Radiographic Testing (RT) is a form of traditional non-destructive testing (NDT) that is used to inspect the internal structure of assets in the oil & gas, power generation, manufacturing, and aerospace industries.

In radiographic testing (RT), a source of X-Ray or Gamma-Ray radiation is used to produce an image of the component on photographic film (by placing the radiation source on one side of the component and the film on the other). Following exposure to radiation, the film is then processed and then viewed on an illuminated screen for visual interpretation of the image. Radiography gives a permanent record (the exposed film), which is a major advantage of the method, and is widely used to detect volumetric flaws (surface and internal).

omputed Tomography (CT) is one of the lab based advanced NDT methods that TWI offers to industry. CT is a radiographic based technique that provides both cross-sectional and 3D volume images of the object under inspection. These images allow the internal structure of the test object to be inspected without the inherent superimposition associated with 2D radiography. This feature allows detailed analysis of the internal structure of a wide range of components.

X-ray equipment ranges from about 20kV to 20MV (the higher the voltage the greater the penetrating power of the radiation and the greater the thickness of component that can be tested). Gamma radiography is carried out using radioactive isotope sources (e.g. Cobalt-60, lridium-192) although its sensitivity is generally less than that achievable by X-ray radiography. lt is widely used for fieldwork because of its greater portability.

The reliability and interpretive value of radiographic images depend on their sharpness and contrast and this is important for the inspector to detect flaws accurately. An Image Quality Indicator (IQI) is placed on the part so that its image will be produced on the radiograph and a standard for sharpness and contrast can be determined.