Uses for Radioactive Substances

Chernobyl accident released large quantities of it. To reduce the likelihood of thyroid damage, people were directed to take large quantities of salt containing non-radioactive iodine-127. This flooding of the thyroid glands with the non-damaging form of iodine made it less likely that the iodine-131 would be absorbed. 

As you saw in the last section, radioactive substances can be damaging to our bodies, but scientists have figured out ways to use some of their properties for our benefit. For example, radioactive nuclides are employed to diagnose lung and liver disease, to treat thyroid problems and cancer, and to determine the ages of archaeological finds. Let s examine some of these beneficial uses. 

Like many other radioactive nuclides used in medicine, cobalt-60 is made by bombarding atoms of another element (in this case iron) with neutrons. The iron contains a small percentage of iron-58, which forms cobalt-60 in the following steps  

Objective 26 One of the most significant advances in medicine in recent years is the development 

Objective 26 A simplified description of how MRI works begins with the fact that protons act 

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There are two main uses for radioactive substances that give off ionising radiations on construction sites. Firstly, tracing water flows and sewers where a low powered radioactive substance is added to the flow and its route followed using special instruments. Only authorised specialists should be allowed to handle the radioactive substance before it is added to the water. Once it is added, it mixes rapidly with the water and becomes so diluted as not to present a hazard. 

The beneficial use of radiation is one of the best examples of how careful characterization of the hazard is essential for its safe use. A radioactive substance can be safely stored or transported if appropriately contained. Depending on the characteristics of the radioactive material, it can be safely handled by using appropriate shielding and safety precautions. Laboratory workers usually wear special badges that quantify radiation exposure to ensure that predetermined levels of exposure, which are considered safe, are not exceeded. Unfortunately, after more than 50 years, society has not yet been able to design and implement a safe way to dispose of radioactive waste. The hazardous properties of radiation are explored further in a subsequent chapter. 

Very little work has been carried out on radiochemical derivatization for analysis of trace amounts of materials. The technique has the advantage of being both selective and sensitive. Die main advantage is that the sample background does not cause interference in the detection as it does in most other methods and which necessitates some degree of clean-up. Also, the reactions used are those for normal derivatization procedures, the only difference being that the reagent is radiolabeled and that appropriate precautions are required for radioactive substances. The few methods described below illustrate the application of this technique. 

Radio-immunology has remained the method of choice for certain studies of clinical medicine and has few applications for the measurement of molecules of low molecular mass, because of the use of radioactive substances. Alternatively, the... 

I Caution. Uranium is a radioactive element and it must be handled with particular care. Fume hoods and other apparatus appropriate for use with radioactive substances must be used. Waste solutions are a source of radioactive contamination, and they must be disposed of properly. 

The contribution of radiotherapy and the use of radioactive substances for diagnostic purposes to overall exposure to radiation may be very great in individual cases, but in relation to the population as a whole it is comparatively small. It is estimated at only a few percent in the form of X-rays. Surface explosions of nuclear weapons released mainly dust-bound fission and activation products about half of these were conveyed into the stratosphere, the other half caused local fallout. About three quarters of the total amount released have already decayed, the remaining external dose is estimated at approximately 0.27 p,Sv in mid-latitudes. It is due primarily to the decay of long-living Cs. 

The use of radioactive substances for equilibrium determinations may offer appreciable advantages [123]. Thus, e.g. S has been used [124]. 

The use of nuclear energy for power generation and the disposal of nuclear wastes from power plants are controversial social and political issues. It is imperative, therefore, that as a citizen with a stake in these matters, you have some understanding of nuclear reactions and the uses of radioactive substances. 

For diverse reasons, such as restrictions on the use of radioactive substances, nonisotopic immunoassays have gained general acceptance, especially in trace analysis and environmental analysis l]-[3]. 

The scientific and medical communities soon realized that these human-made isotopes were potential substitutes for radium. One major impediment to their widespread use was the difficulty of producing them economically in commercial quantities. Using one radioactive substance to produce another was tedious, time consuming and expensive. Isotopes could be manufactured by proton bombardment... 

The elution of radioactive spots of a chromatogram can be used for purification, or even for isolation purposes. The general techniques are applied (3,41) using radioactivity controls. The recovery of is nearly quantitative, but the use of eluates to establish radiochromati rams has no advantage over direct measurements on the spots. No special tech niques have been elaborated for radioactive substances in this field, but the efficiency of the procedure has been shown by the recent isolation of 3,5,3 -triiodo-L-thyronine (41). 

Substitution. Obviously, if it is possible to perform the experiment without the use of radioactive substances, then all exposure is avoided. For example, the ELISA (Enzyme-linked immunosorbant assay) technique has replaced that of RIA (Radioimmuno assay) for many procedures. 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

Barium titanate thin films can be deposited on various substances by treating with an aqueous solution containing barium salts and an alkanolamine-modifted titanate such as TYZOR TE (151). In a similar fashion, reaction of a tetraalkyl titanate with an alkah metal hydroxide, such as potassium hydroxide, gives oxyalkoxide derivatives (KTi O(OR) ), which can be further processed to give alkali metal titanate powders, films, and fibers (152—155). The fibers can be used as adsorbents for radioactive metals such as cesium, strontium, and uranium (156). 

Part V contains amendments to the Radioactive Substances Act 1960, Part VI controls the use, import, containment or release of genetically modified organisms to the environment, and Part VII provided for the reorganization of the Nature Conservancy Council and Countryside Commission. 

A PET scan requires a substance called a tracer. A suitable tracer must accumulate in the target organ, and it must be modified to contain unstable radioactive atoms that emit positrons. Glucose is used for brain imaging, because the brain processes glucose as the fuel for mental and neural activities. A common tracer for PET brain scans is glucose modified to contain radioactive fluorine atoms. Our molecular inset shows a simplified model of this modified glucose molecule. 

As shown in Example, Equation is used to find a nuclear half-life from measurements of nuclear decays. Equation is used to find how much of a radioactive substance will remain after a certain time, or how long it will take for the amount of substance to fall by a given amount. Example provides an illustration of this t q)e of calculation. In Section 22-1. we show that Equation also provides a way to determine the age of a material that contains radioactive nuclides. 

The ICRP (1994b, 1995) developed a Human Respiratory Tract Model for Radiological Protection, which contains respiratory tract deposition and clearance compartmental models for inhalation exposure that may be applied to particulate aerosols of americium compounds. The ICRP (1986, 1989) has a biokinetic model for human oral exposure that applies to americium. The National Council on Radiation Protection and Measurement (NCRP) has also developed a respiratory tract model for inhaled radionuclides (NCRP 1997). At this time, the NCRP recommends the use of the ICRP model for calculating exposures for radiation workers and the general public. Readers interested in this topic are referred to NCRP Report No. 125 Deposition, Retention and Dosimetry of Inhaled Radioactive Substances (NCRP 1997). In the appendix to the report, NCRP provides the animal testing clearance data and equations fitting the data that supported the development of the human mode for americium. 

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