Ionizing Radiation Flashcards
What is radiation?
Energy in the form of rays (waves) or corpuscles (particles) that emanate from a source
Describe background radiation
cosmos produces radiation & sun emits radiation, but only small amount reaches the earth
What happens to most of the energy produced by the cosmos?
energy lost when passing though the atmosphere
Is life still exposed to cosmic radiation?
yes
Where is cosmic radiation exposure the strongest?
at the poles and high elevations
What are the types of ionizing radiation?
- alpha
- beta
- gama
- x rays
- neutrons
What are the types of nonionizing radiation?
- UV
- Visible
- IR
- Microwave/ RF
What is ionizing radiation?
particles with enough energy to push electrons out of a material and generate ions
What is nonionizing radiation?
- particles that have enough energy to excite atoms into higher energy state, but cannot ionize
What effects can nonionizing radiation have?
radiation and field effects
what is the name of the measurement for exposure (x)
roentgen
What is the name of the measurement for absorbed dose (D)?
Rad or gray
What is the measurement for activity (A)?
CUrie or becquerel
What is the measurement for dose equivalent (H)
roentgen equivalent in man or sievert
What are the types of ionizing particles?
- Alpha
- Beta
- Neutrons
- Protons
Are ionizing particles charged?
They can be charged or uncharged
What are the types of ionizing electromagnetic waves
gamma rays
x rays
What are radioactive materials?
unstable forms of elements (radioisotopes or radionuclides) that decay to stable elements
What happens to radioactive materials as they decay?
emit ionizing radiation
Where are radioactive materials found? where are they more concentrated?
soil, water, air
more concentrated in houses, mines
What size elements are unstable?
Anything heavier than 209Bismuth
What is radioactive decay?
atom moves from an unstable to a stable state resulting in a series of emissions of energy and or matter from the atom
Do all radioactive elements decay into a stable element?
No- some decay into different radioisotopes until they are finally stable
Is there always radiation with radioactive material?
Yes
Does radiation always come from radioactive material?
no- can be artificially generated
Are electron microscopes radioactive?
No
What is the defining characteristic of radioactive materials?
radioactivity
Does the presence of radiation always imply a radioactive source
No
How do radiation-producing machines work?
Accelerate a beam of electrons in a vacuum tube and emit x-rays
Can radiation-producing machines be turned on and off?
yes
Give examples of radiation producing machines
medical devises, security, electron microscopes
How do nuclear reactors work?
Split large atoms (fission) by bombarding them with neutrons and generate energy (heat)
What type of testing has left some residues of radioactive material in the atmosphere?
nuclear weapons testing
What are the different forms for sources of ionizing radiation?
- sealed sources
- radiation machines
- radioisotopes + machine
- unique radioisotopes
What are the examples of radiation machines sources?
- x rays
- computed (axial) tomography (CAT Scan)
What are the examples of radioisotopes + machine sources?
- Positron emission tomography (PET, gamma)
- research
What are examples of unique radioisotopes?
- U & Pu
- Hydrogen 3- tritium
Name workplaces where one would find ionizing radiation?
- healthcare
- radiography
- refineries & chemical plants
- fracking
- airport screeners (TSA)
- research
- nuclear plants
- weapons
What workplaces would one find nonionizing radiation?
- outdoor occupations
- ovens, molten metal
- power transmission
- welding
- radar
- lasers
- electrical equipment
What is the relationship between the number of protons and nuetrons in the typical atom?
usually the same
When doesn’t the atom have an electrical charge?
when protons and electrons are the same
What are ions?
atoms of molecules in which the total number of electrons is not equal to the total number of protons (net positive or negative charge)
Give an example of a radioactive element
Uranium
What is given off as a heavy, unstable element like uranium decays?
- alpha particles
- gamma rays
- protons
- beta particles (electrons)
- neutrons
What type of ionizing radiation is the alpha particle?
corpuscular ionizing radiation
How many protons/ neutrons do alpha particles have?
2 neutrons/ 2 protons (Helium nucleus)
Do all alpha particles have the same energy?
yes
How do alpha particles interact with other substances?
- quick interaction with substances and creation of ions
- high ionization along path of emission, releases energy all in one place
What type of LET do alpha particles have?
High linear energy
Are alpha particles externally dangerous?
No- short range and easily stopped
Are alpha particles dangerous internally?
through inhalation or ingestion - very damaging to cells
Give examples of alpha emitters
U-238, Pu-238, Pu-239, Ra-226, Rn-222, Po-210, Am-241
What is LET?
linear energy transfer
What type of radiation are beta particles?
corpuscular ionizing radiation
What are beta particles and how are they formed?
Electrons & Positrons emitted by radioactive material
- breakup of a neutron into electrons and positrons
How do beta particles interact with other atoms?
interact with electrons of materials they go through and ionize
Compare LET between alpha and beta particles
Beta- less interaction than alpha particles and low LET
What are secondary x-rays produced when a beta moves through a material?
Bremsstrahlung radiation
Do beta particles have natural or artificial sources?
both
What industries use beta particles?
medical research and industrial applications
What do health effects of beta particles depend on?
Skin, Eye, and Internal Health risk
Give examples of low energy b emitters
H-3, C-14, S-35, Pu-241
Give Examples of high-energy b emitters
P-31, Sr-90, I-131
What type of ionizing radiation are neutrons?
corpuscular ionizing radiation
What is a neutron?
neutral charge from the nucleus of the atom
What are the different energy levels of the neutron?
- High- travel farther, penetrate more
- Low- less travel distance, less penetration
What are the health risk and exposure risks of neutrons?
