Measured Activity Concentrations Research Articles

A quantitative analysis on the effect of crystal parameters on full energy peak efficiency of a coaxial high purity Germanium detector for the energy range 50 keV-2.5 MeV

High Purity Germanium (HPGe) detectors are essential instruments in gamma-ray spectrometry, offering high sensitivity and exceptional energy resolution. The full-energy-peak (FEP) efficiency is a critical parameter that influences the accuracy of activity concentration measurements of radionuclides. This study examines the FEP efficiency of a coaxial HPGe detector, focusing on variations in crystal length, crystal radius, and crystal hole dimensions. For varying crystal lengths, the efficiency values show negligible differences at low energy (50 keV) but significant increases at higher energies, indicating that longer crystal lengths enhance efficiency. Similarly, the efficiency increases with larger crystal radii across all energy levels suggesting substantial efficiency gains even at low energies. However, variations in crystal hole radius and depth, exhibit minimal impact on FEP efficiency across all tested energy levels. These findings highlight that optimizing crystal length and radius is more crucial for changing detector efficiency compared to modifying hole dimensions, providing valuable insights for optimizing Monte Carlo models and detector design.

Radon exhalation and emanation assessments in the Transdanubian Central Mountain in Hungary

ObjectiveTo determine the radium-226 activity concentration, the massic radon exhalation rate and emanation factor of 55 soil samples from the Central Transdanubian Mountains in Hungary as well as possible radon exhalation hotspots in the sampling area were determined. Further indoor measurements are planned to investigate the possible exposure to radon of the inhabitants. MethodsThe radium-226 activity concentration measurements were carried out with a semiconductor HPGe gamma-ray spectrometer. The massic radon exhalation rate and emanation factor were determined by measuring the radon activity concentrations using the accumulation method with a system developed by our department based on an AlphaGUARD DF2000 portable radon monitor ResultsThe activity concentrations of radium-226 were between 11.4±2.5 and 118.2±3.0 Bq/kg, while their average was 39.51 Bq/kg. The massic radon exhalation rates were between 1.02 ± 3.64 mBq/kg.h and 275.63 ± 4.05 mBq/kg h, while their average was 39.51 mBq/kg h. Finally, the emanation factors were between 0.01 ± 0.04 and 0.80 ± 0.03 with an average of 0.30. ConclusionsIn our study, the results recorded from the bedrock at the sampling sites were analyzed. 9 samples were taken from sites comprised of limestone bedrock, moreover, the average radium-226 activity concentrations and massic radon exhalation rates at these sampling sites were higher than average. It was also concluded that although no regional correlation can be seen from the results, a possible smaller radon hotspot was identified from our measurements where further sampling will be carried out.

Application of the CIEMAT/NIST method to 14C low-level measurements

Radiocarbon dating of samples from benzene synthesis by low-level Liquid Scintillation Counting (LSC) method requires the availability of 14C standards in benzene, which are difficult to obtain, or the use of an absolute measurement which is out of reach for most analytical laboratories. This paper describes how the CIEMAT/NIST method can help to solve this issue and presents the measurements of low activity concentrations performed in the LRI-D using two different benzene base scintillator cocktails.

Exact parameter identification in PET pharmacokinetic modeling using the irreversible two tissue compartment model * *This work was partly funded by the NIH Grants P41-EB017183 and R01-EB031199-02.

Objective. In quantitative dynamic positron emission tomography (PET), time series of images, reflecting the tissue response to the arterial tracer supply, are reconstructed. This response is described by kinetic parameters, which are commonly determined on basis of the tracer concentration in tissue and the arterial input function. In clinical routine the latter is estimated by arterial blood sampling and analysis, which is a challenging process and thus, attempted to be derived directly from reconstructed PET images. However, a mathematical analysis about the necessity of measurements of the common arterial whole blood activity concentration, and the concentration of free non-metabolized tracer in the arterial plasma, for a successful kinetic parameter identification does not exist. Here we aim to address this problem mathematically. Approach. We consider the identification problem in simultaneous pharmacokinetic modeling of multiple regions of interests of dynamic PET data using the irreversible two-tissue compartment model analytically. In addition to this consideration, the situation of noisy measurements is addressed using Tikhonov regularization. Furthermore, numerical simulations with a regularization approach are carried out to illustrate the analytical results in a synthetic application example.Main results. We provide mathematical proofs showing that, under reasonable assumptions, all metabolic tissue parameters can be uniquely identified without requiring additional blood samples to measure the arterial input function. A connection to noisy measurement data is made via a consistency result, showing that exact reconstruction of the ground-truth tissue parameters is stably maintained in the vanishing noise limit. Furthermore, our numerical experiments suggest that an approximate reconstruction of kinetic parameters according to our analytic results is also possible in practice for moderate noise levels. Significance. The analytical result, which holds in the idealized, noiseless scenario, suggests that for irreversible tracers, fully quantitative dynamic PET imaging is in principle possible without costly arterial blood sampling and metabolite analysis.

