Radioisotopes are commonly used in:

• Modern industry uses radioisotopes in a variety of ways to improve productivity and, in some cases, to gain information that cannot be obtained in any other way.

• Sealed radioactive sources are used in industrial radiography, gauging applications and mineral analysis.

• Short-lived radioactive material is used in flow tracing and mixing measurements.

• Gamma sterilization is used for medical supplies, some bulk commodities and, increasingly, for food preservation.

Nuclear techniques are increasingly used in industry and environmental management. The continuous analysis and rapid response of nuclear techniques, many involving radioisotopes, mean that reliable flow and analytic data can be constantly available. This results in reduced costs with increased product quality.

Some concrete application of radioisotopes are the following:

Neutron Techniques for Analysis

Neutrons from a research reactor can interact with atoms in a sample causing the emission of gamma rays which, when analyzed for characteristic energies and intensity, will identify the types and quantities of elements present. The two main techniques are Thermal Neutron Capture (TNC) and Neutron Inelastic Scattering (NIS). TNC occurs immediately after a low-energy neutron is absorbed by a nucleus, NIS takes place instantly when a fast neutron collides with a nucleus.

Most commercial analyzers use californium-252 neutron sources together with sodium iodide detectors and are mainly sensitive to TNC reactions. Other use Am-Be-241 sources and bismuth germanate detectors, which register both TNC and NIS. NIS reactions are particularly useful for elements such as C, O, Al and Si which have a low neutron capture cross section. Such equipment is used for a variety on on-line and on-belt analysis in the cement, mineral and coal industries.

A particular application of NIS is where a probe containing a neutron source can be lowered into a bore hole where the radiation is scattered by collisions with surrounding soil. Since hydrogen is by far the best scattering atom, the number of neutrons returning to a detector in the probe is a function of the density of the water in the soil.

To measure soil density and water content, a portable device with an americium-241-beryllium combination generates gamma rays and neutrons which pass through a sample of soil to a detector. (The neutrons arise from alpha particles interacting with Be-9.) A more sophisticated application of this is in borehole logging.

Gamma and X-ray Techniques in Analysis

Gamma ray transmission or scattering can be used to determine the ash content of coal on line on a conveyor belt. The gamma ray interactions are atomic number dependant, and the ash is higher in atomic number than the coal combustible matter. Also the energy spectrum of gamma rays which have been inelastically scattered from the coal can be measured (Compton Profile Analysis) to indicate the ash content.

X-rays from a radioactive element can induce fluorescent x-rays from other non-radioactive materials. The energies of the fluorescent x-rays emitted can identify the elements present in the material, and their intensity can indicate the quantity of each element present.

This technique is used to determine element concentrations in process streams of mineral concentrators. Probes containing radioisotopes and a detector are immersed directly into slurry streams. Signals from the probe are processed to give the concentration of the elements being monitored, and can give a measure of the slurry density. Elements detected this way include iron, nickel, copper, zinc, tin and lead.

Gamma Radiography

Gamma Radiography works in much the same way as x-rays screen luggage at airports. Instead of the bulky machine needed to produce x-rays, all that is needed to produce effective gamma rays is a small pellet of radioactive material in a sealed titanium capsule.

The capsule is placed on one side of the object being screened, and some photographic film is placed on the other side. The gamma rays, like x-rays, pass through the object and create an image on the film. Just as x-rays show a break in a bone, gamma rays show flaws in metal castings or welded joints. The technique allows critical components to be inspected for internal defects without damage.

Gamma sources are normally more portable than x-ray equipment so have a clear advantage in certain applications, such as in remote areas. Also while x-ray sources emit a broad band of radiation, gamma sources emit at most a few discrete wavelengths. Gamma sources may also be much higher energy than all but the most expensive x-ray equipment, and hence have an advantage for much radiography. Where a weld has been made in an oil or gas pipeline, special film is taped over the weld around the outside of the pipe. A machine called a "pipe crawler" carries a shielded radioactive source down the inside of the pipe to the position of the weld. There, the radioactive source is remotely exposed and a radiographic image of the weld is produced on the film. This film is later developed and examined for signs of flaws in the weld.

