Radioactive Sources

RADIOACTIVE SOURCES, mineral sources of various chemical composition, the water of which contains radioactive substances and their emanations. According to Vernadsky, all natural water is radioactive, and in many cases this radioactivity is explained not only by the presence of emanations in it, but also by uranium, thorium, and radium. Natural waters of springs and artesian wells come into close contact with rocks at elevated temperatures, in the presence of CO₂ and H₂S, which often facilitates the leaching from these rocks, along with inactive elements, also radioactive substances of uranium, radium and thorium and emanations. The radioactivity of mineral waters is mainly due to their activation by emanations from massive rocks. The waters become saturated with gaseous emanations. Such waters over time lose their radioactivity due to the departure of gaseous emanations and their decay. In addition, waters can be saturated with solid radioactive substances that dissolve in the form of salts. In this case, new amounts of emanation should form in the water itself. Most R. i. belong to the first group. Most often, the radioactivity of R. i. depends on the content of radium emanation in the water. The magnitude of radioactivity of R. i. water when the water emerges to the earth's surface depends on several conditions: 1) the duration of contact of water with emanating substance, 2) sufficiency of this contact to achieve the maximum possible level of water radioactivity, 3) state of the emanating medium, since often the amount of emanation released from the medium depends on this state, 4) conditions under which the emanation passes into the liquid (power of the stream, its fragmentation, temperature, influence of the temperature of the stream on the temperature of the emanating rock, changing the conditions of release and solubility of the emanation), 5) the length of the path that the water must travel from the underground emanating source to the earth's surface, since during this path the gradual process of decay of the emanation occurs, 6) mixing of non-radioactive liquid and gas streams with the water, and 7) mechanical release of emanation from the water by gas bubbles, both released from the liquid itself and entering it from outside. The task of measuring the strength of R. i. consists in determining the content of radioactive emanation. When determining the emanation of R. i., it is necessary to ensure that the water sample taken for the experiment has the full content of emanation from the sources, for which it is recommended to carry out measurements on site. If some time elapses between taking the sample and measurement, then destruction of the emanation occurs. Significant losses of emanation occur when pouring water, warming it in bottles, shaking it with air. To determine the radioactivity of R. i. on site, the Engler and Ziveking contactoscope, the Mach and Meyer electrometer, and the Schmidt apparatus are used. The Resort Section of the Scientific Medical Council of the People's Commissariat of Health of the RSFSR in 1930 issued a special instruction for measuring the radioactivity of mineral springs. Since 1921, as a unit for determining the amount of radium emanation in the water of R. i., the "eman" has been used, which is 1.10^-10 curie per 1 liter, 1.10^-13 curie per 1 cm³. The unit often mentioned in medical literature, Mach (M.E.), represents the saturation current strength of 0.001 electrical unit, caused in a condenser by radium emanation from 1 liter of water at the initial moment of its introduction, provided that alpha rays are completely absorbed. 1 Mach unit = 3.64 . 10^-10 curie = 3.64 emans. The radioactivity of natural waters varies within very wide limits, from hundredths of an eman to 20,000 emans. High values of radioactivity are very rare. Grüngut considers the presence of 3.5 Mach units sufficient to recognize the water of a spring as mineral based solely on radioactivity. In medical literature, the classification of R. i. proposed by Noorden has been adopted. According to this classification, water is considered radioactive if it contains at least 20 Mach units (72 emans). Radioactive waters are divided into weakly radioactive, containing from 20 to 50 Mach units (from 72 to 182 emans), and moderately radioactive - from 50 to 100 Mach units (from 182 to 364 emans). These norms are too high, since for therapeutic purposes, R. i. with the following radioactivity are actually used: for feeding emanatoriums - from 10 Mach units (sometimes even less), for baths - from 20 Mach units, for internal use - several hundred Mach units. It is highly probable that the effect of radioactivity in combination with other factors can manifest itself at concentrations lower than necessary for the direct action of one emanation. Therefore, it is believed that the lower limit of radioactivity worthy of being noted can be taken as 3 Mach units (10 emans). The Resort Section of the Scientific Medical Council of the People's Commissariat of Health of the RSFSR proposed to classify as weakly radioactive sources containing from 35 to 100 emans, as sources of medium strength - containing from 100 to 300 emans, and as strongly radioactive - sources containing more than 300 emans. Statistics have shown that among German mineral springs, radioactivity of less than 10 Mach units occurs in 82% of sources, from 10 to 100 Mach units - in 16%, and more than 100 Mach units - in 2% of sources. The radioactivity of sources changes in connection with their flow rate, temperature and chemical composition. A. N. Ogilvy believes that it is often in our power (through proper and rational tapping of R. i.) to create conditions that favor the most complete transition of emanation into water. For tapping R. i., Ogilvy indicates several typical cases. 1) Water passes through an active emanating rock, and the radioactivity of the water reaches a maximum level, and then the stream enters an inactive rock, from which it emerges to the earth's surface. In tapping in this case, it is necessary to increase the flow rate, thanks to which the activating section will be better used and the decay of emanation in the inactive section will be reduced. 2) Water passes a short path through the emanating section, and its radioactivity does not reach the possible maximum. Increasing the flow rate of such R. i., emerging from inactive rock, can affect the radioactivity in various ways and will depend on at what distance from the active section the R. i. emerges. 3) In the case of water emerging directly from active rock during tapping, two possibilities may arise: a) the exit of R. i. is within the rise of the curve of increasing water radioactivity, therefore an increase in the flow rate of such R. i. causes a decrease in radioactivity; b) water emerges from the section of maximum height of radioactivity, and an increase in flow rate (up to certain limits) can give a larger amount of water of the same radioactivity. Water taken from the source should be conducted to the place of consumption in the form of a calmly flowing stream, if possible not releasing gas bubbles. The most important R. i. in the USSR, the magnitude of radio (according to the summary by E. ]I Name of the source, exploited as R. i. for therapeutic purposes, should be measured as often as possible, preferably daily during the treatment season. Numerous studies of R. i. have been carried out in various countries. In different parts of the USSR, the determination of radioactivity of mineral springs was carried out by many researchers: S. A. Artsybyshev (Siberia), I. A. Bagashev (Transbaikalia), E. S. Burkser (Ukraine, Caucasus), E. E. Karstens (Caucasus), R. D. Kuntsis (Transcaucasia), P. G. Mezernitsky, P.P. Orlov (Siberia), M. P. Orlova (Siberia), A. P. Sokolov and others. Hundreds of sources have been subjected to such studies (Linderer in the 1916 list gave information on more than 300 sources; many sources have been surveyed in the last 15 years). According to E. S. Burkser, on the vast territory of the USSR with its diversity of geological structure, strongly radioactive waters undoubtedly exist, which are still waiting for their researchers. This idea receives numerous confirmations in recent studies: strongly radioactive waters (up to 350 emans) were found at the resort of Tskhaltubo (Georgia), more emanation-rich R. i. were discovered in Belokurikha (Western Siberia), sources containing radium salts were found in Ust-Ukhta (Northern Region) and others. Most of the very famous mineral springs for their medicinal properties, both in the USSR and abroad, have insignificant radioactivity (up to several emans). The radioactivity of mineral waters poured into bottles does not exceed 1.2. 10^-18 per 1 liter (Burkser and Klefner). The maximum concentration of radium emanation in radioactive sources reaches 7,000 - 20,000 emans (sources of Oberschlem and Brambach in Germany and Joachimsthal in Czechoslovakia). radioactivity of which exceeds 10 emans S. Burkser).

M. Multanovskii. , RADIOLOGY, see Radiology.