Penetration power describes how easily the particles can pass through another material. Since alpha particles have a low penetration power, the outside layer of the human skin, for example, can block these particles. Alpha decay occurs because the nucleus of a radioisotope has too many protons.
A nucleus with too many protons causes repulsion between these like charges. Examples of this can be seen in the decay of americium Am to neptunium Np. In radioactive nuclei with too many neutrons, a neutron can be converted into an electron, called beta particle. During beta decay, the number of neutrons in the atom decreases by one, and the number of protons increases by one.
Effectively, a neutron was converted into a proton in the decaying nucleus, in the process releasing a beta particle. Some decay reactions release energy in the form of electromagnetic waves called gamma rays. However, unlike visible light, humans cannot see gamma rays, because they have a much higher frequency and energy than visible light. Gamma radiation has no mass or charge. Many medical products today are sterilized by gamma rays from a Co source, a technique which generally is much cheaper and more effective than steam heat sterilization.
The disposable syringe is an example of a product sterilized by gamma rays. Because it is a 'cold' process radiation can be used to sterilize a range of heat-sensitive items such as powders, ointments, and solutions, as well as biological preparations such as bone, nerve, and skin to be used in tissue grafts. Large-scale irradiation facilities for gamma sterilization are installed in many countries. Smaller gamma irradiators, often utilising Cs, having a longer half-life, are used for treating blood for transfusions and for other medical applications.
Sterilization by radiation has several benefits. It is safer and cheaper because it can be done after the item is packaged. The sterile shelf-life of the item is then practically indefinite provided the seal is not broken. Irradiation technologies are used to sterlize almost half of the global supply of single-use medical products. Apart from syringes, medical products sterilized by radiation include cotton wool, burn dressings, surgical gloves, heart valves, bandages, plastic, and rubber sheets and surgical instruments.
Most medical radioisotopes made in nuclear reactors are sourced from relatively few research reactors , including:. Of fission radioisotopes, the vast majority of demand is for of Mo for Tcm. However, NRU ceased production in October , and the other two have limited remaining service life.
Output from each varies due to maintenance schedules. Supply capacity is always substantially e. One challenge is the delivery of fresh supplies in weekdays, in line with demand, to minimize waste.
In it was planning to build a RUR 6 billion radiopharmaceutical plant near Moscow. About half of its radioisotope production is exported. The targets are then processed to separate the Mo and also to recover I However, in medical imaging, the cost of Mo itself is small relative to hospital costs. Mo can also be made by bombarding Mo with neutrons in a reactor. There are three ways to produce Mo The most common and effective method is by fission of uranium in a target foil, followed by chemical separation of the Mo.
This fission is done in research reactors. A second method is neutron activation, where Mo in target material captures a neutron.
A third method is by proton bombardment of Mo in an accelerator of some kind. There are plans to produce it by fission in a subcritical assembly in an accelerator. A number of incidents in pointed out shortcomings and unreliability in the supply of medical isotopes, particular technetium. As indicated above, the world's supply of Mo comes from just six reactors, five of which are over 50 years old.
The Canadian and Netherlands reactors required major repairs over and were out of action for some time. Osiris was due to shut down in but apparently continued to at least An increasing supply shortfall of technetium was forecast from , and the IAEA encouraged new producers. Also, the processing and distribution of isotopes is complex and constrained, which can be critical when the isotopes concerned are short-lived.
A need for increased production capacity and more reliable distribution is evident. It reviewed the Mo supply chain to identify the key areas of vulnerability, the issues that need to be addressed, and the mechanisms that could be used to help resolve them. It requested an economic study of the supply chain, and this was published in by the NEA.
The report identifies possible changes needed. The NEA report predicted supply shortages from , not simply from reactors but due to processing limitations too. Historically reactor irradiation prices have been too low to attract new investment, and full cost recovery is needed to encourage new infrastructure. Transport regulation and denial of shipment impede reliable supply.
