1. 1

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
2

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.
3

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.
4

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
5

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
6

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.
7

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.
8

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
9

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.
10

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
11

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
12

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
13

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.
14

15. Radiation Protection
 Radiation dose should be kept
 “as low as reasonably achievable”

ALARA
 Three factors that influence radiation dose.
 Time
 Distance
 Shielding
15

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
16

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
17

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.
18

19. Radiation Monitors
 Current radiation monitors provide two methods
of measuring radiation.
 REM and counts per minute
 REM being the most important to responders.
19

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.
20

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.
21

22. Types of Radiation Detectors
 Three type that are
common
 Geiger-Mueller tubes
 Scintillation crystals
 Gamma Spectroscopy
22

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
23

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.
24

25. Types of Radiation Detectors
 Gamma Spectroscopy
 Radiation Isotope
Identifier
 Can identify the source
of the radiation.
25

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.
26

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.
27