Radioactive Contamination Of Soil Research Articles

A green approach to efficient soil decontamination using supercritical carbon dioxide and ethanol

As the need for global decommissioning and site remediation of aging and shut-down nuclear power plants continues to grow, it becomes increasingly crucial to efficiently treat contaminated soil while minimizing waste generation. This study explores an innovative soil decontamination approach that utilizes supercritical carbon dioxide (SCCO₂) as the primary solvent, along with ethanol as a co-solvent and specific additives, including a chelate ligand (catechol ligand) and a co-ligand (NEt₄PFOSA). The advantages of SCCO₂, such as its penetration and solubility, coupled with its ability to separate from radioactive waste, are harnessed in this research. The study demonstrates that the combination of SCCO₂, ethanol, and additives significantly enhances decontamination efficiency, particularly for cesium (Cs), strontium (Sr), and uranium (U) contamination. Results indicate that decontamination efficiency varies with soil particle size, with smaller particles presenting greater challenges. This study presents a promising eco-friendly soil decontamination technology using SCCO₂ containing ethanol and specific additives to efficiently reduce radioactive contamination in soil.

Dynamics of radioactive contamination of lingonberry (Vaccinium vitis-idaea L.) in the forests of Zhytomyr Polissia (Ukraine) since the Chernobyl Nuclear Accident

The article presents results of study of levels of radioactive soil contamination and 137Cs activity concentration in the aboveground part of lingonberry (Vaccinium vitis-idaea L.) phytomass and berries on permanent experimental plots in different years since the Chernobyl Nuclear Power Plant accident (forest site type conditions — moist fairly infertile pine site type (B3), soils — soddy-podzolic sandy-loam on fluvioglacial sands). The research was conducted at the Poliskyi Branch of the Ukrainian Research Institute of Forestry and Forest Melioration named after G.M. Vysotsky over the years 1998–2021, utilized methods generally accepted in forest science and radioecology were used. Results were processed using statistical analysis. To substantiate the research, an official reporting data from forestry enterprises of the Volyn, Rivne and Zhytomyr regions were used. An analytical review of the state of research on this problem revealed that at the last 10–15 years there were no scientific publications on the study of 137Cs contamination of lingonberry. It was demonstrated that there was significant reduction in the density of radioactive soil contamination and 137Cs activity concentration in the aboveground part of lingonberry phytomass and berries in the forests of the research region over the observation period. It was found that the main part of the total 137Cs activity is currently located in the upper (10 cm) layer of the mineral part of the soil — 74.7% where root systems of herbaceous and dwarf-shrub species are concentrated in forest ecosystems. It was established that a considerable content of the radionuclide is retained in the aboveground part of lingonberry phytomass even with low density of radioactive soil contamination. It was found that in 1998, at relatively low value of soil 137Cs contamination density (49±5.6 kBq∙m–2), specific activity of 137Cs in aboveground phytomass of lingonberry was 8043±511 Bq∙kg–1, while in 2021 (value of soil 137Cs contamination density 22±0.3 kBq∙m–2) — 1046±182 Bq∙kg–1. The values of radionuclide transfer coefficients in 1998 were quite significant and varied within wide range: in the air-dry aboveground phytomass from 33.4 to 164.1 m2∙kg–1∙10–3 and in the fresh berries, from 9.5 to 26.0 m2∙kg–1∙10–3. Dependencies between density of radioactive soil contamination and the content of 137Cs in the aboveground part of lingonberry phytomass and berries were calculated, which can be applied in the practice of their harvesting. It was found that lingonberry belongs to the group of plants characterized by the high content of 137Cs in the aboveground vegetative phytomass. Harvesting of lingonberry leaves for the production of medicinal products should be restricted in all areas contaminated with 137Cs. Lingonberry fresh berries can be harvested in areas with a radioactive soil contamination density up to 74 kBq∙m–2.

