radionuclide

Examples of radionuclide in the following topics:

• Nuclear Stability

  • An atom with an unstable nucleus, called a radionuclide, is characterized by excess energy available either for a newly created radiation particle within the nucleus or via internal conversion.
  • During this process, the radionuclide is said to undergo radioactive decay.
  • Radionuclides occur naturally but can also be produced artificially.
  • All elements form a number of radionuclides, although the half-lives of many are so short that they are not observed in nature.
  • The heaviest elements (heavier than bismuth) exist only as radionuclides.

• Calculations Involving Half-Life and Decay-Rates

  • The half-life of a radionuclide is the time taken for half the radionuclide's atoms to decay.
  • The half-life of a radionuclide is the time taken for half of the radionuclide's atoms to decay.
  • Half-lives of known radionuclides vary widely, from more than 1019 years, such as for the very nearly stable nuclide 209 Bi, to 10−23 seconds for highly unstable ones.
  • The time constant τ is the e-1-life, the time until only 1/e remains -- about 36.8 percent, rather than the 50 percent in the half-life of a radionuclide.

• Isotopes in Medicine

  • In nuclear medicine procedures, radionuclides are combined with other elements to form chemical compounds.
  • In addition to imaging, radionuclide therapy can be used to treat conditions such as hyperthyroidism, thyroid cancer, and blood disorders.

• Matter and Antimatter

  • The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.

• Natural Radioactivity

  • Radon and its isotopes, parent radionuclides, and decay products all contribute to an average inhaled dose of 1.26 mSv/a.
  • The major radionuclides of concern are potassium, uranium, and thorium and their decay products.

• Rate of Radioactive Decay

  • Particular radionuclides decay at different rates, so each has its own decay constant, λ.
  • At present, it is equal, by definition, to the activity of any radionuclide decaying with a disintegration rate of 3.7 × 1010 Bq, so that 1 curie (Ci) = 3.7 × 1010 Bq.

• Iron Oxidation

  • While these processes may often be less significant ecologically, they are of considerable interest for bioremediation, especially when heavy metals or radionuclides are used as electron acceptors.

• Emission Topography

  • The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.

• Half-Life of Radioactive Decay

  • Given a sample of a particular radionuclide, the half-life is the time taken for half of its atoms to decay.

• The Periodic Table

  • Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.