Protection Unit 4
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What is personnel dosimetry?
the monitoring of radiation exposure to any person occupationally exposed regularly to ionizing radiation
By law, radiation monitoring is required if personnel are expected to receive a dose ___% or more of the annual occupational effective dose limit of _____mSv (___rem).
Health care facilities issue personnel dosimetry devices if a dose of ____mSv (_____mrem) is expected.
What does a personnel dosimeter provide?
an indication of the working habits and working conditions of diagnostic imaging personnel.
The unprotected head, neck, and lenses of the eye can receive as much as ___ to____ times more exposure than the protected body trunk.
10 to 20 times
Placing a dosimeter at the collar level allows for what?
allows for the approximate equivalent dose to the thyroid glad and eyes of the occupationally exposed personnel
When should a second dosimeter be worn?
- during special procedures, health care facilities sometimes require two seperate monitoring devices
- beneith a lead apron at waist level to measure the equivalent dose to the lower body trunk/embryo-fetus
When should TLD ring badges be worn?
Should be worn if the hands are expected to be near the primary beam
What information should be on a TLD ring badge?
- account number
- participants's name and number
- wear date
- indication of hand (R or L)
- ring size
- number of individual ring dosimeter
What are the characteristics of personnel dosimeters?
- easy to carry
- record small and large doses in a consistent manner
- inexpensive to purchase and maintain
- Unfluenced by weather, humidity, and ordinary mechanical shock
Types of personnel dosimeters:
- film badges
- optically stimulated luminescent (OSL) dosimeters
- pocket ionization chambers
- thermo luminescent dosimeters (TLD's)
- extremity dosimeters (TLD ring badges)
Film badges are:
- still used today
- composed of 3 parts:
- -durable/lightweight plastic film holder
- -assortment of metal filters
- -film packet
Film badges sensitivity is from ____mSv (____rem) to as high as _______ mSv (_____rem).
- 0.1 mSv
- 10 rem
- 5000 mSv
- 500 rem
What is the minimum for film badges reported on Landauer Report?
0.1 mSv (10 mrem)
What does a film badges densitometer read?
reads the degree of blackening of the film from radiation exposure.
What is a control badge?
serves as a basis of comparison with remaining film badges after they have been returned to monitoring company (if a control badge has a reading during transport, the reading is subtracted from the batch of badges)
From data, the radiation dose can be evaluated as_______, ______, or _________ occupational exposure of each person.
- deep (penetrating)
What does M represent?
What does P represent?
What does J represent?
represents dosimeter for x-ray, gamma, and fast neutron radiation
What does U represent?
Film badge monitoring reports report what?
cumulative equivalent doses for deep, eye, and shallow radiation exposures for calendar quarter (3 months, the year to date, and lifetime radiation
What is an inception date?
the month and year the monitoring company bean keeping reports for a given individual
Personal data that is on film badges:
- participant's ID number
What is the annual state limit for the whole body (head and trunk), active blood forming organs, and gonads?
5,000 mrem (total effective equivalent dose)
What is the Harvard goal for the whole body, active blood forming organs, and the gonads?
What is the annual state limit of the lens of the eye?
What is the Harvard goal for the lens of the eye?
What is the annual state limit of skin and extremities?
What is the Harvard goal of the skin and extremities?
What is the annual state limit of the embryo/fetus?
500 mrem (9 months)
What is the Harvard goal of the embryo/fetus?
50 mrem (9 months)
What is the minimum report level for X-ray or gamma?
What is the minimum report level for beta?
How do you convert rem to S?
How do you change S to rem?
What is the minimum report level for a neutron?
20 mrem fast, 10 mrem thermal
What is the minimum report level for the fetus?
What is the minimal report level for rings?
What are the main advantages of the film badge?
- provides a permanent record of personnel exposure
- measures x-ray, gamma radiation, and all other beta radiation in a reliable manner
Temperature and humidity cause ________ with film badges?
How can a film badge be read?
must be shipped to monitoring company for processing
How long is a film badge to be worn?
Quarterly monitoring is.....
available for very low exposure or nonexistent exposure in film badge
What is an OSL?
optically stimulated luminescence dosimeter for personnel monitoring that provides the best features of tradiational film and TLD's while eliminating someof its disadvantages.
What should an OSL badge be exchanged?
every 2 months
This badge contains an aluminum oxide detector layer?
After exposure to the layer, this badge is read by exposing the layer to laser light which emits frequencies complimentary of the radiation exposure to the badge.
Where are OSL badges used?
- nuclear power plants
What is the OSL badge filters made of?
aluminum, tin, and copper which absorb different energy ranges
This badge allows the monitoring company to discriminate the energy range of exposure of which differnent energy ranges had been absorbed into the filter.
OSL badges are sensitiva as low as _____mrem for x-ray and gamma ray photons with energies ranging _____ to greater than _____.
OSL badges maximum measurement of x-ray and gamma ray photons is ______rem.
OSL badges detect beta particles energies from____ to excess of ____, dose measurements from _______ to ______.
- 150 keV
- 10 meV
- 10 mrem
- 1000 rem
OSL badges detect neutron energies from _______ to greater than ______ has a dose measurement range from ______ to ______.
- 40 keV
- 35 meV
- 20 mrem
- 25 rem
What is the most sensitive personnel dosimeter?
pocket ionization chamber
Contains an ionization chamber to measure radiation exposure.
pocket ionization chamber
What are the 2 types of pocket ionization chambers?
self reading with a built in electrometer and non-self-reading which requires a special accessory electrometer to read the device
What does a pocket ionization chamber measure?
mR (ionization in air)
What are the advantages of the pocket ionization chamber?
- provide immediate readout
- compact, easy to carry, and convenient
- reasonably accurate and sensitive
- ideal for monitoring short procedures
- sensitive in ranges from 0 to 200 mR (2 R)
What are the disadvantages to the pocket ionization chamber?
- fairly expensive ($150)
- may be inaccurate reading if not read each day
- can be discharged if subjected to mechanical shock which would result in a false reading
- not permanent
- RSO can document if record needed (really hard to get to happen)
What is a TLD?
Looks similar to a film badge?
Contains crystalline form of lithium fluoride (LiF)?
What are the advantages of a TLD over film?
- LiF interacts with radiation like tissues does
- humidity, pressure, and normal temperature changes do not affect the TLD
- can be worn up to 3 months
- LiF can be reused which makes it more cost effective, even though the initial cost is high (2 x's that of film)
What are disadvantages of TLD's
- high initial cost
- readout destroys the stored information in LiF
- necessary to use calibrated dosimeters with TLD's because calibrated dosimeters must be prepared and read with each group of TLD's when they are processed
How is a TLD read?
- As radiation interacts with the lithium fluoride in TLD's, the electrons in the crystalline lattice work are excited to a higher energy level or band.
- In the reader, the excited electrons are exposed to intense heat which causes the electrons to rise to the conduction band.
- At the conduction band, the electrons can return to their normal state once the excess energy is released in the form of visible light.
- The intensity of light is proportional to the amount of radiation exposing the LiF crystals
What are radiation survey insturments?
they are area monitoring devices that detect and measure radiation
Indicates the presence or absence of radiation, whereas a dosimeter system measures only cummulative radiation intensity.
What are the 3 types of radiation survey instruments for area monitoring?
- ionization chamber-type survey meter (cutie pie)
- proportional counter
- geiger-muller (GM) detector
What are the requirements for survey insturments?
- easy to cary; one person to operate
- durable even in surgery
- interacts with ionizing radiation like tissue would
- detects all common types of radiation
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