Maximum Activity Concentration Research Articles

Experimental study of <SUP align=right>41</SUP>Ar activity release rate from the Bangladesh Atomic Energy Commission TRIGA research reactor

The present study focused on the monthly or annual 41Ar activity release rate and ground level activity concentration measurement including the estimation of public dose level at the ground and stack positions of the Bangladesh Atomic Energy Commission TRIGA Research. During the experimental work, a Geiger-Muller (G-M) counter was used for the air sample count rate study. The experimental results demonstrated that the obtained maximum monthly or annual 41Ar activity release rate (2.48 × 1010 Bq/month or 6.25 × 1011 Bq/year) and monthly maximum ground level 41Ar activity concentration (6.40 × 101 Bq/m3) were within the permissible limits set by the regulatory body. This report also confirmed that the estimated public dose levels (0.29 mSv/yr and 0.0002 mSv/yr) at the stack and ground positions were far below the IAEA acceptable limit (1.0 mSv/yr) which was significant for the research reactor safety.

Determination of Water Quality in Springs of Ekaterinburg and Sverdlovsk Oblast

This article reported a study of water quality in 31 springs of the city of Ekaterinburg and the Sverdlovsk Oblast. We determined that water in only 7 springs (22%) fully met the requirements of sanitary norms from the point of view of content of chemical and radioactive pollutants. In 17 cases, water did not meet the requirements of the norms for the chemical factor, in 4 cases – for the radiation factor, and in 3 cases – for both the chemical and radiation factors. Among the natural radionuclides, only 222Rn showed levels higher than intervention level (60 Bq/L); the maximum activity concentration of radon was found to be 161 Bq / l (Pavlovsky spring). At the same time, activity concentrations of uranium and thorium did not exceed the level of intervention. A detailed analysis of the content of natural radionuclides showed the absence of correlations between the activity concentrations of radon, uranium and thorium in spring waters. Inconsistency of spring waters with sanitary standards for chemical factors in the vast majority of cases was associated with excess MPC for iron. Also, in a number of samples, an excess of the MPC for manganese and barium was found, while in the spring Europe-Asia (Yekaterinburg) an almost 9-fold excess of the MPC for barium was found.

A method for radiologically evaluating indoor use of dimension stone considering radon exhalation rates

Background: The use of natural radioactive building materials could be a health risk for both dwellers and mining workers. Therefore, a quick and effective method to test batches of rock samples is needed. Nevertheless, there is no reference value for maximum exhalation rates for building materials, except radiological hazard indices that do not measure gas exhalation rates directly. Objectives: This article investigated the correlations between Gamma Index and radon and thoron exhalation rates, and the proportions of radon and thoron in samples. Moreover, the main objectives were to analyze the feasibility of screening problematic samples for indoor use through a portable radiation detector (CoMo 170), which consists of a quick analysis at very low cost, and to simulate indoor concentration of radon using the measured exhalation rates of dimension stone slabs. Design: Best-selling dimension stone slabs were submitted to the following assays: gamma spectrometry, radon and thoron exhalation analysis using scintillation cell, and radioactivity measurement using a portable detector. Univariate and multivariate statistical analyses were conducted using Statistica 13 software. Results: The average activity concentrations measured were 971 ± 58.6 Bq/kg of 40K, 184 ± 9 Bq/kg of 232Th, and 74 ± 3 Bq/kg of 226Ra. The maximum activity concentrations of 40K, 232Th, and 226Ra series were 1,734 ± 100 Bq/kg, 2,667 ± 109 Bq/kg, and 596 ± 2 Bq/kg, respectively. The average exhalation rate of 222Rn was 406 ± 20 Bq/h m2. Conclusions: The main recommendations arising from this study are as follows: a portable radiation detector (CoMo 170) could be used as a screening method for selected samples; Gamma Index limit value = 1 for dimension stone slabs could be adopted when assessing radon and thoron exhalation; and the surface radon exhalation rate should be measured as a basis of recommendation for surface treatment before sales. Finally, thoron exhalations should be considered in radiological assessment, as 57% of the samples had higher thoron exhalation rates than radon.

