The World of Nuclear Science

Industry

Radiation is used widely throughout industry for various tasks including quality control, maintenance work and assessment of the environment.

Maintenance is a vital part of industry. For example, aircraft welding needs to be checked regularly for cracks and other faults, as well as gas and oil pipelines. The checking for cracks can be done using the radiation emitted by radioisotopes.

Using radioisotopes to check for cracks can be accomplished with a technique called gamma radiography. It is similar to how X-rays are used in hospitals to check for fractures and cracks in bones. In this process, the patient places their arm in front of an X-ray source, and the rays that penetrate through body tissue darken a photographic plate to reveal any cracks in the bones of the arm, etc.

Similarly, gamma radiography involves placing a radiation source on one side of the gas pipeline, and a photographic plate on the other. The radiation that can pass through cracks will show up on the photographic plate. This checking process could have been done using X-rays like in the hospital, except there is a lot of equipment required for X-rays, whereas using gamma radiography requires only a radiation source which can simply be a small pellet of radioactive material. X-rays also require electricity, whereas radioisotopes do not.

The exact process is done by taping a special photographic film over the weld or suspected crack of a pipeline. A pipe crawler carrying the sealed radiation source is then dispatched down the pipe to the weld position. The field technician performing the check then sends a remote control message to the crawler to tell it to expose the radiation. When this happens, the radiation passes through any cracks that may exist, onto the photographic film taped on the outside. This film is then developed and checked for cracks or welding deterioration.

Some industrial machinery contains parts that have small amounts of radioactive materials. This allows easy observation and detection of wear and tear. However, this practice is not common because of public fears about the radiation.

Radioisotopes are commonly used for measuring viscosity, density and thickness in conditions where other methods would be difficult or impossible to apply. Since radiation does not require direct contact (unlike, for example, using a scale or tape-measure) it is used where high heat or corrosive chemicals may exist.

Radiation is reduced in intensity when it passes through many materials. Therefore the amount of stuff between a radiation detector and emitter can be determined by calculating the difference between the intensity of emitted radiation and the intensity of the received radiation. This concept is applied in the manufacture of thin plastic films. The produced film is passed through a radioisotope gauge - the thicker the film, the lower the detected radiation. Changes in the detected level of radiation correspond to a change in thickness of the plastic, so this is a form of quality control.

(The decrease in intensity of visible light as opposed to radiation is used in many photoelectric devices including some smoke detectors. However, light cannot be always used to measure thickness of materials unlike radiation, because light is completly blocked by opaque surfaces or completely transmitted by clear surfaces.)

Radioisotopes can also be used to calculate the efficiency of large mixers, or the flow of materials through blast furnaces. Leaks and other defects can also be detected in building cooling towers and power station heat exchangers.

Radioisotopes are used as power sources for applications requiring small amounts of portable energy, such as for remote weather stations and weather balloons, and navigation beacons and buoys. They are more environmentally friendly than batteries because once all the energy from radioactivity is used, there are few left-over wastes except for the stable atoms formed, whereas used batteries will always contain toxic heavy metals that are hazardous to the environment.

All substances that exist are likely to have radioactive atoms in them occuring naturally. Water is an example of this. Underground bore water in particular is likely to have radioactive minerals and gases present. The rocks underground will often contain small amounts of radioactive elements such as uranium. The decay of uranium will produce other radioactive elements, and these may leak into the bore water.

The concentration of these radioactive elements in the water can be analysed to determine whether the bore water deposits are being used faster than they are being replenished, as well as the "age" of the water (how long it has been untouched).

Ocean pollution can be analysed for radioactivity to trace the source that caused it. Similarly, the dispersion of a known factory's pollutants can be monitored this way.

The rate and extent of soil erosion can be determined through the use of radioisotopes.

See the table below for a list of radioisotopes used in environmental monitoring and other industrial processes. In general, it is the labelling property of radioisotopes that allows them to be used in a wide range of environmental assessment techniques.

Radiation is also used in determining the nature and extent of termite infestation in buildings. This is done by feeding the termites a sample of artificially synthesised radiactive wood. The termites then disperse the radiation when they bury into the building structures, and the spread of radiation is used to give an indication of the nature of termite infestation. This process sometimes is better than physically removing and examining parts of the building, because the radiation can be detected easily through the building materials without needing to dismantle anything.

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