Activity concentration of indoor radon and its short-lived progeny (218Po, 214Pb, and 214Po) and their effect on atmospheric ionization rate in Sana'a, Yemen

Exposure to ionizing radiation inside houses, especially radionuclides of radon and its progeny, poses serious health risks that can be exacerbated when inhaled as a result of interaction with human lung tissue. Also, air ionization is mainly due to these radionuclides. Therefore, accurate measurements of radon activity concentrations and its short-lived progeny are required to assess dose and environmental pollution and estimate ionization rates in indoor environments. For this purpose, we employed a previously tested and approved reliable method, following the three-count procedure. This method is based on airborne radon progeny sampling on polycarbonate membrane filters and alpha counting using a passive α-dosimetry technique with CR-39 detectors. The method also relies on a PC-based software we developed for solving mathematical equations and calculating all the necessary physical quantities. In this study, the concentrations of radon and individual short-lived radon progeny were measured in 20 houses in Sana'a, Yemen. Measurement conditions and meteorological variables were considered. The average activity concentrations of 222Rn, Equilibrium-Equivalent Concentration (EEC), 218Po, 214 Pb, and 214Po were 73.1 ± 6.0, 29.2 ± 2.4, 44.4 ± 3.6, 30.5 ± 2.5, and 23.2 ± 1.9 Bq.m-3, respectively. The calculated average unattached fractions f1(218Po), f2(214 Pb), and fp were found to be 0.24, 0.04, and 0.07 % respectively. The annual average values of ion-pair production rate caused by 222Rn and their progeny and air ion concentration, were 27.25 ions.cm-3s-1 and 1829 ions.cm-3 respectively. The annual effective dose was estimated to be 1.93 ± 0.16 mSv.y−1, well lower than the recommended 10 mSv.y−1.

Radioactivity concentration levels and potential radiotoxicity risk assessment of aquatic superfoods case study of algae supplements

It has been found that algae have a variety of health benefits, although investigations showed that they contain radiotoxic elements, including 226Ra, 232Th, 40K, and 137Cs, which may affect human health. This study is connected to activity concentration measurements of the above radionuclides in the algae supplements available in the Middle East markets. The annual effective radiation doses of measured radionuclides in analyzed algal supplements have been calculated. The highest values of annual effective doses have been estimated for 226Ra in Ecklonia (13.39 μSv/y) and for 232Th in Red Marine Algae (11.80 μSv/y), both from South Korea. In algal “superfoods”, the effective dose of 137Cs is not significantly affected by the Fukushima Nuclear Power Plant. Based on these results, it can be concluded that the activity levels of radionuclides are low, the naturally occurring radionuclides provide the most effective doses, and algae supplements can be considered safe.

Fractal discrete fracture network modeling of radon gas concentration in underground tunnels under Książ Castle in Poland

The numerical modeling of radon concentrations in the fault zone of the underground excavations at Książ Castle was conducted using a stochastic Discrete Fracture Network (DFN) model. Due to the difficulties related with obtaining the exact fractures in a rock mass, the novel approach used in this study incorporates the stochastic model with known site data. The analysis utilized a dataset comprising long-term measurements of 222Rn activity concentration and geodetic measurements for twelve faults in the Książ unit. The parameters considered in the DFN model are: fracture length, Peclet number (Pe = 0.1 and 1.0, respectively), advection velocities (from 10–8 m/s to 10–6 m/s and from range from 10–7 m/s to 10–4 m/s, respectively), radon diffusion (D = 2.1 × 10–61/s), radon decay constant (λ = 1/s), and radon gas generation (q) along the fractures within the range of 1.5 × 10–3 Bq/m3·s to 3.5 × 10–3 Bq/m3·s. The calibration process obtained the best fit when the radon generation rate was uniformly distributed through the rock mass in addition to incorporating a higher value of radon generation rate (q = 3.0 × 10–3 Bq/m3·s) where elevated radon concentrations have been measured. The modeling results also confirmed that the radon generation rate should always be higher where elevated radon activity concentrations were measured regardless of the measurement period. For the indicated “area” the radon generation rate should be higher from 25% to 37.5% between May–October and 18.5% to 40% between November–April. The influence of fracture zones on the recorded radon activity concentrations was noticeable up to a depth of 15 m. Within this range, the highest values of 222Rn activity concentration, ranging from 1,600 Bq/m3 to 2,000 Bq/m3, were consistently observed regardless of the season. However, as the depth increased, the values of 222Rn activity concentration decreased from 800 Bq/m3 to 400 Bq/m3 and became more dispersed.

