Section outline

    • The type of atom classified by the number of protons and neutrons in the nucleus is called nuclide. Radioactive nuclides are called radionuclides (reference: ATOMICA).　
      The type of atom is determined by the number of protons. Even with the same atomic species (same number of protons), there are things with different numbers of neutrons. The nuclide distinguishes them.

      For example, naturally occurring potassium with an atomic number of 19 (19 protons) are three types, potassium 39 (K-39) with an atomic weight of 39 (19 protons and 20 neutrons), and potassium with an atomic weight of 40 (19 protons and 21 neutrons).  and potassium 41 (K-41) with an atomic weight of 41 (19 protons and 22 neutrons), and these are called isotopes. Of these, potassium-39 and potassium-41 are called stable nuclides because they are not radioactive, while potassium-40 is called a radionuclide because it is radioactive (reference: ATOMICA).

    • In this course, radionuclides include man-made radionuclides and natural radionuclides found in nature.

      Artificial radionuclides include:

      ① Those derived from nuclear tests (mostly atmospheric nuclear tests)

      ② Derived from accidents at nuclear-related facilities

      ③ Derived from planned releases under the control of nuclear-related facilities

      there is. Radioactive cesium-137 is explained below for ① to ③.