Is it true that radioactivity can be found in industry?
Yes. In fact, there are wide-spread uses of radiation and radioactivity in industrial operations.
I wonder why?
Well, we take advantage of the following four characteristics of radiation sources for industrial uses: that radiation affects materials; that materials affect radiation; that radiation traces materials; and that radiation produces heat and power in a variety of industries.
How does the fact that radiation affects materials make it useful in industry?
You can compare this characteristic to that of receiving a sun tan. Radiation affects, to various degrees, any materials that are exposed to it. As a result, applications such as pasteurization and sterilization of food, polymerization of organic compounds, sterilization of medical supplies, and elimination of static electricity are possible.
What about the fact that materials affect radiation? How is that useful?
Think of this one as being similar to the use of sunglasses, where the intensity of the sun’s rays is reduced by the use of thicker or darker glasses. Likewise, the intensity of nuclear radiation is reduced by thicker or denser materials that are in the path of the radiation. This is the characteristic that is responsible for such applications as radiographs (i.e., taking pictures through objects), locating or controlling hidden levels of solids and liquids, which is especially helpful if the liquid is hot, corrosive or under pressure, and determining the thicknesses of materials.
What do you mean by the fact that radiation “traces” materials?
Radioactive elements and stable elements have identical chemical behaviors. However, radioactive elements are able to “announce” their presence through the radiations that are given off. So, not only do the radioactive elements take part in the same reaction or process as the stable elements, but they continually show their exact location by the “signals” they give off. All that is necessary is some sort of device to detect their presence. Our ability to trace the location of radioactive elements permits us to test wear, to locate leaks, to trace fluid flow, to evaluate detergent efficiency, and a host of other operations.
You also said radiation produces heat and power. I can kind of see how that might be useful.
You’re right. Whenever an energetic particle or ray is slowed down or stopped, heat is given off. We can take advantage of this characteristic by converting the heat produced to electrical or mechanical energy, or simply using it directly. Among the applications that use this characteristic are electrical generators for unmanned weather stations and buoys, power devices for thrusters in the space program, and heat for diving suits.
So, tell me about some specific uses of radioactivity in industry.
Okay. Let’s start first with applications in the metals industries. In blast furnace operations, radioactivity is used to study the residence time and distribution of constituents in the various metallurgical processes. Other tracer studies compare methods of chemically cleaning copper and stainless steel parts, evaluating plating techniques, and adding to our knowledge of the structure of electroplated coatings. Radionuclides have also been used to evaluate the diffusion of gases into metals (causing brittleness), and they have been used to provide valuable information on the rate of tool wear.
That’s tracing, now what about gauging?
Using radioactivity to gauge thicknesses has been well-recognized by industry. It permits us to impose continuous control of the uniformity of the thicknesses of various kinds of sheets and layers to very close tolerances. Furthermore, these types of systems can be completely automated so that the response to thickness changes can be used to actuate rollers, thus providing closer control than would otherwise be possible. But in addition to thickness, we can also use radioactivity to gauge the density of various materials.
The density of a variety of liquid slurries, powders, and granular solids can be measured by having a radiation source and a detector mounted on opposite sides of the material being measured (i.e., like in a hopper or pipe line). If the detected intensity of radiation from the source increases or decreases, we know that the density of the material has decreased or increased, respectively.
What about radiography?
Well, the major advantage of radiography using radiation sources versus x-ray inspections is portability, the absence of electrical wires and connectors, and the ability to make exposures with the source of radiation placed inside a complex shape. The use of radioactive cobalt for flaw detection in masses of metal was one of the earliest applications of radionuclide radiography. Most foundry operations maintain a selection of radiation sources, including radioactive cobalt, iridium, and cesium, among others. While x-ray machines are still used, radiation sources are the preferred methodology where the shape and accessibility of the casting makes x-ray techniques ineffective.
How do they compare, cost-wise?
