Industrial radiography

Last updated

Making a radiograph RT Film Making a Radiograph.jpg
Making a radiograph

Industrial radiography is a modality of non-destructive testing that uses ionizing radiation to inspect materials and components with the objective of locating and quantifying defects and degradation in material properties that would lead to the failure of engineering structures. It plays an important role in the science and technology needed to ensure product quality and reliability. In Australia, industrial radiographic non-destructive testing is colloquially referred to as "bombing" a component with a "bomb".

Contents

Industrial Radiography uses either X-rays, produced with X-ray generators, or gamma rays generated by the natural radioactivity of sealed radionuclide sources. Neutrons can also be used. After crossing the specimen, photons are captured by a detector, such as a silver halide film, a phosphor plate, flat panel detector or CdTe detector. The examination can be performed in static 2D (named radiography), in real time 2D (fluoroscopy), or in 3D after image reconstruction (computed tomography or CT). It is also possible to perform tomography nearly in real time (4-dimensional computed tomography or 4DCT). Particular techniques such as X-ray fluorescence (XRF), X-ray diffractometry (XRD), and several other ones complete the range of tools that can be used in industrial radiography.

Inspection techniques can be portable or stationary. Industrial radiography is used in welding, casting parts or composite pieces inspection, in food inspection and luggage control, in sorting and recycling, in EOD and IED analysis, aircraft maintenance, ballistics, turbine inspection, in surface characterisation, coating thickness measurement, in counterfeit drug control, etc.

History

Radiography started in 1895 with the discovery of X-rays (later also called Röntgen rays after the man who first described their properties in detail), a type of electromagnetic radiation. Soon after the discovery of X-rays, radioactivity was discovered. By using radioactive sources such as radium, far higher photon energies could be obtained than those from normal X-ray generators. Soon these found various applications, with one of the earliest users being Loughborough College. [1] X-rays and gamma rays were put to use very early, before the dangers of ionizing radiation were discovered. After World War II new isotopes such as caesium-137, iridium-192 and cobalt-60 became available for industrial radiography, and the use of radium and radon decreased.

Applications

Inspection of products

A portable wireless controlled battery powered X-ray generator for use in non-destructive testing and security. GemX-200 (mb).png
A portable wireless controlled battery powered X-ray generator for use in non-destructive testing and security.

Gamma radiation sources, [2] most commonly iridium-192 and cobalt-60, are used to inspect a variety of materials. The vast majority of radiography concerns the testing and grading of welds on piping, pressure vessels, high-capacity storage containers, pipelines, and some structural welds. Other tested materials include concrete (locating rebar or conduit), welder's test coupons, machined parts, plate metal, or pipewall (locating anomalies due to corrosion or mechanical damage). Non-metal components such as ceramics used in the aerospace industries are also regularly tested. Theoretically, industrial radiographers could radiograph any solid, flat material (walls, ceilings, floors, square or rectangular containers) or any hollow cylindrical or spherical object.

Inspection of welding

The beam of radiation must be directed to the middle of the section under examination and must be normal to the material surface at that point, except in special techniques where known defects are best revealed by a different alignment of the beam. The length of weld under examination for each exposure shall be such that the thickness of the material at the diagnostic extremities, measured in the direction of the incident beam, does not exceed the actual thickness at that point by more than 6%. The specimen to be inspected is placed between the source of radiation and the detecting device, usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.

The result is a two-dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation reaching each area. It is known as a radio graph, as distinct from a photograph produced by light. Because film is cumulative in its response (the exposure increasing as it absorbs more radiation), relatively weak radiation can be detected by prolonging the exposure until the film can record an image that will be visible after development. The radiograph is examined as a negative, without printing as a positive as in photography. This is because, in printing, some of the detail is always lost and no useful purpose is served.

Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects. If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish, but this is likely to be limited to those cases in which the surface irregularities (which will be visible on the radio graph) may make detecting internal defects difficult.

After this visual examination, the operator will have a clear idea of the possibilities of access to the two faces of the weld, which is important both for the setting up of the equipment and for the choice of the most appropriate technique.

Defects such as delaminations and planar cracks are difficult to detect using radiography, particularly to the untrained eye.

