Radioactive materials and other tracers are often utilized for non-destructive analysis techniques, as these materials possess the ability to detect hidden flaws through the use of short wavelength electromagnetic radiation that can penetrate many industrial materials. While radiographic testing offers a number of advantages as compared to other non-destructive testing (NDT) methods, there are several health risks associated with the use of this analytical technique.
To further investigate the use of radioactive materials in NDT applications, industrial radiography and neutron radiography, two of the most common and effective NDT radiography techniques, will be discussed in further detail.
Performing x-ray NDT on a weld joint. (Image credit: shiobi/shutterstock)
Basic Principles of Radiography
To briefly explain the radiographic testing principles utilized for NDT purposes, the material to be inspected is placed between the radiation source, which often emits X-ray or gamma radiation, and a piece of film that is sensitive to the given type of radiation. As the radiation is emitted, the thickness of the material will determine the amount of radiation that is capable of penetrating through to the film to form a shadowgraph.
The darkness of the film will therefore vary, depending upon the amount of radiation that is capable of penetrating through the industrial material1. This variation of the shadowgraph darkness determines the thickness or composition of the material being analyzed, and will also provide useful information on the presence of any flaws or discontinuities that may be present within the material.
Industrial radiography utilizes both X-radiation and gamma radiation as its radiation sources. This radiography technique is often used in the industrial setting to analyze the construction and inspection of pipelines, jet engines, pressurized vessels and other structural support systems2. Additionally, industrial radiography plays an important role in locating the presence of materials that are embedded inside other materials, such as the presence of water or electric wires present in concrete.
Neutron radiography typically utilizes a neutron radiation source as compared to gamma or X-ray radiation used for industrial radiography purposes. Both gamma and X-rays are more beneficial in the analysis of denser materials, such as metals. However, neutrons instead interact better with hydrogenous materials such as water, oil, plastic and rubber explosives.
Therefore, this type of radiography technique is often utilized for the inspection of capacitors, adhesives, radioactive objects, such as a gamma source and its shielding, air bags, aluminum corrosion products, or for the presence of hydrogenous foreign substances in sealed units.
Advantages and Disadvantages of NDT Radiography
As compared to other NDT methods, the aforementioned radiography techniques are capable of detecting numerous surface and internal discontinuities consistently without requiring much preparation before analysis. Additionally, these radiography techniques are also capable of inspecting hidden areas within the material, thereby providing a greater depth of information on potential flaws. Additionally, radiography techniques also produce a permanent record following material analysis.
Despite these advantages, radiography used for NDT purposes often poses a significant health risk to any operators or nearby personnel because of the amount of radiation that is emitted from the equipment; especially when used at high settings and for long exposure times. These risks also affect the amount of skill required to handle the equipment, as well as to interpret the data that results from analysis. Radiography equipment can also be relatively expensive, particularly when x-ray sources are utilized.
While there are certain risks associated with the use of radioactive materials in NDT, the benefits these materials provide industrial workers ensures the overall safety and quality control of systems that can have a serious effect on our overall wellbeing.
- “Non-destructive Testing and Radiation in Industry” – International Atomic Energy Agency
- “Nondestructive Testing” – Canadian Nuclear Association