Significant health risk, rare exposure except near reactors or accelerators
How can workers be shielded from neutrons?
high-hydrogen content- water, paraffin, concrete
What type of ionizing radiation are protons?
corpuscular ionizing radiation
What are protons?
positive charge inside the atom’s nucleus
How often are protons encountered?
rarely
What careers may be concerned about protons?
astronauts, doctors, researchers
Describe the LET of protons
lose energy relatively slowly (low LET) until energy spike at the end of their path (high LET)
What wavelengths are capable of producing ionization?
<300 nm
Energy is directly related to ____
frequency
What is directly proportional to E & F
wavelength
What are gamma rays?
energy emission (photons) from the nucleus as a result of radioactive decay
What is the health risk for gamma rays?
significant health risk
What are examples of low energy gamma rays
I-125, I-129, Am- 241
What are examples of medium - high energy gamma rays?
I-131, Cs-137, Co-60, Ir-192
What are x-rays?
energy emission (photons) from the outside of the nucleus when electrons drop to lower energy orbitals
How can x-rays be artificially produced
bombardment of a target chemical with high speed electrons
What is the health risk with x-rays?
significant health risk
What are the different energy and wavelengths for x-rays?
- Hard- shorter wavelength, higher energy, more penetrating
- Soft- longer wavelength, lower energy, less penetrating
Describe penetration of alpha, beta, and gamma rays
alpha- easily stopped, does not penetrate
beta- penetrates skin, stopped by aluminum
gamma- penetrates and stopped by thick lead
Increased energy to tissue ___ risk
increases
What are the key components for any radiation?
1) source
2) transmission
3) receiver
Describe the historical health effects of radiation?
X-rays used since 1898- medical personnel had damage to hands (deterministic exposure) and developed cancer (stochastic exposure)
When are deterministic effects experienced?
When dose is high enough
What is a deterministic effect?
Severity of the outcome depends on the dose
How can you avoid deterministic effects?
stay below threshold
What are examples of deterministic effects?
- radiation detmatitis
- cataracts
- sterility
- microcephaly of babies
- mental retardation of babies
What are stochastic effects?
Occur by chance and without a threshold dose, all or nothing
Describe risk of stochastic effects
- risk of developing condition of disease increase with increase in exposure but only a fraction of those exposed develop the health effects
describe severity of stochastic effects
severity the same regardless of exposure
What are examples of stochastic effects
- smoking and lung cancer (all get the same cancer regardless of the amount smoked)
- birth defects & genetic diseases
What are chronic health effects of ionizing radiation?
1) lung cancer
2) leukemia
3) decreased lifespan
What are acute health effects of ionizing radiation?
1) damage to central nervous system
2) damage to inner lining of GI tract, esp. intestinal villi
3) immune system: destruction of leukocytes (WBC) and stem cells
4) skin burns
What is the average annual dose to natural background radiation?
2.4 mSv
How can uranium cause cancer?
breaks into smaller atoms and particles that enter human cell, strike nucleus and damage DNA. Causing it to divide uncontrollably- cancer
What is the difference between exposure and contamination?
Exposure- energy transmitted to the target in the body
Contamination- radioactive substance on an external surface or in a medium (air, water…) that can usually be removed
Can you have exposure and contamination independent of one another? and together?
can have exposure only, exposure and contamination, and contamination only
Are contaminated substances intrinsically radioactive?
no
If contamination removed is the substance still radioactive?
no
What is the general term for measuring devices for ionizing radiation?
ionization devices
How do ionization devices work?
air molecules in sealed chamber are ionized- current proportional to the exposure
What are examples of area samplers used for ionization?
- ionization chambers
- Geiger Mueller counters
- Proportional counters
What are the limitations of ionization devices?
have limitations with low-energy photon materials
instrument where molecules are ionized producing an emission of light related to the energy output and unique energy level of the specific type of radioisotope
scintillation counters
What are personal sampling devices for ionizing radiation?
1) dosimeter
2) Film badges
3) Thermoluminescence Detector
4) Pocket dosimeter
Describe dosimeters
- passive or instant read
- multiple detectors sensitive to multiple types of radiation or may need to wear multiple
- extremity monitoring common (ie ring)
- do have electronic, limited in functionality
What is the difference between passive dosimeter and instant read dosimeters?
passive- worn for a while then evaluated
Instant read- give immediate result but not available for as wide a range of radiation types as passive
Describe film badges
film exposed to radiation and developed (obsolete)
Describe TLDs
- lithium fluoride reacts with radiation and electrons are excited
- readout device heats the TLD, excites electrons, and they emit light proportional to exposure
Describe the pocket dosimeter
Electrostatic charging of a fiber wand that moves along a scale
What is calibration necessary for?
Electronic dosimeters
What other sampling methods are used for ionizing radiation?
- stationary monitors
- wipe sampling
- alpha track detectors (radon)
How are wipe samples read?
with scintillators
What are the main controls for ionizing radiation?
1) Keep dose ALARA (As Low As Reasonably Achievable)
2) Time (1/2 the time, 1/2 the exposure)
3) Distance (Dose rate decreases with increased distance)
4) Shielding
What is the equation for distance?
DR2=DR1 x r1^2/r2^2
DR2=DR1 x r1^2/r2^2
What is DR1 and r?
DR- dose rate
r1- distance from the point source
SLIDE 4/486- Equation
Slide 46- Equation
What is the half value layer?
thickness of a material required to stop half of the radiation
What are additional controls for ionizing radiation?
- PPE
- Education
- Need to consider other characteristics such as the chemical nature of a radioisotope
- overall radiation safety program
What are the concerns with ionizing radiation?
- money and technology to handle radioactive waste- store locally vs. 1 central storage site?