Without overlooking the negatives of radiographic inspection, radiography does hold many significant benefits over ultrasonics, particularly insomuch that as a 'picture' is produced keeping a semi permanent record for the life cycle of the film, more accurate identification of the defect can be made, and by more interpreters. Very important as most construction standards permit some level of defect acceptance, depending on the type and size of the defect.

To the trained radiographer, subtle variations in visible film density provide the technician the ability to not only accurately locate a defect, but identify its type, size and location; an interpretation that can be physically reviewed and confirmed by others, possibly eliminating the need for expensive and unnecessary repairs.

For purposes of inspection, including weld inspection, there exist several exposure arrangements.

First, there is the panoramic, one of the four single-wall exposure/single-wall view (SWE/SWV) arrangements. This exposure is created when the radiographer places the source of radiation at the center of a sphere, cone, or cylinder (including tanks, vessels, and piping). Depending upon client requirements, the radiographer would then place film cassettes on the outside of the surface to be examined. This exposure arrangement is nearly ideal – when properly arranged and exposed, all portions of all exposed film will be of the same approximate density. It also has the advantage of taking less time than other arrangements since the source must only penetrate the total wall thickness (WT) once and must only travel the radius of the inspection item, not its full diameter. The major disadvantage of the panoramic is that it may be impractical to reach the center of the item (enclosed pipe) or the source may be too weak to perform in this arrangement (large vessels or tanks).

The second SWE/SWV arrangement is an interior placement of the source in an enclosed inspection item without having the source centered up. The source does not come in direct contact with the item, but is placed a distance away, depending on client requirements. The third is an exterior placement with similar characteristics. The fourth is reserved for flat objects, such as plate metal, and is also radiographed without the source coming in direct contact with the item. In each case, the radiographic film is located on the opposite side of the inspection item from the source. In all four cases, only one wall is exposed, and only one wall is viewed on the radiograph.

Of the other exposure arrangements, only the contact shot has the source located on the inspection item. This type of radiograph exposes both walls, but only resolves the image on the wall nearest the film. This exposure arrangement takes more time than a panoramic, as the source must first penetrate the WT twice and travel the entire outside diameter of the pipe or vessel to reach the film on the opposite side. This is a double wall exposure/single wall view DWE/SWV arrangement. Another is the superimposure (wherein the source is placed on one side of the item, not in direct contact with it, with the film on the opposite side). This arrangement is usually reserved for very small diameter piping or parts. The last DWE/SWV exposure arrangement is the elliptical, in which the source is offset from the plane of the inspection item (usually a weld in pipe) and the elliptical image of the weld furthest from the source is cast onto the film.

Airport security

Both hold luggage and carry-on hand luggage are normally examined by X-ray machines using X-ray radiography. See airport security for more details.

Non-intrusive cargo scanning

Gamma-ray image of intermodal cargo container with stowaways VACIS Gamma-ray Image with stowaways.GIF
Gamma-ray image of intermodal cargo container with stowaways

Gamma radiography and high-energy X-ray radiography are currently used to scan intermodal freight cargo containers in US and other countries. Also research is being done on adapting other types of radiography like dual-energy X-ray radiography or muon radiography for scanning intermodal cargo containers.

Art

The American artist Kathleen Gilje has painted copies of Artemisia Gentileschi's Susanna and the Elders and Gustave Courbet's Woman with a Parrot . Before, she painted in lead white similar pictures with differences: Susanna fights the intrusion of the elders; [3] there is a nude Courbet beyond the woman he paints. [4] Then she painted over reproducing the original. Gilje's paintings are exhibited with radiographs that show the underpaintings, simulating the study of pentimentos and providing a comment on the old masters' work.

Sources

Many types of ionizing radiation sources exist for use in industrial radiography.

