Radiation Monitoring 2

Question 1

Thermoluminescent dosimeters

Answer 1

A free-lighy device that contains a crystalline form of Lithium fluoride or calcium sulfate, which is a sensing material.

Question 2

How does the TLD

Answer 2

• Ionizing radiation causes the LiF crystals in the TLD to undergo changes in some of their physical properties.
• When irradiated, some of the electrons in the crystalline lattice structure of the LiF molecule, absorb energy and are excited to higher energy bands.
• The presence of impurities in the crystal causes electrons to be trapped within these bands.
• When the LiF are passed through a special heating process, however, these trapped electrons receive enough energy to rise above their present locations into the conduction band.
• From there the electrons return to their normal states with emission of energy in form of light photons
• The energy emitted is equal to the difference between the electron binding energy of the 2 orbital levels.
• Then a TLD analyzer measures the amount of ionizing radiation to which a TLD badge has been exposed to, and the amount of light is recorded by the photomultiplier tube

Question 3

Part of the TLD

Answer 3

1. Metal filter
2. Plastic
3. Open window

Question 4

Pocket ionization chamber

Answer 4

1. Has 2 electrodes central+ and outside -
2. Quarts fiber is part of the +ve part
3. The quarts fiber casts a shadow on the scale, so that the quantity of charge on the +ve charge electrode determines the position of the shadow along the scale and it’s equivalent to the scale reading at that position.
   * When the electrodes are exposed to gamma or x-rays, the air surrounding the central electrode becomes ionized and discharges the mechanism directly proportional to the amount of radiation to which it has been exposed.

Question 5

Radiation survey instruments for area monitoring requirements

Answer 5

• they must be portable and easy to carry
• Must be durable enough to withstand normal daily use
• Must interact with ionizing radiation the same way human tissue reacts
• Must be cost-effective
• Must be calibrated annually to ensure accurate operation.