What is Radionuclide

In the vast realm of atomic science, radionuclides stand as captivating enigmas, carrying profound implications for our understanding of the natural world. These fascinating entities, also known as radioactive isotopes, are atoms imbued with an unstable nature, eagerly yearning to shed their excess energy and establish a state of equilibrium. Through the intricate process of radioactive decay, radionuclides offer us a glimpse into the intricate fabric of the atomic realm.

Figure 1. Neutron-activated theranostic radionuclides for nuclear medicine. (Tan HY, et al.; 2020)

At the core of every radionuclide lies a nucleus teeming with protons and neutrons, tightly bound together by the strong nuclear force. Yet, despite this harmonious arrangement, some nuclei find themselves in a precarious state, hosting an excess of internal energy. This energy surplus arises from an imbalance in the interplay between protons and neutrons within the nucleus, resulting in an unstable configuration.

Driven by an inherent desire to achieve stability, radionuclides embark on a transformative journey known as radioactive decay. This process involves the spontaneous emission of particles or electromagnetic radiation from the nucleus, ultimately leading to the formation of a different nucleus and the release of energy. Such emissions can take various forms, including alpha particles, beta particles, gamma rays, and even more exotic particles.

Alpha decay, characterized by the emission of an alpha particle—an assemblage of two protons and two neutrons—enables the nucleus to reduce its size and restore a more balanced composition. As the alpha particle escapes from the nucleus, the parent radionuclide transmutes into a new element, often situated higher in the periodic table. This transformation allows the newly formed nucleus to achieve a more favorable energy configuration, inching closer to stability.

In contrast, beta decay unfolds through the emission of beta particles, which can manifest as either electrons or positrons. This type of decay arises when the balance between protons and neutrons is askew. In beta-minus decay, a neutron within the nucleus converts into a proton, while simultaneously emitting an electron and an antineutrino. Conversely, beta-plus decay involves the conversion of a proton into a neutron, accompanied by the emission of a positron and a neutrino. By undergoing beta decay, radionuclides strive to restore the equilibrium between protons and neutrons, fostering a more harmonious nuclear arrangement.

Gamma decay, another prominent mode of radioactive decay, involves the release of gamma rays—energetic photons that carry no charge or mass. Unlike alpha and beta decay, gamma decay does not alter the composition of the nucleus. Instead, it aims to expel excess energy in the form of electromagnetic radiation, allowing the nucleus to attain a more stable state.

The study of radionuclides extends far beyond their mere radioactive properties. These fascinating entities find applications in a multitude of fields, ranging from medicine and industry to environmental monitoring and scientific research. In the realm of medicine, radionuclides serve as invaluable tools for diagnostic imaging and cancer therapy. They can be introduced into the human body, selectively targeting specific organs or tissues, and emitting radiation that can be detected and analyzed to provide valuable medical information.

Furthermore, radionuclides play a crucial role in the field of nuclear energy. Nuclear power plants harness the controlled decay of certain radionuclides to generate electricity. By precisely controlling the release of energy from the decaying nuclei, these facilities can produce vast amounts of power, offering a promising alternative to traditional fossil fuel-based energy sources.

Nevertheless, the allure of radionuclides is not without its risks. The emitted radiation, if not properly managed, can pose hazards to human health and the environment. Hence, the responsible handling and disposal of radioactive materials are of paramount importance to mitigate.

Reference

1. Tan HY, et al.; Neutron-activated theranostic radionuclides for nuclear medicine. Nucl Med Biol. 2020, 90-91:55-68.