Industrial radiography safety depends on the radiation Types, and energy is classified as ionising radiation and non-ionizing. Industrial radiography is a method that allows materials to be inspected for non-visible defects through the penetrating ability of various materials possessed by short-wave ionizing radiation (X-rays, gamma rays, and neutrons). This is an important element of non-destructive testing.
In this blog, we will discuss ensuring radiological safety in industrial radiography used in non-destructive testing including industrial radiography definition, industrial radiography hazards and safety precautions.
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, and licenses and/or undertake special training.
Before conducting any testing, the nearby area should always first be cleared of all other persons and Industrial radiography safety measures should be taken to ensure that workers do not accidentally enter into an area that may expose them to dangerous levels of radiation. Apply the OSHA standard during radiography.
In non-destructive testing, industrial radiography is used to inspect a wide variety of welds, such as those of gas and water pipelines, storage tanks and structural elements, and allows the detection of cracks or defects that otherwise may not be visible. These characteristics have made non-destructive testing a fundamental instrument for quality control, Industrial radiography safety and reliability.
The method is based on the greater or lesser transparency to X or Gamma rays of the materials depending on their nature and thickness. The object is irradiated, the radiation passes through the material is partially absorbed by it and emerges with different intensities which are intercepted by a photographic film.
After film processing, the image and defects are evaluated. X-rays and gamma rays are mainly used in radiographic testing, which are electromagnetic waves that have almost the same physical properties but differ in their origin. These rays can penetrate objects, and this depends on the type of material, thickness, density of the object, and the existence of defects in the piece
The radiation Types
Ionizing radiations are used in industry to correspond to the highest energy radiation (shorter wavelength) within the electromagnetic spectrum. They have enough energy to tear electrons from the atoms with which they interact, that is, to produce ionization. Non-ionizing radiation is those that do not have enough energy to remove an electron from the atom, that is, they are not capable of producing ionization.
Ionizing radiations are those that have enough energy to cause chemical change by breaking chemical bonds and stripping an electron from the atom when they interact with it. Therefore, this phenomenon is known as ionization, hence the name of this type of radiation. Therefore, in this topic, we only give you basic concepts about radiation, hazards and Industrial radiography safety.
The atom and ionising radiation
The atom is made up of a nucleus, composed in turn of protons and neutrons and by a surrounding shell, in which the electrons are found. The subatomic particles that make up the atom cannot exist in isolation except under very special conditions. Ernest Rutherford discovered protons in the early 20th century.
It is an elementary particle that constitutes part of the nucleus of an atom. The number of protons in the atomic nucleus is the atomic number (Z). Protons have a positive electric charge.
The neutron, an elementary particle that constitutes part of the nucleus of atoms, was discovered in 1930 by two German physicists, Walter Bothe and Herbert Becker. The mass of the neutron is slightly higher than that of the proton. Neutrons have no electrical charge. Consequently, the number of protons plus the number of neutrons in the nucleus of an atom constitutes the mass number (A).
The electron was discovered in 1897 by JJ Thomson. The mass of the electron is a negative charge. The electrons move in diffuse orbits surrounding the nucleus at different distances from it. Under normal conditions, an atom has the same number of protons as electrons, which makes the atoms electrically neutral entities. As a result, if an atom captures or loses electrons, it becomes an ion.
Ionizing radiation is of three types:
- Alpha particles – They are helium nuclei ( of two protons and two neutrons). These particles are the ionizing radiation with the highest mass, so their ability to limit penetration, and cannot pass through a sheet of paper or the skin of our body. That is to say, alpha particles are very energetic.
- Beta β particles are a much lower mass than alpha particles, s, they have a greater ability to penetrate matter. In other words, a beta particle can pass through a sheet of paper but can not by a thin sheet of metal or methacrylate.
- Gamma rays γ – They are electromagnetic radiation. So, they have no mass or charge, which makes them have great power to penetrate matter. On the other hand, to stop them a thick layer of lead or a concrete wall is necessary. Gamma rays and X-rays have the same properties, differing only in their origin. However, Gamma rays and Ex-ray are used in industrial radiography.