Vertical distribution of <sup>137</sup>Cs in soddy-podzolic sandy soil in grasslands and forests of the Bryansk region in 2015–2016

Vertical distribution of natural and man-made radionuclides in the soil profile is a decisive parameter when calculating the dose rate of gamma radiation in the air above the ground and the effective dose of external human exposure. The main purpose of this work was to determine vertical distribution of137Cs in soddy-podzolic sandy and sandy-loam soils in forests and grasslands in the south-western districts of the Bryansk region in the remote period after the Chernobyl accident. In 2015–2016, soil cores were sampled in 7 virgin meadows and 13 forested areas to a depth of 20 cm. The cores were cut into horizontal layers 2 cm thick. The137Cs activity in the samples was determined using a semiconductor gamma spectrometer. The activity concentration in samples of dry soil (n = 200) ranged from 6.35 Bq/kg to 83300 Bq/kg with an average of 4550 Bq/kg. In the meadows in three cases, the maximum activity concentration was determined in the uppermost layer. With increasing depth, the activity concentration decreased and reached a minimum in the deepest layers. A difference between the surface layer and the deepest layer was two to three orders of magnitude. The three other meadows showed a relatively uniform distribution of137Cs in the upper 4–6 cm, followed by a decrease in activity concentration with an increase in depth. In one meadow area, a peak of the137Cs activity was found at a depth of 4–6 cm. In the forest, the most typical (in 10 cases) was the presence of a pronounced maximum activity concentration of137Cs in the uppermost layer. The experimentally obtained values of the137Cs inventory in the upper 20 cm of soil at the surveyed sites ranged from 42 to 1940 kBq/m2. The values of137Cs inventory positively and statistically significantly correlated with officially established levels of137Cs surface ground contamination for the territory of nearby settlements. Vertical migration of137Cs in the soil in the surveyed areas was mainly limited to the upper 10 centimeters. The layer on average contained 94% of the total137Cs inventory. Less than 1% of the total137Cs inventory was found in the deepest soil layer sampled (18–20 cm). The obtained137Сs activity distributions were used to calculate kerma rate in the air at a height of 1 m above the ground at the surveyed sites. The air kerma rate ranged from 52 to 2240 nGy/h (on average, 807 nGy/h). The caesium-137 deposit in the upper 6 cm of soil determined about 95% and 90% of the air kerma rate in the forests and in meadows, respectively. Radioactive caesium, which migrated into the soil to a depth of more than 10–12 cm, gave a negligible contribution (less than 1%) to the gamma-radiation dose rate in the air. In practical terms, it indicates that the depth of soil sampling equal to 20 cm is currently quite sufficient to estimate the dose rate of gamma radiation in the air in virgin grasslands and in forests.

Spatial distribution of radionuclides in agricultural soil in the vicinity of a coal-fired brick kiln

The spatial distributions of naturally occurring radionuclides (226Ra, 232Th, and 40K) in agricultural soils collected in the proximity of a coal-fired brick kiln located at Chittagong district were studied using HPGe γ-ray spectrometry. The obtained mean activity concentrations for 226Ra, 232Th, and 40K were slightly higher than the world average values, which indicate the contribution of radionuclides via the fly ash deposition from the kiln. The maximum activity concentrations of 226Ra, 232Th, and 40K in soil samples collected at a distance of 120 m from the kiln were found to be 54.3 ± 11.3 Bq kg−1, 62.1 ± 18.2 Bq kg−1, and 572 ± 123 Bq kg−1, respectively; the levels show further decreasing trend in all directions (towards and away from the kiln). Associated radiological hazard indices were calculated in order to assess the radiation effects to human health and compared with the world-recommended values. Basic multivariate statistical analysis was performed to describe the statistical characteristics of the radionuclides. Lower values of radiological indices indicate that there is no probability of immediate health effect on workers and public living around the kiln due to the presence of natural radioactivity in the agricultural soils.

