++++ Radiation Monitoring Flashcards
Types of Monitoring
Personnel Monitoring
Area/Workplace Monitoring
Personnel Monitoring Devices
Film Badge Dosimeter
Thermoluminescent Dosimeter
Optically Stimulated Luminescence
Pocket Dosimeter
Purposes of personnel monitoring devices
Control of radiation exposure
Identifies high dose
Assessment of working practices
Commonly used to measure and record radiation exposure due to gamma rays, x-rays and beta particles
Film Badge Dosimeter
Film is packaged in a ____ preventing light, moisture or chemical vapors from affecting the film
Light proof, vapor proof envelope
Special film is used which is
Coated with two different emulsions
One side is coated with a ______ that is sensitive to low levels of exposure
Large grain, fast emulsion
Other side of the films is coated with a _____ that is less sensitive to exposure
Fine grain, slow emulsion
Film is contained inside a ____
Film holder or badge
Badge incorporates a ____ to determine the quality of the radiation
Series of filters
Causes of in accuracy (film badge dosimeter)
Effect of heat on film
Effect of dosage on the film but not received by the wearer
Advantages of film badge dosimeter
Provides a permanent record
Able to distinguished between different energies of photons
Measure doses due to different types of radiation
Accurate for exposures greater than 100 millirem
Disadvantages of film badge dosimeter
It must be developed and read by a processor (time consuming)
Prolonged heat exposure can affect the film
Exposures of less than 20 millirem of gamma radiation cannot be accurately measured
Film badges need to be ____ so that the dose they receive accurately represents the dose the wearer receives
Worn correctly
Whole body badges are worn on the body bet ____ , often on the _____
Neck and waist
Belt or shirt pocket
Are worn on a finger of the hand most likely to be exposed to ionizing radiation
Ring badges
Are often used instead of the film badge
Thermoluminescence Dosimeter
Worn for a period of time (usually 3 millirem or less) and then must be processed to determine the dose received
Thermoluminescence Dosimeter
TLD is a phosphor, such as
Lithium fluoride (LiF) Calcium fluoride (CaF), in a solid crystal structure
TLDs can measure doses as low as
1 millirem
TLD have a precision of
Approx. 15% for low doses
Advantages of TLD
Its Linearity of response to dose
Its relative energy independence
Its sensitivity to low doses
It is also reusable
Disadvantages of TLD
No permanent record or re-readability is provided and an immediate, on the job readout is not possible
It is a process in which a pre-irradiated material when subjected to an appropriate optical stimulation, emits a light signal proportional to the absorbed dose
Optically Stimulated Luminescence (OSL)
The characteristic of the OSL material
Wavelength of the emitted light
OSL is thus analogous to TL process except that the stimulation is
Carried out optically rather than thermally
Is a property of the solid state material
Efficiency of OSL
OSL emission is highly influenced by the
Energy and the intensity of the stimulating optical beam
Is the simplest and the most straightforward OSL process in which a pre-irradiated material is stimulated by a light source of constant intensity…
Continuous wave optically stimulated luminescence
Is a process in which the OSL signal from pre-irradiated material is measured after a stimulation light is switch off …
Delayed optically stimulated luminescence
Is 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
The two types (Pocket Dosimeter) commonly used in industrial radiography are the
Direct Read Pocket Dosimeter
Digital Electronic Dosimeter
The dosimeter contains a small ionization chamber with a volume of approx. two milliliters
Direct Read Pocket Dosimeter
Inside the ionization chamber is a ____ and attached to this wire anode is a ____
Central wire anode
Metal coated quartz fiber
The amount of movement is
Directly proportional to the amount of ionization which occurs
The fiber is viewed on a
Translucent scale (which is graduated in units of exposure)
Advantages of Direct Read Pocket Dosimeter
Ability to provide the wearer an immediate reading of his or her radiation exposure
It is reusable
Disadvantages of Direct Read Pocket Dosimeter
Limited range
Inability to provide a permanent record
Potential for discharging and reading loss due to dropping or bumping
These dosimeters record dose information and dose rate
Digital Electronic Dosimeter
The dosimeters (Digital Electronic Dosimeter) most often use
Geiger-Müller counters
The counter then displays the _____ and ___ in digital form
Accumulated exposure
Dose rate
Some Digital Electronic Dosimeter include an
Audible alarm feature which emits an audible signal or chirp with each recorded increment of exposure
Workplace/Area Monitoring Instruments
Ionization chambers
Proportional counters
GM-tubes
Scintillation detectors
Choice of Monitoring Instrument depends on
High or low levels
Particles or photons
Energy of photons
Required accuracy
B - emitters
GM - tube
Proportional counters
Y-emitter (low energy)
GM-tube
Proportional counter
Nal(Tl) scintillation detector
Y-emitter (high energy)
Proportional counter
Nal(Tl) scintillation detector
Simplest of all gas-filled radiation detectors an is widely used for detection and measurement of certain types of ionizing radiation, X-rays and gamma rays and beta particles
Ionization chamber
The essential components of the ionization chamber are
Its two collecting electrodes: anode and cathode
The potential difference between the anode and cathode is often in the
100 to 500 volt range
Most commonly used for quantifying alpha and beta activity, they are also used for neutron detection
Proportional counters
Pulses produce by a proportional counter are
Larger than those produced by an ion chamber
Usually serves as the cathode in a proportional chamber
Cylinder
Serves as the anode in a proportional chamber
Fine metal wire (stretched along the axis of the cylinder)
Occurs near the anode at a distance comparable to the wire’s diameter
Gas amplification
Are filled with an inert gas
Proportional counters
An instrument used for measuring ionizing radiation such as alpha particles, beta particles and gamma rays using the ionization effect produced in a Geiger-Muller tube
Geiger counter
Used to detect presence of low level radioactive particles and rays (
Geiger counter
Means emitting light when heated
Thermoluminescent
