This document discusses radiation sources, types of radiation, and radiation detection devices for emergency responders. It identifies common radiation sources, describes how radiation can impact humans, and defines key radiation measurement terms like absorbed dose, equivalent dose, and half-life. The document outlines different types of radiation detectors including Geiger-Mueller tubes, scintillation crystals, and gamma spectroscopy devices. It stresses that responders need training to understand radiation monitoring and detection to safely respond to potential radiation incidents.

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2. Objectives
 Identify sources of radiation
 Describe the basis of radiation
 Identify types of radiation
 Describe radiation dose and its impact on humans
 Identify the common types of radiation detection
devices
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3. Introduction
 Most responder are uncomfortable in dealing with a
radiation response
 They lack in-depth understanding of radiation and its
hazards.
 With terrorism on the rise responders need to be
comfortable with the detection and monitoring
radiation.
 Nuclear detonation is very unlikely.
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4. Introduction
 Radiological dispersion device (RDD) is, using a conventional
explosive to distribute radioactive materials.
 There is any number of potential sources of radiation
that could be used.
 Radiation detectors for responders are divided into two major
groups.
 One measures exposure to radiation.
 One measures the current amount of radiation in the
area.
 To be effective measure radiation you will need at least two
detectors. There is not one detector that measures all 5 types
of radiation.
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5. Sources of Radiation
 We are subject to radiation every day
 Our bodies have radioactive substances
 We eat foods containing radiation every day
 We breathe in radiation with out harm everyday
 Our exposure to common radiation sources far exceeds
those that would be found at a nuclear power plant
 Television, Medical test, Elevation
 We are subjected to radiation that causes us no harm under normal
circumstances
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6. How Can Radiation Hurt Us
 Basic atom (nucleus)
 Electrons, neutrons, and protons
 Protons and neutrons reside in nucleus
 Electrons are negatively charged and orbit the
nucleus
 Protons have a positive charge and determine the
element or type of atom
 Neutrons are same size as protons but neutral
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7. How Can Radiation Hurt Us
 Each element, with a given number of protons, can
assume several forms, or isotopes.


Which are determined by the number of neutrons in the
nucleus?
The chemical properties of each isotope of an element are the
same.
 If there are too few or too many neutrons the nucleus
becomes unstable.
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8. Radioisotopes
 Isotopes, whose nuclei are unstable, are radioactive
and emit radiation to regain stability.
 This emission of radiation, is known as radioactive
decay

Usually takes form of Gamma radiation. May also be Alpha,
Beta, or Neutron?
 Unstable materials may become stable after one or two
decays.

Others may take many decay cycles.
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9. Radioisotopes
 Radioisotope decays by
the emission of an alpha
or beta particle.

The number of protons in
the nucleus changes.
 The radioisotope
becomes a different
element
 Examples
 Uranium is the base for
the development of
Radon


Common radioactive gas
found in homes
Radon decays into lead.
 Cobalt-60


Beta and Gamma energy
emitted
Decays to form Nickel-60
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10. Half-Life
 Amount of time for half of a radioactive source to
decay
 Activity of a source of radioactive material is a measure
of the number of decays per second that occur within
it.
 Physical size of radioactive source is not an indicator
of radioactive strength or activity.
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11. Radiation Dose
 As confusing as understanding the makeup of a radioactive
material, so is the calculation of the radiation dose.
 Three measurements can be used to describe radiation
dose.
$499

Absorbed dose

Equivalent dose

$595
Effective dose
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12. Absorbed Dose
 Measurement of energy transferred to a material by
radiation
 Measured in units called


Gray (Gy)
Radiation absorbed dose (rad)
 I gray = 100 ra
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13. Absorbed Dose
 Impact on humans, we need to understand the
absorbed energy on the body and potential biological
damage of radiation on humans. And convert the
absorbed dose to equivalent dose.
 Basic unit of equivalent dose is roentgen.

This value provides for the amount of ionization in air caused
by X-ray or Gamma radiation.