X-Ray generators

X-ray generators produce X-rays by applying a high voltage between the cathode and the anode of an X-ray tube and in heating the tube filament to start the electron emission. The electrons are then accelerated in the resulting electric potential and collide with the anode, which is usually made of Tungsten. [5]

The X-rays that are emitted by this generator are directed towards the object to control. They cross it and are absorbed according to the object material's attenuation coefficient. [6] The attenuation coefficient is compiled from all the cross sections of the interactions that are happening in the material. The three most important inelastic interactions with X-rays at those energy levels are the photoelectric effect, compton scattering and pair production. [7] After having crossed the object, the photons are captured by a detector, such as a silver halide film, a phosphor plate or flat panel detector. [8] When an object is too thick, too dense, or its effective atomic number is too high, a linac can be used. They work in a similar way to produce X-rays, by electron collisions on a metal anode, the difference is that they use a much more complex method to accelerate them. [9]

Sealed Radioactive Sources

Radionuclides are often used in industrial radiography. They have the advantage that they do not need a supply of electricity to function, but it also means that they can't be turned off. The two most common radionuclides used in industrial radiography are Iridium-192 and Cobalt-60. But others are used in general industry as well. [10]

These isotopes emit radiation in a discrete set of energies, depending on the decay mechanism happening in the atomic nucleus. Each energies will have different intensities depending on the probability of a particular decay interaction. The most prominent energies in Cobalt-60 are 1.33 and 1.17 MeV, and 0.31, 0.47 and 0.60 MeV for Iridium-192. [11] From a radiation safety point of view, this makes them more difficult to handle and manage. They always need to be enclosed in a shielded container and because they are still radioactive after their normal life cycle, their ownership often requires a license and they are usually tracked by a governmental body. If this is the case, their disposal must be done in accordance with the national policies. [12] [13] [14] The radionuclides used in industrial radiography are chosen for their high specific activity. This high activity means that only a small sample is required to obtain a good radiation flux. However, higher activity often means higher dose in the case of an accidental exposure. [15]

Radiographic cameras

A series of different designs have been developed for radiographic "cameras". Rather than the "camera" being a device that accepts photons to record a picture, the "camera" in industrial radiography is the radioactive photon source. Most industries are moving from film based radiography to a digital sensor based radiography much the same way that traditional photography has made this move. [16] Since the amount of radiation emerging from the opposite side of the material can be detected and measured, variations in this amount (or intensity) of radiation are used to determine thickness or composition of material.

Shutter design

One design uses a moving shutter to expose the source. The radioactive source is placed inside a shielded box; a hinge allows part of the shielding to be opened, exposing the source and allowing photons to exit the radiography camera.

This torch-type camera uses a hinge. The radioactive source is in red, the shielding is blue/green, and the gamma rays are yellow. Torchradiographycamerawithhinge.png
This torch-type camera uses a hinge. The radioactive source is in red, the shielding is blue/green, and the gamma rays are yellow.

Another design for a shutter is where the source is placed in a metal wheel, which can turn inside the camera to move between the expose and storage positions.

This torch-type camera uses a wheel design. The radioactive source is in red, and the gamma rays are yellow. Wheelradiographymachine.png
This torch-type camera uses a wheel design. The radioactive source is in red, and the gamma rays are yellow.

Shutter-based devices require the entire device, including the heavy shielding, to be located at the exposure site. This can be difficult or impossible, so they have largely been replaced by cable-driven projectors.

Projector design

Modern projector designs use a cable drive mechanism to move the source along a hollow guide tube to the exposure location. The source is stored in a block of shielding that has an S-shaped tube-like hole through the block. In the safe position the source is in the center of the block. The source is attached to a flexible metal cable called a pigtail. To use the source a guide tube is attached to one side of the device while a drive cable is attached to the pigtail. Using a hand-operated control the source is then pushed out of the shield and along the source guide tube to the tip of the tube to expose the film, then cranked back into its fully shielded position.

A diagram of the S-shaped hole through a metal block; the source is stored at point A and is driven out on a cable through a hole to point B. It often goes a long way along a guide tube to where it is needed. Sshapedirradation machine.png
A diagram of the S-shaped hole through a metal block; the source is stored at point A and is driven out on a cable through a hole to point B. It often goes a long way along a guide tube to where it is needed.

