Distribution Of Radionuclides Research Articles

Distribution of radiocaesium (137Cs) and radiopotassium (40K) during the cheese production

Distribution of radionuclides depends on various factors, and milk processing into cheese is recommended as one of the significant measures of radiation protection during radioactive contamination of the environment. A total of 16 milk and 16 cheese (soft and hard) samples were examined using HPGe gamma‐ray spectrometry to obtain 137Cs and 40K activity concentrations. The Pearson's correlation coefficients between 137Cs and 40K were determined (0.73, 0.68, 0.19, −0.23), followed by determination of distribution of 137Cs and 40K from cow milk to two types of cheeses using food processing retention factors (0.07–0.34). Transfer of 137Cs obtained could serve a great purpose for predicting its distribution during cheesemaking.

Air kerma rate from radionuclides distributed in forest ecosystem

This study evaluates the air kerma rate in radioactively contaminated forests. The air kerma rates created by plane sources of monoenergetic photons in the energy range 0.02–3 MeV located at different depths in soil up to 50 g cm−2 and at different heights in the forest medium from 0.05 to 50 m were calculated using numeric solution of the transport (Boltzmann) equation. To simplify the practical use of the results obtained by solving the Boltzmann equation, the study additionally includes approximation formulae for calculating air kerma rate separately from contaminated soil, crowns and trunks of trees in a forest ecosystem for 20 radionuclides - fission products that significantly contribute to the external dose. Biomaterial of trunks and crowns was modeled as uniformly distributed in corresponding layers and homogeneously mixed with air. Different distributions of radionuclides in soil were considered including plane source located at different depths, exponential and uniform distribution. Based on the results, the effect of forest biomass presence as an absorbing and scattering medium on the air kerma rate at 1 m above soil was evaluated. The estimated relative difference in air kerma rate at 1 m above soil in the forest medium and in free air for monoenergetic photon sources with energies 0.1 MeV, 0.66 MeV and 3 MeV did not correlate significantly with the energy of photons. Its maximum value in forest medium with biomass density of 5 kg m−3 was 15–20% for the source at soil depth ∼0.3 g cm−2, decreasing to less than 5% when it is at soil depth greater than 7 g cm−2. An example calculation of the air kerma rate dynamics is presented for the initial period after radioactive fallout considering weathering processes (rainfall and wind action) that contribute to the transfer of activity from the canopies to the forest floor. The differences in air kerma rate values, as an integral characteristic of the gamma radiation field from a radioactive cloud in the forest and in the open area, were evaluated.

Radioactivity level evaluation in granite building raw material production area in Cenxi, China.

This study was conducted to evaluate the radioactivity level in the granite building raw material production area in Cenxi, China. Natural radionuclide concentrations, γ absorbed dose rates (ADRs) and radon exhalation rates were measured in the area. The spatial distribution of natural radionuclides, γ ADR and radon exhalation rate were mapped with GPS information. The radioactivity levels in the study area were analysed based on the descriptive statistics and frequency distribution of measurement data. According to the Chinese standard, the granite raw materials used for building and decoration in this region were classified based on their radiological hazards. In addition, radiation protection measures were proposed for the mining of local granite building materials products as well as environmental protection around the work area and resident safety.

Diffusion of tritium, technetium, cesium, and uranium from phosphate glass leachates in pore solution of clay materials

The through diffusion method at room temperature was used to study the migration of radionuclides (3H, 99Tc, 137Cs, 233U) in compacted samples of clay materials during pore diffusion from a model leachate of the RW phosphate matrix with a total salt content of about 400 mg/L. Based on the results of the experiments, the effective diffusion coeffcients and coeffcients of the sorption distribution of radionuclides for the studied barrier clay materials were determined. Regularities of the diffusion transfer of tritium, cesium and uranium depending on the structure, mineral composition of clay materials and the content of radionuclides in the pore solution are revealed. Numerical modeles are proposed for calculating the effective pore di usion coeffcients of these radionuclides. There are still insuffcient data to analyze the factors affecting the diffusion of technetium.