Radioactivity characteristics of lignite and hard coals: Case study of Zonguldak (Kozlu), Konya (Karapınar) and Antalya (Pamucakyayla) in Türkiye

Abstract In this study, the radioactivity contents of Carboniferous Zonguldak-Kozlu hard coals, Carboniferous Antalya-Pamucakyayla hard coals and Pliocene Konya-Karapınar lignites were determined, then compared with the limit values determined by the authorized institutions and their hazard indexes were determined. The range of measured activity concentrations was from 16.2 Bq·kg−1 to 227.6 Bq·kg−1 for 238U, 20.6 Bq·kg−1 to 67.5 Bq·kg−1 for 232Th and 211.9 Bq·kg−1 to 515.5 Bq·kg−1 for 40K. The calculated mean absorbed gamma dose rate (D), radium equivalent activity (Raeq) and annual equivalent dose (AED) were 105.7 nGy·h−1, 227.9 Bq·kg−1 and 129.6 μSv·h−1, respectively. Although 238U and 232Th radionuclide activity concentrations are comparable to literature values, 40K activity concentrations were around three or four times higher than in UNSCEAR (2000) reports. As it poses a radiological risk, it is necessary to take the necessary precautions to reduce the negative effects on the environment and human health due to use of coals from Konya-Karapınar, Antalya-Pamucakyayla basins and to burn in a controlled manner.

Assessment of Indoor and Water Radon Concentrations in Esenyurt and Beylikdüzü Districts of Istanbul, Marmara Region, Turkey

The radon activity concentration measurements for indoor and tap water were studied in Esenyurt and Beylikdüzü districts of Istanbul Province, Turkey. The mean radon concentration value received from thirty-six passive radon detectors was obtained as 63.56 Bq/m3. The mean annual effective dose for indoor radon measurements is 1.60 mSv/y in this measurement period. The radon activity results of calculated tap water samples were under 0.8 Bq/L. The annual effective doses resulting from ingestion and inhalation were calculated to evaluate the health risk across various age groups. All radon measurement results, and the associated calculated data for ingestion and inhalation remained below the threshold values established by international organizations

Field-based soil-plant uptake measurements of natural radionuclides for key vegetables and ghaf leaves in Abu Dhabi

With the thriving fossil fuel and nuclear based industries in the nation, radioecology has become necessary for the radiation safety and emergency-preparedness for the United Arab Emirates (UAE). Environmental radiation transport modelling in the UAE and the Arabian Peninsula are severely limited, as we discuss in this paper, due to lack of experiments specific to arid desert climates. To fill the missing gaps in the baseline arid region radioecological database, especially for the soil-plant uptake studies, rigorous field works have been conducted for the first time on the soil and plant in the farms and open fields of the UAE. We present Abu Dhabi based measurements of activity concentrations of radionuclides of natural origins, in soils, key vegetables (cucumber, tomato, and bell pepper), and leaves of ghaf - a prominent native tree. The empirical data are utilized to get the first published estimates of UAE-specific plant-soil concentration ratios (CR), measuring root uptake of radionuclides in nonleafy vegetables and native trees. Such systematic studies are very rare for arid sandy soils. For the 27 samples analyzed, the activity concentrations' (unit Bq kg−1) ranges are: 169–1746 for 40K, 12–19.5 for 226Ra, and 2.7–23.1 for 228Ra. Likewise, wide variability is seen in the averages of concentration ratios also, ranging in 1.05–4.94 for 40K, 0.14–1.82 for 226Ra, and 0.53–2.78 for 228Ra. A net bioaccumulation (concentration ratio >1) of some of these natural radionuclides is found in many samples, but no significant doses or hazard indices are found due to these three radionuclides in the UAE's soils and vegetations. The paper discusses the careful work through tens of field sampling exercises, well controlled sample processing, high resolution gamma spectrometry, and treatment of data from gamma counting rates to accumulated dose rate estimations.