Neutrons

In some rare cases, radiography is done with neutrons. This type of radiography is called neutron radiography (NR, Nray, N-ray) or neutron imaging. Neutron radiography provides different images than X-rays, because neutrons can pass with ease through lead and steel but are stopped by plastics, water and oils. Neutron sources include radioactive (241Am/Be and Cf) sources, electrically driven D-T reactions in vacuum tubes and conventional critical nuclear reactors. It might be possible to use a neutron amplifier to increase the neutron flux. [17]

Safety

Radiation safety is a very important part of industrial radiography. The International Atomic Energy Agency has published a report describing the best practices in order to lower the amount of radiation dose the workers are exposed to. [18] [19] It also provides a list of national competent authorities responsible for approvals and authorizations regarding the handling of radioactive material. [20]

Shielding

Shielding can be used to protect the user of the harmful properties of ionizing radiation. The type of material used for shielding depends on the type of radiation being used. National radiation safety authorities usually regulate the design, commissioning, maintenance and inspection of Industrial Radiography installations. [21]

In the industry

Industrial radiographers are in many locations required by governing authorities to use certain types of safety equipment and to work in pairs. Depending on location industrial radiographers may have been required to obtain permits, licenses and/or undertake special training. Prior to conducting any testing the nearby area should always first be cleared of all other persons and measures should be taken to ensure that workers do not accidentally enter into an area that may expose them to dangerous levels of radiation.

The safety equipment usually includes four basic items: a radiation survey meter (such as a Geiger/Mueller counter), an alarming dosimeter or rate meter, a gas-charged dosimeter, and a film badge or thermoluminescent dosimeter (TLD). The easiest way to remember what each of these items does is to compare them to gauges on an automobile.

The survey meter could be compared to the speedometer, as it measures the speed, or rate, at which radiation is being picked up. When properly calibrated, used, and maintained, it allows the radiographer to see the current exposure to radiation at the meter. It can usually be set for different intensities, and is used to prevent the radiographer from being overexposed to the radioactive source, as well as for verifying the boundary that radiographers are required to maintain around the exposed source during radiographic operations.

The alarming dosimeter could be most closely compared with the tachometer, as it alarms when the radiographer "redlines" or is exposed to too much radiation. When properly calibrated, activated, and worn on the radiographer's person, it will emit an alarm when the meter measures a radiation level in excess of a preset threshold. This device is intended to prevent the radiographer from inadvertently walking up on an exposed source.

The gas-charged dosimeter is like a trip meter in that it measures the total radiation received, but can be reset. It is designed to help the radiographer measure his/her total periodic dose of radiation. When properly calibrated, recharged, and worn on the radiographer's person, it can tell the radiographer at a glance how much radiation to which the device has been exposed since it was last recharged. Radiographers in many states are required to log their radiation exposures and generate an exposure report. In many countries personal dosimeters are not required to be used by radiographers as the dose rates they show are not always correctly recorded.

The film badge or TLD is more like a car's odometer. It is actually a specialized piece of radiographic film in a rugged container. It is meant to measure the radiographer's total exposure over time (usually a month) and is used by regulating authorities to monitor the total exposure of certified radiographers in a certain jurisdiction. At the end of the month, the film badge is turned in and is processed. A report of the radiographer's total dose is generated and is kept on file.

When these safety devices are properly calibrated, maintained, and used, it is virtually impossible for a radiographer to be injured by a radioactive overexposure. The elimination of just one of these devices can jeopardize the safety of the radiographer and all those who are nearby. Without the survey meter, the radiation received may be just below the threshold of the rate alarm, and it may be several hours before the radiographer checks the dosimeter, and up to a month or more before the film badge is developed to detect a low intensity overexposure. Without the rate alarm, one radiographer may inadvertently walk up on the source exposed by the other radiographer. Without the dosimeter, the radiographer may be unaware of an overexposure, or even a radiation burn, which may take weeks to result in noticeable injury. And without the film badge, the radiographer is deprived of an important tool designed to protect him or her from the effects of a long-term overexposure to occupationally obtained radiation, and thus may suffer long-term health problems as a result.

There are three ways a radiographer will ensure they are not exposed to higher than required levels of radiation: time, distance, shielding. The less time that a person is exposed to radiation the lower their dose will be. The further a person is from a radioactive source the lower the level of radiation they receive, this is largely due to the inverse square law. Lastly the more a radioactive source is shielded by either better or greater amounts of shielding the lower the levels of radiation that will escape from the testing area. The most commonly used shielding materials in use are sand, lead (sheets or shot), steel, spent (non-radioactive uranium) tungsten and in suitable situations water.

