Materials radioactive

Recommendations define radioactive materials as materials for which the specific activity is greater than 0.002 Ci/g. Exposure to radioactivity causes physical difficulties and may influence the integrity of genetic information. With respect to evaluation methods for these substances, which are beyond the scope of this book, the interested reader should refer to technical books specializing in the subject. 

Regulations applicable to the shipment of radioactive materials provide an acceptable level of control of radiation, criticality, and thermal hazards to persons, property, and the environment during routine, normal, and accidental conditions by all modes, as governed by the International Atomic Energy Agency. These rules are promulgated in the Regulations for the Safe Transport of Radioactive Materials (RFT). 

The principles associated with the transport of dangerous goods by air are contained in Annex 18 to the Convention of International Civil Aviation— 

It should be noted that the majority of otherwise forbidden materials may be diluted, protected, refrigerated, mixed, or stabilized to enable their transportation by one or more modes. 

Dangerous goods. Articles or substances which are capable of posing a significant risk to health, safety or property when transported by air and which are classified according to Part 2, Chapters 1 to 10. ICAO 1-3.1 

A radionuclide refers to any type of radioactive material including elements and isotopes of elements. Most radioactive materials used in nuclear medicine consist of isotopes since individual medical treatment may require an isotope with specific radioactive properties. Radioisotopes show how the disease process alters the normal function of an organ. A patient swallows, inhales, or receives an injection of a tiny amount of a radioisotope. Cameras then reveal where the isotope accumulates in the body. Laboratory tests use radioisotopes to measure important substances in the body including thyroid hormones. Some facilities use isotopes to sterilize hospital itans such as sutures, syringes, catheters, and hospital clothing otherwise destroyed by heat sterilization. Sterilization using radioisotopes can prove valuable because the process permits the itans to ranain in their sealed packages. NRC rules outline minimum safety requiranents for workers and patients. 

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Other compounds which may be found in crude oil are metals such as vanadium, nickel, copper, zinc and iron, but these are usually of little consequence. Vanadium, if present, is often distilled from the feed stock of catalytic cracking processes, since it may spoil catalysis. The treatment of emulsion sludges by bio-treatment may lead to the concentration of metals and radioactive material, causing subsequent disposal problems. 

Care must be taken in handling radon, as with other radioactive materials. The main hazard is from inhalation of the element and its solid daughters which are collected on dust in the air. Good ventilation should be provided where radium, thorium, or actinium is stored to prevent build-up of the element. Radon build-up is a health consideration in uranium mines. Recently radon build-up in homes has been a concern. Many deaths from lung cancer are caused by radon exposure. In the U.S. it is recommended that remedial action be taken if the air in homes exceeds 4 pCi/1. 

Fluorine, which does not occur freely in nature except for trace amounts in radioactive materials, is widely found in combination with other elements, accounting for ca 0.065 wt % of the earth s cmst (4). The most important natural source of fluorine for industrial purposes is the mineral fluorspar [14542-23-5] CaF2, which contains about 49% fluorine. Detailed annual reports regarding the worldwide production and reserves of this mineral are available (5). A more complete discussion of the various sources of fluorine-containing minerals is given elsewhere (see Fluorine compounds, inorganic). 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

As the result of many years of nuclear reactor research and development and weapons production in U.S. defense programs, a large number of sites were contarninated by radioactive materials. A thorough cleanup of this residue of the Cold War is expected to extend well into the twenty-first century and cost many billions of dollars. New technologies are needed to minimi2e the cost of the cleanup operation. 

Several modes of waste management are available. The simplest is to dilute and disperse. This practice is adequate for the release of small amounts of radioactive material to the atmosphere or to a large body of water. Noble gases and slightly contaminated water from reactor operation are eligible for such treatment. A second technique is to hold the material for decay. This is appHcable to radionucHdes of short half-life such as the medical isotope technetium-9 9m = 6 h), the concentration of which becomes negligible in a week s holding period. The third and most common approach to waste... 

Nuclear utiUties have sharply reduced the volume of low level radioactive waste over the years. In addition to treating wastes, utiUties avoid contamination of bulk material by limiting the contact with radioactive materials. Decontamination of used equipment and materials is also carried out. For example, lead used for shielding can be successfully decontaminated and recycled using an abrasive mixture of low pressure air, water, and alumina. 

Spent fuel casks are of type B. For the movement of spent fuel, computer tracking systems are used. State radiological safety units are informed of shipments of spent fuel and other high activity radioactive materials so that these units may respond in case of accident. 

The safety record for transport of radioactive materials including spent fuel and wastes is excellent. Information about transportation of radioactive materials including waste is managed by DOE. Codes such as RADTRAN that can calculate pubHc radiation dose owing to the passage of shipments have been developed. The maximum dosage from such shipments is a very small fraction of the typical annual radiation dose from all other sources. 

The biological and medical sciences are ripe for iastmmentation advances. Whereas most immunoassays (qv) use radioactive materials, the implementation of chemiluminescent methods, enzyme techniques, and electrochemical methods is expected to become more important. New and better noninvasive methods of iavestigation are expected to become more routine. In addition, real-time measurements, whereby analyses of a number of... 

Concerns over safe handling of radioactive materials and issues around the cost and disposal of low level radioactive waste has stimulated the development of nonradiometric products and technologies with the aim of replacing radioactive tracers in research and medical diagnosis (25). However, for many of the appHcations described, radioactive tracer technology is expected to continue to be widely used because of its sensitivity and specificity when compared with colorimetric, fluorescent, or chemiluminescent detection methods. 

Conservation of Energy. Because the naturally occurring radioactive materials continued to emit particles, and thus the associated energy, without any decrease in intensity, the question of the source of this energy arose. Whereas the conservation of energy was a firmly estabUshed law of physics, the origin of the energy in the radioactivity was unknown. 

Generally, labeled compounds are prepared by procedures which introduce the radionuchde at a late stage of the synthesis. This allows for maximum radiochemical yields, and reduces the handling time of radioactive material. When dealing with short half-life isotopes, a primary consideration is the time required to conduct synthetic procedures and purification methods. 

Radiation Dosimetry. Radioactive materials cause damage to tissue by the deposition of energy via their radioactive emissions. Thus, when they are internally deposited, all emissions are important. When external, only those emissions that are capable of penetrating the outer layer of skin pose an exposure threat. The biological effects of radiation exposure and dose are generally credited to the formation of free radicals in tissue as a result of the ionization produced (17). 

The diversity of radionucHde half-life and chemical nature of commonly used radiopharmaceuticals demands a variety of formulation matrices, packaging containers, and storage conditions. The containers, ingredients, and processes used in these products must meet the stringent requirements for parenteral pharmaceuticals, as well as provide safe conditions for storage, handling, and disposal of the radioactive material. 

Nuclear Regulatory Commission NRG ensures that radioactive materials are used and nuclear faciHties are operated with regard for environment and pubHc health, safety, and security... 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

The NRC also imposes special security requirements for spent fuel shipments and transport of highly enriched uranium or plutonium materials that can be used in the manufacture of nuclear weapons. These security measures include route evaluation, escort personnel and vehicles, communications capabiHties, and emergency plans. State governments are notified in advance of any planned shipment within their state of spent fuel, or any other radioactive materials requiring shipment in accident-proof. Type B containers. 

Radioactivity associated with Re can be detected only by using sophisticated laboratory equipment because of the low energy of the emitted P-particles. This radioactivity poses no health or safety ha2atds. Samples of the metal and its compounds ate not labeled as radioactive, and typical precautions associated with radioactive materials ate not taken during use and handling of the element or its compounds. 

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