Effectiveness of new agromeliorations under barley cultivation in radionuclide soil contamination

Based on the results of three-year production tests, the effectiveness of new agromeliorants (PhosAgro NPK complex fertilizer and Gumiton organo-mineral complex) was evaluated when growing barley on radioactively contaminated sandy loam soddy-podzolic soils of Novozybkovsky district of Bryansk region. It is shown that non-root treatment of barley crops in the earing phase with Gumiton (1 l/ha) without the use of fertilizer contributed to an increase in grain yield by 17-29% relative to the control, depending on the year. The introduction of PhosAgro NPK fertilizer (0.3 t/ha) gave an increase in yield of 22-39%. The combined use of fertilizer and the drug increased the yield by 18-72%. The multiplicity of the decrease in the intake of 137Cs in grain during the treatment of crops with Gumiton was up to 2.3 times, with the combined use of the drug and fertilizer - up to 4.7 times compared with the control. The use of Gumiton and PhosAgro NPK guaranteed the production of grain with a content of 137Cs corresponding to the standards of Sanitary Rules and Regulations 2.3.2. 2650-10. The conditional net income per 1 ruble of costs for processing barley crops with Gumiton amounted to 3.75-17.6 rubles, depending on the year. Both the introduction of PhosAgro NPK and the treatment of barley crops with Gumiton did not significantly affect the grain quality indicators: the content of protein, ash, fat, fiber. Thus, it is shown that the organo-mineral complex Gumiton and complex fertilizer PhosAgro NPK are effective agromeliorants in barley cultivation technologies in conditions of radioactive contamination of soils.

Impact of radioactive contamination of soils on the diversity of micropopulation and the transformation of organic substances

Aim. To study the impact of different levels of radioactive contamination on the organic matter decomposition and the population development of microbial decomposers of organic matter in soil. Methods. Gamma-spectrometry for the determination of the relative activity of 137Cs and beta-spectrometry for the determination of the relative activity of 90Sr in order to choose the contamination range for the studies; Tea Bag Іndex (TBI), the standard glob- ally accepted method to determine the rate of organic matter decomposition; gas chromatography – to determine the impact of the investigated factors on the formation of the biomass of microorganisms by means of the СО2 production potential; classic microbiological methods, using elective media to estimate the population densities of culturable microbial decomposers. Results. The studies (from April to September 2021) comprised two soils with different radioactive contamination ranges: Range No. 1 in Narodychi district of Zhytomyr region (the village Khrystynivka, 3 sampling points) in the unconditional (obligatory) resettlement zone after the catastrophe in the Chornobyl nuclear power plant (ChNPP) (it has an absorbed dose rate gradient, evaluated for soil microorganisms, from 0.2 μGy/h (at sampling point Narodychi-1: 51,24076°N, 29,21497°E) to 1.57 μGy/h (at sampling point Naro- dychi-3: 51,23815°N, 29,22245°E)), located on the agricultural field, abandoned after the catastrophe and Range No. 2, located on the afforested area, directly bordering the territory of the so-called Red Forest in the ChNPP ex- clusion zone (4 sampling points – the first three points – natural ecosystems, and 4th – pyrogenically transformed territory after fires in 2020) with the absorbed dose rate gradient from 3.7 μGy/h (at sampling point ChEZ-1: 51,38595°N, 30,03035°E) to 84.0 μGy/h (at sampling point ChEZ-4: 51,38231°N, 30,03298°E). The dependence of the studied indicators on the gradient of soil contamination with radionuclides was demonstrated and these are the conditions that the difference is more than 400 times in the values of the ionizing radiation absorbed dose rates formed by radionuclides in soil. In Range No. 1 (on the fallow land), with the increase in the dose rate up from 0.2 to 1.57 μGy/h, there was statistically significant increase of mineralization coefficient and percentage of reduced weight of rooibos tea between the least and most contaminated sampling points), stimulation of the development of micromycetes (by 1.2–2.3 times), cellulose-decomposing bacteria (by 7.1–7.9 times), and ammonifying bacteria (by 1.8–6.3 times) due to a significant increasing the number of colony-forming units in points with higher radio- nuclide contamination and an increase of microbial biomass in soil more than twofold between the least and most contaminated sampling point of Range No. 1.In Range No. 2, in the ChNPP exclusion zone, characterized by low parameters of sod-podzolic soil fertility (humus content from 1.2 ± 0.2 to 0.9 ± 0.1 %, exchangeable acidity from 4.0 ± 0.1 to 5.0 ± 0.7), the number of micromycetes and ammonifying bacteria in soil was one-two orders below the indices of Range No. 1. Micromycetes dominated in the groups of cellulose-decomposing microorganisms. There was statistically significant increase of mineralization coefficient and percentage of reduced weight of rooibos tea with increasing of radionuclide contamination level for the first three plots: ChEZ-1, ChEZ-2 and ChEZ-3 of Range No. 2. Conclusions. In the fallow land of the unconditional (obligatory) resettlement zone, the increase of the radia- tion absorbed dose rate in soil by one order from 0.2 to 1.57 μGy/h does not inhibit the development of microorgan- isms in soil, rather it stimulates their activity and increases their numbers. On poor sod-podzolic soils in the exclu- sion zone of the Chernobyl nuclear power plant, the preponderance of development of micromycetes over bacterial cellulolytics is noticeable. The radioactive contamination affected the development of soil microorganisms and the biological processes in soils not only in the first years after the Chornobyl catastrophe, which has been described in the literature, but has had its influence for rather a long time (for over thirty years after the accident). Among the microorganisms of a saccharolytic mode of organic plant residuals decomposition, the micromycetes dominate.