Numerical modelling of 137Cs content in the pelagic species of the Japanese Pacific coast following the Fukushima Dai-ichi Nuclear Power Plant accident using a size-structured food-web model.

As result of the great east Japan earthquake on March 2011 and the damages of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), huge amount of radionuclides, especially 137Cs, were released to the Japanese Pacific coast. By consequence, several marine species have been contaminated by direct uptake of radionuclides from seawater or through feeding on contaminated preys. In the present study we propose a novel radioecological modelling approach aiming to simulate the radionuclides transfer to pelagic marine species by giving to the organism body-size a key role in the model. We applied the model to estimate the 137Cs content in 14 commercially important species of the North-Western Pacific Ocean after the FDNPP accident. Firstly, we validated the model and evaluated its performance using various observed field data, and we demonstrated the importance of using such modelling approach in radioecological studies. Afterwards, we estimated some radioecological metrics, such as the maximum activity concentration, its corresponding time and the ecological half-life, which are important in assessment of the previous, current and future contamination levels of the studied species. Finally, we estimated the time duration required for each species to reach the pre-accident 137Cs activity concentrations. The results showed that the contamination levels in the planktivorous species have generally reached the pre-accident levels since about 5 years after the accident (since 2016). While in the case of the higher trophic level species, although the activity concentrations are much lower than the regulatory limit for radiocesium in seafood in Japan (100 Bq kg-1), these species still require another 6–14 years (2018–2026) to reach the pre-accident levels.

Effect of process parameters on aqueous extraction of thymol and other phytonutrients from herbal seed Ajwain (Trachyspermum ammi L.)

Ajwain (Trachyspermum ammi L.) is a therapeutic herbal spice with many benefits and a good source of phytonutrients. The optimum process conditions were evaluated for aqueous extraction of phytonutrients from ajwain. Seed to water ratio (0.25 to 1 g/mL), extraction time (10 to 60 min) and extraction temperature (30 °C to 60 °C) were selected as independent variables and their effects on the concentration of protein, thymol, total solids and antioxidant activity were examined. The linear and combined effects of independent process variables on quality parameters were analyzed by response surface methodology. The second-order polynomial model was generated by analysis of variance for each response and its significance and adequacy were judged statistically by the coefficient of determination, the coefficient of variance, lack of fit test and adequate precision. Numerical optimization was carried out to evaluate the optimum operating conditions subject to maximum thymol concentration and antioxidant activity and minimum concentration of protein and total solids, and optimum conditions evaluated as: seed to water ratio: 0.30 g/mL, extraction time: 16 min and extraction temperature: 52 °C. At the optimal conditions, 2.1 mg of thymol was extracted per kg of ajwain seeds. Eigenvalue analysis was also undertaken to corroborate the findings from numerical optimization. The numerically optimized result was validated with experimental results by conducting a separate set of experiments and observed that the experimental results are within the range of ±10% of the generated numerical optimization results, thereby confirming the optimum conditions.

Quantitative performance of 124I PET/MR of neck lesions in thyroid cancer patients using 124I PET/CT as reference

