outside, only the skin layer is damaged. However, there may be intense burns and the resulting long-term effects such as skin cancer. If the eye is exposed to radiation, the lens may become cloudy. If beta emitters are absorbed (coupled) into the body, exposure to high levels of radiation may occur in the vicinity of the transmitter.

Thyroid cancer is well documented as a result of radioactive iodine-131 (131I) accumulating in the thyroid gland. There is also concern in the literature that strontium -90 (90Sr) may cause bone cancer and leukemia because strontium, like calcium, builds up in bones.

Beta decay – and +

There are two forms of beta – decay, + decay and emission, which produce electrons and positrons, respectively.

Beta particles occur with a negative or positive charge (β- or +) and are known as electrons or positrons, therefore beta decay represents radioactive decay, where beta particles are emitted. The kinetic energy of beta particles has a continuous spectrum.

Beta-minus radioactivity is the emission of electrons and antineutrinos that accompany the transformation of a neutron into a proton. Beta-plus radioactivity, in contrast, is the transformation of protons into neutrons by the emission of positrons and neutrinos. Neutrinos or antineutrinos are nearly undetectable particles.

Read also: Neutron Radiation | Risks and Effects on Health, Role in Nuclear fission

These are electrons thrown away from beta decay. According to Fajans law, if an atom emits a beta particle, its electric charge increases by one positive unit and its mass number does not change.

This is because the mass or mass number only represents the number of protons and neutrons; in this case the total number is unaffected, because the neutrons become protons, emitting electrons. It should be noted that the emitted electrons come from the atomic nucleus (transformations between quarks) and not from their orbitals.

Beta minus decay

If the number of neutrons in the nucleus is more, the neutron will undergo the following transformation: n –> p + – + e*, that is, the neutron will be converted into a proton by beta-minus emission of particles (electrons) and antineutrinos. Antineutrinos have no rest mass or electric charge and do not readily interact with matter.

For an isotope that undergoes – decay, each nucleus emits an electron and an antineutrino. The mass number remains the same but the atomic number increases by one.

There are many examples of beta minus transmitters in nature like 14C, 40K, 3H, 60Co etc. An important example in radiology is the decay of cobalt-60: 60Co –> 60Ni + – + *.

Beta plus decay

If the number of neutrons in the nucleus is less than the number of protons in an unstable nucleus, protons will undergo the following transformations: p –> n + + + e, i.e. protons will be converted into neutrons by emission of positrons (β+ or beta plus particles) and neutrinos . Similar to antineutrinos, neutrinos have no electric charge or rest mass.

In the case of + decay, each decaying nucleus emits a positron and a neutrino, reducing its atomic number one by one while the mass number remains the same.

A positron does not exist for a long period of time in the presence of matter. It then combines with an electron, with which it undergoes annihilation. The masses of the two particles are then replaced by electromagnetic energy emitted from the annihilation in the form of two 511-keV gamma rays emitted in almost opposite directions.

There are no positron emitters in nature. They are produced in nuclear reactions. The most important positron emitters in medicine are 11C, 15O, 18F, 30P etc.

Sources: PinterPandai, ARPANSA, Science Direct, U.S. Environmental Protection AgencyHealth Physics SocietyMinistry of the Environment Government of JapanOccupational Safety & Health AdministrationNational Center for Biotechnology Information (NCBI)

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