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Handling of radioactive substances – Commercial applications
Industrial use is made of the impact of ionising radiation to process, modify or examine materials. Gamma radiation can be used to polymerise plastics (radiation chemistry) or harden metals. In semiconductor technology dopants are introduced in substrates (ion implantation) with the specific purpose of making structural changes (doping) and influencing the macroscopic characteristics of the material. A simple, tried and tested method for the non-destructive examination of materials is gamma radiography.
Gamma radiography involves placing the test material between a source of gamma radiation and a detector. The detector consists of a sensitive film which is blackened by ionising radiation or a suitable measuring device (counter tube or scintillation counter). Any material defects and their location are revealed by their characteristically different material density (e.g. as a result of inclusions of air). The penetrating gamma radiation is weakened (absorbed) differently at the defective location in comparison with the surrounding material. A film detector behind the test material registers a different level of density and a measuring device produces a varying detector display. Where detection behaviour is good the procedure allows for high measuring speeds and can also be used for the uninterrupted control of workpieces on the production line (quality assurance in production processes). For the most part gamma radiography makes use of sealed radioactive sources with cobalt-60, caesium-137 or iridium-192 with activities at giga through to terabecquerel levels.
Radiometric radiation methods are also used to monitor levels of liquids and bulk goods in closed (non-transparent) containers. Penetrating radiation does away with the need to install measuring instruments within containers – which is an advantage, particularly when monitoring levels in high-pressure boilers, blast furnaces, coal bunkers or containers with chemically aggressive or explosive contents. The radionuclides cobalt-60 or caesium-137 are used as sources of radiation for this purpose.
Both gamma and beta radiation is used in the radiometric measurement of the thickness and density of layered or extended materials (sheet metal, paper, film, textiles, etc.). The radiation type and energy are critical for the respective application purpose. Radionuclides with long half-lives and activities reaching into the gigabequerel range are used to keep maintenance costs low. Typical beta emitters include krypton-85, strontium-90/yttrium-90, promethium-147 and thallium-204. Cobalt-60 or caesium-137 are used as gamma emitters. Mobile measuring devices work using the back scattering technique which involves exploiting the partial reflection effect of radiation when it impacts material. The back scatter rate correlates with the thickness of the layer and material. The source of radiation and the radiation detector may be on the same side of the measured object and be compactly integrated in a single device. The back scattering technique allows surface layers (such as the thickness and density of road surfaces) or piping and boiler walls which are only accessible from one side (gas/water pipes) to be measured.
Particularly important in the engineering industry are so-called wear measurements which provide information about the optimum material which can be used in a machine or engine. Potential wear parts are marked radioactively and the lubricant which is then used under conditions of permanent machine/engine stress is examined for radioactivity. If radioactive particles are detected in the lubricant after a relatively short period of time, this is an indication of the rapid wear and tear of the examined part.
Ionising radiation has a disinfecting effect at high doses. This property is used in the manufacture of medical equipment (instruments) and materials (bandages, syringes, hypodermic needles, catheters, plastic implants etc.) for sterilisation purposes. The advantages are that ionising radiation has penetrating powers, which makes it possible to sterilise an object even after it has been hermetically sealed in an airtight package, and that the sterilised material is only marginally heated by the radiation (known as “cold sterilisation” in contrast to conventional steam or hot air sterilisation). The highly radioactive cobalt-60 is used as the source of radiation.
These very different examples illustrate how important radioactive materials and ionising radiation are in industry and technology. There is hardly any branch of industry today which does not value the use of radiation.
Gamma radiography involves placing the test material between a source of gamma radiation and a detector. The detector consists of a sensitive film which is blackened by ionising radiation or a suitable measuring device (counter tube or scintillation counter). Any material defects and their location are revealed by their characteristically different material density (e.g. as a result of inclusions of air). The penetrating gamma radiation is weakened (absorbed) differently at the defective location in comparison with the surrounding material. A film detector behind the test material registers a different level of density and a measuring device produces a varying detector display. Where detection behaviour is good the procedure allows for high measuring speeds and can also be used for the uninterrupted control of workpieces on the production line (quality assurance in production processes). For the most part gamma radiography makes use of sealed radioactive sources with cobalt-60, caesium-137 or iridium-192 with activities at giga through to terabecquerel levels.
Radiometric radiation methods are also used to monitor levels of liquids and bulk goods in closed (non-transparent) containers. Penetrating radiation does away with the need to install measuring instruments within containers – which is an advantage, particularly when monitoring levels in high-pressure boilers, blast furnaces, coal bunkers or containers with chemically aggressive or explosive contents. The radionuclides cobalt-60 or caesium-137 are used as sources of radiation for this purpose.
Both gamma and beta radiation is used in the radiometric measurement of the thickness and density of layered or extended materials (sheet metal, paper, film, textiles, etc.). The radiation type and energy are critical for the respective application purpose. Radionuclides with long half-lives and activities reaching into the gigabequerel range are used to keep maintenance costs low. Typical beta emitters include krypton-85, strontium-90/yttrium-90, promethium-147 and thallium-204. Cobalt-60 or caesium-137 are used as gamma emitters. Mobile measuring devices work using the back scattering technique which involves exploiting the partial reflection effect of radiation when it impacts material. The back scatter rate correlates with the thickness of the layer and material. The source of radiation and the radiation detector may be on the same side of the measured object and be compactly integrated in a single device. The back scattering technique allows surface layers (such as the thickness and density of road surfaces) or piping and boiler walls which are only accessible from one side (gas/water pipes) to be measured.
Particularly important in the engineering industry are so-called wear measurements which provide information about the optimum material which can be used in a machine or engine. Potential wear parts are marked radioactively and the lubricant which is then used under conditions of permanent machine/engine stress is examined for radioactivity. If radioactive particles are detected in the lubricant after a relatively short period of time, this is an indication of the rapid wear and tear of the examined part.
Ionising radiation has a disinfecting effect at high doses. This property is used in the manufacture of medical equipment (instruments) and materials (bandages, syringes, hypodermic needles, catheters, plastic implants etc.) for sterilisation purposes. The advantages are that ionising radiation has penetrating powers, which makes it possible to sterilise an object even after it has been hermetically sealed in an airtight package, and that the sterilised material is only marginally heated by the radiation (known as “cold sterilisation” in contrast to conventional steam or hot air sterilisation). The highly radioactive cobalt-60 is used as the source of radiation.
These very different examples illustrate how important radioactive materials and ionising radiation are in industry and technology. There is hardly any branch of industry today which does not value the use of radiation.