Examining the Radiological Health Risks Associated with Water Sourced from the Ogwashi-Uku Earth Dam in Ogwashi-Uku, Delta State, Nigeria

Given the increased human activities and population growth in Ogwashi-Uku, there is a possibility of potential contamination of the water in the dam with elevated levels of alpha and beta radiation. Therefore, this study aimed to assess the radiological health risks associated with water obtained from the Ogwashi-Uku Earth dam by analyzing the concentrations of gross alpha and gross beta activity in the water. The results indicate that the measured activity concentrations of gross alpha and gross beta in the water samples are below the permissible limits of 0.1 Bq/l and 1.0 Bq/l respectively. Additionally, the average annual effective dose equivalent calculated for all the water samples is lower than the recommended dose limit of 0.1 mSv for radionuclides in water. These findings suggest that the assessed life cancer risk associated with the water consumption is low, indicating that the water from the Ogwashi-Uku Earth dam is safe for consumption.

Radionuclide intake due to food drying surfaces: implications for individual ingestion effective dose in Ogbomoso, Southwestern Nigeria

Measurement of low-level radionuclide transfer from food drying surfaces is of radiological importance in environmental protection, especially in West Africa where farmers commonly preserve their foodstuffs by a low cost method of sun-drying on surfaces such as rock, asphalt, concrete, wood, metals, or roofing sheets which are reported sources of natural radionuclides. The transfer coefficient of natural radionuclides from drying surfaces into food samples is therefore a concern for dietary intake for the consumers. The radioactivity measurements of commonly used food drying surfaces in Ogbomoso, as well as cassava flour sun-dried on these surfaces were performed via gamma-ray spectrometry. Cassava flour was sun-dried on fabric raised 1 meter above the ground to serve as control sample (CF control ). Activity concentrations of 40 K, 238 U, 232 Th in rock, asphalt, concrete and cassava flour dried on these surfaces were determined using a lead-shielded NaI(Ti) detector crystal. Food consumption data and the measured activity concentrations in dried cassava flour were used to estimate ingestion effective dose of radionuclide intake from cassava flour due to these drying surfaces. Annual ingestion effective doses (mSvy−1) in cassava flour dried on concrete, rock, asphalt and fabric were estimated to be 0.72, 0.59, 0.42 and 0.26, respectively. Radionuclide addition was observed in cassava flour dried on concrete, rock and asphalt with transfer variation maximum in rock surface and minimum in asphalt surface. Result of this study is useful for radiometric data analysis in the study area especially on food safety regulations.

Assessment of Extent of Radiological Exposures in Subsurface Dumpsite Sediments around the Residential Area of Oru-Ijebu South-West Nigeria

Assessment of naturally occurring radionuclides was carried out from 20 sampling points in a dumpsite systematically collected from varying subsurface depth intervals of 0-0.2m, 0.2-0.4m, 0.4-0.6m, 0.6-0.8m and 0.8m-1.0m, while the control samples were taken from two sampling points located 200m away from the dumpsite. The samples were consequently analyzed in the laboratory for natural radioactive emission where each activity concentration measurements of the radionuclides were determined; the natural radionuclides identified were 226Ra, 238U, 232Th, 40K utilizing gamma ray spectrometry with NaI (IT) detector. The mean activity concentrations recorded in Bqkg-1 for 226Ra, 238U, 232Th and 40K in the subsurface soil samples were respectively 2.53±0.60, 31.50±2.01, 27.20±1.63 and 340.39±19.48 in depth 0m−0.2m; 1.96±0.37, 28.2455±2.50, 23.84±3.07 and 320.59±24.07 respectively in depth 0.2m-0.4m; 1.24±0.41, 24.197±3.66, 19.86±2.46 and 290.71±28.99 respectively in depth 0.4m−0.6m; 0.80±0.34 Bqkg-1, 20.10±4.133, 16.10±1.54, and 259.04±34.22 in depth 0.6m−0.8m and 0.68±0.25, 18.509±2.08, 14.50±0.91 and 247±30.13 for 0.8-1.0m. The levels of radioactivity were then used to assess public dose rates and radioactive contamination thereby predicting changes in environmental radioactivity caused by poor waste management, industrial activities, and other human activities. In all the investigated sampling point 40K exhibited the highest activity concentration in 0-0.2m depth with the value of 383.45±19.4883 while Pr exhibited the lowest activity concentration with the value of 0.08±0.4252 in depth 0.8-1.0m. The mean activity concentration of 238U, 232Th and 40K, in the soil samples at the dumpsite were 20.80, 20.3 and 291.54 Bqkg-1respectively for 0-0.2m depth. These results were lower than the world permissible standard stated by UNSCEAR. It was generally observed that the activity concentrations reduced with 0-0.2m having the highest concentration values for both the dumpsite and the control sites, while the mean activity concentrations of 238U, 232Th and40K for the control sites were found to be 31.5045±2.0123, 13.145±1.4637 and 183.415±21.4465 respectively for 0-0.2m depth.