BackgroundIn patients with differentiated thyroid cancer (DTC), serial 124I PET/CT imaging is, for instance, used to assess the absorbed (radiation) dose to lesions. Frequently, the lesions are located in the neck and they are close to or surrounded by different tissue types. In contrast to PET/CT, MR-based attenuation correction in PET/MR may be therefore challenging in the neck region. The aim of this retrospective study was to assess the quantitative performance of 124I PET/MRI of neck lesions by comparing the MR-based and CT-based 124I activity concentrations (ACs). Sixteen DTC patients underwent PET/CT scans at 24 and 120 h after administration of about 25 MBq 124I. Approximately 1 h before or after PET/CT examination, each patient additionally received a 24-h PET/MR scan and sometimes a 120-h PET/MR scan. PET images were reconstructed using the respective attenuation correction approach. Appropriate reconstruction parameters and corrections were used to harmonize the reconstructed PET images to provide, for instance, similar spatial resolution. For each lesion, two types of ACs were ascertained: the maximum AC (max-AC) and an average AC (avg-AC). The avg-AC is the average activity concentration obtained within a spherical volume of interest with a diameter of 7 mm, equaling the PET scanner resolution. For each type of AC, the percentage AC difference between MR-based and CT-based ACs was determined and Lin’s concordance correlation analysis was applied. Quantitative performance was considered acceptable if the standard deviation was ± 25% (precision), and the mean value was within ± 10% (accuracy).ResultsThe avg-ACs (max-ACs within parentheses) of 74 lesions ranged from 0.20 (0.33) to 657 (733) kBq/mL. Excluding two lesions with ACs of approximately 1 kBq/mL, the mean (median) ± standard deviation (range) was − 4% (− 5%) ± 14% (− 28 to 29%) for the avg-AC and − 9% (− 11%) ± 14% (− 33 to 33%) for the max-AC. Lin’s concordance correlation coefficients were ≥ 0.97, indicating substantial AC agreement.ConclusionsQuantification of lesions in the neck region using 124I PET/MR showed acceptable quantitation performance to 124I PET/CT for AC above 1 kBq/mL. The PET/MRI-based 124I ACs in the neck region can be therefore reliably used in pre-therapy dosimetry planning.

How Long of a Dynamic 3'-Deoxy-3'-[18F]fluorothymidine ([18F]FLT) PET Acquisition Is Needed for Robust Kinetic Analysis in Breast Cancer?

To quantitatively evaluate the minimally required scanning time of 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT) positron emission tomography (PET) dynamic acquisition for accurate kinetic assessment of the proliferation in breast cancer tumors. Within a therapeutic intervention trial, 26 breast tumors of 8 breast cancer patients were analyzed from 30-min dynamic [18F]FLT-PET acquisitions. PET/CT was acquired on a Gemini TF 64 system (Philips Healthcare) and reconstructed into 26 frames (8 × 15s, 6 × 30s, 5 × 1min, 5 × 2min, and 2 × 5min). Maximum activity concentrations (Bq/ml) of volume of interests over tumors and plasma in descending aorta were obtained over time frames. Kinetic parameters were estimated using in-house developed software with the two-tissue three-compartment irreversible model (2TCM) (K1, k2, k3, and Ki; k4 = 0) and Patlak model (Ki) based on different acquisition durations (Td) (10, 12, 14, 16, 20, 25, and 30min, separately). Different linear regression onset time (T0) points (1, 2, 3, 4, and 5min) were applied in Patlak analysis. Ki of the 30-min data set was taken as the gold standard for comparison. Pearson product-moment correlation coefficient (R) of 0.9 was chosen as a limit for the correlation. The correlation of kinetic parameters between the gold standard and the abbreviated dynamic data series increased with longer Td from 10 to 30min. k2 and k3 using 2TCM and Ki using Patlak model revealed poor correlations for dynamic PET with Td ≤ 14min (k2: R = 0.84, 0.85, 0.86; k3: R = 0.67, 0.67, 0.67; Ki: R = 0.72, 0.78, 0.87 at Td = 10, 12, and 14min, respectively). Excellent correlations were shown for all kinetic parameters when Td ≥ 16min regardless of the kinetic model and T0 value (R > 0.9). This study indicates that a 16-min dynamic PET acquisition appears to be sufficient to provide accurate [18F]FLT kinetics to quantitatively assess the proliferation in breast cancer lesions.