ANALYSIS OF RADIOACTIVE CONTAMINATION FOR THE REGIONS OF UKRAINE AND POLAND

Problem statement. The problems of environment radioactive contamination are considered. The analysis of contamination is shown on studies of soil, water and air for the territories of Ukraine and Poland. Knowledge of radiation, its effects on living organisms and the environment, and methods of protection against radiation can help reduce the environmental hazards of radiation. During studying of disciplines related to radioactive contamination and radiation protection, it is necessary to emphasize to future specialists about possible threats from radiation, methods and means to reduce this type of contamination, and methods of protection for workers and the general population from radioactive irradiation. The purpose of the article is to analyse radioactive contamination of soil, air, surface waters of Ukraine and Poland, study the causes of contamination for different regions of these countries, monitor radioactive contamination of regions, protect the population from the negative effects of radiation. It is also necessary to train specialists who must professionally solve the problem of contamination, assess the risk of radionuclides entering natural sites and determine the best ways to reduce the negative impact of radiation on natural sites and the population. Conclusions. The study of problems related to the environmental contamination with radioactive elements is relevant both for our country and for all countries of the world. If we analyze this type of pollution in Ukraine, we need to carefully study the situation with radiation, and at least in neighboring countries, because there are no borders for this type of pollution.

Peculiarities of radioactive soil contamination in places of underground nuclear tests in the Semipalatinsk test site

The article highlights the results of a radioecological survey of the surface areas of combat boreholes at the Sary-Uzen site located on the territory of the Semipalatinsk Test Site (STS), where underground nuclear tests in these boreholes were conducted earlier. The surface areas of boreholes were examined the levels of radioactive contamination of the soil were determined. A total of 2 main groups were identified. The first group includes boreholes with radioactive contamination of the soil on the surface area. The second group includes boreholes with no radioactive contamination of the surface soil layer. The first group can be divided into boreholes with a deformation of the ground surface and without it. For each variety, depending on the specifics of the nuclear test, the characteristic features of radioactive contamination were determined. Based on the results of the survey, the ranges of specific activity values were established.

Determination of <sup>238</sup>U Content by Gamma Radiation Emitting from <sup>234m</sup>Pa Radionuclide