Experience from radon in soil gas comparison measurements held in Czech Republic and in other countries, 1992–2022

Radon 222Rn, an inert natural radioactive gas, a daughter product in the 238U natural decay series, a source of alpha radiation, together with its short-lived decay products is a dominant source of absorbed radiation doses in the population. Rocks and building materials are fundamental sources of radon in dwellings. Elevated indoor radon activity concentration in houses and workplaces, surpassing recommended reference levels, is not desirable. Since radon penetrates into the houses from the geological basement, various technical aids for protection of houses have been developed. Their individual application derives from the radon potential of a building site. Radon risk mapping of building sites became a standard procedure for gauging the local radon potential. Various instruments and techniques of measurements of radon activity concentration in soil gas (Bq/m3) at building sites are available. Since radon in soil gas and radon measurement techniques are affected by several natural and technical conditions, resultant values of radon risk mapping by individual organizations vary, sometimes fundamentally. Radon comparison measurements at selected reference sites are an important tool for single organizations to verify their radon measuring procedures and reliability of their reported results. Based on legislative regulations, comparison measurements at established radon reference sites are a part of the obligatory activities for radon risk mapping at building sites in the Czech Republic. Experience and analyses of 30-year radon in soil gas comparison measurements in the Czech Republic show the dispersion of values reported by participating organizations and indicate that more than 10% of participants do not fulfill the established local criteria. This paper introduces requirements for the establishment of radon reference sites, documents their natural variability, recommends the procedure of radon comparison measurement, and analyses its results. A long-term experience was gained by testing organizations from the Czech Republic (1992–2022) as well as from the international comparison measurements organized in the Czech Republic and in several other countries (2010–2021).

Radiological hazards assessment of building materials used in Swakopmund, Namibia

A Canberra coaxial High Purity Germanium (HPGe) gamma-ray spectrometry detector was used to measure activity concentrations of radionuclides in commonly used building materials in Swakopmund, Namibia. The activity concentrations in, Bq.kg−1, for 226Ra, 232Th and 40K in all sample groups of building materials (cement, sand, cement bricks and roof tiles) were found to be in the range of 18.002–499.266, 14.069–132.508 and 162.794–1747.260, respectively. The average activity concentration of 40K was found to be two times higher than the critical level of 500 Bq.kg−1 in sand, cement bricks, clay bricks and roof tiles. The measured activity concentrations were used to estimate average dose rates and radiological hazard parameters. The absorbed dose rate (D) both due to indoor and outdoor exposure was higher than the international acceptable safe limits in all sample groups while the annual effective dose equivalent (AEDE) due to indoor exposure was higher in sand, cement bricks and clay brick samples. AEDE due to outdoor exposure was within acceptable safe limits for all sample groups. Radium equivalent (Raeq), external hazard (Hex) and gamma (Iγ) hazard indices were found to be higher than the acceptable safe limit only in clay bricks samples. The internal hazard (Hin) index was only higher than the acceptable safe limit in cement and clay bricks while the alpha (Iα) index was higher in sand, cement bricks and clay bricks. The Excess Lifetime Cancer Risk (ELCR) exceeded the acceptable safe limits in all sample groups. Our study showed that most of the computed radiological parameters were significantly higher than prescribed safe limits in most of the samples and therefore may pose a health risk to the inhabitants of Swakopmund.