Radiocesium contamination of the moss Hypnum plumaeforme caused by the Fukushima Dai-ichi Nuclear Power Plant accident

We investigated 134Cs and 137Cs activity concentrations in the common Japanese moss species Hypnum plumaeforme collected from 32 sites within ca. 100 km radius of the Fukushima Dai-ichi Nuclear Power Plant. A total of 32 samples of H. plumaeforme were collected during the field surveys from November 2013 to September 2014. The maximum radiocesium activity concentrations in H. plumaeforme were 60.9 ± 1.8 kBq kg−1 for 134Cs and 123 ± 2.3 kBq kg−1 for 137Cs. The mean value for the 134Cs/137Cs was 1.17 ± 0.05, and the mean Tag value was 0.09 ± 0.13. Positive correlations were obtained between total 134Cs + 137Cs activity concentrations in H. plumaeforme and the air dose rate with a correlation coefficient (r) of 0.55 (P = 0.001), and between 137Cs activity concentration in H. plumaeforme and 137Cs deposition density on soil with r of 0.55 (P = 0.001). These results suggest that the perennial moss species H. plumaeforme could be more suitable and useful as a qualitative indicator for the radiocesium pollution compared to vascular plants spreading over the lowlands including human habitation in Fukushima Prefecture.

Quantitative analysis of phantom studies of 111In and 68Ga imaging of neuroendocrine tumours

BackgroundNuclear medicine imaging of neuroendocrine tumours is performed either by SPECT/CT imaging, using 111In-octreotide or by PET/CT imaging using 68Ga-radiolabelled somatostatin analogs. These imaging techniques will give different image quality and different detection thresholds for tumours, depending on size and activity uptake. The aim was to evaluate the image quality for 111In-SPECT and 68Ga-PET imaging, i.e. the smallest volume possible to visualize for different source-to-background activity ratios. The accuracy of quantification of lesion volume and activity was also investigated to develop an objective evaluation for radionuclide therapy eligibility.The phantom study was performed using the NEMA IEC Body Phantom with six hot spheres having inner diameters of 10, 13, 17, 22, 28, and 37 mm, filled with either 68Ga or 111In with sphere-to-background ratios (SBRs) of no background activity, 5:1, 2.5:1, and 1.25:1. Activity ratios of 1.25:1 and 2.5:1 are clinically found for lesions close to the liver and spleen. Clinical acquisition and reconstruction protocols were applied. Line profiles were drawn to evaluate the smallest detectable volume within a given SBR. Recovery curves based on threshold-based VOIs, threshold-based VOIs adapted to the background and CT-based ROIs were obtained for all SBRs and sphere diameters, allowing for quantification.ResultsThe 10-mm sphere was not possible to detect in SPECT images. It was detectable in PET images for SBRs of 2.5:1 and higher. In a background corresponding to the activity uptake in the liver, spheres larger than 22–37 mm were detectable in the 111In-SPECT images and spheres larger than 13–22 mm were detectable in the 68Ga-PET images. The maximum activity concentration was accurately quantified for spheres larger than 22 mm in the PET images; however, the quantification was impaired by sphere size and background activity.ConclusionsIt was not possible to detect the 10-mm sphere in any of the SPECT images. In a background corresponding to the activity uptake in the liver, spheres larger than approximately 30 mm were visible in the 111In-SPECT images and spheres larger than approximately 17 mm were visible in the 68Ga-PET images. Sphere diameter and background activity strongly affect the possibility of a correct quantification.

Modelling Radionuclides Transport in a Groundwater System Around a Goldmine Site in Burkina Faso

Radionuclides transport in groundwater system is described using a numerical method in MatLab. The activity concentration and annual committed effective dose (ACED) to the public from consumption of the natural radionuclides 238 U and 232 Th were determined. The maximum activity concentrations were around 0.3 Bq/L, and 0.08 Bq/L for 238 U and 232 Th respectively. The activity concentration tends to be neglected at 1500 m for 238U and 1000 m for 232 Th. from the discharged point. The corresponding annual committed effective dose estimated was 0.022 mSv/y. The results obtained for this study are far below the recommended levels of 10.0 Bq.L -1 and 1.0 Bq.L -1 for 238 U and 232 Th respectively for drinking water established by the WHO and 1 mSv per year dose limit recommended by the ICRP for public radiation exposure.