X-ray sets can be used when electric power is available and the object to be x-rayed can be taken to the x-ray source and radiographed. Radioisotopes have the supreme advantage in that they can be taken to the site when an examination is required - and no power is needed. However, they cannot be simply turned off, and so must be properly shielded both when in use and at other times.

Non-destructive testing is an extension of gamma radiography, used on a variety of products and materials. For instance, ytterbium-169 tests steel up to 15 mm thick and light alloys to 45 mm, while iridium-192 is used on steel 12 to 60 mm thick and light alloys to 190 mm.

Gauging

The radiation that comes from a radioisotope has its intensity reduced by matter between the radioactive source and a detector. Detectors are used to measure this reduction. This principle can be used to gauge the presence or the absence, or even to measure the quantity or density, of material between the source and the detector. The advantage in using this form of gauging or measurement is that there is no contact with the material being gauged.

Many process industries utilize fixed gauges to monitor and control the flow of materials in pipes, distillation columns, etc., usually with gamma rays.

The height of the coal in a hopper can be determined by placing high energy gamma sources at various heights along one side with focusing collimators directing beams across the load. Detectors placed opposite the sources register the breaking of the beam and hence the level of coal in the hopper. Such level gauges are among the most common industrial uses of radioisotopes.

Some machines which manufacture plastic film use radioisotope gauging with beta particles to measure the thickness of the plastic film. The film runs at high speed between a radioactive source and a detector. The detector signal strength is used to control the plastic film thickness.

In paper manufacturing, beta gauges are used to monitor the thickness of the paper at speeds of up to 400 m/s.

When the intensity of radiation from a radioisotope is being reduced by matter in the beam, some radiation is scattered back towards the radiation source. The amount of 'backscattered' radiation is related to the amount of material in the beam, and this can be used to measure characteristics of the material. This principle is used to measure different types of coating thicknesses.

Gamma Sterilisation

Gamma irradiation is widely used for sterilizing medical products, for other products such as wool, and for food. Cobalt-60 is the main isotope used, since it is an energetic gamma emitter. It is produced in nuclear reactors, sometimes as a by-product of power generation.

Large-scale irradiation facilities for gamma sterilization are used for disposable medical supplies such as syringes, gloves, clothing and instruments, many of which would be damaged by heat sterilization.

Smaller gamma irradiators are used for treating blood for transfusions and for other medical applications. Irradiation of blood & blood products by gamma rays is a new and safe method to eliminate the risk of reaction, known as Graft vs Host Disease (T-GVHD), at the time of blood transfusion particularly in patients going for bone marrow transplant or tissue transplant.

Food preservation is an increasingly important application, and has been used since the 1960s. In 1997 the irradiation of red meat was approved in USA. Some 41 countries have approved irradiation of more than 220 different foods, to extend shelf life and to reduce the risk of food-borne diseases.

Scientific Uses

Radioisotopes are used as tracers in many research areas. Most physical, chemical and biological systems treat radioactive and non-radioactive forms of an element in exactly the same way, so a system can be investigated with the assurance that the method used for investigation does not itself affect the system. An extensive range of organic chemicals can be produced with a particular atom or atoms in their structure replaced with an appropriate radioactive equivalent.

Using tracing techniques, research is conducted with various radioisotopes which occur broadly in the environment, to examine the impact of human activities. The age of water obtained from underground bores can be estimated from the level of naturally occurring radioisotopes in the water. This information can indicate if groundwater is being used faster than the rate of replenishment. Trace levels of radioactive fallout from nuclear weapons testing in the 1950s and 60s is now being used to measure soil movement and degradation. This is assuming greater importance in environmental studies of the impact of agriculture.