Industrial radiography appears to have one of the worst safety profiles of the radiation professions, possibly because there are many operators using strong gamma sources (> 2 Ci) in remote sites with little supervision when compared with workers within the nuclear industry or within hospitals. [22] Due to the levels of radiation present whilst they are working many radiographers are also required to work late at night when there are few other people present as most industrial radiography is carried out 'in the open' rather than in purpose built exposure booths or rooms. Fatigue, carelessness and lack of proper training are the three most common factors attributed to industrial radiography accidents. Many of the "lost source" accidents commented on by the International Atomic Energy Agency involve radiography equipment. Lost source accidents have the potential to cause a considerable loss of human life. One scenario is that a passerby finds the radiography source and not knowing what it is, takes it home. [23] The person shortly afterwards becomes ill and dies as a result of the radiation dose. The source remains in their home where it continues to irradiate other members of the household. [24] Such an event occurred in March 1984 in Casablanca, Morocco. This is related to the more famous Goiânia accident, where a related chain of events caused members of the public to be exposed to radiation sources.

List of standards

International Organization for Standardization (ISO)

European Committee for Standardization (CEN)

ASTM International (ASTM)

American Society of Mechanical Engineers (ASME)

American Petroleum Institute (API)

See also

Notes

    Related Research Articles

    <span class="mw-page-title-main">X-ray</span> Form of short-wavelength electromagnetic radiation

    X-ray is a high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it X-radiation to signify an unknown type of radiation.

    <span class="mw-page-title-main">Radiography</span> Imaging technique using ionizing and non-ionizing radiation

    Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography and industrial radiography. Similar techniques are used in airport security. To create an image in conventional radiography, a beam of X-rays is produced by an X-ray generator and is projected toward the object. A certain amount of the X-rays or other radiation is absorbed by the object, dependent on the object's density and structural composition. The X-rays that pass through the object are captured behind the object by a detector. The generation of flat two dimensional images by this technique is called projectional radiography. In computed tomography an X-ray source and its associated detectors rotate around the subject which itself moves through the conical X-ray beam produced. Any given point within the subject is crossed from many directions by many different beams at different times. Information regarding attenuation of these beams is collated and subjected to computation to generate two dimensional images in three planes which can be further processed to produce a three dimensional image.

    <span class="mw-page-title-main">Nuclear technology</span> Technology that involves the reactions of atomic nuclei

    Nuclear technology is technology that involves the nuclear reactions of atomic nuclei. Among the notable nuclear technologies are nuclear reactors, nuclear medicine and nuclear weapons. It is also used, among other things, in smoke detectors and gun sights.

    <span class="mw-page-title-main">Radiology</span> Branch of Medicine

    Radiology is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography, but today it includes all imaging modalities, including those that use no electromagnetic radiation, as well as others that do, such as computed tomography (CT), fluoroscopy, and nuclear medicine including positron emission tomography (PET). Interventional radiology is the performance of usually minimally invasive medical procedures with the guidance of imaging technologies such as those mentioned above.

    <span class="mw-page-title-main">Nondestructive testing</span> Evaluating the properties of a material, component, or system without causing damage

    Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing. NDT is commonly used in forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art. Innovations in the field of nondestructive testing have had a profound impact on medical imaging, including on echocardiography, medical ultrasonography, and digital radiography.

    <span class="mw-page-title-main">X-ray generator</span> Machine that generates X-rays

    An X-ray generator is a device that produces X-rays. Together with an X-ray detector, it is commonly used in a variety of applications including medicine, X-ray fluorescence, electronic assembly inspection, and measurement of material thickness in manufacturing operations. In medical applications, X-ray generators are used by radiographers to acquire x-ray images of the internal structures of living organisms, and also in sterilization.

    Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.

    Digital radiography is a form of radiography that uses x-ray–sensitive plates to directly capture data during the patient examination, immediately transferring it to a computer system without the use of an intermediate cassette. Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also, less radiation can be used to produce an image of similar contrast to conventional radiography.

    <span class="mw-page-title-main">Radiographer</span> Healthcare professional

    Radiographers, also known as radiologic technologists, diagnostic radiographers and medical radiation technologists are healthcare professionals who specialise in the imaging of human anatomy for the diagnosis and treatment of pathology. Radiographers are infrequently, and almost always erroneously, known as x-ray technicians. In countries that use the title radiologic technologist they are often informally referred to as techs in the clinical environment; this phrase has emerged in popular culture such as television programmes. The term radiographer can also refer to a therapeutic radiographer, also known as a radiation therapist.