ATMOSPHERIC PARTICULATE AND XENON RADIOISOTOPES MONITORING OVER CANADA AND HEALTH IMPACT ESTIMATION BEFORE AND AFTER THE FUKUSHIMA NUCLEAR ACCIDENT.

This article presents the results of atmospheric radioactivity monitoring obtained by three Canadian radiation monitoring stations before, after and during Fukushima-Daiichi accident. It includes 210Pb, 212Pb and 7Be (naturally occurring radionuclides) and 131I, 132I, 129Te, 129mTe, 132Te, 134Cs, 136Cs, 137Cs and 133Xe (Fukushima contaminants). The maximum activity concentrations were in range of 2.3-3.7 Bq/m3 for 133Xe; 2.0-4.4 mBq/m3 for 131I in aerosol form; 0.27-0.83 mBq/m3 for 137Cs depending on monitoring locations. The effective inhalation and cloudshine dose due to the Fukushima contaminants for an adult was estimated in range of 0.8-1.1 × 10-4 mSv, out of which the proportions of 133Xe and 131I were in range of 64-83% and 15-33%, respectively. During this period, the dose resulting from exposure to naturally occurring radionuclides was estimated in range of 0.60-1.8 × 10-3 mSv, one order of magnitude higher than those of the Fukushima contaminants. The dose impact from exposure to the Fukushima contaminants was negligible.

Catalyzed Oxidation of Chlorine and Bromine in Room Temperature Chloroaluminate and Bromoaluminate Melts

The use of haloaluminate room temperature molten salts has potential for interesting battery chemistries. This is particularly true for acidic (excess Lewis acid, e.g. AlCl3, over the organic chloride salts) compositions. In that case, Al is readily plated and stripped, as we discussed some time ago.1 A particularly interesting battery combination arises when the aluminum negative electrode is paired with the evolution of the halogen from the acidic melt. In that case, maximum redox active species concentration is achieved and maximum voltage can be obtained since the entire electrochemical window is utilized. However, several issues with chlorine evolution are known. First, in an acidic melt chlorination of imidazolium cations occurs. This can be partly mitigated by appropriate modification of the cation. A second problem is the somewhat sluggish catalysis of chlorine evolution observed on carbon surfaces. In this work, we report results of efforts to improve on the latter aspect. Specifically, we describe the catalysis of chlorine evolution by catalytically active surfaces. In particular, we show significant enhancements in onset potential for chlorine evolution using supported Ru catalysts. In Figure 1, we compare the chlorine evolution voltammetry in 1.5:1.0 AlCl3:EMIC on bare glassy carbon to that observed on the same electrode coated with a sample of 60 wt% Ru on multiwalled nanotubes (prepared in-house). The onset of chlorine evolution occurs on the order of 300 mV less positive with the supported Ru catalysts. We have deposited the Ru on various carbon structures to explore the applicability of this catalyst system for batteries and flow batteries. Studies of the same reaction on Pt electrodes show that the supported Ru nanoparticles have similar activity to that of Pt for this reaction. In addition, similar results were also obtained for bromine evolution. In that case, the lower volatility of the product allowed us to readily observe the bromine oxidation on the reverse scan. This reaction is substantially more reversible on these catalyzed surfaces. Figure 1: Voltammetry of 60%Ru on MWNT on glassy carbon compared to that of the bare glassy carbon electrode. Figure 1

Impact of air masses on the distribution of 210Pb in the southeast of Iberian Peninsula air