Tracing/Mixing Uses

Even very small quantities of radioactive material can be detected easily. This property can be used to trace the progress of some radioactive material through a complex path, or through events which greatly dilute the original material. In all these tracing investigations, the half-life of the tracer radioisotope is chosen to be just long enough to obtain the information required. No long-term residual radioactivity remains after the process.

Sewage from ocean outfalls can be traced in order to study its dispersion. Small leaks can be detected in complex systems such as power station heat exchangers. Flow rates of liquids and gasses in pipelines can be measured accurately, as can the flow rates of large rivers.

Mixing efficiency of industrial blenders can be measured and the internal flow of materials in a blast furnace examined. The extent of termite infestation in a structure can be found by feeding the insects radioactive wood substitute, then measuring the extent of the radioactivity spread by the insects. This measurement can be made without damaging any structure as the radiation is easily detected through building materials.

Radionuclide generator systems continue to play a key role in providing both diagnostic and therapeutic radionuclides for various applications in nuclear medicine, oncology, and interventional cardiology. Although many parent/daughter pairs have been evaluated as radionuclide generator systems, there are a relatively small number of generators, which are currently in routine clinical and research use. Essentially every conceivable approach has been used for parent/separation strategies, including sublimation, thermochromatographic separation, solvent extraction, and adsorptive column chromatography. The most widely used radionuclide generator for clinical applications is the 99Mo/99mTc generator system, but recent years have seen an enormous increase in the use of generators to provide therapeutic radionuclides, which has paralleled the development of complementary technologies for targeting agents for therapy.http://www.springerreference.com/docs/html/chapterdbid/206088.html

Food irradiation is the process of exposing foodstuffs to a source of energy capable of stripping electrons from individual atoms in the targeted material (ionizing radiation). This ionizing radiation is emitted by a radioactive substance or generated by high-energy accelerators including X-ray converters. Irradiation (in this context "ionizing radiation" is implied) is also used for non-food applications, such as medical devices, plastics, tubes for gas pipelines, hoses for floor heating, shrink-foils for food packaging, automobile parts, wires and cables (isolation), tires, and even gemstones. (Source: http://en.wikipedia.org/wiki/Food_irradiation).

The use of gamma radiation to make food free from microbial contamination has been an experimental practice since long. A lot of research in this regard is also currently going on.

Processing of foods using gamma radiation to eradicate the chances of microbial contamination is experimented a lot. The most common microbe in such cases has been Deinococcus radiodurans. The interesting part is that it can withstand upto 16kgray of gamma radiation where it is sufficient to kill humans in some grays. This aspect of microbial research is quite encouraging.

Nuclear medicine uses radiation to provide diagnostic information about the functioning of a person's specific organs, or to treat them. Diagnostic procedures are now routine.

Radiotherapy can be used to treat some medical conditions, especially cancer, using radiation to weaken or destroy particular targeted cells.

Tens of millions of nuclear medicine procedures are performed each year, and demand for radioisotopes is increasing rapidly.

http://www.world-nuclear.org/info/Non-Power-Nuclear-Applications/Radioisotopes/Radioisotopes-in-Medicine/

The classic application of industrial X-ray 3D computed tomography (CT) is the inspection and three-dimensional measurement of metal and plastic castings. However, phoenix|x-ray’s high-resolution X-ray technology opens up a variety of new applications in fields such as sensor technology, electronics, materials science and many other natural sciences.4D X-ray Computed Tomography allows users to reconstruct a complete 3D CT model that includes time and motion, creating a truly dynamic volumetric dataset. Because this is an X-ray Computed Tomography process, both the internal and external structures of an object are obtained. This new and exciting technology makes it possible to study form, structure and now – function.

The industrial radioisotopes applications are divided into radiotracer applications and sealed source applications. The considered radiotracer applications in this thesis are RTD measurement, mixing time measurement, flow rate measurement, detection of blockage or leaks in the buried pipelines, and detection of leaks in heat exchanger. The considered sealed source applications are scanning of the distillation columns using a gamma source, and defect detection in welded pipes using a gamma source.