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Radionuclides in Drinking Water

Module 1: Basics of Radioactivity


The structure of the atom is essential to the study of radioactive decay and radiochemistry. The module "Basics of Atomic Radioactivity"

  • describes the fundamental concepts related to the structure of the atom,
  • explains the nature of the particles that make up the atom,
  • identifies the difference between ionic and covalent bonding,
  • puts into perspective the size of the nucleus, the atoms components and the entire atom, and
  • defines terms used in nuclear and radiochemistry with regard to the nucleus.

The module is an overview of these concepts and should take about 20-25 minutes to complete.

The second part of this module develops the laws of radioactive decay parent and progeny relationships, types of radioactive decay and calculations involved with determination of activity. Several examples are provided for a more thorough understanding of the basic concepts behind the natural radioactive decay chains and the relationship of these radionuclides. It is essential to work through the many examples provided in this module in order to become familiar with the radioactive decay laws. This module should take about 60-70 minutes to complete.

Instructional Resources

This module is divided into 3 tutorials. Each tutorial is presented as a self-paced Adobe Flash video with audio narration. The learning aids that are provided for you to use in this module, which you may access via the links in the "Instructional Resources" panel on the right, include the "Multi-Agency Radiological Laboratory Analytical Protocols Manual" (MARLAP) section on radioactive decay and equilibrium, a Periodic Table of the Elements and example diagrams of radioactive decay chains. You may wish to print out the PDF transcript of the audio narration, also available from a link in the "Instructional Resources" panel. The "Links to Additional Information" provide more in-depth discussions of these topic areas.


Tutorial 1.1 - Basics of Atomic Theory

At the end of this tutorial you will be able to:

  • Explain the basic structure of an atom by describing the location, mass and charge of protons, neutrons, and electrons, and describe the concept of electron orbitals.
  • Define the terms "atom," "element," "atomic number," and "mass number."
  • Discuss the relationship between valence electrons, electronegativity, ionic bonding and covalent bonding.
  • Calculate the mass of each stable isotope in a mixture based on its molecular weight and its isotopic abundance.
Tutorial 1.2 - Introduction to Radioactivity

At the end of this tutorial you will be able to:

  • Define the term "activity" and state its units.
  • Define the term "half-life".
  • Understand the relationship between half-life and decay constant.
  • Calculate the mass of a radionuclide based on its activity.
  • Calculate activity of a radionuclide in a sample either in the past or in the future.
Tutorial 1.3 - Decay Chains and Radiochemical Equilibria

At the end of this tutorial you will be able to:

  • Define the terms "decay chain," "parent," and "progeny" as they apply to radionuclides.
  • Describe the difference between ingrowth period, transient equilibrium, secular equilibrium, and no equilibrium in parent-progeny mixtures.
  • Explain why it is necessary to account for radiochemical equilibrium when analyzing for radionuclide concentration.
  • Calculate the amount of time required for a progeny radionuclide to achieve maximum activity after purifying the parent radionuclide.

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