8 Categories of Radiation Dosimeters for Dose and Exposure Monitoring and Worker Safety
29 Feb.,2024
Dosimeter Equipment Category
Description
Advantages and Disadvantages
Handheld survey meters
Examples:
-
Geiger-Muller (G-M) detectors (see photo above),
this category also includes some ion chambers, and
scintillator-based handheld meters.
-
More photo examples of this category on REMM
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See page 16 for more photo examples of survey
meters.)
-
Detect surface contamination in the
environment and on people
-
Low range: operate up to at least
10 mR per hour
-
High range: designed to operate up
to 1000 R per hour
Advantages:
-
These meters have long been used for regulatory
compliance of radiological or nuclear facilities.
-
Occupational workers are very familiar with their
use.
Limitations:
-
Requires training to understand the option to
display more than one scale of units, AND
which probe to use.
Personal dosimeter
Examples:
-
More photo examples on REMM
-
Small radiation monitor that is worn by an
individual
-
Passively assesses accumulated personal dose
equivalent
-
Usually processed outside the workplace after dose
has been accumulated
-
Common individual dosimeters contain film, TLD,OSL,
or direct-ion storage as the radiation detector
Advantages:
-
Can record personal dose equivalent very accurately,
at the position where it is worn
-
Some OSL dosimeters can be read using portable
equipment, allowing readings in the field
immediately after exiting the Hot Zone and before
next mission assignment.
Limitations:
-
Only records accumulated exposures. Because it
lacks real time display or alarm,
it CANNOT prospectively help responders avoid dose
of concern.
Pocket ionization chamber
Examples: in photo below older versions on top, newer
version on bottom of photo below
-
More photo examples of dosimeters
(ORAU - See page section for "pocket ionization
chambers")
-
Small, strong, simple device worn by an
individual
-
To read dose, look through device to see deflection
of needle
- Typically the size of a large writing pen
-
Options for monitoring various exposure ranges
-
Other names: quartz-fiber dosimeter, self-indicating
pocket dosimeter, self-reading pocket dosimeter
Advantages:
-
Can be read in the field in real time so user can
avoid dose of concern
- Minimal maintenance
- Can operate without batteries
Limitations:
- Does not alarm
- Must be charged before use
-
All dose readings must be recorded at the end of the
single work period as device does not retain a
record of the exposure
-
Can be difficult to read in the field, especially if
user wearing respiratory PPE
-
May provide false reading if mechanically
shocked
-
Must match specific device selected with possible
dose range from exposure to protect wearer
safety
Electronic personal dosimeter (EPD)
Examples:
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See page 14 of this document for more photo
examples of EPDs)
-
High range, alarming, active dosimeter, designed to
be worn by occupational radiation workers in
planned exposure situations, to
measure personal dose equivalence for regulatory
compliance, typically in industrial and medical
settings
- Displays dose AND dose rate
-
Some will alarm if either preset threshold is
exceeded
-
Typically use semiconductor detectors such as
metal-oxide semiconductor field-effect transistor
Advantages:
-
Provides immediate information and alarm functions
to help control exposure
-
Can function like a survey meter when displaying
dose rate
Limitations:
-
Some devices not suited for tough emergency response
conditions
-
Some lack large displays, or loud enough alarm noise
or strong enough vibration alarms
-
Because they are used for regulatory confirmation of
occupational worker dose, ANSI standard requires
that the user be unable to change key alarm and dose
parameters that would make them more useful in an
emergency response situation.
-
Standard requires measures up to dose rate of
100 rem per hour (1 Sv per hour) dose limit of 100
rem (1 Sv per hour), but some devices exceed this.
Personal emergency radiation detectors (PERDs) and
monitors
Examples:
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See pages 13-14 for more photo examples.)
-
More photo examples of PERD monitors
(Mirion Technologies, Inc.)
-
An alarming personal radiation detector worn on the
body to detect photons and alarm if preset
thresholds for either exposure rate or accumulated
dose are
exceeded.
-
Designed to be used in harsh environments, with high
exposure rates (>10 R per hour) for emergency
response applications.
-
Appropriate device for responder dose monitoring and
control
Advantages
-
Is the preferred tool for responders because the
device ranges allow use multiple response zones:
Cold Zone, Hot Zone, and Dangerous-radiation Zone
-
Accuracy the same as EPD but the higher dose rate
range [0.001 to 999 R per hour (~10 micro Gy per
hour to ~10 Gy per hour)] ensures that the device
will NOT be saturated in an emergency exposure
situation.