    <span class="mw-page-title-main">Dental radiography</span> X-ray imaging in dentistry

    Dental radiographs, commonly known as X-rays, are radiographs used to diagnose hidden dental structures, malignant or benign masses, bone loss, and cavities.

    <span class="mw-page-title-main">Projectional radiography</span> Formation of 2D images using X-rays

    Projectional radiography, also known as conventional radiography, is a form of radiography and medical imaging that produces two-dimensional images by X-ray radiation. The image acquisition is generally performed by radiographers, and the images are often examined by radiologists. Both the procedure and any resultant images are often simply called 'X-ray'. Plain radiography or roentgenography generally refers to projectional radiography. Plain radiography can also refer to radiography without a radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy, which are technically also projectional.

    <span class="mw-page-title-main">Cargo scanning</span>

    Cargo scanning or non-intrusive inspection (NII) refers to non-destructive methods of inspecting and identifying goods in transportation systems. It is often used for scanning of intermodal freight shipping containers. In the US it is spearheaded by the Department of Homeland Security and its Container Security Initiative (CSI) trying to achieve one hundred percent cargo scanning by 2012 as required by the US Congress and recommended by the 9/11 Commission. In the US the main purpose of scanning is to detect special nuclear materials (SNMs), with the added bonus of detecting other types of suspicious cargo. In other countries the emphasis is on manifest verification, tariff collection and the identification of contraband. In February 2009, approximately 80% of US incoming containers were scanned. To bring that number to 100% researchers are evaluating numerous technologies, described in the following sections.

    Weld quality assurance is the use of technological methods and actions to test or assure the quality of welds, and secondarily to confirm the presence, location and coverage of welds. In manufacturing, welds are used to join two or more metal surfaces. Because these connections may encounter loads and fatigue during product lifetime, there is a chance they may fail if not created to proper specification.

    X-ray Markers, also known as: anatomical side markers, Pb markers, lead markers, x-ray lead markers, or radiographic film identification markers, are used to mark x-ray films, both in hospitals and in industrial workplaces. They are used on radiographic images to determine anatomical side of body, date of the procedure, and may include patients name.

    <span class="mw-page-title-main">Panoramic radiograph</span> Type of X-ray

    A panoramic radiograph is a panoramic scanning dental X-ray of the upper and lower jaw. It shows a two-dimensional view of a half-circle from ear to ear. Panoramic radiography is a form of focal plane tomography; thus, images of multiple planes are taken to make up the composite panoramic image, where the maxilla and mandible are in the focal trough and the structures that are superficial and deep to the trough are blurred.

    <span class="mw-page-title-main">Neutron imaging</span>

    Neutron imaging is the process of making an image with neutrons. The resulting image is based on the neutron attenuation properties of the imaged object. The resulting images have much in common with industrial X-ray images, but since the image is based on neutron attenuating properties instead of X-ray attenuation properties, some things easily visible with neutron imaging may be very challenging or impossible to see with X-ray imaging techniques.

    Vidisco is an Israeli based developer and manufacturer of portable digital X-ray inspection systems.

    Welding of advanced thermoplastic composites is a beneficial method of joining these materials compared to mechanical fastening and adhesive bonding. Mechanical fastening requires intense labor, and creates stress concentrations, while adhesive bonding requires extensive surface preparation, and long curing cycles. Welding these materials is a cost-effective method of joining concerning preparation and execution, and these materials retain their properties upon cooling, so no post processing is necessary. These materials are widely used in the aerospace industry to reduce weight of a part while keeping strength.

    A variety of non-destructive examination (NDE) techniques are available for inspecting plastic welds. Many of these techniques are similar to the ones used for inspecting metal welds. Traditional techniques include visual testing, radiography, and various ultrasonic techniques. Advanced ultrasonic techniques such as time of flight diffraction (TOFD) and phased-array ultrasonics (PAUT) are being increasingly studied and used for inspecting plastic pipeline welds. Research in the use of optical coherence tomography (OCT) and microwave reflectrometry has also been conducted.

    Douglas Harris Crofut was an American radiographer who inspected oil and natural gas pipelines. He died in intensive care as a result of radiation burns and radiation poisoning. His death was the first of its kind in the United States since the 1940s, when radiation deaths occurred during the Manhattan Project at Los Alamos, New Mexico. It is the only U.S. death attributable to an unknown source of radiation, and the only known case in the U.S. of a suspected suicide undertaken via radiation exposure.