Radionuclide 238U is one of the most important radioactive elements that must be controlled in nuclear power engineering, geological exploration, control of radioactive contamination of soils and raw materials used in construction. The most optimal way to control 238U is to use the 234mPa radionuclide, the activity of which, due to its short lifetime (≈ 1.2 min), is unambiguously related to the activity of 238U even if the secular equilibrium is disturbed in the sample under studyРossibility of use of the 234mPa nuclide gamma radiation to determine 238U with a scintillation detector in a medium containing natural radionuclides is investigated and demonstrated using the simplest examples. The proposed algorithm for determining of the 238U content is based on the Monte Carlo simulation of the detector response to the radiation of the 234mPa radionuclide at its 1001 keV energy line and subsequent processing of the experimental spectrum, including the Wiener filtering of the signal. This method makes it possible to determine the content of 238U in a continuous homogeneous medium while presence of natural radionuclides in it.The algorithm for determining of 238U content includes several main steps. Filtering based on the Wiener algorithm allows selecting a slowly changing part of the spectrum. Results of Monte Carlo simulations make it possible to determine the detection efficiency in a limited informative region of the spectrum, which includes, along with the 1001 keV peak from the 234mPa nuclide, which is a decay product of the radionuclide 234Th, and the peak of an interfering radionuclide from the decay chain of 232Th. This part of the spectrum does not contain any other lines of gamma radiation from natural radionuclides – decay products of both thorium and uranium chains. These two peaks in the spectral region under study can be separated from each other in a medium with a typical concentration of 234Th.Analysis of results of the activity of depleted uranium metal measuring in accordance with the proposed algorithm shows the possibility of determining of 238U content with an uncertainty of 3–5 %.

RADIATION SAFETY ASSESSMENT OF CARROT AND BEET PRODUCTS CULTIVATED IN THE BLACK EARTH ZONE OF RUSSIA IN THE OREOL OF THE EASTERN CHERNOBYL TRACE

On the territory of the Plavsky radioactive hotspot of the Tula region of Russia, formed as a result of the accident at the Chernobyl nuclear power plant in 1986, an assessment of the radiation safety of growing carrots and beets was carried out in 2019. It has been established that at present the content of 137Cs in arable leached chernozems of the surveyed lands is 90–170 kBq/m2 , which is 2.5–4.5 times higher than the permissible level of density of surface radioactive contamination of soils. However, the specific activity of the radionuclide in carrot and beetroot crops does not exceed 5 Bq/kg, which is significantly less than the maximum permissible level of 137Cs accumulation in vegetables (600 Bq/kg for absolutely dry weight). The accumulation coefficients of 137Cs in the total biomass of carrots and beets are 2.0·10−2 and 7.5·10−2, and in eaten root crops – 1.1·10−2 and 2.0·10−2, respectively, which is in good agreement with the IAEA estimate for the intensity of the transition 137Cs in the production of vegetable roots from loamy and clayey soils.

Radiation survey and environmental impact assessment at the site of temporary storage at Andreeva Bay (16 years of studies)

The site of temporary storage for spent fuel and radioactive waste at Andreeva Bay is a largest nuclear legacy site in the Russian Northwest. The radiation situation within the industrial site and in the surrounding health protection zone (HPZ) is characterised by significant local contamination of the topsoil, which is a source of environmental contamination and potential spread of radioactivity within and outside the HPZ, including the adjacent marine environment. The highest levels of radioactive contamination of soil due to manmade radionuclides have been registered around the spent nuclear fuel storage facilities, where the specific activity of Cs-137 reaches 5 × 107 Bq kg−1, and that of Sr-90, 5.7 × 106 Bq kg−1. Determination of the mobility of these main dose-forming radionuclides has demonstrated that about 90% of the Sr-90 and 30% of the Cs-137 in the soil are in a mobile form. The corresponding figures for bottom sediments are 75% and 60%. The assessment of the impact of contamination in the different areas of the Andreeva Bay site, and the assessment of the adequacy of the previously developed remediation criteria for environmental protection (Sneve et al 2015 J. Radiol. Prot. 35 571) demonstrated that when carrying out remedial work according to any scenario provided for in the Guidelines ‘Criteria and norms for remediation of sites and facilities contaminated with manmade radionuclides’, of the Federal State Unitary Enterprise ‘The Northern Federal Enterprise for Radioactive Waste Management’ for the supervision area, recommendations for environmental protection are followed. For scenarios such as conversion and conservation, reference levels of biota exposure for some species of representative organisms could be exceeded, based on a preliminary conservative assessment.