Although the purchase price of a radioactivity-bearing device can be much less than the price of an x-ray machine, compliance costs for users of radioactivity tend to be much higher than for users of radiation-producing machines.
Okay, that’s the metals industry. What about, say, the electrical industry?
There are uses there too! One example is the use of radioactive krypton gas for leak testing. This procedure involves exposing electronic components to the gas under pressure for some period of time, during which any leaky components are at least partially filled with the gas. After the exposure period, the surfaces of the components are cleaned, and the leaky components are quickly identified by detecting the residual radioactivity. Kind of a clever way to go.
Are there other uses of tracers in the electrical industry?
Yes there are. For example, they are used to study adsorption and desorption of mercury by glass surfaces in mercury switches. In addition, there are studies of corrosion of silver contacts by fused salt, the development of a high- integrity compression seals, evaluation of methods for cleaning metal surfaces prior to electroplating or enameling, wear testing of bearings, determination of lubrication and seal characteristics, and improving the doping of semiconductors by investigating the mechanisms of the diffusion.
Any gauging applications?
Gauging in the electrical industry is limited. We don’t typically see many applications here.
What about radiography?
Yes, there are some uses here. Radiation sources are used to check the integrity of welds on structural components of heavy industrial electrical equipment.
Any thing else in the electrical industry?
Yes. Radiation sources are also used for static elimination, in fire detection equipment, and in luminous dials, gauges and signs. Certain navigational lights also contain radioactivity. In addition, there has been considerable interest in the use of radionuclides to replace batteries and related power sources.
Okay. That’s metals and electrical. What about chemical applications?
The use of radionuclides in this industry is widespread and includes pretty much all conceivable categories. In fact, petroleum refiners were among the first industrial operations to use radionuclides.
Why is that?
Refineries pump a lot of fluids, including raw materials and other in-plant inventory and products. Radiation sources are used as part of the automatic (computerized) control of the flow of these fluids. They also let the operators know if a blockage occurs! However, by far the most extensive use of radionuclides in this and other chemical industries is as a tracer.
How is radioactivity used in chemical processing?
There are many, many types of radiation sources used in this industry . . . too numerous to mention here. For example, radioactive sulfur can be used to determine the efficiency of separation; radioactive gold and iodine can be used to determine the thoroughness of mixing; radioactive sodium and bromine are used for locating leaks; and radioactive cobalt and cesium are used for gauging liquid or solid levels. Other radiation sources might be used to study process stream flow patterns, locate pipe obstructions, study mass balances in refinery streams, measure flow velocities, study catalyst movement, study carbon deposits in fuel research for drug metabolism studies, determine tire wear, study diffusion in glass, eliminate static, and sterilize medical supplies. I could go on.
I also understand radioactivity is involved in things that I, as a consumer, use every day.
Absolutely. Let me just give you a few ways in which radioactivity is used in our consumer product industries. I don’t mean radioactivity that is incorporated into products themselves, which is another subject for another day. I mean how radioactivity is used to improve the products that we use and take for granted.
Okay. Give me a couple of examples.
Radioactivity is sometimes used for determining the rate of wear in floor wax. It can also be used to assess laundering efficiencies of various detergents.
Imagine that! Are there more?
Yes. Radioactivity has been used to determine the firmness of cigarettes, the rate of pesticide removal from surfaces, the metabolism of food additives, biosynthesis, the movement of textile layers, the control of solid and liquid levels of foods and beverages in their containers, sterilization and pasteurization of food, and even the migration of dyes in the printing business.
Wow. I didn’t know there were so many uses of radiation and radioactivity in industry.
You know, the world as we know it today would be a very different place without the use of radioactive elements. A number of the examples I just gave you are seldom, if ever used today, but they certainly served their purpose when they were employed. On the other hand, we are seeing even more applications coming our way. Every day there are new uses of radioactivity in such industries as natural gas production, mining, utilities, agriculture, aerospace, and even environmental uses. In the case of industry, radiation and radioactivity are definitely beneficial!