The applications of radioisotopes in industry are numerous. Many types of thickness gauges exploit the fact that gamma rays are attenuated when they pass through material. By measuring the number of gamma rays, the thickness can be determined. This process is used in common industrial applications such as:
- The automobile industry–to test steel quality in the manufacture of cars and to obtain the proper thickness of tin and aluminum
- The aircraft industry–to check for flaws in jet engines
- Construction–to gauge the density of road surfaces and subsurfaces
- Pipeline companies–to test the strength of welds
- Oil, gas, and mining companies–to map the contours of test wells and mine bores, and
- Cable manufacturers–to check ski lift cables for cracks.
The isotope 241Am is used in many smoke detectors for homes and businesses (as mentioned previously), in thickness gauges designed to measure and control metal foil thickness during manufacturing processes, to measure levels of toxic lead in dried paint samples, and to help determine where oil wells should be drilled.
The isotope 252Cf (a neutron emitter) is used for neutron activation analysis, to inspect airline luggage for hidden explosives, to gauge the moisture content of soil and other materials, in bore hole logging in geology, and in human cervix-cancer therapy.
In addition, there are manifold uses in agriculture. In plant research, radiation is used to develop new plant types to speed up the process of developing superior agricultural products. Insect control is another important application; pest populations are drastically reduced and, in some cases, eliminated by exposing male insects to sterilizing doses of radiation. Fertilizer consumption has been reduced through research with radioactive tracers. Radiation pellets are used in grain elevators to kill insects and rodents. Irradiation prolongs the shelf-life of foods by destroying bacteria, viruses, and molds.
The useful application of radioisotopes extends to the arts and humanities. Neutron activation analysis is extremely useful in identifying the chemical elements present in coins, pottery, and other artifacts from the past. A tiny unnoticeable fleck of paint from an art treasure or a microscopic grain of pottery suffices to reveal its chemical makeup. Thus the works of famous painters can be “fingerprinted” so as to detect the work of forgers.
Neutron scattering has proved to be a valuable tool for studying the molecular structure and motion of molecules of interest to manufacturing and life processes. Accelerators and reactors produce low-speed neutrons with wavelength appropriate to “see” structures of the size of magnetic microstructures and DNA molecules. Neutrons can penetrate deeply into bulk materials and use their magnetic moment or strong interaction forces to preferentially scatter from magnetic domains or hydrogen atoms in long chain nucleosomes.
Neutron techniques for analysis
Neutron activation analysis (NAA) is a nuclear process used for determining the concentrations of elements in a vast amount of materials. NAA relies on excitation by neutrons so that the treated sample emits gamma-rays. It allows the precise identification and quantification of the elements, above all of the trace elements in the sample. NAA has applications in chemistry but also in other research fields, such as geology, archeology, medicine, environmental monitoring and even in the forensic science.
The method is based on neutron activation and therefore requires a source of neutrons. The sample is bombarded with neutrons, causing the elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element are well known. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for analysis of works of art and historical artifacts.
NAA can detect up to 74 elements depending on the experimental procedure, with minimum detection limits ranging from 10-7 to 10-15g/g, depending on the elements and matrix materials. Some nuclei can capture a number of neutrons and remain relatively stable, not undergoing transmutation or decay for many months or even years. Different nuclei have different cross sections and half lives, and the intensities of the emitted gamma-rays can also vary – therefore the detection limits are quite variable. Rare earth elements (REE) have very high thermal neutron cross sections and NAA is usually the first choice for the determination of REEs in a trace elements analysis.
Gamma and Xrays in analysis
Over the years, x-ray technology and nondestructive testing methods have advanced, in order to accommodate the growing needs of the industry. With different types of radiographic techniques and x-ray inspection, users are able to access full part data for different applications. Commonly, users outsource nondestructive testing projects for more accurate part results.
Industrial radiography is a form of nondestructive testing of products, utilizing different techniques, on the foundation of x-ray technology. X-ray and radiography are similar in the sense that “x-ray” is a technique used to develop a “radiograph.” However, commonly these terms are mistakenly used interchangeably.
Furthermore, industrial radiography is concerned with industrial applications only, whereas x-ray could cover a broad range, including medical applications. Industrial radiography uses ionizing electromagnetic radiation in order to observe, evaluate and analyze the subject being tested. Industrial radiography is primarily concerned with the inspection of parts and structures nondestructively, by utilization radiation.