RADIATION DETECTION MONITORING DEVICES AND THEIR USE Module

RADIATION DETECTION MONITORING DEVICES AND THEIR USE Module V

Instruments for detecting and measuring radiation l Survey meters Geiger-Mueller (GM) instruments n Ionization chamber instruments n Scintilation instruments n Laboratory counters l Personnel dosimeters l Photographic film dosimeters n Thermoluminescent dosimeters n Pocket dosimeters n Module Medical V 2

Primary use of radiation instrument Level of radioactive contamination Radiation dose rate in area Survey meters l Identity and quantity of radioactive material Laboratory counters l Accumulated dose to individuals in area Personnel dosimeters l l Module Medical V 3

Gas filled detectors Module Medical V 4

Geiger-Mueller (GM) instruments Close-up view of probe Module Medical V Top: shield open Bottom: shield closed 5

Determination of contamination level Module Medical V G-M survey meter with pancake probe 6

Reading scale of GM detector Module Medical V 7

How should you monitor? Module Medical V 8

Surveying patient using GM counter Module Medical V 9

Limitations of GM counters l will not detect very low energy betas such as those from tritium l may miss alpha contamination if any type of shielding is present, such as gauze, thin layer of blood or more than 5 cm of air Module Medical V 10

Alpha monitoring alpha monitor Module Medical V 11

Measurement of radioactivity: well counter Module Medical V 12

Radionuclide dose calibrator Module Medical V 13

Airborne activity samplers Module Medical V 14

Ionization chamber survey meters Module Medical V 15

Scintilation detectors Module Medical V 16

Scintilation survey meters Module Medical V 17

Determination of type and activity of radioactive material Module Medical V 18

Crystal scintillation gamma spectroscopy Module Medical V 19

Liquid scintillation counting Module Medical V 20

In-vivo measurements whole body counters Module Medical V 21

Thyroid uptake detection Module Medical V 22

Personnel dosimeters Film badge Electronic dosimeter TLD Module Medical V 23

Photographic film dosimeters l Advantages n Permanent record n Energy and nature of exposure n Cost Module Medical V l Disadvantages n Energy dependence n Fading n Size 24

Thermoluminescent dosimeters Module Medical V 25

Pocket dosimeters Module Medical V 26

Digital pocket dosimeter Module Medical V 27

Review points • Determination of contamination level often most important measurement in medical emergency setting Usually done with GM probe called pancake detector • Identification of radioactive material typically done by relatively sophisticated lab equipment (gamma- or alphaspectrometer) Samples collected from patient or clothing often used for analysis • Instruments to measure accumulated dose commonly referred to as dosimeters, worn by person to measure accumulated individual dose. Two types normally used: direct read-out devices (pocket dosimeters) and indirect TLDs & film badges