Origin and age of an ongoing radioactive contamination of soils near La hague reprocessing plant based on 239+240Pu/238Pu and 241Am/241Pu current ratios and 90Sr and Ln(III) soil contents

Nuclear reprocessing plants are sources of environmental contamination by gaseous or liquid discharges. Numerous radionuclides are of concern, with actinides and 90Sr being the most radiotoxic. Environmental radioactivity survey programs mostly use γ-spectrometry to track contaminations because γ-spectrometry is very cost effective and can be carried out on raw samples. On the other hand, the determination of β- or α-emitting radionuclides in environmental samples requires rather sophisticated analytical methods, and are thus dedicated to specific goals. However, measuring radionuclides such as Pu, Am, and Sr often provides more information about the presence of a current or prior contamination and on its origin, based on the isotopic composition of the samples. We found that the analysis of 241Pu, 239+240Pu, 241Am, and 90Sr of a few selected soil samples taken near the nuclear reprocessing plant of La Hague, France, revealed the presence of a previous environmental contamination originating from several incidents in La Hague site involving atmospheric transfer and leaks in flooded waste pits. The 241Am-241Pu dating method indicated a contamination period prior to 1983. The presence of elevated levels of light non-radioactive lanthanides and yttrium in the soil samples confirmed the involvement of cold fuel. Our results demonstrate how long-lived actinides are likely to reveal a long-term contamination of the environment by spent fuel. Our study indicates that there is a requirement to use more sophisticated tools than γ-spectrometry when surveying the environments surrounding industrial plants for nuclear power and nuclear reprocessing with a potential for the accidental release of radioactivity into the environment.

Comparing the radioactive contamination of marsh Labrador tea (Ledum palustre L.) Over different periods since Chernobyl accident

Radioactive contamination of the above-ground phytomass of marsh Labrador tea (Ledum palustre L.) in different periods after the Chernobyl accident was studied. Marsh Labrador tea is widely used in official and folk medicine. The studied species grows in over-moistened pine (less mixed) forests and open oligotrophic and mesotrophic marshes. It was found that in the first four years since the beginning of observations (1991), the magnitude of the specific activity of 137Cs in above-ground vegetative phytomass of marsh Labrador tea, depending on a permanent sample area (PSA), decreased by 1.2–1.4 times. After 10 years, it decreased by 1.6–1.7 times, after 16 years by 1.9–2.1 times, after 21 years by 2.7–3.1 times, and after 27 years by 3.1–6.5 times. An increase in the magnitude of transitions factors was also observed on all PSA over time. Thus, the minimal increase within 1991–2018 was recorded in PSA 11 – by 1.2 times and on PSA 13 – by 1.4 times. The maximum decrease in the magnitude of transition coefficient was observed in PSA 16 – by 2.7 times, in PSA 15 – by 3.0 times, and in PSA 18 – by 2.0 times. It was found that marsh Labrador tea belongs to the group of plants that are characterized by the high content of 137Cs in the above-ground vegetative phytomass. Within the observation period (1991–2018), this content significantly exceeds the admissible levels of radionuclide content in plant medicinal raw materials that are used for manufacturing medical preparations. In the PSA with maximum magnitudes of soil contamination density (400.5±50.73 kBk·m-2) this excess made up 158.4 times in 1991, and 33.7 times (166.9±23.56 kBk·m-2) in 2018. For 27 years of observations, there has been a decrease in the density of radioactive soil contamination by 2.1–2.7 times, which is due to radionuclide decomposition, its vertical migration in the soil, and towards the components of forest ecosystems

Soil sampling when examining forests for radioactive contamination

Forest ecosystems are complex areas in terms of rehabilitation of radioactively contaminated areas, so conducting an up-to-date examination of these areas for radioactive contamination is relevant. The paper considers the improvement of methods of soil sampling for obtaining representative materials in the estimation of vertical migration of 137 Cs in the soil profile and the level of soil contamination with 137 Cs. The density of radioactive soil contamination was studied by reducing the number of selected samples from 30 to 3 in the layers of 10, 20, and 30 cm. The results show that when the number of soil samples decreases, the average magnitudes of soil contamination with 137 Cs are not significantly different within each analyzed layer. It was noted that at sampling in the 10-centimeter layer, the studied indicator was 1.3–1.4 times lower than in the layers of 20 and 30 cm, and there is no difference between the latter. To obtain reliable levels of radioactive contamination of the territory, it is necessary to perform 10-time repeated sampling in the forest soil layer of 30 cm. At a decrease in the number of soil samples from 10 to 3, the fluctuation of average values of the specific activity of 137 Cs in different layers of soil profile is low. To obtain representative magnitudes of 137 Cs content in each layer of the soil profile, it is necessary to make various samplings. Thus, for 4-time repeated sampling, is sufficient for all layers of forest litter, and 6-time repeated sampling is enough for the humus-eluvial horizon. It is necessary to perform 8-time repeated sampling for the eluvial and illuvial horizon, and 10-time repeated sampling for illuvial sand and parent rock. The obtained results make it possible to carry out up-to-date examination of forests for radioactive contamination based on the updated methodology and using the obtained data on 137 Cs migration in forest soils