One roentgen equals 1 REM
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14. Absorbed Dose
 Radiation monitors measure three scales.
 REM (R)
 MilliRem (mR)
 MicroRem (µR)
 The dose of radiation is expressed by a time factor,
typically an hour.
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15. Radiation Protection
 Radiation dose should be kept
 “as low as reasonably achievable”

ALARA
 Three factors that influence radiation dose.
 Time
 Distance
 Shielding
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16. Radiation Protection
 Minimize dose,
 Stay near the radiation source for as little time as
possible.
 Stand as far away from the source and place as much
shielding between people and the source as possible.
 Time is important as in many cases a human can
sustain a short exposure to radiation without being
harmed.
 Example


Limit your exposure to 1 (mR/hr). Your source is 60 (mR/hr)
You could be at the source for 1 minute
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17. Radiation Protection
 Distance from the source also plays a factor.
 Inverse square law
 Source has a radiation level 20mR/hr at 2 feet
 Moving back 4 feet provides an exposure level of 5
mR/hr.
 Moving 6 feet would result in an exposure level of 1.25
mR/hr
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18. Action Levels
 1mR/hr Isolation zones
 Public protection levels
 5 R Emergency response
 All activities
 10 R Emergency response
 Protecting valuable property
 25 R Emergency response
 Lifesaving or protection of large populations
 ˃ 25R Emergency response
 Lifesaving or protection of large population. Only on a
voluntary basis for persons who are aware of the risk
involved.
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19. Radiation Monitors
 Current radiation monitors provide two methods
of measuring radiation.
 REM and counts per minute
 REM being the most important to responders.
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20. Radiation Monitors
 There are a variety of detection devices out there,
the important consideration is the probe
attached to the unit.
 Probe determines the what type of radiation can be
detected

Alpha, Beta, Gamma
 Most common probe are pancakes, this is useful for
Alpha radiation.
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21. Radiation Monitors
 When the amount of
radiation becomes higher
we need to switch to the
internal probe.
 These are designed for
the higher level of
radiation
 When the monitor is
turned on it will pick up
background radiation.
 This is naturally occurring
radiation and it should
read in micro/rem.
 It is important that you go
do some field testing in
your area to determine
normal background.
 Then responders know
when they are being
exposed to radiation at
higher levels than
background.
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22. Types of Radiation Detectors
 Three type that are
common
 Geiger-Mueller tubes
 Scintillation crystals
 Gamma Spectroscopy
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23. Types of Radiation Detectors
 GM tubes can detect Alpha, Beta, Gamma
 Uses electric current, a reaction takes place when
radiation interacts with the walls of the tube.
 Electrons are freed from the atom and flows to the
anode which is in the center of the tube.
 This induces an electrical “pulse” which is used to
determine when and how much radiation entered
the GM tube.
 These detectors are generally coupled with a
proportional counter, which counts the electrical
impulses.

You have a choice to count in radiation dose or counts per
minute
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24. Types of Radiation Detectors
 Scintillation Crystals
 Uses a crystal that emits visible
light when hit by radiation.
 Most common is sodium
iodide
 Radiation hits the crystal, a
pulse of light is produced
which is detected by and
amplified.
 This produces a electrical
signal which is measured to
determine the amount of
radiation that hit the crystal.
 Scintillation detectors
are best for Gamma.
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25. Types of Radiation Detectors
 Gamma Spectroscopy
 Radiation Isotope
Identifier
 Can identify the source
of the radiation.
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26. Types of Radiation Detectors
 Radiation Pagers/
Dosimeter
 Detect X-ray and Gamma
radiation, but also will
detect high levels of beta.
 When the pager is turned
on it calibrates itself to the
background.
 They are designed to alert
and provide reading of
one-ten times above
background.
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27. Summary
 Responders need to become familiar with radiation
detection.
 Possibility exists for future events.
 Many radioactive substances exist and when we deal
with unidentified materials we need to check for
radiation.
 Knowing how to monitor for it is as important as
knowing the action levels.
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