DISTRIBUTION OF NATURAL RADIONUCLIDES IN ASHES, COLLECTED BY THERMAL POWER PLANTS ELECTROSTATIC PRECIPITATOR

Link for citation: Nazirov R.A., Vede P.Yu., Tarasov I.V., Zhuikov A.V., Sergunicheva E.M., Tolochko O.R. Distribution of natural radionuclides in ashes, collected by thermal power plants electrostatic precipitator. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 177-186. In Rus. Relevance. In the context of the global trend towards sustainable development, there is a problem of utilization of ash and slag waste from thermal power plants. The use of these wastes in the construction industry is of particular importance, due to the resource intensity of the production of building materials. Fly ash in the building materials composition can influence to a large extent the natural radioactivity of structures and increase the background radiation in the buildings. This is due to the fact that when coal combusting, fly ash is enriched with natural radionuclides. Purpose: to study the radioactivity of fly ash deposited on various fields of the electrostatic precipitator. Object: fly ash deposited on the fields of electrostatic precipitators from the combustion of Kansk-Achinsk brown coal in power boilers BKZ-420-140 PT-2. Methods. Content of Ra-226, Th-232 and K-40 was determined by gamma-spectrometric method, the value of the normalized indicator of specific effective activity for fly ash was calculated. The granulometric composition of the studied samples was determined by the method of laser diffraction analysis. Cluster analysis was used for statistical processing of test results. Results. The presence of two clusters in the content of natural radionuclides was established. In the first cluster, which has high radioactivity, the first and second fields of UGZ-4 electrostatic precipitators are combined, and in the second – the third and fourth fields. A correlation dependence was established between the numbers of fields of electrostatic precipitators, the size of ash particles, the content of Ra-226 and specific effective activity was established. No such dependence was found for Th-232. Conclusions. Particle distribution in the fields of electrostatic precipitators is multimodal. The nature of the distribution of each mode approaches the lognormal law. The content of radium and the value of the specific effective activity depend on the size of ash particles and are described by an exponential function. The highest content of Ra-226 is observed in the ashes deposited on the third and fourth fields of electrostatic precipitators, which indicates the enrichment of finer ash particles with this radionuclide. The conclusions obtained correspond to the well-known thesis about the increased radioactivity of ash particles that are not deposited by ash collection systems and enter the atmosphere together with flue gases. The proposed method for studying the distribution of natural radionuclides over the fields of electrostatic precipitators can be used to predict the radioactivity of particles that are not captured by the flue gas cleaning system and released into the environment.

Distribution of Radionuclides in the Surface Covering of the Barun Uranium Mining Area in Erlian Basin, Inner Mongolia

In order to identify the distribution pattern of radionuclides in the surface soil in the area of a sandstone-type uranium deposit, and to explore its spatial relationship with the location of the orebody, soil radon measurements and ground gamma-ray spectroscopy were carried out in the Barun study area, and soil properties were analyzed. The results show that the soil radon concentrations exhibited a bimodal feature, while the uranium content showed a decreasing trend along the tendency direction of the orebody. In the ground projection area of the orebody, radon concentration showed a positive correlation with uranium content, with both showing relatively low values. Combined with the results of field geological observation and soil property analysis, it is believed that the relatively low radon concentration and uranium content above the orebody is related to the soil being mainly sandy soil. Relatively high uranium values are distributed within approximately 1.5 km north of the northern boundary of the orebody and near the southern boundary of the orebody. High-value radon anomalies occur within about 2 km north of the northern boundary of the orebody and within about 1.3 km south of the southern boundary of the orebody.

Distribution of radionuclides and associated radiological risk assessment of soils from Niška Banja, Serbia

Distribution of radionuclides and associated radiological risk assessment of soils from Niška Banja, Serbia

Distribution of natural radionuclides in NORM samples from North Abu Rusheid area, Egypt

The North Abu Rusheid area in Egypt is a well-known high background natural radiation area (HBNRA) due to the existence of naturally occurring radioactive materials (NORMs) in mylonitic rocks. In this study, 27 rock samples were selected for dose estimation studies. 238U and 232Th were measured using inductively coupled plasma mass spectrometry (ICP-MS) and 40K was measured using sodium iodide (thallium) gamma-ray spectroscopy. The ranges of activity concentrations (Bq/kg) of 238U, 232Th and 40K in the samples varied from 270 ± 2 to 2120 ± 29, 350 ± 2 to 1840 ± 27 and 20 ± 2 to 1390 ± 35 with mean values of 980 ± 349, 770 ± 351, and 640 ± 402 Bq/kg, respectively. The radiological hazard parameters were estimated from activity concentrations of 238U, 232Th and 40K and compared to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) values. The present study revealed that the hazard parameters were several times higher than the worldwide averages. The U/Th concentration ratio ranged from 0.7 to 3 and could be attributed to the presence of kasolite, uranothorite, zircon, and columbite in mylonitic rocks. From the radiological protection viewpoint, it is necessary to monitor natural radionuclides in these rocks prior to their use in residential and commercial construction materials.

Geochemical distributions of natural radionuclides in surface soils and sediments impacted by lead-zinc mining activity

This study investigated the distribution features of uranium-238 (238U), radium-226 (226Ra), thorium-232 (232Th), and potassium-40 (40K) and evaluated the associated environmental radiological hazards of the topsoil and river sediments in the Jinding lead-zinc (Pb-Zn) mine catchment from Southwest China. The activity concentrations of 238U, 226Ra, 232Th, and 40K ranged from 24.0 ± 2.29–60.3 ± 5.26 Bq.kg-1, from 32.5 ± 3.95–69.8 ± 3.39 Bq.kg-1, from 15.3 ± 2.24–58.3 ± 4.92 Bq.kg-1, and from 203 ± 10.2–1140 ± 27.4 Bq.kg-1, respectively. The highest activity concentrations for all these radionuclides were primarily found in the mining areas and decreased with increasing distance from the mining sites. The radiological hazard indices, including radium equivalent activity, absorbed gamma dose rate in the air, outdoor annual effective dose equivalent, annual gonadal dose equivalent, and excess lifetime cancer, revealed that the highest values were observed in the mining area and downstream, specifically in the vicinity of the ore body. These elevated values exceeded the global mean value but remained below the threshold value, suggesting that routine protection measures for Pb-Zn miners during production activities are sufficient. The correlation analysis and cluster analysis revealed strong associations between radionuclides such as 238U, 226Ra, and 232Th, indicating a common source of these radionuclides. The activity ratios of 226Ra/238U, 226Ra/232Th, and 238U/40K varied with distance, suggesting the influence of geological processes and lithological composition on their transport and accumulation. In the mining catchment areas, the variations in these activity ratios increased indicated the impact of limestone material dilution on the levels of 232Th, 40K, and 238U in the upstream region. Moreover, the presence of sulfide minerals in the mining soils contributed to the enrichment of 226Ra and the removal of 238U caused those activity ratios decreased in the mining areas. Therefore, in the Jinding PbZn deposit, the patterns of mining activities and surface runoff processes in the catchment area favored the accumulation of 232Th and 226Ra over 40K and 238U. This study provides the first case study on the geochemical distributions of natural radionuclides in a typical Mississippi Valley-type PbZn mining area and offers fundamental information on radionuclide migration and baseline radiometric data for PbZn deposits worldwide.

Monitoring of <sup>37</sup>C, <sup>90</sup>Sr and <sup>40</sup>Kin Sod-Podzolic Soils and Plants of Reference Sites of the Ivanovo Region

The results of radiation monitoring of sod-podzolic soils of reference agricultural plots of the Ivanovo region, conducted in 2014 and 2021, are presented. Background values of the specific activities of the studied radionuclides in the soils of reference sites have been established. According to the pollution density of the arable horizon of soils 137Cs and 90Sr, the level of the ecological situation was determined, which made it possible to attribute the soils of all reference areas of the region to uncontaminated territories suitable without restrictions for agricultural use. The power of the exposure dose of gamma radiation of soils and the contribution of 40K and 137Cs to the formation of the gamma background of soils were determined. Correlation analysis determined the influence of individual physical and chemical properties of soils on the behavior and distribution of radionuclides in the soil and the relationship between the content of the radionuclides themselves. Based on the values of the specific activity of 137Cs and 90Sr in plant products grown in 2014 and 2021, rows of cultivated plants with a decreasing ability to accumulate these radionuclides from the soil were constructed. All grown plant products of all types of crops fully met the veterinary standards required to limit the content of 137Cs and 90Sr in plant feeds (green mass, straw and feed grain). The coefficients of accumulation and transition of 137Cs and 90Sr from soil to plants are calculated. The coefficients of linear correlation between the values of the specific activity of 137Cs and 90Sr in soils and plants revealed the strength and nature of these dependencies.

BACKGROUND GEOECOLOGICAL CONDITIONS OF ELKON GOLD-URANIUM ORE REGION

The Elkon ore region is located in the southern part of Sakha Republic (the largest federal subject of the Russian Federation). Elkon gold-uranium fields have the richest deposits of uranium ore, but they have not been developed. Although the natural landscapes of mountain taiga are already changed due to about-century-long geological exploration, we have the last chance to fix the environmental conditions before the start of developing. The paper deals with the characteristics of distribution of radionuclides and element in soils, plants and water of El’kon region and is based on field works performed in 2007–2008 (immediately after the decision on exploration). The Elkon horst is the part of Aldan Shield, an exposed basement of the Siberian craton not covered by the latest sediments. The uranium mineralization is confined to igneous Mesozoic complexes. Weathering and erosion cause dispersion halo of elements and radionuclides which may become probable pollutants. The studied area is divided into four geological formations, but soil probes reveal no distinction in geochemistry specialization. So landscapes were divided into three groups by level, slope exposition and vegetation condition. Each group was measured by couple of samples. The main migration features were assessed by the distribution of elements and radionuclides (some local peaks were found for 90Sr, As, Th, and Mo). The As, Pb (rarely Mn, Hg) contamination of soils is proved. The main co-locations were computated for soils. The total contamination was estimated acceptable to moderate rates, therefore, there were found local high-polluted areas in dump zones. The combined database could be used as a reference point for further environmental research.

Environmental and Health Impacts: Presence of Radionuclides and Toxic Metals in Mining Areas in Niger State, Nigeria

The distribution of radionuclides and heavy metals (carcinogenic and non-carcinogenic) in soil and plants grown in lead contaminated areas were determined using gamma spectrometry and AAS (Atomic Absorption Spectrometry). The values of Dout (outdoor dose rate) and Din (indoor dose rate) were found to vary from 49.10 to 96.59 nGy h-1 with a mean value of 73.75 nGy h-1 and 97.30 to 191.67 nGy h-1 with a mean value of 143.39 nGy h-1 for Kawo; 51.64 to 105.26 nGy h-1 with a mean value of 75.36 nGy h-1 and 104.43 to 205. 87 nGy h-1 with a mean value of 157.13 nGy h-1 for Magiro. The weighted mean concentrations of Pb, Cu, Fe, Cr, Cd and Ni in mg kg-1 in soil and crop were (2.20,2.29), (3.14, 0.16), (15.10, 19.33), (0.16, 0.25), (0.24, 0.05), (0.43, 0.06) and (3.00, 3.18), (6.09, 0.34), (16.83, 10.10), (0.22,0.36), (0.25, 0.05), (0.43, 0.06) for Kawo and Magiro respectively. The total incremental lifetime cancer risk ΣILCR for both adults (0.73 x 10-2) and children (1.03 x 10-2) were above tolerable acceptable risk (given as 1 x 10-6 to 1 x 10-4). Therefore, the areas need remedial action and proper monitoring.

Airborne gamma-ray mapping using fixed-wing vertical take-off and landing (VTOL) uncrewed aerial vehicles.

Low-cost uncrewed aerial vehicles (UAVs) are replacing manned aircraft for airborne radiation mapping applications such as nuclear accident response scenarios or surveying ore deposits and mine sites because of their cost-effectiveness and ability to conduct surveys at lower altitude compared to manned counterparts. Both multi-rotor UAVs and fixed-wing UAVs are well established technologies for aerial radiation mapping applications, however, both also have drawbacks: multi-rotor UAVs are very limited in flight time and range, and fixed-wing UAVs usually require facilities for take-off and landing. A compromise solution is introduced in this work, using a fixed-wing vertical take-off and landing (VTOL) UAV that combines the flexibility of a multi-rotor UAV with the range and flight time of a fixed-wing UAV. The first implementation of a VTOL with radiation mapping capabilities is presented, based on a commercial WingtraOne UAV augmented with CsI scintillator and CZT semiconductor gamma spectrometers. The radiation mapping capabilities of the prototype are demonstrated in a case study, mapping the distribution of radionuclides around the South Terras legacy uranium mine in the south of England, United Kingdom, and the results are compared with previous studies using multi-rotor and manned aircraft to survey the same area.

The uncertainty of estimation of doses to the bone marrow from <sup>89,90</sup>Sr due to the variability of the chemical composition and bone density

Dosimetric modeling of radiation transport in skeletal bone tissues using computational phantoms provides the doses of internal exposure to active marrow. Computational phantoms of ICRP are created for reference people with anatomical and physiological characteristics typical of an average individual. The doses calculated with such phantoms will correspond to certain population-average values. Individual variability will introduce a stochastic component of uncertainty into the dose estimation. The objective of this study is to assess the influence of variability of chemical composition and bone density on the results of dosimetric modeling. The phantoms are represented by simple geometry figures filled with trabecular structures and bone marrow and covered with a cortical layer. Radiation transport was simulated using the Monte Carlo method. The dose factors to convert the radionuclide activity concentration to absorbed dose rates in active marrow were calculated assuming uniform radionuclide distribution in the volume of the trabecular and cortical bone. As a result of the numerical experiments, it has been shown that variations in chemical composition do not introduce an error of more than ± 4% into dosimetric modeling. The effect of bone density on active marrow dose formation depends on the size of a phantom. For computational phantoms with linear dimensions exceeding two electron free path lengths (~ 0.44 cm), variability of bone density within ± 3% leads to a similar relative uncertainty of the dose conversion factor. However, for smaller phantoms, bone density variability leads to uncertainties of 6% or 13% for a source deposited in the trabecular or cortical bone, respectively. The results obtained will be used to assess the uncertainty of bone marrow dosimetry, taking into account the uncertainty of all parameters including the variability of morphometric characteristics of bones, the variability of the active marrow distribution in skeletal sites, as well as the uncertainties introduced by model approximations.

Radiotoxic fission products and radiological effects in the Mediterranean Sea biota from a hypothetical accident in Akkuyu Nuclear Power Plant

A combined hydrodynamic/radiobiological model was used to calculate the distribution and dose rate of significant radionuclides in the Mediterranean Sea marine organisms in the event of an accident at the Akkuyu Nuclear Power Plant (ANPP). The Hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model was applied to simulate the dispersion and deposition of artificial radionuclide concentrations. Environmental Risk from Ionising Contaminants: Assessment and Management (ERICA) tools were utilized to assess issues related to sea health and potential hazards in case of an accident. The scenario source term profile was derived from the Fukushima nuclear power accident. Volumetric concentrations and deposition levels of pollutants increased from 1 MBqm−3 to 1 × 103 MBqm−3 and from 1 × 10−1 MBqm−2 to 1 × 10−7 MBqm−2 after 48 h. In terms of dose rates to the various marine biotas, polychaete worms had the greatest overall dose rate and the highest contribution to total dose rates attributable to 137Cs radionuclide.

Membrane and Nuclear Absorbed Doses from 177Lu and 161Tb in Tumor Clusters: Effect of Cellular Heterogeneity and Potential Benefit of Dual Targeting-A Monte Carlo Study.

Early use of targeted radionuclide therapy to eradicate tumor cell clusters and micrometastases might offer cure. However, there is a need to select appropriate radionuclides and assess the potential impact of heterogeneous targeting. Methods: The Monte Carlo code CELLDOSE was used to assess membrane and nuclear absorbed doses from 177Lu and 161Tb (β--emitter with additional conversion and Auger electrons) in a cluster of 19 cells (14-μm diameter, 10-μm nucleus). The radionuclide distributions considered were cell surface, intracytoplasmic, or intranuclear, with 1,436 MeV released per labeled cell. To model heterogeneous targeting, 4 of the 19 cells were unlabeled, their position being stochastically determined. We simulated situations of single targeting, as well as dual targeting, with the 2 radiopharmaceuticals aiming at different targets. Results: 161Tb delivered 2- to 6-fold higher absorbed doses to cell membranes and 2- to 3-fold higher nuclear doses than 177Lu. When all 19 cells were targeted, membrane and nuclear absorbed doses were dependent mainly on radionuclide location. With cell surface location, membrane absorbed doses were substantially higher than nuclear absorbed doses, both with 177Lu (38-41 vs. 4.7-7.2 Gy) and with 161Tb (237-244 vs. 9.8-15.1 Gy). However, when 4 cells were not targeted by the cell surface radiopharmaceutical, the membranes of these cells received on average only 9.6% of the 177Lu absorbed dose and 2.9% of the 161Tb dose, compared with a cluster with uniform cell targeting, whereas the impact on nuclear absorbed doses was moderate. With an intranuclear radionuclide location, the nuclei of unlabeled cells received only 17% of the 177Lu absorbed dose and 10.8% of the 161Tb dose, compared with situations with uniform targeting. With an intracytoplasmic location, nuclear and membrane absorbed doses to unlabeled cells were one half to one quarter those obtained with uniform targeting, both for 177Lu and for 161Tb. Dual targeting was beneficial in minimizing absorbed dose heterogeneities. Conclusion: To eradicate tumor cell clusters, 161Tb may be a better candidate than 177Lu. Heterogeneous cell targeting can lead to substantial heterogeneities in absorbed doses. Dual targeting was helpful in reducing dose heterogeneity and should be explored in preclinical and clinical studies.

Modeling the Distribution of Radionuclides in the Air and on the Soil Surface

Mathematical and numerical methods are used to simulate physical and chemical processes when building models of pollutants dispersion in the air and on the soil surface. Based on meteorological data and information on the source of emissions, these models characterize both the primary pollutants entering the atmosphere directly and the secondary ones formed as the result of complex chemical reactions. These models are important for the air quality management system, as they allow monitoring emissions into the atmosphere, predicting their distribution, as well as developing effective strategies intended for reducing harmful substances in the atmosphere. The article presents an overview of computational methods used to simulate the pollutants dispersion in atmospheric air and on the soil surface, such as the Gaussian torch model, the Lagrangian dispersion stochastic model, and the Eulerian model of atmospheric diffusion. The practical application of the considered models showed sufficient reliability and validity of the air and soil pollution levels forecast. The simulation uses computer programs that include algorithms for solving the mathematical equations that control pollutant dispersion. The dispersion models are used to estimate the concentration of air pollutants or toxins. They can also be used to predict future concentrations under certain scenarios. They are useful for studying the pollutants that disperse over long distances and can initiate reactions in the atmosphere. Such software products are as follows: AEROPOL, AERMOD, GRAL, TAPM CSIRO, CALPUFF, HYSPLIT, etc. A method of processing information about the pollution sources and the environmental parameters, based on the HYSPLIT program, is proposed to form maps of the volume and surface activity of radionuclides. This method was applied to analyze the process of the plutonium isotopes dispersion as a result of the movement of air masses in the places of fires in April 2020 in the exclusion zone of the Chornobyl NPP, as well as the associated hazard for the population health and the environment.

Assessment of natural radioactivity and radiological hazards of soil collected from rabia town in nineveh governorate (North Iraq)

The effects of the environment on human exposure to radiation from naturally occurring radioactive elements have been investigated around the world. In the group of natural radionuclides under examination, the study’s objective is to ascertain the distribution, potential anthropogenic origins, and activity of the radionuclides 226Ra, 232Th, 40K and their radiological risk parameters in twelve soil samples taken from Rabia town in Nineveh Governorate, North Iraq using NaI (Tl) detector. For the examined region, the activity concentrations of 238U, 232Th, and 40K ranged from 4.79 ± 0.211 to 21.77 ± 0.675 Bq kg−1, 11.21 ± 0.942 to 33.57 ± 2.185 Bq kg−1, and 112.8 ± 32.074 to 312.2 ± 95.463 Bq kg−1, respectively. The estimated radiological hazard parameters for the examined samples included the absorbed dose rate (Dair), annual effective dose equivalent (AED), gamma-ray hazard index (I), and annual gonadal dose equivalent. Furthermore, the current work revealed the distribution of radionuclides and their relationships with the mineralogical composition. Based on obtained results, this soil is safe for the population living in the study area and can be used as a building material or for other human activities without posing any radiological danger.

Radiological assessment in beach sediment of coastline, Ghana

The natural and artificial radioactivity in beach sediment sampled from the coastline of Ghana were analyzed using High Purity Germanium gamma ray detector. The overall average activity concentrations of 226Ra, 232Th, 40K and 137Cs were estimated to be 43 ± 6, 22 ± 1, 393 ± 74 and 8.4 ± 0.5 Bqkg−1, respectively. Apart from 226Ra the mean activity concentrations of the measured radionuclides were below the world averages of 32, 45, 412 and 18.2 Bqkg−1 respectively. High 137Cs mean concentration of 109.8 Bqkg−1 was observed for one of the locations, which might be due to the occurrence of a nuclear incidence or other factors. The evaluated radiological parameters also had values below world averages, except for some coastal areas which recorded Annual Gonadal Dose Equivalent (AGDE) values higher than the reference level of 300 μSvy−1. There was no significant risk associated with the radionuclide activities evaluated along the coast of Ghana. The correlation between the radionuclides and the radiological parameters were analyzed with the Pearson correlation matrix, cluster and PCA analysis, and they all showed similar outcomes. Spatial distribution maps were also created using ArcGIS software for a pictorial view of the distribution of radionuclides along the study area.

Research on calculation and verification of hazardous area for radioactive sewage entering into the ocean

To improve the emergency disposal capacity of radioactive sewage entering into the ocean, concentration distribution and hazardous area were observed and calculated. Haiyang nuclear power station and its surrounding coastal waters were selected as the research object. Based on Euler method, calculation model of concentration distribution and hazardous area with radioactive sewage entering into the ocean was established with a resolution of 1′ × 1'. Radionuclide concentration distribution and hazardous area were calculated under an assumed nuclear leakage accident and an assumed radioactive sewage discharge event with a plan. The study show that, under the given conditions of an assumed nuclear leakage accident, radionuclides of 137Cs are mainly distributed within about 81 km east, 39 km south and 33 km west of the nuclear power station after fourteen days. While under the given conditions of an assumed radioactive sewage discharge event with a plan, radionuclides of 3H are mainly distributed within about 58 km east, 14 km south and 23 km west of the nuclear power station after fourteen days. Compared with the total amount of source term, the high concentration is reduced by about 8 orders of magnitude. Area with radioactivity lower than 100 Bq/L is considered to be safe area, that more than 100 Bq/L（105Bq/m3）to be hazardous area, then the hazardous area account for about 50% of the main radionuclide distribution area. The hydrodynamic result was verified, and the maximum error between calculation and measurement velocities in flow field was less than 10%. The radioactive result was verified, and changes of radionuclide concentration in this research basically agreed with the monitoring data from the Fukushima Daiichi nuclear accident. So the model is considered to be reasonable and credible.