This document provides information on detection and measurement of ionizing radiation. It discusses different types of radiation monitors used for source monitoring, environmental monitoring, and individual monitoring. These include dose rate meters, contamination monitors, Geiger counters, scintillation counters, film badges, and thermoluminescent dosimeters (TLDs). It also covers topics like instrument ranges, surface contamination limits, and control standards for radiation exposure. The goal of radiation measurement is to evaluate radiation conditions, assess potential exposures, and review classification of controlled areas.

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5th BAERA Training Course on Radiation Protection for Radiation Control
Officers (RCOs) of Industrial Practices
Bangladesh Atomic Energy Regulatory Authority
Agargaon, Dhaka
06-09 November 2017
L7: DETECTION AND MEASUREMENT
OF IONIZING RADIATION

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Ionizing & Non-Ionizing Radiation
Ionizing Radiation:
Radiation is energy transmitted as particles
or waves. Ionizing radiation has sufficient
energy to dislodge orbital electrons, thereby
producing ions.
Examples: alpha, beta, gamma, neutron, and x-rays
Non-Ionizing Radiation:
Radiation that does not have sufficient
energy to dislodge orbital electrons.
Examples: visible light, infra-red , micro-waves,
radio-waves, and radar

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Radiation Exposures
Medical exposure - Which is principally the
exposure of persons as part of their diagonisis
or treatment
Occupational exposure - Which is the exposure
incurred at work, and principally as a result of
work
Public exposure -Which comprise all other
exposures (from nature and other environment
or artifical )

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CATEGORIES
SOURCE MONITORING: The measurement of activity in
radioactive materials being released to the environment or of
external dose rates due to sources within a facility or activity;
ENVIRONMENTAL MONITORING: The measurement of
external dose rates due to sources in the environment or of
radionuclide concentrations in environmental media;
INDIVIDUAL MONITORING: Monitoring using measurements
by equipment worn by individual workers, or measurements of
quantities of radioactive materials in or on their bodies.

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Measurement of Ionizing
Radiation
Provide information which allows :-
evaluation of radiation conditions
assessment of potential exposures
ongoing review of classification of
controlled and supervised areas

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SOURCE MONITORING
Associated with a source;
Scale and frequency depending on the
magnitude and specific of involved source;
Usually to measure dose rates or discharge
rates of radionuclides;
Depending on continuity or discontinuity of
discharges, location of the source and/or
composition of discharges.

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INDIVIDUAL MONITORING
Carried out directly on people;
Rarely used in routine monitoring, but
can be used in accidental situations;
Can support scientific purposes;
Can comprise external and/or internal
dosimetry.

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REGULATORY BODY –RESPONSIBILITIES
Establish technical requirements for monitoring,
including arrangements for emergency monitoring and
quality assurance, and regularly review them;
Check the monitoring data provided by operators;
Provide evidence to satisfy the public that authorized
sources are being suitably monitored and controlled.

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Health Physics Instruments
Installed instruments (dose rate alarms,
hand/foot monitors, air samplers, stack samplers etc)
Portable instruments (dose rate meters,
contamination monitors, air samplers)
Personal monitoring instruments
(TLD/film badges, electronic digital dosimeters, personal air
samplers, whole body monitors)
Laboratory instruments (counting castles,
multi-channel analysers, liquid scintillation counters, gas flow
proportional counters etc.,)

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Making Measurements
•Switch on before entering
•Move monitor slowly
•Change scale if necessary
radiation area
•Check batteries

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Dose rate meters (1)

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Dose rate meters (2)

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Contamination monitors

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Surface contamination
measurements
•hold probe close to
surface
•move probe slowly
•avoid damage
•beware of high dose
rates

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Detection of Ionizing Radiation
Various instruments and devices are used for the detection of
radiations. The best known device is the Geiger-Muller counter. This
device consists of two parts, a detecting tube and a counter. The heart
of the system is the detecting tube, which consists of a pair of
electrodes surrounded by an ionizable gas. As radiation enters the tube,
it ionizes the gas. The ions produced travel toward the electrodes,
between which there is a high voltage. The ions cause pulses of current
at the electrodes, which are picked up and recorded on the counter.
The Geiger tube is most sensitive to beta radiation. Gamma radiation can
pass right through the tube without being counted, and some alpha
radiation can't make it through the window of the tube. The Geiger-Muller
counter indicates the counts per minute of radiation entering the tube, but
it doesn't tell you the energy of the radiation.