Outage reserve capacity needs to be sourced, valued, and paid for by the supply chain. Fission is the most efficient and reliable means of production, but Canada and Japan are developing better accelerator-based techniques. A review of the situation in mid showed that the market had substantially restructured following the supply crisis, and that restructuring had led to increased efficiencies in the use of material at the different layers in the supply chain. The latest NEA data confirms a relatively flat market demand of around six-day TBq Mo per week at the end of radiochemical processing.
In addition, several sources of supply had ramped up production to lift the baseline supply capacity for the and periods to a level safely above the revised market demand. Also it called for proposals for an LEU-based supply of Mo for the US market, reaching six-day TBq per week by mid, a quarter of world demand. Tenders for this closed in June , but evidently no immediate progress was made.
In December Congress passed the American Medical Isotope Production Act of to establish a technology-neutral program to support the production of Mo for medical uses in the USA by non-federal entities. In February , the Department of Energy's National Nuclear Security Administration NNSA selected four companies to begin negotiations for potential new cooperative agreement awards for the supply of molybdenum, mostly from accelerators.
Niowave is developing superconducting electron linear accelerators, NorthStar Medical Radioisotopes is planning to irradiate Mo targets to produce Mo in a reactor, while in the longer term it is developing a method using a linear accelerator. See below for fuller descriptions. Such Mo has relatively low specific activity, and there are complications then in separating the Tc The company received approval to begin routine production in August , and aims eventually to meet half of US demand with six-day TBq per week.
MURR runs on low-enriched uranium. Longer-term NorthStar is considering a non-reactor approach. In , NorthStar Medical Radioisotopes signed an agreement with Westinghouse to investigate production of Mo in nuclear power reactors using its Incore Instrumentation System. It is aiming to set up a 44, m 2 radioisotope production facility in Columbia, Missouri.
The NRC approved the plans in May However, Nordion withdrew from the project in April citing delays and cost overruns that had increased the project's commercial risk. An earlier proposal for Mo production involving an innovative reactor and separation technology has lapsed. They planned to use Aqueous Homogeneous Reactor AHR technology with LEU in small kW units where the fuel is mixed with the moderator and the U forms both the fuel and the irradiation target.
As fission proceeds the solution is circulated through an extraction facility to remove the fission products with Mo and then back into the reactor vessel, which is at low temperature and pressure. In mid Los Alamos National Laboratory announced that it had recovered Mo from low-enriched sulphate reactor fuel in solution, raising the prospect of this process becoming associated with commercial reprocessing plants as at La Hague in France.
JSC Isotope was founded in and incorporated in Brazil is a major export market. Its product portfolio includes more than 60 radioisotopes produced in cyclotrons, nuclear reactors by irradiation of targets, or recovered from spent nuclear fuel, as well as hundreds of types of ionizing radiation sources and compounds tagged with radioactive isotopes.
It has more than 10, scientific and industrial customers for industrial isotopes in Russia. The Karpov Institute gets some supply from Leningrad nuclear power plant.
Australia's Opal reactor has the capacity to produce half the world supply of Mo, and with the ANSTO Nuclear Medicine Project will be able to supply at least one-quarter of world demand from Tcm or Mo can also be produced in small quantities from cyclotrons and accelerators, in a cyclotron by bombarding a Mo target with a proton beam to produce Tcm directly, or in a linear accelerator to generate Mo by bombarding an Mo target with high-energy X-rays.
It is generally considered that non-reactor methods of producing large quantities of useful Tc are some years away. At present the cost is at least three times and up to ten times that of the reactor route, and Mo is available only from Russia. If Tc is produced directly in a cyclotron, it needs to be used quickly, and the co-product isotopes are a problem. An LEU target solution is irradiated with low-energy neutrons in a subcritical assembly — not a nuclear reactor.
The neutrons are generated through a beam-target fusion reaction caused by accelerating deuterium ions into tritium gas, using a particle accelerator. SHINE is an acronym for 'subcritical hybrid intense neutron emitter'.