    References

    1. Loughborough University Library – Spotlight Archive Archived 2008-12-07 at the Wayback Machine . Lboro.ac.uk (2010-10-13). Retrieved on 2011-12-29.
    2. Sunder, Mridula; Mumbrekar, Kamalesh D.; Mazumder, Nirmal (1 January 2022). "Gamma radiation as a modifier of starch – Physicochemical perspective". Current Research in Food Science. 5: 141–149. doi:10.1016/j.crfs.2022.01.001. ISSN   2665-9271. PMC   8760443 . PMID   35059645. S2CID   245826072.
    3. Behling, Rolf (2015). Modern Diagnostic X-Ray Sources, Technology, Manufacturing, Reliability. Boca Raton, FL, USA: Taylor and Francis, CRC Press. ISBN   9781482241327.
    4. Hubbell, J. H.; Seltzer, S. M. (July 2004). "X-Ray Mass Attenuation Coefficients: NIST Standard Reference Database 126". National Institute of Standards and Technology. Retrieved 25 May 2020.
    5. Frank Herbert Attix (19 November 1986). Introduction to Radiological Physics and Radiation Dosimetry. WILEY‐VCH Verlag GmbH & Co. KGaA. ISBN   9783527617135.
    6. Martz, Harry E.; Logan, Clinton M.; Schneberk, Daniel J.; Shull, Peter J. (3 October 2016). X-Ray Imaging: Fundamentals, Industrial Techniques and Applications. Boca Raton, Fl, USA: Taylor and Francis, CRC Press. p. 187. ISBN   9781420009767.
    7. Hansen, H.J. (1998). "Radio frequency linear accelerators for NDT applications: Basic overview of RF linacs". Materials Evaluation. 56: 137–143.
    8. Woodford, Colin; Ashby, Paul. "Non-Destructive Testing and Radiation in Industry" (PDF). IAEA International Nuclear Information System. Retrieved 31 May 2020.
    9. "Radio Isotope (Gamma) Sources". NDT Resource Center. Retrieved 31 May 2020.
    10. "Sealed Radioactive Sources" (PDF). International Atomic Energy Agency. Retrieved 6 June 2020.
    11. "Sealed Source Tracking". Canadian Nuclear Safety Commission. 15 July 2010. Retrieved 6 June 2020.
    12. "Review of Sealed Source Designs and Manufacturing Techniques Affecting Disused Source Management" (PDF). International Atomic Energy Agency. Retrieved 6 June 2020.
    13. Radiation source use and replacement : abbreviated version. Washington, D.C.: National Academies Press. 2008. pp. 135–145. doi:10.17226/11976. ISBN   9780309110143.
    14. Hogan, Hank (Summer 2015). "Nondestructive Technology". Aviation Aftermarket Defense. 11: 35.
    15. J. Magill, P. Peerani, and J. van Geel Basic aspects of sub-critical systems using thin fissile layers. European Commission, Institute for Transuranium Elements, Karlsruhe, Germany
    16. International Atomic Energy Agency (1999). Safety Reports Series #13 : Radiation protection and safety in industrial radiography (PDF). ISBN   9201003994.
    17. Canadian Nuclear Safety Commission. "Working Safely with Industrial Radiography" (PDF). Retrieved 25 May 2020.
    18. "National Competent Authorities Responsible for Approvals and Authorizations in respect of the Transport of Radioactive Material" (PDF). International Atomic Energy Agency. Retrieved 6 June 2020.
    19. "REGDOC-2.5.5, Design of Industrial Radiography Installations". Canadian Nuclear Safety Commission. 28 February 2018. Retrieved 6 June 2020.
    20. Radiation protection and safety in industrial radiography. Safety reports series No. 13. IAEA, Austria, January 1999 ISBN   92-0-100399-4
    21. P. Ortiz, M. Oresegun, J. Wheatley Lessons from Major Radiation Accidents. International Atomic Energy Agency
    22. Alain Biau Radiation protection of the workers in industrial radiography: the point of view of the regulatory body in France. Office de Protection contre les Rayonnements Ionisants