Зміна вмісту 137CS у чорниці (Vaccinium myrtillus L.) у лісах Полісся України з часу аварії на ЧАЕС

Досліджено багаторічну (30 років) динаміку радіоактивного забруднення найпоширенішої ягідної рослини лісів Полісся України – чорниці, яка відіграє велику роль в опроміненні населення регіону. На всіх постійних пробних площах відзначено вищі значення питомої активності 137Cs у ягодах чорниці порівняно зі значеннями цього показника у її вегетативній надземній фітомасі – в 1,1-1,7 раза. Це, вірогідно, можна пояснити її біологічними особливостями. За період спостережень відбулося значне зниження радіоактивного забруднення чорниці звичайної: у свіжих ягодах чорниці – у 3,7-8,3 раза, у сухій надземній фітомасі – у 8,2-19,2 раза. Значення коефіцієнтів переходу до надземної фітомаси та свіжих ягід чорниці в 1994 р. відповідно становили 49,2-178,1 та 8,9-34,3 м2кг-1·10-3. У 2016 р. продовжує тривати досить інтенсивне надходження 137Cs до чорниці: значення коефіцієнтів переходу до свіжих та сухих ягід змінювалися у межах 6-8 та 24-61 м2кг-1·10-3 відповідно, а для сухої надземної фітомаси – 17-53 м2кг-1·10-3. Триває вертикальна міграція 137Cs з верхніх до більш глибоких шарів ґрунту. У 1991 р. основна частка сумарної активності радіонукліду у вологих суборах була зосереджена у напіврозкладеному та розкладеному шарах лісової підстилки та 0-2-сантиметровому шарі мінеральної частини ґрунту (близько 60-70 %). У 2016 р. найбільше значення цього показника характерне для верхнього 10-сантиметрового шару гумусово-елювіального горизонту – 69,87 %, що в 1,3 раза більше, ніж у 2000 р. (54,91 %). Цей шар ґрунту насичений кореневими системами численних лісових рослин, зокрема чорниці, що підвищує інтенсивність надходження радіонуклідів.

Radioactive Rock Dumps in the Elkon Uranium Ore Area (South Yakutia)

We examine the geographical features in the distribution and the radiation parameters of radioactive rock dumps in the Elkon uranium ore area on the territory of South Yakutia. It is pointed out that the dumps under study are geomorphologically located on the Elkon horst which is a protrusion of crystalline basement rocks, towering over the territory of the Aldan highlands. It is found that most of these dumps lie within streambeds and in the bottoms of mountain rivers of the zone of hypergenesis and, geochemically, they are influenced by steep-slope topography, a cold humid climate and mountain-taiga vegetation dominating land cover. It is shown that these rock dumps were formed in the last third of the 20th century, during a large-scale and intense geological exploration for radioactive raw materials in this area. Radiation parameters of the dumps under study, such as the gamma radiation exposure dose, the content of 238U, 232Th and 40K, as well as the effective specific activity of these radionuclides were determined. It is found that the most active rock dumps, in their radiation parameters, approach radioactive ores. The dumps under study were ranked according to the degree of radiation danger to the population on the basis of the particular values of the gamma radiation exposure dose and effective specific activity of these radionuclides. It is established that the main source of radioactive contamination of soil and vegetation cover and the surface waters in the Elkon uranium ore area on the territory of South Yakutia are 40 rock dumps which are unevenly distributed in the total area of about 500 km2 of the mountain-taiga permafrost landscapes. It is determined that more than half of these dumps, in their radiation parameters, are classified as hazardous and specially hazardous.

