Basic Principles
In radiographic testing, the part to be inspected is placed
between the radiation source and a piece of radiation
sensitive film. The radiation source can either be an Xray machine or a radioactive source (Ir-192, Co-60, or in
rare cases Cs-137). The part will stop some of the
radiation where thicker and more dense areas will stop
more of the radiation. The radiation that passes through
the part will expose the film and forms a shadowgraph
of the part. The film darkness (density) will vary with the
amount of radiation reaching the film through the test
object where darker areas indicate more exposure
(higher radiation intensity) and liter areas indicate less
exposure (higher radiation intensity).