DEQ Technical Sales, LLCIndustrial Use of Nuclear Technology

 

 Overview

 

Industrial RadiographyDid you know that you don't have to be a nuclear engineer or scientist to work with nuclear technology?  The unique characteristics of nuclear materials have found application in many areas unrelated to the traditional nuclear fields.  In particular, radioisotopes - either naturally or manufactured radioactive material - have found broad application in tools, gauges, and imaging machines.  Such equipment has been used by a diverse range of occupations including law enforcement, the oil industry, archeologists, farmers and manufacturers of common consumer products. At the core of these applications is the radioisotope.  Although radiation can't be seen, it can still be easily detected with the right instruments.  Its penetrating nature and its unique detectability provide the real advantage of this technology.

 

 Industry: Gauging

 

Radioisotopes are used during manufacturing processes in a number of different ways.  One application is in gauging (measuring precisely).  Gauging works because radiation loses energy as it passes through substances.  This principle can be used to measure the presence or the absence of material between the source and the detector.

The radiation that passes through a material is measured and compared with the radiation that would pass through a required thickness of the material.  If more radiation is measured, the material is too thin; if less radiation is measured, the material is too thick.  During manufacturing, instruments that are sensitive to the measurements will activate controls to maintain the proper thickness.  The advantage in using this form of gauging or measurement is that there is no contact with the material being gauged.  For example:

 

Some machines, that manufacture plastic film use radioisotope gauging 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 as it is continuously made.
 

The height of the coal in a hopper can be determined by placing high-energy radioactive 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.  A light beam could not do the same job in a very dusty atmosphere.
 

When the intensity of radiation from a radioisotope is 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 too can be used to measure characteristics of the material.  This principle is used to measure different thicknesses of coatings.

 

 Industry: Gamma - Radiography

 

Another application of radioisotopes in the manufacturing process is called gamma-radiography.  This process uses gamma-ray radioisotopes to test materials for flaws such as invisible cracks, defects and occlusions in welds, etc.  The advantage of gamma radiography compared to non-nuclear technologies is that gamma radiography can be done thoroughly and non-invasively (one does not have to cut the material open), as well as more rapidly and cheaply.  It can even be done continuously as objects pass by on a conveyor belt.

The process is very similar to x-ray radiography in a hospital or x-ray screening of luggage at an airport.  The difference is that instead of using x-rays, gamma radiography uses a source that is more penetrating, such as cobalt-60, and that is portable and easy to use.  X-ray sets can only be used when electric power is available and when 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 electric power is needed.  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 and in place.

Because isotopes can be transported easily, gamma radiography is particularly useful in remote areas where, for example, it has been used to check welds in pipelines that carry natural gas or oil.  Where a weld has been made, 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.

 

 Industry: Neutron Activation

 

Neutron Activation is a method of determining the concentration of elements in a wide variety of samples, accurately and precisely.  It is another example of how radioisotopes can be used to help scientists and researchers, and even criminal investigators.  The method is based on the detection and measurement of gamma rays, which have energies characteristic of the sample under irradiation by neutrons.

The sample is exposed to a field of neutrons, which causes most of the elements within the sample to become radioactive ("activate") temporarily.  The emissions can be analyzed to determine exactly what that sample consists of, and the energy and intensity of the emissions reveal the identity of the element and the amount present, respectively, within the sample.  Every material has a unique signature so that it can be identified.

Neutron activation is capable of simultaneous determination of many elements in samples even when parameters are selected to optimize detection sensitivity of one particular element.  Information on the additional elements is obtained with no additional effort or expense.  The process is routinely used to determine concentrations of as many as 40 elements in geological, botanical, and human and animal tissues. Neutron activation can also detect elements at extremely low concentrations, at sensitivity levels that are superior to those attainable by non-nuclear methods, on the order of parts per billion or better.  This process also allows us to identify the material much faster and for much less expense than with non-nuclear technologies.

In addition, because of its accuracy and reliability, neutron activation is generally recognized as the "referee method" of choice when new procedures are being developed or when other methods yield results that do not agree. Worldwide application of neutron activation is so widespread it is estimated that approximately 100,000 samples undergo analysis each year.  A few examples include:

 

Companies who process materials such as coal or concrete use neutron activation to analyze the material for quality
 

Investigators, police, and other security groups use neutron activation to detect explosives, such as mines, and to detect drugs and weapons
 

In medicine, and more specifically, in sports, neutron activation is used to measure the human body composition to study the workings of the human body
 

The exploration industry will use neutron activation to explore ores, to find out what ores they encounter

 

 Industry: Use of Tracers

 

Radioisotopes can also be used as tracers not just in medicine, but also in industry.  These radiotracers emit gamma rays and/or beta particles that can be detected and measured by a variety of different counters -- either in situ or from samples in labs.  By proper analysis the quantity of the tracer can be determined at any point in a pathway through which it is traveling.  The tracers used are specific to the use.

For example, one wouldn't want a long-lived tracer to measure pollution in a stream that only took a day to empty into the river.  On the other hand, one might be interested in longer-lived species if one was also interested in how plants along the way took in the fluids and in what happened to them as a consequence.  The activity selected would also depend on the decay time because you still need to take accurate measurements later in time.  Then from a combination of the original characteristics of the tracer and its dilution and elapsed time and quantity of the measured sample, the absolute origin and time-of-passage are easily identifiable. The radiotracers can be applied in different ways:

 

Mixing efficiency of industrial blenders can be measured: radiotracers are added to various solutions that are to be mixed together to allow the manufacturer to determine when his mixture has reached uniformity.
 