-
Ruggedly engineered, with robust vibration and sound
alarm thresholds adequate for emergency situations
-
Monitors are similar to detectors but may not meet
certain ANSI standards for extended range or
durability
Limitations
-
ANSI standard for PERDs only requires an effective
dose-rate range down to 1 mR per hour (1 micro Gy
per hour) which may limit their use in the cold
zone, although many devices have a larger effective
range.
Non-alarming PERDs
Examples: RadTriage50Sensor® formerly known as
SIRAD®
(card details)
-
Typically a colorimetric card with a sensitive area
that darkens or changes color with increasing dose
from exposure
-
Provides a visual indication of exposure to the user
- Designed to be worn or carried on user's body
- Does NOT have an active alarm
Advantages
-
Provide a visual indication of whether or not safety
levels have been reached or exceeded, making them an
appropriate back-up safety system to active
monitoring with an alarm
-
Size of credit card, inexpensive, safe, robust in
harsh circumstances
Limitations
-
Not very sensitive and generally cannot demonstrate
exposure below 1 rem (10 mSV)
- Does NOT alarm
-
Cannot alert the worker of hazardous conditions
- May be difficult to interpret
Personal radiation detectors (PRDs)
Examples:
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See page 11 for more photo examples of PRDs.)
-
Similar in appearance to electronic dosimeters
-
Used to detect low levels of radiation for
law-enforcement activities
-
Developed to help find and interdict potential
radiological or nuclear terrorism threats and
identify radioactive material out of regulatory
control
- Primarily used by law-enforcement agencies
Advantages
-
Can alert the wearer to any unexpected,
low levels of nearby radiation,
including levels near background
-
Potentially useful during emergency response for
activities OUTSIDE the Hot Zone
Limitations
-
ANSI standard for this device does not have a
requirement for tracking integrated exposure over
time, although some manufacturers add this option.
-
ANSI standard only requires an exposure rate range
up to 2mR per hour (~20 micro Gy per hour), which is
a low range; therefore, these devices often
"saturate" a relatively low radiation
levels and cannot be used in the higher dose
response zones such as the Hot Zone or
Dangerous-radiation Zone.
Extended range personal radiation detectors
(ER-PRDs)
Examples:
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See page 12 for more photo examples.)
-
More photo examples of ER-PRD
(ThermoFisher Scientific - RadEye device)
-
PRD with dual detector system that allows PRD to
have an extended (high) dose-rate range without
sacrificing the low dose-rate sensitivity
-
In addition to sensitive crystal or plastic
scintillators, these devices may have a second, less
sensitive detector such as a small G-M or
solid-state detector
Advantages
-
If the ER-PRD is designed to track exposure rate AND
total exposure during wear time, it would be
appropriate for responder protection and monitoring
in the Hot Zone.
-
If the device can support exposure rates up to 500 R
per hour (~5 Gy per hour), it would be appropriate
for the Dangerous-radiation Zone.
-
This could be a reasonable tool for both general
public safety and security applications.
Limitations
-
Alarm set points must be changed to match the needs
of the mission or task
-
Alarms set points for PRD use (low dose end), would
not be appropriate for emergency response operations
when dose from exposure could be in higher ranges.
Radioisotope identification device (RIID)
Examples:
-
Preventive Rad/Nuc Detection Equipment
Categorization for Consequence Management
(See page 15 for more photo examples of
RIIDs.)
-
Developed to help search for and identify
radioactive material in the field using gamma-ray
spectroscopy
- Used by law-enforcement and HAZMAT agencies.
-
For the Preventive Rad/Nuke Detection mission, hand
held RIIDs can be used either as the primary search
(detection) device to survey pedestrians, packages,
cargo and motor vehicles for contraband material OR
as a secondary search device for verifying and
characterizing alarms from fixed detectors or PRDs.
-
For the public safety mission, RIID's ability to
identify the radionuclide can help inform proper
response protocols and safety considerations.
-
These devices require high quality scintillator or
solid-sate detectors to discriminate different
gamma-ray energies, detectors such as HPGe, NaI(TI),
etc.
- Complex, expensive devices
Advantages
-
Can alert the wearer to any unexpected, low levels
of nearby radiation
-
Useful in emergency response operations OUTSIDE the
Hot Zone
-
Identifying the detected radionuclide could help
determine if any altered controls (dose or dose rate
or PPE) are needed for responder safety.
- Can be programmed to provide dose estimates
Limitations
-
ANSI standard does NOT require ability to track
integrated (accumulated) dose from exposure,
although some devices have this capacity
-
ANSI standard only requires an exposure rate range
up to 2 mR per hour (~20 microGy per hour), a low
dose rate. Therefore, with this sensitivity, these
devices often "saturate" at relatively low
radiation levels, making them NOT useful in the Hot
Zone or Dangerous-radiation Zone.
If you have any questions on radiation detectors. We will give the professional answers to your questions.