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A scintillation counter is a device that not only counts radioactivity,
but also enables the operator to determine the energy of the
radiation. The principle of operation involves the radiation reacting
with a crystal containing sodium iodide and thallium iodide, which
produces a series of flashes of varying intensity. The intensity of the
flashes is proportional to the energy of the radiation.
Film badges are small portable devices that are worn by people such as
x-ray technicians and nurses, who may be exposed to radiation. The
badge contains a piece of photographic film that is removed monthly and
developed. The darker the film badge, the greater the degree of
exposure.
Another device called a dosimeter is quickly replacing the film badge.
One type of dosimeter works on the property of thermoluminescence, and
is called a TLD for short. The TLD consists of a penlike device and a
reading unit. The penlike device, which is worn by the individual, contains a
crystal such as lithium fluoride, which absorbs radiation. When the lithium
fluoride crystal absorbs the radiation, its structure changes slightly. To
determine the amount of radiation that the crystal has absorbed, the
penlike device is placed in its reading unit, where it is heated quickly. This
causes the lithium fluoride crystal to return to its original state.

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 Recombination region applies to very low voltage; as
voltage increase, the pulse size increases
 Ionization chamber region pulse size does not change
as the voltage increases
 Proportional region pulse size increases as voltage increases
 Limited proportional region pulse size again increases as
voltage increases
 Geiger-Mueller (GM) region pulse size increases slightly as
voltage increases, but not nearly as fast as in the limited
proportional region
 Continuous discharge region pulse size is extremely large.

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Radiation Monitors
radiation
detector
amplifier
signal
processor
display

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Ionization Chamber
A
+
-
radiation
ion +
electron-
100-300 V

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GM-Tube
thin end
window
ionization
event
cascade
radiation
-
+
500 V
noble gas

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Scintillation detector
scintillator
photomultiplier tube
amplifier

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Direct-Reading
1
2 5
10
30
Sv/h
1
10 100
1k

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Indirect-Reading
1
10 100
1k
counts per second
(cps)
1
10 100
1k
2k
A conversion factor is
required

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Instrument Range and
Sensitivity
Make sure you have the right instrument for the right job.
Type of
Monitoring
Range
Occupational Sv h-1
to a few mSv h-1
Environmental nSv h-1
to a few Sv h-1
Emergency mSv h-1
to a few Sv h-1

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Radiation Measurement

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Restriction of access
Controlled area
Radiation
No unauthorized entry

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Surface contamination limits
Surface contamination limits are in Bq
per unit area
Ingestion, inhalation and external
radiation pathways are all considered
and the most restrictive pathway is used
The inhalation pathway is generally the
most restrictive

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Control standard for control area
ＩＣＲＰ Ｐｕｂｌ．６０ （1.Ａｐｒ．2004～）
prescriptive regulatory limit
（ＩＣＲＰ Ｐｕｂｌ．７４）
Categories Control Standard values
Effective dose per week or
per time
Effective dose rate
Effective dose in controlled area 1.3 mSv/ 3 months
(for stay time 40h/w)
> 0.5 Sv/h
Effective dose in shielding of
the place frequently by the
personnel
 1 mSv/week  25 Sv/h
Effective dose in the boundary
of the facility
250 Sv/ 3 months
(for Stay time 168h/w)
< 0.2 Sv/h
Outside the partitation walls of controlled area
When frequently by personnel , Effective dose rate < 0.2 Sv/h
When not frequently by personnel, Effective dose rate < 2.5 Sv/h

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TLD（Thermo luminescence Dosimeter）
γ、β
DL：0.1ｍSv
Individual Dose meter
≦５０ｍＳｖ／ｙｅａｒ
ｏｒ
≦１００ｍＳｖ／５ｙｅａｒｓ
prescriptive regulatory limit
≦２０ｍＳｖ／ｙｅａｒ
Ａｎｄ
≦１３ｍＳｖ／ ３ｍｏｎｔｈｓ
restrictions

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Is the lecture useful for you
?????????
Radiation workers!