Atomic Structure: Essential for understanding ionizing radiation.
Components of an Atom:
Nucleus: Contains neutrons and protons
Neutrons: Neutral charge
Protons: Determine atomic number
Electrons: Found in rings around the nucleus
Definitions:
Ionization: Removal of an electron from an atom, creating an ion pair.
Results in a negatively charged electron and a positively charged residual atom.
Consequences of Ionization:
Can lead to cell injury or death.
Alters cell reproduction, division, and may cause mutations, leading to outcomes such as cancer.
Types of Ionizing Radiation
Overview of Radiation Types
Focus on:
Alpha Radiation
Beta Radiation
Positron Radiation
Neutron Radiation
X-Rays
Gamma Rays
Alpha Radiation
Nature: Consists of helium nuclei (2 protons and 2 neutrons).
Charge: +2
Mass: Heavy compared to other forms.
Energy: 4 to 8 mega electron volts (MeV).
Range: Limited range (cannot travel more than 60 microns in tissue). Shielding is easy (e.g., skin).
Sources: Common isotopes include uranium and radium.
Linear Energy Transfer (LET): High, with a quality factor of 20.
Beta Radiation
Nature: High-speed electrons emitted from the nucleus, can be positively or negatively charged.
Mass: Much lighter than alpha particles.
Energy: 0.1 kiloelectron volts (keV) to 5 MeV.
Range: Can travel in air for several feet; limited range in tissue (few millimeters).
Quality Factor: 1.
Sources: Common isotopes include tritium, carbon-14, strontium-90, and phosphorus-32.
Hazards: Can cause damage through ingestion or inhalation, easily shielded by materials such as glasses.
Gamma and X-Rays
Nature: Consist of photons ejected from the nucleus with no charge.
Energy Level: Typically in the range suitable for ionization.
Range: Unlimited, similar to the speed of light.
Quality Factor: 1, low compared to particle radiation.
Shielding Needs: Requires materials such as concrete or lead.
Common Emitters: Potassium-40, iodine-131, cobalt-60.
Neutron Radiation
Nature: Free neutrons emitted from the nucleus usually as a byproduct of nuclear fission.
Stability: Man-made and unstable; decay occurs through beta emission.
Quality Factors: Varies based on speed—slow (thermal), intermediate, and fast.
Neutron Activation: Ability to initiate radioactivity in other substances, including human tissue.
Electromagnetic Spectrum and Ionizing Radiation
Positioning in Spectrum: Ionizing radiation appears on the right side of the electromagnetic spectrum, characterized by higher frequency, shorter wavelength, and high energy.
Types and Effects: The energy from ionizing radiation can produce ionization in materials.
Decay Rates: Different isotopes have distinct half-lives affecting control strategies and decay rates.
Control of Ionizing Radiation
Risk Assessment and Application
Key factors in assessing risk: source, intensity, and duration of exposure.
Exposure Types: Chronic exposure versus acute effects.
Chronic exposure (long-term) linked to cancer and organ failure.
Acute effects, such as gastrointestinal issues from exposure to high doses.
Measurement Units
Units of Exposure:
Roentgen (R): Measures ionization in air due to x-rays and gamma rays.
Radiation Absorbed Dose (rad): Measures energy absorbed per mass of matter (measured in Joules/kg).
Dose Equivalent (rem): Adjusted based on quality factor; helps assess biological effects.