To detect external contamination, a radiation survey meter must be equipped with a probe appropriate for the
Radiation type (alpha, beta, gamma)
Radiation energy strength being measured (in kV, MV)
Internal contamination will be detected by appropriate radiation survey meters only if the radiation has sufficient energy to penetrate from inside the body to the body surface, where it can be detected.
Examples of internal contamination detectable by external survey monitors include high energy gamma and sufficiently high energy beta radiation.
Internal contamination with either low energy beta or alpha radiation is not detectable by external survey meters.
Pancake Geiger-Mueller Detector (round wand), with radiation meter
Source: Steve Sugarman, REAC/TS
Source: Steve Sugarman, REAC/TS
Used for monitoring/detecting radioactive contamination.
For surveying a potentially contaminated individual, detector is passed over the body in a systematic way to identify contamination on the front and back of all parts of the body, as well as the head, sides, armpits, groin, etc.
The probe should be held about 1/2 inch from the surface being surveyed, with a scan rate of 1 to 2 inches per second.
If an elevated count rate is found, hold the probe over the area for approximately 10 seconds. This is the count rate.
Results of the survey are recorded on a body chart diagram (PDF - 49 KB) before and after each decontamination cycle, if manpower permits.
Survey meter doesn't detect every radiation emission that occurs, only a percentage; the emissions it sees are registered as counts.
A health physicist will identify the isotope and apply the appropriate efficiency to ascertain the proper number of disintegrations per minute (DPM) actually occurring.
Detection efficiency of alpha particles may be as low as 2-3%, while it may be upwards of 25% for certain beta emitters.
Divide the CPM by the efficiency to get DPM. Example: 100 CPM at 20% efficiency = 100/0.2 = 500 DPM
The long, thin, black tubes are typically worn on the trunk area of the body on the outside of any clothing.
To read dose that is registered by the dosimeter, hold the eyepiece (end with the plastic cap) up to the light and read the scale to determine accumulated dose (reading exit - reading enter = accumulated dose).
Electronic dosimeter
The long white device
Can be set to alarm at a certain dose rate or at an accumulated dose point.
