The article presents the results of alpha, gamma spectrometric analyzes of samples, dosimetry, radon monitoring of the estimated areas in the Istiklol city. It has been established that the specific activity of radionuclides for uranium and radium in the tailing materials are in the range: 1405 – 2140, 5935 – 9843 Bq / kg, respectively. Based on the results of the monitoring of gamma radiation and radon volume activity at Istiklol city sites, it has been established that gamma radiation ambient equivalent dose rate varies from 0.52 to 1.78 μSv / h, and radon volume activity in air ranges from 20 and 45 Bq / m3. It is shown that the radon concentration in the air above the surface of tailings is not high. However, the exhalation of radon from the soil surface of all the tailings dumps examined is above the standard (1 Bq / (m2·s). The results of measurements of radon volume activity in the air of residential buildings and facilities located on the territory of Istiklol city have shown that the value of radon volume activity is within the limits of 44 – 195 Bq / m3. A high value of radon volume activity is noted in the former dilapidated plant (1319 Bq / m3). Gamma and alpha spectrometric studies revealed that the average values of the activity concentration of uranium and radium in the soils for tailings and the pit are for 234U – 65365 Bq / kg, for 238U – 50295 Bq / kg, and for 226Ra – 3800 Bq / kg. To estimate the doses of population irradiation via the water pathway were taken the average values of the volumetric activity of 234U, 238U, 226Ra in the waters. Maximum values of volumetric activity of radionuclides were observed in samples of drainage water, Bq / m3: 234U – 530000, 238U – 390000, 226Ra – 185. To calculate the contributions of various radiation factors to an additional annual dose of irradiation, the population was divided into four hypothetical groups. The time duration of stay of various hypothetical population groups in the areas of potential irradiation, radiation dose due to water use from contaminated water sources and additional factors in Istiklol were taken into account.The main contributor to the additional radiation dose received by hypothetical population groups is external irradiation during the stay on the territory of the FBR and tailing dumps, and internal irradiation due to the use of contaminated water.
The article presents the results of radon monitoring on the territory of Northern Tajikistan. Analysis of the results of the monitoring shows that at present, relatively high values of radon concentration in the atmospheric air are found in the areas where uranium tailings are located, primarily in the city of Istiklol and the Dehmoy tailings dam. This is primarily due to the lack of protective coatings on the surface of the tail material, which turns this area, in fact, into radon-prone areas of technogenic origin. In different parts of the Dehmoy tailings dam, the radon concentration in the atmospheric air varies between 200 and 1000 Bq/m3, and the radon flux density from the surface reaches 65,000 mBq/(m2∙s). On the territory of tailings dam in the city of Istiklol, the value of radon concentration in the atmospheric air is in the range of 44–195 Bq/m3. At the same time, it was found that the radon potential of the tailings dams, where the surface has a protective coating, is much lower. For example, the radon flux density from the surface of the Gafurov tailings dam, where surface is covered with loess-like loams up to 2.5–3.0 m thick, does not exceed 100 mBq/(m2∙s), with average values of 40-60 mBq/(m2∙s); the radon concentration in the atmospheric air is about 55 Bq/m3. Despite the intense exhalation of radon from the surface of some tailings dams, their territory is not currently a residential zone and, accordingly, does not affect the radon situation in buildings located in the settlements nearby. In the cities of Khujand, Buston, Gafurov, Istiklol and the village of Adrasman, the average values of indoor radon concentration do not exceed maximum permissible levels. It is recommended to conduct a full rehabilitation of uranium legacy sites, primarily uranium tailings dams in the city of Istiklol and Dehmoy tailings dam, for the improvement of the radon situation in Northern Tajikistan with consideration for possible expansion of the settlements.
The results of the study on the processing of uranium waste and waste dumps from Adrasman of the Republic of Tajikistan are presented. The chemical, granulometric and mineralogical compositions of uranium wastes, as well as their activities, have been determined. The optimal parameters for the processing of uranium waste and waste dumps have been found.
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