Monitoring devices

Question 1

Film Badges

Answer 1

The main features of the film badges are:

• they consist of a coloured plastic frame containing a variety of different metal filters and a small radiographic film which reacts to radiation.
• they are worn on the outside of the clothes, for 1-3 months before being processed
• they are the most common form of personal monitoring device currently in use.

ADVANTAGES:

• provide a permanent record of dose received
• may be checked and reassessed at a later date
• can measure the type and energy of radiation encountered
• simple, robust and relatively inexpensive

DISADVANTAGES

• no immediate indication of exposure
• processing is required which may lead to errors
• the badges are prone to filter loss

Question 2

Thermoluminescent dosimeters (TLDs)

Answer 2

The main features of TLDs are:

• They are used for personal monitoring of the whole body and/or the extremities, as well as measuring the skin dose from particular investigation.
• they contain materials such as lithium fluoride (LiF) which absorb radiation and then release the energy in the form of light when heated
• the intensity of the emitted light is proportional to the radiation energy absorbed originally
• personal monitors consist of a coloured plastic holder, like the film badge for 1-3 months

ADVANTAGES:

• the lithium fluoride is reusable
• read- out measurements are easily automated and rapidly produced
• suitable for a wide variety of dose measurements

DISADVANTAGES:

• read-out is destructive, giving no permanent record, and the results cannot be checked or reassessed
• only limited information is provided on the type and energy of the radiation
• dose gradients are not detectable
• relatively expensive

Question 3

OPTICALLY STIMULATED LUMINESCENCE DOSIMETERS (OSLDs)

Answer 3

the main features of OSLDs are:

• they are used for personal monitoring of the whole body
• they consist of badge containing an aluminium oxide detector and metal and plastic filters
• the detector is read by exposing it to a light source, which releases the stored radiation energy in the aluminium oxide as blue light
• the radiation exposure can be calculated from the amount and intensity of blue light released

ADVANTAGES:

• quick, non-destructive readout
• multiple readouts possible so radiation doses can be verified if required
• good sensitivity and respond to a wide range of energies
• relatively robust

DISADVANTAGES:
- no immediate indication of exposure - all information is retrospective

Question 4

PERSONAL ELECTRONIC DOSIMETERS:

the main features of personal electronic dosimeters are: