Artificial Radionuclides Research Articles

Radioecological monitoring in the vicinity of Rostov NPP. The analysis of results of long-term investigations

The purpose of this work was to assess the influence of the Rostov NPP (consisting of 4 units with VVER1000 reactors) on the radioecological situation in the region of the station location within 18 years from the start of the first power reactor. Based on the results of observations at the radioecological monitoring network established in 2001, which included seven control sites and five control points, the content of natural and artificial radionuclides in environmental objects, agricultural products and foodstuffs was analyzed. It was shown that over the entire period under consideration, the average content of 90Sr in the soils of agroecosystems of the 15-km zone of influence of the Rostov NPP varied within 1.7-7.4 Bq/kg, and 137Cs – 7.5-14.9 Bq/kg. It was not detected any trends to increase in the concentrations of artificial radionuclides in the soil throughout the considered territory. The variation range of the average content of natural radionuclides in soils was 561-634 Bq/kg for 40K, 23.4-27.5 Bq/kg for 226Ra and 32.7-35.9 Bq/kg for 232Th. The average concentration of 90Sr in the grain was in the range of 0.1-0.68 Bq/kg, and 137Cs – 0.23-0.54 Bq/kg. Even the maximum specific activity values of artificial radionuclides in food grain were below the SanPiN standards 55 times for 90Sr and 65 times for 137Cs. The maximum levels of 137Cs in vegetables and potatoes and vine crops were 80 times lower than the SanPiN standards. The maximum levels of specific activity of 90Sr in milk were more than 400 times lower than the SanPiN standard (25 Bq/kg), and for 137Cs (standard 100 Bq/kg) this difference was 600 times. Vegetable crops were characterized by minimal transfer factors (TFs) of radionuclides. TFs of 90Sr in vegetables, depending on the product type, was in the range of 0.04-0.17, and for 137Cs it was in the range of 0.008-0.2 (Bq/kg)/(kBq/m2 ). Maximum TFs of radionuclides were noted in grasses. TF of 90Sr in natural and perennial grass was 0.75-2.2, and for 137Cs it was 0.28-0.86 (Bq/kg)/(kBq/m2 ). The differences in transition factors between vegetables and grass reached 50 times, and on average, they were 10-20 times. It was noted that all types of crops accumulated 90Sr on average 2-5 times more in comparison to 137Cs ac cumulation. It was shown that the content of artificial radionuclides in the water of the Tsymlyansk reservoir is 163 and 183 times lower than the permissible level for 90Sr and 137Cs, respectively. The analysis of 18-year results of observations of the radioecological situation in the vicinity of the Rostov NPP allows to conclude that the operation of this NPP in normal mode and the commissioning of new power-generating units did not lead to a recorded increase in the content of artificial radionuclides in agricultural products, foodstuffs and environmental objects.

In-Situ Environmental Gamma Radiation Monitoring at Ramna Thana, Dhaka, Bangladesh

Environmental gamma radiation dose rates were measured using a digital portable Gamma-Scout detector from April-May 2018. For this, total 22 monitoring points (MP) were selected in the outdoor environment in the area of Ramna Thana under Dhaka city. The MPs were marked-out using Global Positioning System (GPS) navigation. The GPS reading of the sampling locations were varied from E: 90o23.568' to E: 90o24.895' and from N: 23o44.031' to N: 23o45.018'. The measured dose rates due to natural radionuclides were ranged from 0.115 ± 0.042 µSv.hr-1 to 0.186 ± 0.051 µSv.h-1 with an average of 0.145 ± 0.044 µSv.h-1. The annual effective dose to the population from outdoor environmental gamma radiation was varied from 0.201 ± 0.073 mSv to 0.326 ± 0.090 mSv with an average of 0.255 ± 0.073 mSv. This kind of study is required to detect the presence of natural radionuclides and artificial radionuclides (if any) releasing from nuclear and radiological facilities in the country or from neighboring countries for normal operations or in case of accident/incident. From this study, it can be concluded that there is no radiation burden to the environment due to man-made sources.

Influence of Physicochemical Factors on Radionuclide Leaching from Soil

The degree of radionuclide leaching from soil in the region of the Atomic Lake (Kazakhstan) was determined. The 3H and 90Sr concentrations in aqueous extracts increase with increasing time of interaction of the soil with the leaching solution. A decrease in the 239+240Pu transfer into the solution with time may be due to the formation of colloids in the course of leaching, followed by their deposition or sorption onto soil components. Despite relatively high initial content of γ-emitting radionuclides (137Cs, 241Am, 152,154Eu, 60Co) on the level from n × 102 to n × 104 Bq kg−1 in the soil, in leaching experiments the content of these radionuclides in aqueous extracts was below the detection limit of the procedure used (<1 Bq L−1). The influence exerted on the leaching by the grain-size distribution of soil, pH of the medium, degree of mineralization, and chemical composition of water was determined. The tests performed suggest that the transfer of artificial radionuclides from the soil into water by leaching is one of the main mechanisms of radioactive contamination of the Atomic Lake water.

A STUDY OF DISTRIBUTION OF NATURAL RADIONUCLIDES IN SOILS AND ASSESSMENT OF EXPOSURE HAZARDS FROM TERRESTRIAL -RADIATION IN THE REGION OF TSALKA (GEORGIA)

Gamma-spectroscopy method has been used to determine the activity concentrations (in Bq kg -1 ) of natural radionuclides such as 238 U, 232 Th, and 40 K in soil samples collected from Tsalka region of south Georgia. Based on which contents of radionuclides in soil (in g kg -1 and ppm) were calculated. In addition, concentrations of artificial radionuclide of 137 Cs were determined, which has shown contamination character of study area. Based on the results of the analysis, some crucial physical values have been calculated, which are necessary for assessment of radiation exposure hazards for the population. Relevant conclusions have been drawn by comparing the results with previous work and recommendations of the international organizations.

Time-dependent trends of artificial radionuclides in biota of the Yenisei River (Siberia, Russia)

We investigated time-dependent trends of artificial radionuclides in aquatic moss, zoobenthos (amphipods and caddisfly larvae), and three abundant wild fish species (Northern pike, Arctic grayling, and Siberian dace) inhabiting the Yenisei River in the vicinity of the radioactive discharge site in 2007–2015, in a period before and after the shutdown of the last nuclear reactor plant at the Mining-and-Chemical Combine (MCC), which occurred in 2010. From our research, we learned that concentrations of short-lived radionuclides, whose discharges to the Yenisei either stopped or declined after the shutdown of the reactor plant at the MCC (24Na, 46Sc,51Cr, 54Mn, 58Co, 59Fe, 60Co, 65Zn, 103Ru, 141,144Ce, 152,154Eu, 239Np), decreased in biota samples as well. The ecological half-life (EHL) of 65Zn (0.4–0.7 y) was similar to the physical half-life of this isotope, the EHLs of 60Co (1.2–2.1 y) and 152Eu (1.8 y) were shorter than the physical half-lives of these isotopes. Concentration of 137Cs did not decrease significantly in biota of the Yenisei after the shutdown of the last reactor plant because the discharges of this radionuclide to the Yenisei continued at the same level. On a longer-term scale (since 1973 and since 1991), concentration of 137Cs in fish muscle had significantly decreased, following the decrease in annual discharges of this radionuclide to the Yenisei, and the EHL of 137Cs was estimated as 6.5–12.8 y. Statistically significant correlation with annual discharges of 137Cs was revealed for the concentration of this radionuclide in grayling (whole bodies and muscle); dace (muscle), and amphipods. Despite their ability to accumulate high concentrations of 137Cs, aquatic moss and caddisfly larvae (analyzed together with their stony casings) were not sensitive to interannual fluctuations in the releases of this radionuclide to the Yenisei. Among the analyzed fish species of the Yenisei, the highest activity concentration of 137Cs was revealed in pike (body and muscle), indicating biomagnification of this radionuclide in the top level of the trophic chain.

Airborne radionuclides and heavy metals in high Arctic terrestrial environment as the indicators of sources and transfers of contamination

Abstract. A survey of airborne radioactive isotopes (137Cs, 238Pu, 239+240Pu, 241Am, and 210Pb) and trace metals (Pb, Cu, Zn, Cd, Fe, Al) in tundra soils and cryoconite hole material sampled from several locations in the Kaffiøyra region of Spitsbergen revealed significant variability in spatial concentration. Lithogenic radionuclides (230Th, 232Th, 234U, 238U) show less variability than the airborne radionuclides because their activity concentrations are controlled by mixing of local material derived from different types of bedrock. Activity ratios of the artificial radionuclides in most cryoconite samples differ from global fallout signatures. The contribution of radionuclides from additional and more specific sources might be enhanced by non-continuous exposure of cryoconite to atmospheric deposition. We assumed that the main source of Pu, which was detected only in cryoconite samples, is derived from nuclear tests and non-exploded weapons-grade material. Approximately one-third of the total observed Pu activity concentration is 238Pu, most likely originating from the SNAP9A satellite re-entry, which was powered by a 238Pu thermoelectric generator. In samples from Waldemarbreen the influence of glacial local morphology on the capability of cryoconite for trapping and accumulating airborne radionuclides is apparent. Local glacial morphology plays an important role in determining the accumulation of airborne pollutants. Trace metal concentrations in soils were typical or slightly higher than concentrations characteristic for the natural background; the 206Pb∕207Pb signature was also close to the natural ratio of the parent rocks. Conversely, trace metal concentrations in cryoconite samples (Pb and Cd) were higher than in soil samples and exceeded natural values. Cryoconite is an effective monitor of the spread of artificial radionuclides and heavy metals in their surrounding environment.

Distribution and accumulation of artificial radionuclides in marine products around Korean Peninsula

We investigated the distributions of the artificial radionuclides 137Cs, 239+240Pu, and 90Sr in the various marine products around Korean Peninsula collected in 2015–2017. The activities of 137Cs, 239+240Pu, and 90Sr were in the ranges of 12.2–258.4 mBq kg−1, 0.014–1.879 mBq kg−1, and 11.3–18.3 mBq kg−1, respectively. The higher 239+240Pu (a factor of 10–50) relative to fishes were observed in mollusks. 137Cs in fishes were significantly enriched with growths. The calculated concentration factors (CFs) of 137Cs, 239+240Pu, and 90Sr in marine products were 7–143, 3–407, and 15–25, respectively. Overall, no noticeable artificial radioactivity was detected in marine organisms when comparing these results with previous data reported before the Fukushima nuclear accident and recommended CF values. The annual effective doses of 137Cs, 239+240Pu, and 90Sr by seafood consumption in South Korea were estimated to be 1.1 × 10−4, 1.6 × 10−5 and, 2.9 × 10−5 mSv yr−1, respectively, which is insignificant relative to that of natural radionuclides.

The assessment of radioactivity and radiological hazards in soils of Bolu province, Turkey

The radioactivity levels in soil samples of Bolu province of north-western Turkey have been determined. There has been no information about radioactivity measurement reported in soil samples in Bolu province so far. For this reason, the activity concentrations of natural and artificial radionuclides (226Ra, 232Th, 40K, and 137Cs) were measured in soil samples collected from 40 different points in Bolu province of north-western Turkey using gamma spectrometry technique with a high-purity germanium detector. The average activity concentrations (range) of 226Ra, 232Th, 40K, and 137Cs were found to be 18.2 (3.8–49.9) Bq/kg, 17.3 (4.1–37.9) Bq/kg, 258.3 (64.6–518.9) Bq/kg, and 7.5 (0.6–43.6) Bq/kg, respectively. At the end of the analysis, the radioactivity values were lower than the world average values reported by United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR). In order to evaluate the radiological hazards resulting from natural radioactivity, radium equivalent activity (Raeq), gamma index (Iγ), external hazard index (Hex), absorbed dose rate in air (D), annual gonadal dose rate (AGDE), the annual effective dose rate (AEDE), and excess life time cancer risk (ELCR) were calculated and found in the range of 14.8–129.8 Bq/kg, 0.1–0.5, 0.0–0.4, 7.0–60.2 nGy/h, 49.8–417.5 µSv/y, 8.6–73.8 µSv/y, and 0.3 × 10−4 to 2.6 × 10−4, respectively. These results were compared with recommended values (370 Bq/kg for Raeq, <1 for Iγ, <1 for Hex, 55 nGy/h for D, 300 µSv/y for AGDE, 70 µSv/y for AEDE, and 2.9 × 10−4 for ELCR) by European Commission (EC), UNSCEAR and International Commission on Radiological Protection (ICRP). As a result, health hazards originated by natural radiation from soil samples of the Bolu province is low and insignificant.

IN-SITU GAMMA-RAY SPECTROMETRY FOR RADIOACTIVITY ANALYSIS OF SOIL USING NaI(Tl) AND LaBr3(Ce) DETECTORS.

In this study, the full energy peak count rates to radioactivity conversion factors of 3″Ø × 3″ NaI(Tl) and 2″Ø × 2″ LaBr3(Ce) detectors for radioactivity analysis in the soil were determined on site using a semi-empirical method with point-like gamma-ray sources. To validate the conversion factors derived for the detectors, in-situ gamma-ray measurements were performed in wide open fields with almost flat surface and compared with the sampling analysis for the radioactivity of U-series, Th-series, and 40K in the soil. As a result, radioactivity concentrations of 40K, 208Tl and 214Bi by in-situ and laboratory measurements agreed well with each other within 5%, and the MDAs for artificial radionuclides were estimated under the condition of fresh deposition considering a radiation emergency situation.

Current state and trends in the content of 137Cs and 90Sr in abiotic and biotic components of Arctic ecosystems (Barents and Kara Seas case study)

This publication summarizes long-term data on radioactive contaminants in seawater, bottom sediments, and marine fish and describes current patterns in radionuclide distribution using data collected by the Murmansk Marine Biological Institute during cruises to the Barents and Kara Seas in 2015–2017. During the study period, no short-lived artificial radionuclides were found in the Barents and Kara Seas. 137Cs and 90Sr isotopes with a longer half-life are still registered in Atlantic waters that are the main source of radioactive contamination in these Arctic seas. Volumetric activity of 137Cs and 90Sr was compared at different depths. A uniform distribution of 137Cs in the vertical column of water and a tendency to increase the volume activity of 90Sr from surface to bottom were observed in the Barents Sea. Bottom sediments in the Kara Sea contain on average 2 times more 137Cs than the Barents Sea. Atlantic cod is characterized by an extremely low concentration of 137Cs in muscular tissue, about an order of magnitude lower than in the period of maximum contamination of Barents Sea waters observed in 1982. Currently there is a decreasing trend in concentrations of anthropogenic radioisotopes in the environment and biota. Processes of 137Cs and 90Sr removing from biotic and abiotic components are described with exponential functions. Due to natural marine purification processes, the decrease of 137Cs and 90Sr concentrations in the Barents and Kara Seas occur 2–4 times faster than the physical radioactive decay of these radionuclides.

In-situ CeBr3 gamma-ray spectrometry for radioactivity analysis of soil

A CeBr3 scintillation detector was applied for in situ gamma-ray spectrometry for radioactivity assessment of soil. The full energy peak count-to-radioactivity conversion factors were determined using a semi-empirical method. In-situ measurements using the detector system were implemented in three open fields. The radioactivity concentration of natural radionuclides in the soil and the detection limit for artificial radionuclides assuming artificial radionuclide deposited on the soil surface in a radiation emergency situation were estimated. The radioactivity concentration of 40K, 208Tl and 214Bi by in situ gamma-ray measurement agreed well with the sampling analysis results within 5%.

Discussions on the driving mechanism of postdepositional migration of 241Am and 137Cs in organomineral sediments (Lake Krugloe, Tomsk region, Russia).

A core of bottom sediments from Lake Krugloe located within the 30km influence zone of the Siberian Chemical Plant (located in the city of Seversk "Tomsk-7") was studied to determine scales and rates of migration of artificial radionuclides 137Cs and 241Am in organomineral sediment. It was found that the main portion of 137Cs and 241Am was contained in the sediment interval above 10cm. This means that the horizon of 10cm corresponds to 1950-the time of the start of widespread tests of nuclear weapons. The 210Pbex dates also confirm that this particular horizon was formed in the 1950s. Pore waters in the core above the 10cm horizon are in oxidizing conditions. The depth of the oxidized/reduced boundary was determined from the distribution of redox-sensitive elements Fe and U dissolved in the pore solution. The core distribution of 137Cs is a slightly sloping step, with the lower edge at the 10cm level. The smearing of the lower boundary of this distribution showing the scale of 137Cs migration made it possible to estimate the diffusion mobility of 137Cs. Its diffusion coefficient turned out to be of the order of 10-8cm2s-1. As shown by measurements, the scale of migration of 241Am and the scale of migration of 137Cs have similar values. Theoretical analysis carried out in this work shows that the most probable mechanism of 137Cs and 241Am migration in the pore solution of lake sediment is the migration of colloidal particles to which these radionuclides are strongly bound. Calculation of the diameter of such particles by the Stokes-Einstein formula shows that they have submicron dimensions (d≈ 400nm). No evidence was found that the change in redox conditions in the sediment had an effect on migration of Am ions in pore solution.

Assessment of the Quality of Bottom Sediments in the Middle Reaches of the Yenisei River by Allium test

The harmful potential of bulk bottom sediments of the Yenisei River has been assessed by the Allium test. Sediment samples have been taken in ten sites on a plot of about 100 km in length in the middle reaches of the Yenisei River affected by urban activity of the city of Krasnoyarsk and industrial plants. The samples of sediments differ considerably in the content of potentially toxic substances (heavy metals, artificial radionuclides, and organic pollutants) and nutrients and in physical properties. We use the mean length of onion root as an indicator of general toxicity, the mitotic index as an indicator of cytotoxicity, and the percentage of anatelophase cells in the apical root meristem with abnormal chromosomes as an indicator of genotoxicity. Both the stimulation and inhibition of indicator endpoints are revealed in sediment samples of the Yenisei River relative to the control (artificial sediments). An increased genotoxicity is recorded in the sample of sediments contaminated by a mixture of organic and chemical toxicants. A significant positive correlation between the percentage of abnormal cells and the content of copper and petrochemicals in the samples is revealed. No extremely strong reactions of onion endpoints to the quality of sediment samples are revealed, which is probably related to relatively low contamination of the sediments studied. This is in agreement with the data of chemical analyses. Based on the testing results, we can conclude that the endpoints of the Allium test are sensitive enough to the quality of bottom sediments of the Yenisei River and can be used for their biotesting.

Evaluation of Environmental Contamination and Estimated Radiation Exposure Dose Rates among Residents Immediately after Returning Home to Tomioka Town, Fukushima Prefecture.

On 1 April 2017, six years have passed since the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, and the Japanese government declared that some residents who lived in Tomioka Town, Fukushima Prefecture could return to their homes. We evaluated environmental contamination and radiation exposure dose rates due to artificial radionuclides in the livelihood zone of residents (living space such as housing sites), including a restricted area located within a 10-km radius from the FDNPS, immediately after residents had returned home in Tomioka town. In areas where the evacuation orders had been lifted, the median air dose rates were 0.20 μSv/h indoors and 0.26 μSv/h outdoors, and the radiation exposure dose rate was 1.6 mSv/y. By contrast, in the “difficult-to-return zone,” the median air dose rate was 2.3 μSv/h (20 mSv/y) outdoors. Moreover, the dose-forming artificial radionuclides (radiocesium) in the surface soil were 0.018 μSv/h (0.17 mSv/y) in the evacuation order-lifted areas and 0.73 μSv/h (6.4 mSv/y) in the difficult-to-return zone. These findings indicate that current concentrations of artificial radionuclides in soil samples have been decreasing in the evacuation order-lifted areas of Tomioka town; however, a significant external exposure risk still exists in the difficult-to-return zone. The case of Tomioka town is expected to be the first reconstruction model including the difficult-to-return zone.

IMPACT ON ABSORBED DOSE RATE IN AIR IN KANTO REGION BY FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT.

Absorbed dose rates in air were measured for the whole area of the Kanto region in 2015, 2016 and 2017 (n = 31 147). The mean absorbed dose rates in air for each prefecture measured by car-borne surveys were from 44 to 67 nGy h-1 (13-289 nGy h-1). The absorbed dose rate in air from artificial radionuclides (134Cs + 137Cs) measured by fixed-point observation (n = 507) was from 1 to 14 nGy h-1 (0-105 nGy h-1), and meaning that the contribution ratios of 134Cs and 137Cs were 3-22%. The deposited location of artificial radionuclides was less than 1000 m from ground level and depended on the topography, wind direction and precipitation field.

Analysis of the influence of nuclear facilities on environmental radiation by monitoring the highest nuclear power plant density region

Abstract Monitoring of environmental radioactivity is essential for ensuring the radiological safety of residents who live near nuclear power plants. Ulsan, South Korea, is surrounded by 16 nuclear power plants, the highest density in the country. In addition, the city contains facilities for conducting radiological nondestructive testing and using radioisotopes for medical purposes. It makes the confirmation of radiological safety particularly necessary. In this study, sampling points were selected based on regional characteristics, and surface water samples were pretreated and analyzed for gross beta and gamma radiation levels. In addition, the distribution of the city’s gamma dose rate was determined using a mobile monitoring system and distribution visualization program. The results showed that there is no effect on the gross beta and gamma nuclides of artificial radionuclides, and the gamma dose rate of the entire region did not exceed the environmental radiation level in South Korea overall, confirming the radiological safety of the city.

Investigation of the dependence of the activity concentration of natural and artificial radionuclides on particle size in surface soil

Surface soil radioactivity is being studied at NED-NTUA since almost thirty years. The last few years this research has expanded to the study of soil particle size fractionation of radionuclides. The purpose of the present work was to study the tendency of many radionuclides to accumulate in the smaller particle size fractions. To this end, soil samples were collected from an area in the NTUA Campus where 241Am contamination, due to a failed 241Am-tipped lightning rod, had been previously detected. The samples were separated into size fractions using a sieving machine and analyzed by gamma spectrometry to determine 210Pb, 241Am, 234Th, 228Ra, 228Th, 226Ra, 7Be, 137Cs and 40K. The activity concentrations of these nuclides were found to significantly differ among the size fractions examined.

Natural and artificial radionuclides in moss samples from the region of Northern Greece

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Radiological impact assessment in the terrestrial environment of Greece using innovative tools – Adaptation of ERICA Tool to actual measurements

In the present study, the radioactivity levels in terrestrial non-human biota and the transfer pathways in the ecosystem are examined. Grass of Poaceae family and herbivore mammals (ruminants) of Bovidae family and soil samples were collected during the period of 2010 to 2014, from grasslands of the Greek rural territory where sheep and goats were free-range grazing. Natural background radionuclides (226Ra, 228Ra, 228Th) and artificial radionuclides (137Cs, 134Cs, 131I) were detected in the collected samples using gamma spectrometry. The actual measured activity concentrations and site- specific data of the studied organisms were imported in ERICA Assessment Tool (Version 1.2.1, February 2016) in order to provide an insight of the radiological dose rates. Natural radionuclides exhibited significantly higher contribution to the total dose rate than the artificial ones. The radiological exposure to Fukushima-derived radionuclides was quite low and owed to internal exposure, mainly derived through the ingestion pathway. According to the screening levels, the calculated dose rate to the studied non-human biota was below the threshold levels. However, the obtained results may be proved useful in further research regarding the possible impact of protracted low level ionising radiation to non-human biota on the various levels of life’s organization.

Comparison of MCNP and ERICA codes in two different marine areas

The internal and external dose rates received by a marine organism, were calculated using the MCNP-CP code and the ERICA Assessment Tool. MCNP/MCNPX is a general purpose Monte Carlo code for the transport of all kinds of particles, while ERICA is a more specified software tool for assessing the radiological risk to terrestrial, freshwater and marine biota. A pelagic organism living only in the water medium, was chosen as a start for this comparison. Additionally, two different coastal areas: Stratoni port at Ierissos Gulf, Greece [1] and Shatt al-Arab estuary at Arabic or Persian Gulf [2] were selected. Both areas are receiving the impact of anthropogenic activities as those related with metal mining (Stratoni port) and oil and gas exploration (Arabic/Persian Gulf). The measured concentrations of natural 40K, 210Pb and 208Tl and artificial (137Cs) radionuclides in the surface sediment, were included in the calculations for the estimation of the activity concentrations in the water using the sediment-water distribution coefficient (Kd) of the ERICA database. The preliminary results of MCNP-CP simulations were in good agreement with those of ERICA for all radionuclides.