Sealed gamma ray sources - DOE-HDBK-1141-2001

Radiological Assessor Training

DOE-HDBK-1141-2001

Student's Guide

primary beam to the hands or eyes that can

occur during sample changing or beam

alignment procedures with the shutter

inadvertently open. The primary beam is very

small, but may have an intensity of up to 40,000

R/min. At this exposure rate, even short

exposures of the hands and fingers could result

in severe injury, and potential loss of fingers.

V. Sealed gamma ray sources

Sealed gamma ray sources are used for a variety of

applications in industry. Gamma ray sources are

the most common sealed source encountered,

although others are used and are discussed later.

Radiography is probably the most common use, and

may be performed with the gamma rays from sealed

sources of Cobalt-60, Cesium-137, or Iridium-192.

Other uses of sealed gamma ray sources are

thickness gauges (e.g., to determine the thickness

of sheet metal), level gauges (e.g., to determine a

fluid level in a container), and density gauges (e.g.,

to measure the geologic formation porosity during

oil and mineral logging).

The hazard from these sources is primarily an

external dose hazard. The most common cause of

overexposure incidents with gamma radiography

sources results from radiographers failing to

perform radiation surveys to verify that the gamma

source is back in the shielded position. Also, if

mechanical damage to the source encapsulation

occurs, radioactive material contamination will be a

hazard as well.

VI. Other sealed sources

Sealed sources of beta particles may be used as

thickness gauges (e.g., measurement of dust on

filter paper, or gauging thickness of thinner plastics).

Module 12 - 6