The current research has been developed in the southern of the Iberian Peninsula in order to better understand the atmospheric processes and also the influence of the air masses origin and pathways in the transport of 210Pb-aerosols in the atmosphere. Simultaneous measurements of the radionuclides 7Be and 210Pb on airborne have been routinely carried out at Granada (Spain 37.177N, 3.598 W, 687 m a.s.l.) from 2010 to 2014. The long term monitoring evolution on 210Pb is discussed in this study and also the useful ratio 7Be/210Pb.The maximum monthly activity concentration for 210Pb at ground level in Granada was detected during summer and early autumn (September), whereas minimum activity was measured in the winter. The monthly mean activity concentration for 210Pb was 617.8 ± 33.0 μBq·m−3. The results show that the annual average 210Pb concentrations in samples collected during the same period were almost constant.The lowest activity concentration for 210Pb are associated with maritime air masses coming from Atlantic and Norwest of Spain, while the highest activity concentrations for this radiotracers were positively correlated with the arrival of mineral dust linked to continental air masses coming from Mediterranean, Africa and Local area. The concentrations values show a nice agreement with the relevant reported results.

Radioactive caesium (134Cs and 137Cs) in mushrooms of the genus Boletus from the Reggio Emilia in Italy and Pomerania in Poland

ABSTRACTActivity concentrations of 134Cs and 137Cs were determined in mushrooms of the Boletus species B. aereus, B. reticulatus, B. appendiculatus, B. calopus, B. edulis, B. erythropus, B. fechtneri, B. pinophilus, B. pseudoregius, B. rhodopurpureus, B. rhodoxanthus collected in the Reggio Emilia, Italy, in 1993 and 1994 and in B. edulis collected in Pomerania in northern Poland in the period from 1995–2015. Boletus edulis from the Reggio Emilia showed presence of 137Cs at 330 ± 220 Bq kg−1 dry biomass in 1993 and at 370 ± 180 Bq kg−1 dry biomass in 1994. In B. edulis sampled in the Reggio Emilia in 1993 and 1994, the pre-Chernobyl 137Cs from global fallout amounted to 39–46 % of the total activity concentrations of isotope 137Cs. B. edulis from Pomerania contained 137Cs in caps at 270 ± 15 Bq kg−1 dry biomass in 1995, and in whole fruiting bodies it was found to be 470 ± 9 Bq kg−1 dry biomass in 2015. The activity concentrations of 137Cs determined in fruiting bodies of B. edulis from Pomerania fluctuated but persisted over the period from 1995 to 2015, while the maximum activity concentrations were well below the tolerance limit of 600 Bq kg−1 fresh product.

Radionuclide pollution inside the Fukushima Daiichi exclusion zone, part 1: Depth profiles of radiocesium and strontium-90 in soil

In June 2013 and July 2014, soil samples were collected from unremediated locations within Fukushima prefecture, with special focus on the Fukushima exclusion zone. The soil samples were analyzed for radiocesium by gamma spectroscopy, and then 90Sr by liquid scintillation counting (LSC) after ion specific extraction chromatography. Activity concentrations are compared between sampling years, sampling sites, and soil layers, revealing a general downward trend in activities but also some inconsistencies. Maximum activity concentrations of 137Cs in soil were found in close vicinity of the gate of Fukushima Daichi Nuclear Power Plant and reached up to 106 Bq·kg−1 in 2013. Thirteen months later, these maximum levels were lower by a factor of at least 5. Activity ratios of 90Sr/137Cs were usually around 2 · 10−4, but locally increased to the 10−3 range, and in one spot even to the 10−1 range. Finally, attempts were made to analyze rare radionuclides in environmental samples from this area, in particular tritium (3H) and 60Fe, however no traces were found in the vegetation and soil samples, respectively.