Construction at Janesville, Wisconsin commenced in August on 'Building One' and in May on the main production facility, which would eventually be capable of producing over one-third of global Mo demand.
A hour test run of Phoenix's high-flux neutron generator was in June Its Cassiopeia plant at Janesville is to produce , doses of Lu per year from Carbon 5, years Used to measure the age of organic material up to 50, years old.
Chlorine , years Used to measure sources of chloride and the age of water up to 2 million years old. Lead Chromium Manganese Produced in reactors. Cobalt 5. Also used to irradiate fruit fly larvae in order to contain and eradicate outbreaks, as an alternative to the use of toxic pesticides.
Zinc Produced in cyclotrons. Technetiumm 6. Produced in 'generators' from the decay of molybdenum, which is in turn produced in reactors. Caesium Ytterbium Iridium Also used to trace sand to study coastal erosion. Gold 2. Also used to trace factory waste causing ocean pollution, and to study sewage and liquid waste movements.
Americium Radioisotope Half-life Use Phosphorus Yttrium 64 hours Used for liver cancer therapy. Molybdenum Iodine 8. Samarium Lutetium 6. Used to treat a variety of cancers, including neuroendocrine tumours and prostate cancer. Radioisotope Half-life Use Carbon Also used to detect heart problems and diagnose certain types of cancer.
Nitrogen 9. Radiotracers are widely used in medicine, agriculture, industry, and fundamental research. Radiotracer is a radioactive isotope; it adds to nonradioactive element or compound to study the dynamical behavior of various physical, chemical, and biological changes of system to be traced by the radiation that it emits. The tracer principle was introduced by George de Hevesy in for which he was awarded the Nobel prize.
The sustainability of radioisotope production is one of the critical areas that receive great attention. There are more than different radioisotopes that are used regularly in different fields; these isotopes are produced either in a medium or in high-flux research reactors or particle accelerators low or medium energy [ 21 ]. Some of the radioisotopes produced by the reactor and particle accelerators and their applications are given in Table 4.
Some of the radioisotopes produced by the reactor and particle accelerators and their applications. Nowadays radiotracer has become an indispensable and sophisticated diagnostic tool in medicine and radiotherapy purposes. The most common radioactivity isotope used in radioactive tracer is technetium 99 Tc. Tumors in the brain are located by injecting intravenously 99 Tc and then scanning the head with suitable scanners.
Kidney function is also studied using compound containing I. Tritium 3 H is frequently used as a tracer in biochemical studies. A most recent development is positron emission tomography PET , which is a more precise and accurate technique for locating tumors in the body.
A positron emitting radionuclide e. This technique is also used in cardiac and brain imaging. Compound X-ray tomography or CT scans.
The radioactive tracer produces gamma rays or single photons that a gamma camera detects. Emissions come from different angles, and a computer uses them to produce an image. CT scan targets specific area of the body, like the neck or chest, or a specific organ, like the thyroid [ 22 ]. The most common therapeutic use of radioisotopes is 60 Co, used in treatment of cancer. Sometimes wires or sealed needles containing radioactive isotope such as Ir or I are directly placed into the cancerous tissue.
When the treatment is complete, these are removed. This technique is frequently used to treat mouth, breast, lung, and uterine cancer. Development of high yielding varieties of plants, oil seeds, and other economically important crops and protection of plant against the insects are the thrust area of agricultural research.
The irradiated seeds of wheat, rice, maize, cotton, etc. These varieties of crops are more disease resistant and have high yields. Several countries all over the world produce new variety of crops from radiation-induced mutants [ 23 ]. The best technique for the control of insects and pests is sterile insect technique SIT.
Irradiation is used to sterilize mass-reared insects so that, while they remain sexually competitive, they cannot produce offspring. As a result, it enhances the crop production and preservation of natural resources.