A PBPK model for PRRT with [177Lu]Lu-DOTA-TATE: Comparison of model implementations in SAAM II and MATLAB/SimBiology

Physiologically based pharmacokinetic (PBPK) models offer the ability to simulate and predict the biodistribution of radiopharmaceuticals and have the potential to enable individualised treatment planning in molecular radiotherapy. The objective of this study was to develop and implement a whole-body compartmental PBPK model for peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-TATE in SimBiology to allow for more complex analyses. The correctness of the model implementation was ensured by comparing its outputs, such as the time-integrated activity (TIA), with those of a PBPK model implemented in SAAM II software. MethodsA combined PBPK model for [68Ga]Ga-DOTA-TATE and [177Lu]Lu-DOTA-TATE was developed and implemented in both SAAM II and SimBiology. A retrospective analysis of 12 patients with metastatic neuroendocrine tumours (NETs) was conducted. First, time-activity curves (TACs) and TIAs from the two software were calculated and compared for identical parameter values. Second, pharmacokinetic parameters were fitted to activity concentrations, analysed and compared. ResultsThe PBPK model implemented in SimBiology produced TIA results comparable to those generated by the model implemented in SAAM II, with a relative deviation of less than 0.5% when using the same input parameters. The relative deviation of the fitted TIAs was less than 5% when model parameter values were fitted to the measured activity concentrations. ConclusionThe proposed PBPK model implemented in SimBiology can be used for dosimetry in radioligand therapy and TIA prediction. Its outputs are similar to those generated by the PBPK model implemented in SAAM II, confirming the correctness of the model implementation in SimBiology.

How to obtain the image-derived blood concentration from 89Zr-immuno-PET scans

BackgroundPET scans using zirconium-89 labelled monoclonal antibodies (89Zr-mAbs), known as 89Zr-immuno-PET, are made to measure uptake in tumour and organ tissue. Uptake is related to the supply of 89Zr-mAbs in the blood. Measuring activity concentrations in blood, however, requires invasive blood sampling. This study aims to identify the best delineation strategy to obtain the image-derived blood concentration (IDBC) from 89Zr-immuno-PET scans.MethodsPET imaging and blood sampling of two 89Zr-mAbs were included, 89Zr-cetuximab and 89Zr-durvalumab. For seven patients receiving 89Zr-cetuximab, PET scans on 1–2 h, 2 and 6 days post-injection (p.i.) were analysed. Five patients received three injections of 89Zr-durvalumab. The scanning protocol for the first two injections consisted of PET scanning on 2, 5 and 7 days p.i. and for the third injection only on 7 days p.i. Blood samples were drawn with every PET scan and the sample-derived blood concentration (SDBC) was used as gold standard for the IDBC. According to an in-house developed standard operating procedure, the aortic arch, ascending aorta, descending aorta and left ventricle were delineated. Bland–Altman analyses were performed to assess the bias (mean difference) and variability (1.96 times the standard deviation of the differences) between IDBC and SDBC.ResultsOverall, the activity concentration obtained from the IDBC was lower than from the SDBC. When comparing IDBC with SDBC, variability was smallest for the ascending aorta (20.3% and 17.0% for 89Zr-cetuximab and 89Zr-durvalumab, respectively). Variability for the other regions ranged between 17.9 and 30.8%. Bias for the ascending aorta was − 10.9% and − 11.4% for 89Zr-cetuximab and 89Zr-durvalumab, respectively.ConclusionsImage-derived blood concentrations should be obtained from delineating the ascending aorta in 89Zr-immuno-PET scans, as this results in the lowest variability with respect to sample-derived blood concentrations.

