Radium radon and

Radon is a naturally occurring radioactive decay product of uranium. A great deal of attention 222 228 centers around radon, which is the first decay product of radium. Radon and radon... 

Emitted by heavy atoms, such as uranium, radium, radon, and plutonium (to name a few), alpha particles are helium nuclei, making them the most massive kind of radiation. Alpha radiation can cause a great deal of damage to the living cells it encounters, but has such a short range in tissue (only a few microns) that external alpha radiation cannot penetrate the dead cells of the epidermis to irradiate the living cells beneath. If inhaled, swallowed, or introduced into open wounds, however, alpha radiation can be very damaging. In nature, alpha radiation is found in rocks and soils as part of the minerals, in air as radon gas, and dissolved in water as radium, uranium, or radon. Alpha emitters are also found in nuclear power plants, nuclear weapons, some luminous paints (radium may be used for this), smoke detectors, and some consumer products. Objects and patients exposed to alpha radiation may become contaminated, but they do not become radioactive. 

Gilkeson RH, Cowart JB. 1987. Radium radon and uranium isotopes in groundwater from Cambrian-Ordovician sandstone aquifers in Illinois USA. In Graves B, ed. Radon in ground water, radon, radium and other radioactivity in ground water Hydrogeologic impact and application to indoor airborne contamination Proc National Water Well Association conference, Somerset, NJ, April 7-9, 1987. Chelsea, MI Lewis Publishers, Inc., 403-422. 

Morse, R.H., 1969. Radium geochemistry applied to prospecting for uranium. Can. Min. J., 90 75-76. Morse, R.H., 1970. The surficial geochemistry of radium, radon and uranium near Brancroft, Ontario, with applications to prospecting for uranium. Unpubl. Ph.D. thesis. Queen s Univ., Kingston, Ontario, 186 pp. 

The uranium decay series provides the most important isotopes of elements radium, radon, and polonium, which can be isolated in the processing of uranium minerals. Each ton of uranium is associated with 0.340 g of Ra. Freshly isolated Ra reaches radioactive equilibrium with its decay products to Pb in about two weeks (see Fig. 1.2). Many of these products emit energetic y-rays, which resulted in the use of Ra as a y-source in medical treatment of cancer (radiation therapy). However, the medical importance of radium has diminished greatly since the introduction of other radiation sources, and presently the largest use of radium is as small neutron sources (see Table 12.2). 

Radon is still produced for therapeutic use by a few hospitals by pumping it from a radium source and sealing it in minute tubes, called seeds or needles, for application to patient. This... 

Argon-40 [7440-37-1] is created by the decay of potassium-40. The various isotopes of radon, all having short half-Hves, are formed by the radioactive decay of radium, actinium, and thorium. Krypton and xenon are products of uranium and plutonium fission, and appreciable quantities of both are evolved during the reprocessing of spent fuel elements from nuclear reactors (qv) (see Radioactive tracers). 

Ra.don Sepa.ra.tion, Owing to its short half-life, radon is normally prepared close to the point of use in laboratory-scale apparatus. Radium salts are dissolved in water and the evolved gases periodically collected. The gas that contains radon, hydrogen, and oxygen is cooled to condense the radon, and the gaseous hydrogen and oxygen are pumped away. 

Mill tailings are another form of nuclear waste. The residue from uranium ore extraction contains radium, the precursor of short-Hved radon and its daughters. Piles of tailings must be properly covered. 

Morawska L, Philhps CR (1992) Dependence of the radon emanation coefficient on radium distribution and internal stractnre of the mineral. Geochim Cosmochim Acta 57 1783-1797 Neretnieks I (1980) Diffusion in the rock matrix an important factor in radionuclide retardation J Geophys Res 88 4379-4397... 

In U.S. EPA Office of Radiation Program s New House Evaluation Program (NEWHEP), two builders in the Denver area, two in Colorado Springs, and one in Southfield, Michigan, installed various radon-resistant features in houses during construction. A sampling of subsequent measurements of indoor radon, adjacent soil gas radon, and soil radium content is summarized in Table 31.6.36... 

Factors influencing the production and migration of radon in soils have been examined, and various sources of geographic data have been discussed. Two significant soil characteristics include air permeability and, less importantly, radium concentration. While there are, at present, few opportunities to compare the larger-scale data with on-site field measurements, those comparisons that have been made for both surface radium concentrations and air permeability of soils show a reasonable correspondence. Further comparisons between the aerial radiometric data and surface measurements are needed. Additional work and experience with SCS information on soils will improve the confidence in the permeability estimates, as will comparisons between the estimated permeabilities and actual air permeability measurements performed in the field. 

The main parameters determining the indoor radon concentration in detached houses are the effective radium concentration (product of the radium concentration and the emanation factor) and the permeability of the ground. The effects of other factors are not so easy to ascertain from the existing data. 

