An overview of Radioactivity Definition & Meaning

What is Radioactivity

Unstable atomic nuclei disintegrate spontaneously to form more stable nuclei. This process of decomposition is known as radioactivity. Radiation refers to the energy and particles emitted during the breakdown process. In other words, they are the particles emitted from the nuclei due to nuclear instability. 

Natural radioactivity is the process through which unstable nuclei break down in nature. Artificial radioactivity is when we induce the decomposition of unstable nuclei in the laboratory. Several naturally occurring elements and artificially manufactured isotopes emit radioactive radiation as a feature. 

A radioactive element’s half-life is the time it takes for one-half of any given quantity of the isotope to decay. Some nuclei have half-lives of more than 1024 years, while others have half-lives of less than 10-23 seconds. 

The daughter of the parent isotope, i.e., the outcome of radioactive radiation, may be unstable, in which case it will decay. The procedure repeats until the creation of a stable nuclide.

Types of Radioactivity/Radiation

There are three main types of radioactivity based on the particles emitted as radiation.

• Alpha Radiation: 

Alpha radiation or alpha rays are heavy, short-range particles created when a helium nucleus is expelled. Radium, thorium, uranium, and radon are some alpha emitters.

Although alpha radiation only goes a small distance (a few inches) in the air, it poses no external threat. The majority of alpha radiation does not penetrate human skin. Moreover, clothing does not allow alpha radiation to pass through. However, alpha-emitting materials can be dangerous to people if absorbed through open wounds.

Because alpha radiation is not penetrating, instruments cannot detect it through even a tiny coating of water, dust, paper, or other material. Researchers have developed several instruments to monitor alpha radiation. Among these devices, the Geiger-Mueller (GM) probe with a thin window is popular. For reliable measurements, special training to operate these instruments is necessary. 

• Beta Radiation: 

Beta radiation or beta rays are short-range, light particles created on the expulsion of an electron. Strontium-90, tritium, carbon-14, and sulphur-35 are some beta emitters.

Beta radiation is moderately penetrating and can travel many feet in the air. This radiation can penetrate the ‘germinal layer’ where new skin cells are formed. Skin damage can occur if large quantities of beta-emitting pollutants remain on the skin for an extended period. Clothing can help shield from beta radiation. If beta-emitting pollutants are accumulated internally, they can be hazardous. 

A piece of survey equipment and a thin-window GM probe can discover most beta emitters (e.g., “pancake” type). On the other hand, specific beta emitters generate low-energy, weakly penetrating radiation that is difficult to detect. Hydrogen-3 (tritium), carbon-14, and sulphur-35 are examples of these difficult-to-detect beta emitters. 

• Electromagnetic Radiation: 

Electromagnetic radiation consists of visible light, radio waves, ultraviolet light, gamma, and X-rays. The sole difference between these electromagnetic radiations is the quantity of energy they contain. The most energetic of them are gamma and X-rays. Iodine-131, radium-226, cobalt-60, cesium-137, and technetium-99m are some gamma emitters.

Both X-rays and gamma rays are highly penetrating electromagnetic radiations. They are commonly referred to as “penetrating” radiations since they can easily permeate most things. Humans are primarily at risk from sealed radioactive sources and machines that release gamma radiation and X-rays. 

Gamma radiation may travel hundreds of feet in the air and several inches into human flesh. Shielding from gamma radiation necessitates dense materials. Clothing offers minimal protection against penetrating radiation, although it does protect the skin from gamma-emitting radioactive elements. 

Gamma radiation can be easily detected using survey metres with a sodium iodide detection probe. During radioactive radiations, gamma and distinctive X-rays commonly accompany the emission of alpha and beta radiations. 

Units of Radioactivity

Radioactivity is a physical phenomenon, not a biological one. We can assess a sample’s radioactivity by counting the number of atoms that undergo spontaneous decay per second. We can use sensors to identify the specific type of radiation produced by each “decay” or disintegration. 

The number of disintegrations per second may be pretty significant. As a type of shorthand, scientists have agreed on a set of common units of radioactivity. As a result, a curie is simply a shorthand for “37,000,000,000 disintegrations per second.” It indicates the rate of disintegration in 1 gram of radium. 

The becquerel (abbreviated “Bq” and named after Henri Becquerel, the discoverer of radioactivity) is a more recent International System of Measurements (SI) for units of radioactivity.

Artificially Produced Radioactivity

Radioactivity can occur spontaneously and also as a result of human involvement. Neutron activation is an example of artificially generated radioactivity. 

The discharge of a neutron from a nucleus (splitting atoms) can cause nuclear fission. This principle is the atomic bomb’s central concept. 

Neutron activation is the underlying idea of boron-neutron capture therapy for certain brain tumours. A boron solution is injected into a patient, and cancerous cells absorb it more than their normal counterparts. The boron nuclei quickly absorb (catch) neutrons fired at the brain tumour site. As a result, these nuclei become unstable and produce radiation, destroying cancer cells. 

While simple, in theory, the treatment has proven complex and contentious in practice. Researchers still consider this therapy highly experimental even after half a century of its invention.

Conclusion

Radioactivity is the process by which particles are emitted from nuclei due to nuclear instability. There are three types of radioactivity: alpha radiation, beta radiation, and electromagnetic radiation. The SI unit of radioactivity is Bq or becquerel.  

This article has discussed everything you need to know about radioactivity. It discusses the definition, types, and measurement of radioactivity.