РАДИОЭКОЛОГИЧЕСКАЯ ОБСТАНОВКА В РАЙОНЕ ПЛОЩАДКИ УРАНОВОГО НАСЛЕДИЯ – ШАХТА «СТЕПНАЯ» (КАЛМЫКИЯ)

Purpose: To study the radio-ecological situation on the “uranium legacy” site of the former Stepnaya mine in the Republic of Kalmykia. Material and methods: To measure the ambient dose equivalent rate (ADER), the pedestrian gamma survey method was used using a portable spectrometric complex MKC-01A Multirad-M and dosimeter-radiometer MKC-AT6101c. The activity of gamma-emitting radionuclides in soil samples was measured using a stationary gamma spectrometer from CANBERRA. The activities of 210Po and 210Pb were measured using a radiometric installation UMF-2000 following their radiochemical separation from samples. Short-term measurements of activity concentration (AC) and equivalent equilibrium activity concentration (EEAC) of radon were carried out with an aerosol alpha radiometer for radon and thoron RAA-20P2 Poisk. Doses of radiation exposure to biological objects were estimated using dose coefficients provided by ICRP Publication 136 taking into account recommendations R52.18.820-2015. Results: Gamma ADER values at the mine site vary over the range from 0.1 to 0.36 µSv/h, and on 80 % of the area these values do not exceed the background value of 0.14 µSv/h. Along the road from the mine to Narta village the ADER values do not exceed background values with exception of the area around the dam, where in a local part of this area of about 300 m2 these values reach 0.49 µSv/h. The specific activities of natural radionuclides in the soil are below the criteria for classification as solid radioactive waste (SRW). Under the certain weather conditions, radon EEAC inside the buildings on the site reaches 13 kBq/m3, and on the territory 1-1.5 kBq/m3. Ecological risk for the terrestrial biological objects under consideration (grass, soil worm, snake and mouse-like rodents) does not exceed 0.025. Conclusions: The radiation situation at the Stepnaya mine site meets the requirements of SP LKP-91, which were in force until 2020. However, in order to transfer the facility to a local government body, reclamation work should be carried out in accordance with the Federal Law “On the Transfer of Lands or Land Plots from One Category to Another” dated December 21, 2004 No. 172-FZ and GOST R 59057— 2020 «Environmental Protection. Lands. General Requirements for Reclamation of Affected Lands». Doses of exposure to biological objects do not impact significantly on morbidity, reproduction and life expectancy of terrestrial biological objects.

Radiological Risk Assessment of Soil Using RESRAD-OFFSITE Code in Communities around Indorama Fertilizer Company Eleme, Port-Harcourt, Rivers State, Nigeria

Anthropogenic activities around a fertilizer company can cause elevation in the concentration of naturally-occurring radioactive materials (NORMs) within surrounding soils, as a result of effluent discharge or heaping of rocks used as raw materials. The aim of this study was to evaluate the human risk associated with exposure to NORMs in soils from communities around Indorama Fertilizer Company Eleme, Port-Harcourt, Rivers State, Nigeria. A sodium-iodide doped with thallium [NaI(TI)] detector was used to measure activity concentrations of these NORMs in 22 soil samples within the study area. The residual radioactivity (RESRAD) offsite modeling program(version 4.0) was then used to estimate the radiation doses and the cancer morbidity risk of uranium-238 (238U), thorium-232 (232Th) and potassium-40 (40K) for hypothetical resident farmer scenario. According to the RESRAD prediction, the maximum total effective dose equivalent (TEDE) during 100 years was found to be 2.82 x 10-5 mSvy-1 at year 12, while the maximum total excess cancer morbidity risk for all the pathways was 3.52E-08 at year 6. Therefore, results obtained from the RESRAD-OFFSITE code in this study has shown that the health risk from effluent discharge within the study area is within acceptable levels according to international standards.

Estimation of natural radioactivity in the soil samples around the uranium site, royal village, Khandela, Sikar district, Rajasthan.

The measurements of activity concentration of radium ( 226Ra ), thorium ( 232Th) and potassium ( 40K ) natural radionuclides using high purity germanium ( HPGe ) detector to assess harmful effects on people residing around Royal Uranium Site, Sikar, Rajasthan, India. The activity concentrations range from 29.03±3.72 to 69.95±4.07Bq/kg for 226Ra with a mean value of 47.01Bq/kg, 57.99±6.13 to 113.94±6.54Bq/kg with a mean value of 86.56Bq/kg for 232Th,678.19±76.36 to 1426.55±81.32Bq/kg for 40K with a mean value of 1195Bq/kg. Average Radium Equivalent Activity was measured 261.59±35.48Bq/kg. The total outdoor absorbed gamma dose rate ranged from 78.42 to 157.91 nGy/h with a mean value of 122.12 nGy/h.The average annual effective dose equivalent outdoors and indoors was found 0.75mSv.Mean external (Hex) and internal (Hin) hazard indices are measured 0.70 and 0.82, respectively, for the study area.