Understanding NRT- Reading 1- 2 of 2- Radiogaphic Testing A

Advantages of gamma ray sources include portability and the ability to
penetrate thick materials in a relativity short time. As can be noted above
cobalt will produce energies comparable to a 1.25 MeV x-ray system. Iridium
will produce energies comparable to a 460 kV x-ray system. Not requiring
electrical sources the gamma radiography is well adapted for use in remote
locations.
■ Co-60 comparable to a 1.25 MeV x-ray system
■ Ir-192 comparable to a 0.46 MeV x-ray system
Disadvantages include shielding requirements and safety considerations.
Depleted uranium is used as a shielding material for sources. The storage
container (camera) for iridium sources will contain 45 pounds of shielding
materials. Cobalt will require 500 pounds of shielding. Cobalt cameras are
often fixed to a trailer and transported to and from inspection sites. Iridium is
used whenever possible, and not all companies using source material will
have a cobalt source. Source materials are constantly generating very
penetrating radiation and in a short time considerable damage can be done to
living tissue. Technicians must be trained in potential hazards to themselves
and the public associated with use of gamma radiography.
Charlie Chong/ Fion Zhang