Food irradiation has more advantages than conventional methods. All types of radiations are not recommended for food irradiation; only three types of radiation are recommended by CODEX general standard for food irradiation which are 60 Co or Cs, X-rays, or electron beams from particle accelerators [ 24 ].
No radiation remains in the food after treatment. This not only conserves energy but also prevents sweetening of potato, commonly occurring at low temperatures.
It gives advantage to the manufacturers of chips as low-sugar potato gives desired lighter color to fries and chips. Irradiated fruits all kinds of mangoes of these at hard mature pre-climacteric stage at 0. These doses are also effective in destroying quarantine pests. Under ice, sea food such as fish and prawns, fish-like Bombay duck, pomfret, Indian salmon, mackerel, and shrimp can be stored for about 7—10 days. Studies have demonstrated that irradiation at 1—3 kGy followed by storage at melting ice temperatures increases its shelf-life nearly threefold.
Radiation treatment has been employed to enhance the shelf-life of intermediate moisture meat products. While transporting the spices, due to inadequate handling and processing conditions, spices get contaminated with insect eggs and microbial pathogens. When incorporated into semi-processed or processed foods, particularly, after cooking, the microbes, both spoilers and pathogens, in spices can outgrow causing spoilage and posing risk to consumers.
Many of the spices develop insect infestation during storage, and unscrupulous traders convert them into spice powders. A dose of 10 kGy brings about near sterility or commercial sterility while retaining the natural characteristics of spices. Irradiation at higher doses can also be employed for total sterilization of diets for immunocompromised patients, adventure sports, military, and astronauts.
Radioisotopes are commonly used in industry for checking blocked water pipes and detecting leakage in oil pipes. For example, small quantity of radioactive 24 Na is placed in a small enclosed ball and is allowed to move in pipe with water.
The moving ball containing radioisotope is monitored with a detector. If the movement of ball stops, it indicates the blocked pipe. Similarly, radioisotope 24 Na is mixed with oil flowing in an underground pipe. With radiation detector, the radioactivity over the pipe is monitored. If there is a leakage place, the radiation detector will show large activity at that particular place. Radioisotopes are also used to monitor fluid flow and filtration, detect leaks, and gauge engine wear and corrosion of process in equipment.
Radioactive materials are used to inspect metal parts and the integrity of welds across a range of industries. The titanium capsule is a radioactive isotope which is placed on one side of the object being screened, and some photographic film is placed on the other side. The gamma rays pass through the object and create an image on the film. Gamma rays show flaws in metal castings or welded joints.
The technique allows critical components to be inspected for internal defects without damage. Radiotracer is also used to inspect for internal defect without damage. In industries, the production methods need to be constantly monitored in order to check the quality of products and to control the production process.
The monitoring is carried out by quality control devices using the unique properties of radiation; such devices are called nuclear gauges. They are more useful in extreme temperature, harmful chemical process, molten glass, and metals.
The gauges are also used to measure the thickness of sheet materials, including metals, textiles, paper, and plastic production. Radiation passing through the material breaks the bonds by removing the electron of an atom or molecules; this induces physical, chemical, and biological changes.
Ionizing radiation focuses large amount of energy into a highly localized areas of irradiated materials. Damage is caused by the interaction of this energy with nuclei or orbiting electrons. The material structure may be modified through this energy interaction; as a result the mechanical property of bulk material changes.
Radiation creates a point defect in metals; this had been recognized by Wigner in The radiation effects on metals depend on type and duration of the radiation.
Ionizing radiation can affect the metal in two ways, 1 lattice atoms are removed from their regular lattice sites, that is, displacement damage production and 2 chemical composition of the target can be changed by ion implantation or transmutation.
Neutron-irradiated metals at room temperature show increase in electrical and thermal resistance, hardness, and tensile strength and higher yield strength along with decrease ductility in metals [ 25 ]. At higher temperature it is found that the strength and ductility return to the same values as before irradiation. A metal under stress at higher temperature exhibits the phenomenon of creep, that is, the gradual increase in strain with time.