Temporal changes in radiocesium contamination derived from the Fukushima Dai-ichi Nuclear Power Plant accident in oceanic zooplankton in the western North Pacific

We investigated temporal changes of the contamination of oceanic zooplankton with radiocesium (134Cs and 137Cs) derived from the Fukushima Dai-ichi Nuclear Power Plant accident one month to three years after the accident at subarctic and subtropical stations (1900 and 900–1000 km from the plant, respectively) in the western North Pacific. The maximum activity concentrations of 137Cs in zooplankton were two orders of magnitude higher than the pre-accident level. In the first four months after the accident, the activity concentrations of radiocesium in subtropical zooplankton decreased rapidly, but no similar change was observed at the subarctic station. The radiocesium derived from atmospheric deposition rapidly decreased as a result of seawater mixing. Thus, most of the subtropical zooplankton (with short lifespans) that had taken up radiocesium just after the accident were probably replaced by newly hatched zooplankton within four months of the accident, whereas subarctic zooplankton (with long lifespans) that were highly contaminated with radiocesium were still alive four months after the accident. By the end of the study, 137Cs activity concentrations in subtropical zooplankton were still high, whereas the activity concentrations in subarctic zooplankton had decreased to nearly the pre-accident level. The former concentrations were probably influenced by a secondary supply of radiocesium via advection of subtropical mode water that was highly contaminated with Fukushima-derived radiocesium. Unexpectedly, at the subarctic station, the radiocesium activity concentrations in surface zooplankton were lower than those in subsurface zooplankton, whereas the opposite relationship was observed in surface and subsurface seawater. Because carnivores predominated in the subsurface zooplankton community, we hypothesize that the higher radiocesium activity concentrations in subsurface zooplankton were influenced by bioaccumulation. We conclude that radiocesium activity concentrations in zooplankton are influenced not only by the supply of radiocesium to the environment but also by the characteristics of the zooplankton community.

A novel electro-chlorinator using low cost graphite electrode for drinking water disinfection

A unique electro-chlorination reactor was designed with six numbers each of cylindrical shaped graphite anodes and stainless steel cathodes. A series of experiments were run in the laboratory scale applying lower current densities. Maximum active chlorine concentration of 0.75 mg/l was obtained at an optimum current density of 1.5 mA/cm2 from an available chloride concentration of 8.5 mg/l found naturally in the tap water. It was observed that with an increase in the current density, there was a marked decrease of chloride conversion from 50 to 42%. The maximum chloride conversion rate of 57.3% was achieved corresponding to an electrolysis time of 30 min. There was no marked change in pH after the electrolysis which may be attributed to the neutralization of hydroxyl ions generated at the cathode with the protons spitted at the anode. A maximum energy consumption of 0.083 kWh/m3 was required for generating a maximum active chlorine concentration of 2 mg/l from chloride concentration of 50 mg/l added externally in the water. After a continuous operation of 3 months, it was found that the graphite electrodes were corroded at the rate of 0.005 mm/h. A strong positive Pearson correlation of 0.988 was obtained among the parameters current density, chloride concentration, time, pH and active chlorine, whereas a negative correlation coefficient of −0.902 was obtained between electrolysis time and formation rate of active chlorine. The present work provides a simple reactor design strategy to use affordable graphite electrodes in the field application of electrochemical point of use of drinking water disinfection.

Natural radioactivity investigation in Dam sediments of northeast Algeria using gamma spectroscopy

Current research paper intends to estimate the natural radioactivity levels in sediments samples collected from Beni Haroun Dam in the northeast Algeria, using high resolution HPGe detector. The mean activity concentrations values measured for the radionuclides 232Th, 226Ra and 40K are 18.9 ± 1.9, 37.3 ± 2.7 and 149.9 ± 5.5 Bq/kg, respectively. The 137Cs anthropogenic radionuclide has been observed with maximum activity concentration value of 0.8 ± 0.4 Bq/kg, which is considered an insignificant amount. In order to assess the radiological threat of gamma radiations emitted by these radionuclides on the health of the population, absorbed dose rate, annual effective dose equivalent and radiation hazard indices were had been calculated. The obtained values are compared with the world wide average ones.