There is a fourth type of ionizing radiation, neutrons. Although, it is necessary to know that these are not ionizing by themselves. However, when they collide with an atomic nucleus, they can activate it or cause it to emit a charged particle or a gamma-ray likewise. So, they are indirectly ionizing. Neutrons are the ionizing radiation with the highest penetration capacity.
The radiation sources that the present work deals with, in the radiographic industrial application, are the radioisotopes, constituting iridium-192, cobalt-60, cesium-137, and gamma-ray sources commonly used for their abundance and safety of operation.
Industrial radiation hazards
High-energy radiation such as X-rays, gamma rays, alpha particles, beta particles, and neutrons can cause damage to DNA and lead to cancer. About half of the ionizing radiation we are exposed to comes from nature. It is in the rock, the soil and the atmosphere. The other half comes from man-made sources, such as medical tests and treatments, industrial radiography and nuclear power plants.
If the radiation dose is small, the cells (by themselves) are capable of repairing the damage caused or replacing cells killed by the radiation. But if the dose is high, the destruction of a large number of cells and/or the induction of cancer occurs as a result of irreversible damage to DNA (mutations) that could not be repaired. In other words, cells have various repair strategies against radiation until, after a certain dose, they are not capable of repairing all the damage caused.
Radon is formed when the element radium decays. Radium in turn is formed when the radioactive elements uranium and thorium decay and cause an increased risk of lung cancer. If you live in an area of the country that has high concentrations of radon in rocks and soil, you may want to test your home for this gas. Home radon tests are easy to use and don’t cost much.
Most hardware stores sell test kits. There are many ways to lower the amount of radon to a concentration that is not dangerous in the home. For more information on radon, see the Radon page and the Radon and Cancer fact sheet.
What factors determine health risk?
The two main parameters to assess the risk of radiation are the dose and the exposure time. Radiation doses are measured in either sievert (Sv) or rem (100 rem equals 1 sievert), and the higher this dose, the greater the chance of getting sick or dying from radiation. The other important factor is the time since continued exposure to radiation whose dose is, in principle, low can also cause significant damage to health.
All of us are continuously exposed to radiation, in fact, in one month we receive on average a dose of 0.3 millisieverts (mSV) or 0.03 rem. When we take a chest X-ray, for example, we are receiving average radiation of 0.1 mSv. In general, the human body suffers virtually no direct health effects from radiation up to 1,000 MSV.
From 1,000 mSV, the first and main symptoms of radiation poisoning begin to appear: Nausea With 2,000-3,000 mSV, in addition to nausea, vomiting, hair loss and diarrhoea appear in some affected. With 5,000 mSV all people are affected by the above symptoms and signs. With 8,000 MSV they intensify and haemorrhages and infections can appear.
The probability of death among people exposed to single radiation doses of 3,000 and 4,000 mSV is 50%, with doses around 10,000 mSV death occurring with complete certainty after a few weeks and with 20,000 mSv in hours or days. In addition to the direct health effects mentioned above caused by radiation, we must also take into account the indirect and long-term effects of the increase in the frequency of cancers as a consequence of genetic damage.
Industrial radiography safety precautions
The radiation, of certain wavelengths, called ionizing radiation, has enough energy to damage DNA and cause cancer. Ionizing radiation includes X-rays, gamma rays, and other forms of high-energy radiation. Lower energy, non-ionizing forms of radiation, such as visible light and cell phone energy, have not been found to cause cancer in people. The safety equipment usually includes four basic items:
- A radiation survey meter (such as a Geiger meter),
- An alarming dosimeter,
- A film badge or thermoluminescent dosimeter (TLD).
- The time, shield and distance
The survey meter: 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.
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 over a preset threshold.
The film badge or TLD is used to measure the radiographer’s total exposure over time (usually a month).
Time distance and shielding in radiography
There are three ways a radiographer will ensure they are not exposed to higher than required levels of radiation, time, distance, and shielding.
