Overview
This lecture introduces the basics of ionizing radiation, its sources, key concepts, and typical human exposure, aiming to provide foundational knowledge for various professionals.
Introduction to Radiation
- Radiation is energy from a source that travels through space at the speed of light, often as electromagnetic waves.
- Visible light is a familiar form of radiation and part of the electromagnetic spectrum.
- The electromagnetic spectrum includes radiation with energies lower and higher than visible light, such as infrared, microwaves, ultraviolet, x-rays, and gamma rays.
- Specialized instruments are required to detect most types of radiation outside the visible spectrum.
Ionizing Radiation
- Ionizing radiation includes x-rays and gamma rays, which have enough energy to remove electrons from atoms (ionization).
- Only higher energy radiation (ultraviolet, x-rays, gamma rays) is ionizing; lower energy types like radio waves and microwaves are not.
Radioactive Atoms and Isotopes
- Atoms consist of protons, neutrons (in the nucleus), and electrons.
- Stability depends on the balance between protons and neutrons; imbalance leads to radioactivity.
- Radioactivity is the spontaneous release of energy from an unstable atom as it becomes more stable.
- Isotopes are versions of the same element with different numbers of neutrons; radioactive isotopes are called radionuclides.
Types and Sources of Radioactive Material
- Radioactive materials can be solids, liquids, or gases.
- Primordial radionuclides (e.g., uranium, thorium, potassium-40) have existed since the planet’s formation.
- Cosmogenic radionuclides (e.g., carbon-14) are produced by cosmic rays interacting with the atmosphere.
- Man-made radionuclides (e.g., cesium-137) result from human activities like nuclear fission and are used in medicine and industry.
- Some ionizing radiation, like that from x-ray machines and CT scanners, is machine-generated and does not involve radioactive materials.
Radiation Exposure and Dose
- The amount of radiation exposure is called dose, measured in millirems (mrem) in the U.S.
- The average person receives ~3 mrem from natural sources (cosmic rays, ground, food, radon) and ~3 mrem from medical procedures annually.
- Radon gas from soil is the largest natural source of background radiation.
- Individual dose varies based on factors like smoking, elevation, medical procedures, and lifestyle.
Risks and Benefits
- Medical uses of radiation, such as x-rays and CT scans, provide significant health benefits despite exposure risks.
- Risk-benefit analysis is important when considering exposure to ionizing radiation.
Key Terms & Definitions
- Radiation — Energy that originates from a source and travels through space.
- Ionizing Radiation — Radiation with enough energy to remove electrons from atoms.
- Radioactivity — Spontaneous release of energy from an unstable atom.
- Radionuclide/Radioactive Isotope — Radioactive atoms of the same element with different neutron numbers.
- Radioactive Decay — Process by which an unstable atom becomes stable by emitting radiation.
- Dose — Amount of radiation exposure received, measured in millirems (mrem).
- Half-life — Time required for half the quantity of a radioactive substance to decay.
Action Items / Next Steps
- Complete the remaining segments of this training for a deeper understanding.
- Visit the CDC website for additional resources and training products.
- Consider submitting feedback or questions via email as invited.