Application of Spectrometric Gamma-Logging for Specification of Characteristics of Soil Radioactive Pollutions

The experience of using the method of spectrometric gamma-logging of wells for assessment of radioactive contamination of soils on the sites of foundation pits excavation for the New Safe Confinement foundations is presented in the article. Analysis of the photopic/Compton ratio in the gamma-ray spectra of the wellbore allowed us to identify the types of soil contamination: the volumetric contamination, which is associated with real radioactive contamination, and the surface contamination, which is identified as introduced by drilling. This task is especially relevant for determining the boundaries of contaminated/clean soils, which had an impact on determining the depth of pits and, as a result, on the volume of soils to be developed. The use of spectrometric gammalogging of wells made it possible to correctly predict the categories and volumes of radioactive waste, which were soil to be extracted during excavation. Directions for further improvement of the method of spectrometric gamma-logging to clarify the characteristics of radioactive waste are considered in the article.

Радіоактивне забруднення конвалії звичайної (Convallaria Majalis L.) у лісах Житомирського Полісся

Наведено результати досліджень з вивчення динаміки радіоактивного забруднення надземної фітомаси конвалії звичайної (Convallaria majalis L.) у вологих сугрудах Житомирського Полісся (1991–2018 рр.). Відзначено зменшення щільності радіоактивного забруднення ґрунту за період спостережень. На всіх постійних пробних площах встановлено вищі значення питомої активності 137Cs у суцвіттях конвалії звичайної відносно величини цього показника у її траві – в 1,3–2,5 раза. Встановлено зменшення вмісту 137Cs у траві конвалії звичайної за 27 років (1991–2018 рр.) в 11,1–17,3 раза. Виявлено підвищення цього показника в окремі роки та періоди, що пов'язано з погодними умовами конкретного року та, можливо, циклічністю міграції 137Cs у лісовому біогеоценозі. Інтенсивність надходження радіонуклідів до досліджуваних частин конвалії звичайної дещо вища у 1998 р. порівняно з отриманими результатами у 2018 р., проте зберігається співвідношення між обома роками спостережень. Величини коефіцієнта переходу радіонукліду як до суцвіть (3,8–8,2 м2×кг-1×10-3), так і до трави (1,9–5,1 м2×кг-1×10-3) конвалії звичайної невеликі, що дає підстави віднести цю рослину до помірних накопичувачів 137Cs. З'ясовано, що на сьогодні у лісовій підстилці вологих сугрудів міститься лише 1,3 % від сумарної активності 137Cs у ґрунті, а основна його частина перемістилася у верхній 10-сантиметровий мінеральний шар ґрунту, і становить – 90,06 %. Внаслідок встановлено сучасну залежність між щільністю радіоактивного забруднення ґрунту 137Cs та питомою активністю радіонукліду у траві та суцвіттях конвалії звичайної.

Динаміка радіоактивного забруднення зелених мохів в умовах свіжого бору у лісах Житомирського Полісся

Досліджено зміну вмісту радіонуклідів у фітомасі зелених (брієвих) мохів в умовах свіжого бору Українського Полісся впродовж 2016–2018 рр. Середня щільність радіоактивного забруднення ґрунту на пробній площі становила 199±52 кБк/м2. З'ясовано, що величини питомої активності та інтенсивності надходження радіонуклідів до фітомаси аналізованих видів мали значні коливання. Вміст радіонукліду у фітомасі дикрану багатоніжкового за період спостережень зменшився в 1,3 раза, а для плевроцію Шребера подібне зменшення становило 1,2 раза. Виявлено, що дикран багатоніжковий характеризується більшими величинами концентрації 137Cs порівняно з плевроцієм Шребера, в середньому – в 1,5 раза за досліджуваний період. Відзначено загальну закономірність щодо розподілу вмісту 137Cs за фракціями зелених мохів. За величиною радіоактивного забруднення фракції моху можна розмістити у вигляді такого ряду: очос > жива фракція > мертва фракція. Упродовж трьох років спостережень середній вміст 137Cs в очосі верхоплідного та бокоплідного мохів зменшився в 1,4 та 1,2 раза відповідно, а для живої та мертвої фракцій таке зменшення становило 1,3 раза. Інтенсивність надходження радіонуклідів до фітомаси плевроцію Шребера в 1,4 раза менша порівняно з дикраном багатоніжковим. Виявлено тенденцію до зниження значень коефіцієнта переходу 137Cs, як до фітомаси загалом, так і до окремих фракцій обох досліджуваних видів моху.