Time: For people who are exposed to radiation in addition to natural background radiation, limiting or minimizing the time of exposure decreases the dose they receive from the radiation source.
Distance: in the same way that the heat of the fire loses intensity when we move away, the radiation dose decreases drastically with increasing distance from the source.
Shielding: Lead, concrete, or water barriers protect against gamma and X-ray penetration. This is why some radioactive materials are stored underwater or in rooms lined with concrete or lead, and why whereby dentists place a lead blanket over patients having their teeth x-rayed. Therefore, placing adequate shielding between you and a radiation source will greatly reduce or eliminate the dose you will receive.
Non-ionizing radiation includes
Non-ionizing radiation is low energy. They are not capable of ionizing with which they interact. These radiations can be classified into two large groups:
- Electromagnetic radiation
- Solar Radiation
Electromagnetic radiation: includes radiation generated by power lines or by static electric fields. Other examples are radiofrequency waves, used by radio stations and microwaves used in household appliances and the area of telecommunications likewise.
The Sun provides the energy necessary for life to exist on Earth. The Sun emits radiation throughout the entire electromagnetic spectrum from infrared to ultraviolet. Not all solar radiation reaches the Earth’s surface, because of the shorter ultraviolet waves, and due to gases in the atmosphere. Infrared rays, visible light and ultraviolet radiation belong to this group.
This part of the spectrum, which can be detected with our eyes, allows us to see and provides the energy to plants to produce food through photosynthesis.
The light we can see is just a tiny slice in the middle of the spectrum.
- Welding arcs
We cannot see this part of the spectrum, but it can damage our skin if it is not well protected, and can cause serious burns to skin cancer. Ultraviolet (UV) radiation is electromagnetic radiation. Excess UV rays can have serious consequences for health, as it is capable of causing cancer, ageing and other skin problems such as burns.
It can also cause cataracts and other eye injuries and can alter the immune system. Children must learn to take care of the sun because excessive exposure during childhood and youth can lead to skin cancer later on.
There are three types of ultraviolet radiation, which have different energy or wavelengths: UVA, UVB and UVC. Most of the UV radiation that reaches the earth is of the UVA type (longer wavelength), with some UVB.
Infrared rays are a type of electromagnetic radiation with a higher wavelength than visible light, but shorter than that of microwaves. The name infrared means below red because its beginning is adjacent to this colour in the visible spectrum.
Infrared belongs to heat, because at normal temperatures objects spontaneously emit radiation in the infrared range. Another of the many applications of infrared radiation is using infrared emitting equipment in the industrial sector. In this sector, infrareds have multiple applications, such as drying paints, varnishes or paper, thermo-fixing of plastics, preheating welds, curvature, and tempered and laminated glass, among others.
Industrial radiography safety
Microwaves are shot wave-length radio waves of high frequency and therefore of very short wavelength, hence their name. Within the electromagnetic spectrum, microwaves are located between infrared rays (whose frequency is higher) and conventional radio waves.
Naturally occurring microwaves are low-temperature radiation that reaches the Earth’s surface from space. Electronic devices also generate artificial microwaves. Subsequently, today the microwave oven has become an almost essential appliance in our kitchens. Microwaves have the property of exciting the water molecule, which is what makes food containing these molecules heat up.
But microwaves have many other applications, such as in radio and television, radar, meteorology, satellite communications, distance measurement or in the investigation of the structure and properties of matter.
Industrial radiography safety
Radio waves are very low-frequency radiation (long wavelength). Any electromagnetic wave longer than a microwave is called a radio wave. Electromagnetic waves travel in a straight line. Consequently, if we send a radio signal over a long distance, the signal will move away from the Earth’s surface to space. However, radio waves have the property of reflection in the upper layers of the atmosphere, specifically in the ionosphere.
However, the ionosphere is the layer of the atmosphere located between 90 and 400 km in height. It has the peculiarity that in it the atoms ionize and release electrons due to the effect of sunlight. In a way, since there is an electronic cloud in the ionosphere, it behaves like a screen for electrical signals. However, depending on the ion concentration, there will be more or less “shielding” against the signals.
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