The thermal neutrons have less significant effect on the mechanical properties of metals. They can be captured by nuclei of irradiated material which will become radioactive. Radiation causes the viscosity of oil and grease to increase as gummy, tar-like polymers are formed. Radiation causes soap-oil-type greases to become more fluid. Plastics undergo drastic changes when exposed to radiation. The rubber may become harder or softer depending on its types.
Concrete under radiation exposure heats up. This drives the water out of its internal structure. Swelling, cracking, and spalling result [ 25 ]. Ionizing radiation can alter the molecular structure and macroscopic properties of the polymer.
These processes in the target molecules lead to breaking of original bonds, production of ionized and excited species, bond rearrangement, chain scission, radical formation, etc. All these processes are responsible for the modification of chemical, electrical, mechanical, and optical properties of polymers leading to their applications in different scientific and technological fields [ 25 ].
During radiation polymerization, the interaction takes place between two free radical monomers which combine to form intermolecular bond leading to three-dimensional network of cross-linked high molecular polymer.
These cross-linked polymers show high thermal resistance and strong mechanical strength [ 26 ]. Grafting is a method wherein monomers are covalently bonded modified onto the polymer chain. This method involves the formation of free radical sites near the surface of polymers on to the polymeric backbone as a result of irradiation. Hence microenvironment suitable for the reaction among monomer or polymer and the active site is formed, leading to propagation to form side chain grafts.
The radiation-induced grafting is used in variety of applications such as biomedical, environmental, and industrial uses [ 26 , 27 , 28 ]. The radiation grafting can be performed by two major methods: pre-irradiation technique and mutual or simultaneous method [ 29 ]. Radiation-induced degradation technology is a new application to develop viscose, pulp, paper, food preservation, pharmaceutical production, and natural bioactive agent industries.
Controlling the degree of degradation of polymers in industries is very important. Irradiation of polymers induces molecular chain branching, cross-linking, and molecular degradation or scissioning.
Chain branching increases the molecular weight of the polymer. Cross-linking forms the insoluble three-dimensional polymer network, while degradation or scissioning causes a reduction of initial molecular weight [ 30 , 31 ]. The polymer irradiated in air by solar radiation results in the formation of free radicals and can also react with oxygen, giving rise to oxidative degradation. All these molecular modifications can modify the properties of polymers. The study of degradation of polymer is important in using polymeric materials in radioactive environments such as in nuclear power plants, space, or the sterilization of polymeric medical disposals or food plastic packaging [ 32 ].
The splitting of polymeric macromolecules to form free radicals is employed for synthesizing modified polymers. At the same time, polymer degradation may often be considered as an undesirable side reaction occurring during the chemical transformation, fabrication, and usage of polymers.
The harmful effects that are produced in human beings who are exposed to radiations are called health effects. The result of all the physical interaction processes between incident radiation and the tissue of a cell is a trail of ionized atoms and molecules. The radiation is directly interacting with sensitive critical sites of the tissue DNA to produce damage by breaking chemical bonds.
The chemically active free radicals are indirectly produced by interaction of primary radiation with DNA of the tissue. Both direct and indirect damages produced in DNA by radiation are shown in Figure 2. The mechanism by which damage occurs in the cell by direct and indirect action of radiation. Radiation attacks DNA molecule directly Figure 2 ; as a result the ionization is produced and the bond is disrupted within a few nanometers of the DNA molecule.
Free radicals are important since they can diffuse far enough to reach and induce chemical changes at critical sites in biological structures.
The chemical damage produced by the breaking of DNA by the action of free radicals. The formation and action are as follows:. Ionization of a water molecule produces a free electron and a positively charged molecule:. The released electron is most likely to be captured by another water molecule converting it into a negative ion:. Formation of free radicals is denoted by OH 0 and H 0. These free radicals interact with organic biomolecules RH again to produce organic free radicals denoted by R 0 :.
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