The air circulation must continue at least three hours. It is not only necessary to distribute the radon accumulated in the radium solution bottle into the entire system (for this purpose a shorter time would be sufficient) but it takes three hours to establish the equilibrium between radon and its short-lived daughters in the medium. 

Key et al. [27] have described improved methods for the measurement of radon and radium in seawater and marine sediments using manganese dioxide impregnated fibres. The basic method that these workers used was that of Broecker [28]. Seawater samples were taken in 30 litre Niskin bottles. 

Radon is the heaviest of the noble gases and is the only one that is radioactive. It is the decay product of radium, thorium, and uranium ores and rocks found underground. As it decays, it emits alpha particles (hehum nuclei) and is then transmuted to polonium and finally lead. The Earth s atmosphere is just 0.0000000000000000001% radon, but because radon is 7.5 times heavier than air, it can collect in basements and low places in buildings and homes. 

Radon s source is a step in the transmutation of several elements uranium —> thorium — radium —> radon —> polonium —> lead. (There are a number of intermediate decay products and steps involved in this process.) Radon-222 forms and collects just a few inches below the surface of the ground and is often found in trapped pockets of air. It escapes through porous soils and crevices. 

When thorium emits alpha particles, it disintegrates into other daughter radionuclides (radioactive materials), such as radium-226 and radon-222 (from thorium-230 in the uranium-238 decay series) or radium-228 and thoron (radon-220 from thorium-232 in the thorium decay series). It eventually decays to stable lead-208 or -206, which is not radioactive. More information about the decay of thorium can be found in Chapter 3. The toxicological characteristics of radon, radium, and lead are the subject of separate ATSDR Toxicological profiles. 

Thorium is commonly found in combination with other actinide elements, with organic and inorganic chemicals, and with acids and bases during occupational exposure. The health effects of occupational exposures to thorium on humans, therefore, cannot necessarily be attributed to thorium. The daughter products of thorium have unique properties that also add to the radiological toxicity of thorium. For further information, see the toxicological profiles on uranium, radon, and radium. 

In the environment, thorium and its compounds do not degrade or mineralize like many organic compounds, but instead speciate into different chemical compounds and form radioactive decay products. Analytical methods for the quantification of radioactive decay products, such as radium, radon, polonium and lead are available. However, the decay products of thorium are rarely analyzed in environmental samples. Since radon-220 (thoron, a decay product of thorium-232) is a gas, determination of thoron decay products in some environmental samples may be simpler, and their concentrations may be used as an indirect measure of the parent compound in the environment if a secular equilibrium is reached between thorium-232 and all its decay products. There are few analytical methods that will allow quantification of the speciation products formed as a result of environmental interactions of thorium (e.g., formation of complex). A knowledge of the environmental transformation processes of thorium and the compounds formed as a result is important in the understanding of their transport in environmental media. For example, in aquatic media, formation of soluble complexes will increase thorium mobility, whereas formation of insoluble species will enhance its incorporation into the sediment and limit its mobility. 

N. Yamada, and P. Mercier, she published a number of researches on other radioactive elements, including radium C, radium C, radon, radium A, and radium E. 

Other sources include building materials such as concrete that are made from the earth s crustal materials and hence can contain significant amounts of uranium and radium (Nazaroff and Nero, 1988). Radon dissolves in water, and hence degassing from household water can also be a source. For example, Osborne (1987) reported that the radon concentration in a bathroom increased by more than two orders of magnitude during a 15-min period that a shower was running. 

The rarity of polonium is evident from a calculation (1) which shows that the outermost mile of the earth s crust contains only 4000 tons of the element, whereas radium, usually classed as rare, is present to the extent of 1.8 X 107 tons. The abundance of polonium in uranium ores is only about 100 Mg per ton and hence separation of the element from such mineral sources cannot seriously be considered. However, radium, at equilibrium with its daughters, contains 0.02 wt % of polonium and, until recently, most of the element was obtained either from radium itself or, more usually, from expended radon ampoules which, after the radon decay is complete, contain radium-D and its daughters. Fortunately, however, the parent of polonium in these sources, bismuth-210, can be synthesized by neutron bombardment of natural bismuth [Bi209 (n,y) Bi210] and with the advent of the nuclear reactor it has become practicable to prepare milligram amounts of polonium. Almost all of the chemistry of the element recorded in the recent literature has been the result of studies carried out with polonium-210 prepared in this way. 

Uranium-238 emits an alpha particle to become an isotope of thorium. This unstable element emits a beta particle to become the element now known as Protactinium (Pa), which then emits another beta particle to become an isotope of uranium. This chain proceeds through another isotope of thorium, through radium, radon, polonium, bismuth, thallium and lead. The final product is lead-206. The series that starts with thorium-232 ends with lead-208. Soddy was able to isolate the different lead isotopes in high enough purity to demonstrate using chemical techniques that the atomic weights of two samples of lead with identical chemical and spectroscopic properties had different atomic weights. The final picture of these elements reveals that there are several isotopes for each of them. 

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