Radiation-ecological evaluation of rock dumps in the south zone of the Elkon uranium mine region (the Southern Yakutia)

This study aims at investigating the allocation conditions of rock dumps in the South zone located in the Elkon uranium mine region (the Southern Yakutia), and also at determining their radiation parameters as sources of technogenic contamination of the soil-vegetation cover and surface waters, and assessing the danger of these dumps for people. In this study, the generally accepted geographical methods were used, including comparative geographical and geochemical methods, as well as a combination of various radiometric research methods. The radiation parameters of the rock dumps of the South zone of the Elkon uranium mine region, the content and distribution of uranium, radium and radon in surface waters, as well as 238U content in technogenic soils at different distances from radioactive contamination sources were studied. It was found that the most active dumps, in terms of their radiation parameters, are located close to the radioactive ores, with the EDR of 1600-2150 R/h, effective specific activity - 20441-23640 Bq/kg, and uranium content of 1637-1888 mg/kg. The ranking of the studied dumps according to the degree of radiation hazard showed that 12 out of 31 dumps (39%) belong to the safe category, 6 (19%) belong to the category of potentially dangerous, and 5 and 8 (16% and 26%) were classified as dangerous and very dangerous respectively. In the conditions of the mountainous terrain, cold and humid climate of the studied area, these rock dumps, which are unevenly spread in mountain and taiga landscapes over the area of about 500 km2, are the main source of radioactive contamination of soil and vegetation cover and surface waters. The maximum contents of uranium, radium and radon in the studied surface waters were 18010-7 g/L, 4.710-12 g/L and 256.8 Bq/L respectively, which are 100, 8 and 198 times higher than their background concentrations in waters of natural landscapes. In the studied technogenic zones, a direct relationship was registered between the pollution intensity in surface water and that in the drained alluvial soils formed in the floodplains of these watercourses.

Prompt Mapping of Radioactively Contaminated Areas

The paper presents a methodology for prompt mapping of radioactively contaminated areas. The efficiency of obtaining cartographic information is achieved by using correlation dependences between the characteristics of radioactive contamination obtained during various radiological surveys of contaminated areas. The method of spatial interpolation based on regression-kriging is used to formalize the data on radioactive contamination. This method allows combining the information resulting from direct measurements of density of territory contamination by radionuclides we are interested in with the information contained in other characteristics of radioactive contamination received at the surveyed area (for example, ER). Such an approach allows more accurate mapping of 137Cs deposition density and concentration of its activity in the root layer of soil, as well as significant reduction of the time and cost to survey the mapped area (sampling, sample preparation and measurement of samples). This, in turn, accelerates and reduces the cost for mapping of radioactively contaminated territories (fields, lands, sites). The methodology has been tested on the fields contaminated by radionuclides resulting from the Chornobyl accident in the Narodychi, Polissia and Ivanivka Districts and has proved its performance and efficiency. Comparison and analysis of the obtained maps of radioactive contamination of the territory show that in the conditions of limited amount of data on direct measurements and time limit, the use of correlation dependences between the characteristics of radioactive contamination of soil is often the only possible way to increase the information content and accuracy of the obtained cartographic information.

Logistical Simulation Modeling for Planning a Soil Remediation Process

This paper describes the development of a discrete event simulation model using the FlexSim software to support planning for soil remediation at Korean nuclear power plants that are undergoing decommissioning. Soil remediation may be required if site characterization shows that there has been radioactive contamination of soil from plant operations or the decommissioning process. The simulation model was developed using a dry soil separation and soil washing process. Preliminary soil data from the Kori 1 nuclear power plant was used in the model. It was shown that a batch process such as soil washing can be effectively modeled as a discrete event process. Efficient allocation of resources and efficient waste management including volume and classification reduction can be achieved by use of the model for planning the soil remediation process. Cost will be an important criterion in the choice of suitable technologies for soil remediation but is not included in this conceptual model.