Worker who occasionally works in a controlled area and may receive significant occupational exposure needs to be
Monitored indivudually
Personnel Monitoring Devices
FPOT
Film badge dosimeter
Pocket dosimeter
Optically stimulated luminescence
Thermoluminescent dosimeter
Purpose of personnel monitoring devices are
ICA
Identifies high dose
Control of radiation exposure
Assessment if working places
Commonly used to measure and record radiation exposure sue to gamma rays, X-rays and beta particles
Film badge dosimeter
The film in film badge dosimeter
Packed in a light proof, vapor proof envelope preventing light, moisture or chemical vapors from affecting the film
Film is coated with
Two emulsion
Emulsions in FBD
- Large grain, fast emulsion that is sensitive to low levels of exposure
- Fine grain, slow emulsion that is less sensitive to exposure
Causes of inaccuracy of FBD
EDEH
Effect of dosage on the film but not received by the wearer
Effect of hear on film
Advantages of FBD
ACAP
Accurate for exposures greater than 100mrem
Can measure doses due to different types of radiation
Able to distinguish diff energies of photons
Provides permanent record
Worn between the neck and the waist
Whole body badges
Worn on a finger of the hand most likely to be exposed too ionizing radiation
Ring badges
It is worn for a period of tine (3 months pr less)
Thermoluminescence Dosimeter (TLD)
TLD is a phosphor such as
Lithium Fluoride
calcium Fluoride
TLD’s can measure doses as low as
1 mrem
Advantages of TLD
RRLS
Reusable
Relative energy independence
Linearity of response to dose
Sensitive to low doses
Disadvantage of TLD
No permanent record
It means emitting light when heated
Thermoluminiscent
It is a process in which a pre-irradiated material when subjected to an appropriate optical stimulation, emits light signal proportional to the absorbed dose
Optically Stimulated Luminescence
Stimulation is carried out
Optically rather than thermally
OSL emission is highly influenced by
Energy
Intensity of the stimulating optical beam
It is the simplest and the most straight forward OSL process in which a pre-irradiated material is stimulated by a light source of constant intensity
Continuous wave optically stimulated luminescence
A process in which the optically stimulated luminescence signal from a pre-irradiated material is measured after a stimulation light is switched off
Delayed optically stimulated luminescence
A form of DOSL in which the luminescence is recorded intermittently following a stimulation by very short pulses with a frequency of about thousands of hertz
Pulsed optically stimulated luminescence
These are used to provide the wearer with an immediate reading of his or her exposure to x-rays and gamma rays
Pocket dosimeter
They are commonly worn in the pocket
Pocket dosimeter
Two types of pocket dosimeter
DD
Direct read pocket dosimeter
Digital electronic doaimeter
The dosimeter contains a small ionization chamber with a volume of approximately two millemeters
Direct read pocket dosimeter
The electrons produced by ionization are attracted to, and collected by
Positively charged central anode
The amount of movement is ________________ to the amount of ionization which occurs
Directly proportional
It is viewed on a translucent scale which is graduated in units of exposure
Fiber
Advantages of DRPD
Immediate reading
Reusable
Disadvantages of DRPD
Limited range
Inability to provide a permanent record
Reading loss due to dropping
These dosimeters record dose information and dose rate
Digital electronic dosimeter
DED most often use
Geiger Müller counters
Digital electronic dosimeter includes what feature which emits an audible signal or chirp with each recorded increment of exposure
Audible alarm
Types of workplace/ area monitoring
PIGS
Proportional counters
Ionization chambers
GM tubes
Scintillation detectors
The choice of monitoring instrument depends on
PHER
Photons or particles
High or low levels
Energy of photons
Required accuracy
Contamination detectors for Beta emitters
GM tube
Proportional counter
It is the simplest of all gas-filled radiation detectors, and is widely used for the detection and measurement of certain types of ionizing radiation, x-rays and gamma rays and beta particles
Ionization Chamber
The essential component of ionization chamber are the
Anode and cathode
The potential difference between the anode and cathode
100-500 volt range
The most commonly used for quantifying alpha and beta activity, they are also used for neutron detection
Proportional counters
The pulses produced by a proportional counter are larger that those produced by
Ionization chamber
In proportional counters it usually serves as the cathode
Cylinder
In a proportional counters the anode is made up of
Fine metal wire stretched along the axis of the cylinder
It occurs near the anode at a distance comparable to the wire’s diameter
Gas amolification
Proportional counter are filled with
Inert gas
It is an instrument used for measuring ionizing radiation such as alpha particles, beta particles and gamma rays using ionization effect produced in a Geiger-Müller tube
Geiger counter
Used to detect presence of low-level radioactive particles and rays
Geiger counter
The Gm tube is filled with an inert gas such as
Helium
Argon
Neon
The most important resource a radiographer has
Survey meters
To determine
The presence and intensity of radiation
Are portable radiation detection and measurement instruments used to check personnel, equipment and facilities for radioactive contaminatin
Survey meters
To measure external or ambient ionizing fields
Survey meters
One of the oldest type of radiation detector bc measurements could be made with photographic film
Scintillation detectors
A material that exhibits scintillation when exposed bu ionizing radiation
Scintillator
Types of inorganic scintillators
Cesium iodide with thalium
Cesium iodide with sodium
Sodium iodide with thanlium
The most common type of material is a type of salt called
Sodium-iodide
The light produced from the scintillation process is reflected through a clear window where it interacts with device called
Photomultiplier tube
To minimize contamination risks
Use protective gloves and clothing
Adopt clean operating conditions
Adopt good laboratory practice
Types of monitoring
PA
Personnel monitoring
Area/Workplace monitoring