Radiotracers are used to trace down sources of pollution.  For example, if one injects a known amount of radioactive tracer at a source of pollution (say at an outflow from an industrial plant or even a point of soil wash into a stream), its pathway downstream can be identified.  In this way, it might be found that the industrial plant was the culprit for pollution washed ashore miles away, or (equally likely) that that particular pollutant came from a different source.  Similarly, looking at soil washed into streams, it would be possible to determine which farmer (or even which cows) where the culprits by using different tracers.  In the old days a colored dye might be used as an indicator, but no accurate measurements could be taken.
 

Small leaks can be detected in complex systems such as power station heat exchangers or oil pipelines in a refinery.
 

Flow rates of liquids and gases in pipelines can be measured accurately, as can the flow rates of large rivers.
 

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.
 

Using tracers, research is conducted 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 it is being replenished.  Tracer radioactive fallout from nuclear weapons' testing in the 1950s and 1960s is now being used to measure soil movement and degradation.  This is assuming greater importance in environmental studies of the impact of agriculture.
 

Radioisotopes are used to test material parts and products such as metals, tire rubber, and engine oil for wear.  Radioisotopes are added to these products, and then with the use of sensitive radiation detectors, the location and amount of wear of these products is determined.  These tests help the manufacturer to produce the best quality and most reliable products.
 

In agricultural laboratories, radioisotopes are used to determine how plants take up nutritional materials or fertilizers to improve the efficiency.  In the past, the improvement of plant species took several plant generation times as those with good characteristics (say, disease resistance, or nutritional value, or smell -- in herbs) were weeded out and propagated in favor of those with poor characteristics.  Now by use of radioactive labeling, it is possible to shorten the time considerably and even arrange that a plant be generated with all the desirable characteristics (both disease resistance and oil flavor in the case of the peppermint plant).

 Industry: Radiocarbon Dating

 

Archeologists determine dates of samples, that were once alive (e.g. in bone, charcoal, leather) by a technique called "radiocarbon dating", so called because this method of scientific dating relies on the carbon-14 isotope.  Carbon-14 is a naturally occurring, long-lived radioisotope that is present in all living things.  All living things contain carbon, a proportion of which is radioactive C-14.  As living organisms take up natural radiocarbon along with other carbon atoms, the ratio between the two forms remains constant.  However, when they die, the radiocarbon decays and is not replaced.  Since it decays at a known constant rate, the decreasing concentration of C-14 can be measured and the date when the material died estimated. Two classic applications of C-14 dating are the determination of the age of the Dead Sea Scrolls as about 2000 years, and the proof that the Shroud of Turin was made in the 14th Century.

 

 Industry: Consumer Products

Radioisotopes are used in a number of consumer products, so much so, that probably not a day goes by, without you having run into some consumer product that relied on some radioisotope application.  Indeed they are now vital to industry.  Here are a few examples:

 

Smoke detectors - a smoke detector contains a small amount of americium-241 in the sensing unit that triggers the alarm when there is smoke
 

Soft drink bottles - radioisotopes are used to measure and control how much soda there is in soft drink bottles
 

● Shrink wrap film/plastic insulation on wires -- the plastic is shrunk by radiation instead of using heat, which damages the insulation

 

 Industry: Benefits

 

Faster, less expensive and thorough results -- When we wanted to identify material or check the quality of material in the past, we either had to do a chemical analysis of the material, which is a very slow process, or we had to do a sample destructive analysis of the material quality (destroy the material), which was very expensive.  For example, In determining whether a casting is whole and there are no occlusions (holes) within it, or at least there are only small numbers, castings had to be sampled and cut open.  All you could find out was whether the casting you had just destroyed was okay or not.  It was an act of faith to say that the other castings were okay.  Sampling is a little better than an act of faith if the process that produced the castings was carefully controlled, of course.  Then you have a better chance that a sample is representative of the rest.  However, these methods of testing materials or quality were always batch processes.  They were not continuous.  Today, thanks to nuclear science and technology we can analyze materials thoroughly and continuously, with less expenses and much faster.

 

 Industry: Safety

 

Safety always comes first, for all types of applications of nuclear science and technology, including industrial applications.  This is done through a number of ways:

 

The operator is kept away from the beam by simply shutting off the machine whenever a violation (say of entry into the space) occurs.
 

There is no residual radioactivity in the tested materials.  Much the same safety measures that might apply to a mechanical saw would be used on a neutron generator.  However, sources are more difficult since they are continuously and strongly radioactive.  They emit radioactivity all the time and, therefore, must be carried in containers, which shield the operator from the radioactivity.  Interlocks are used to avoid humans entering the working area when the source is exposed.  Usually the casing also has a shutter, which can be opened for the neutron stream.  These shutters can be remotely operated.  Sealed sources are stored in shielded containers when they are not used.
 

After use, when the source has decayed some, it is also necessary to carefully dispose of the source at a licensed disposal site.  However, there have been cases of accidents in both systems over the years.  In Mexico, an operator entered an accelerator room before it was shut off.  In Brazil and recently in Malaysia, sources were not disposed off correctly.  They were stolen and treated by the thief as nice scrap metal with resulting exposure of a number of people.  This is why careful regulation is important.
 

Tracers are custom made for specific jobs so that their activity will last for the length of the job but be of no concern afterwards.  Just as a person leaving hospital after a procedure in which radioactive isotope has been used may be slightly radioactive for the next day or so, it quickly decays -- so too no radiation is left in the environment above background levels.
 

In the laboratory, under controlled conditions it is possible that some gloves, swabs, syringes, even some test plants might be treated as low-level waste for disposal.


Source: American Nuclear Society (ANS)