Study of 222−220Rn Measurement Systems Based on Electrostatic Collection by Using Geant4+COMSOL Simulation

Using Monte Carlo (with Geant4) and COMSOL simulations, the authors have defined a useful tool to reproduce the alpha spectroscopy of 222Rn, 220Rn and their ionized daughters by measurement systems based on electrostatic collection on a silicon detector, inside a metallic chamber. Several applications have been performed: (i) simulating commercial devices worldwide used, and comparing them with experimental theoretical results; (ii) studying of realization of new measurement systems through investigation of the detection efficiency versus different chamber geometries. New considerations and steps forward have been drawn. The present work is a novelty in the literature concerning this research framework.

High resolution plutonium-239/240 mixture alpha spectroscopy using centrifugally tensioned metastable fluid detector sensor technology

This paper presents a novel and rapid, wet chemistry technique for spectroscopically detecting trace (∼10−3 Bq mL−1) level alpha emitting radionuclides mixtures with under 10 keV alpha energy resolution – with 100% gamma–beta rejection.

241Am and 137Сs in the Khoiniki district of Belarus: updated radiological assessment of the local existing exposure situation

The results covered in this paper relate to the “Khoiniki” research sub-unit of a larger-scale sequence of studies focused on the local assessments of the present-day 241Am and 137Cs concentrations in the soils and locally produced foods, with the estimation of the public internal radiation doses in the residential areas of the Gomel region of the Republic of Belarus most closely adjacent to the ChNPP resettlement zone. The objective was to make a conservative estimate of a committed annual dose of internal exposure from 241Am and 137Сs received by the villagers of 96 farmsteads in 30 settlements of the private sector of Khoiniki countryside through both, inhalation and consumption of local foodstuffs. The results obtained in this study include an update of the existing contamination levels of 241Am and 137Сs present in the local soils and foods grown or produced in private backyards and households. 241Am in food samples was determined by alpha-spectroscopy radiochemical analysis with the use of selective extraction-chromatographic resins. Gamma-spectrometry techniques were used to measure 241Am in soil samples and 137Сs in soil and food samples. Based on our findings, the present-day deposition density of 241Am in the soils does not exceed 4 kBq/m2 , while the values of 137Cs contamination are by one to two orders of magnitude higher than that of 241Am and vary between 30 and 500 kBq/m2 . Generally, the values of activity concentration of 241Am detected in local soils are well within 10 Bq/kg in the majority of inspected villages, with the exception of three sites where higher levels of 241Am contamination is soils were detected ranging from 14 to 16 Bq/kg. The ambient dose rates in the countryside range from 0.05 to 0.38 μSv/hour, with the average of 0.15 μSv/hour. No cases of 137Сs contamination above the established reference levels of 80, 100 and 90 Bq/ kg have been found in the local food samples of, respectively, potatoes, vegetables (incl. roots and tubers) and grains. The content of 241Am in the staple foods produced in the area varies from single digits to tenths of mBq/ kg, which is less by three orders of magnitude than 137Сs activities concentrationd found in the same staples. Of the two pathways contributing to the local committed internal exposure from 241Am, the dominant one is through inhalation (0.006–0.038 mSv/year) prevailing over the consumption pathway of this same radioisotope by at least one order of magnitude. At the time of gardening and other household field works, the existing levels of 241Am contamination in soils are estimated to produce from 85 to 98% of the internal radiation dose received by individuals from inhaling the total of 241Am and 137Сs. The maximum committed annual doses of internal exposure from 137Сs are estimated to be above 1 mSv/year in 6 out of 30 villages engaged in our study. At the same time, the estimated internal radiation dose due to 241Am does not surpass 0.04 mSv/year. The 137Сs major contribution to the internal exposure of villages in the Khoiniki countryside is through food consumption.

Radon concentration measurement in water reservoirs for some areas of north Baghdad by RAD7

Radon is a naturally occurring, odorless, colorless, radioactive, tasteless, and noble gas. Radon concentrations have been measured by the usage of alpha spectroscopy (RAD-7). The RAD-7 measuring process is based on detecting alpha particles produced from the disintegration of radon and its products using a solid-state alpha detector (usually silicon), and then converting alpha radiation directly to an electrical signal. The radioactivity of radon gas was measured in forty-two samples from reservoir water for different areas north of Baghdad utilizing a RAD7 detector. This study proved that the high value of radon concentrations was less than the permissible limit as recorded by the World Health Organization.

Investigations on the Interaction of EDTA with Calcium Silicate Hydrate and Its Impact on the U(VI) Sorption

The interaction of EDTA with calcium silicate hydrate (C-S-H) and its impact on the sorption of U(VI) by C-S-H in the presence of EDTA at varying concentrations has been investigated under N2 and ambient atmosphere. The solid phase characterization was performed by FTIR, XRD and TGA measurements and the uranium concentration in solution has been determined by alpha-spectroscopy. At increased EDTA concentrations ([EDTA] > 0.1 M) calcium is complexed and extensively extracted from the solid resulting in a quantitative dissolution of the Ca(OH)2 phase and deterioration of C-S-H. At lower EDTA concentrations ([EDTA] ≤ 0.01 M), EDTA is sorbed into the solid phase and the associated adsorption capacity (qmax = 0.67 mol/kg) has been evaluated by fitting the corresponding data with the Langmuir isotherm model. The incorporation of EDTA in the C-S-H matrix was corroborated by FTIR, XRD and TGA measurements. Regarding the effect of EDTA on the U(VI) sorption by C-S-H, evaluation of the experimental data reveal a significant decrease of the Kd values in the presence of EDTA most probably due to the stabilization of U(VI) in the form of U(VI)-EDTA complexes in solution. Under ambient conditions a further decrease of the Kd values is observed because of the formation of U(VI)-carbonato complexes related to CO2 dissolution and hydrolysis.

Radon Concentration in Water and Health Threat to Region of Balakot-Bagh (B-B) Fault Line, Lesser Himalayas, North Pakistan

The current study was carried out near and surrounding fault line areas of Balakot-Bagh (B-B). The study aimed to find radon concentration levels in drinking water sources near and away from the fault line. The comparison was carried out for the radon level in those samples taken from the area near with those taken away from the fault line. Also, to evaluate health hazard from these drinking water to the people of the area. This area had received an earthquake of magnitude 7.6 in 2005. An active technique, RAD-7, based on alpha spectroscopy was used. The study period for the current study was three months, from 16th May to 15th August 2020. Radon concentrations were found higher in bore water with the mean value of 20.6 BqL− 1. These were 19.5 BqL− 1 and 9.3 BqL− 1 in spring and surface water, respectively. The mean value in all type of sources in the study area was 16.5 BqL− 1 which is higher than the maximum contaminated level of 11.1 BqL− 1 recommended by the U.S. The calculated doses from the radon levels were 0.0532 mSv, 0.0562 mSv and 0.0254 mSv and 0.0449 mSv, respectively.

Lyman-alpha spectroscopy of extreme [O iii] emitting galaxies at z ≃ 2-3: implications for Lyα visibility and LyC leakage at z > 6

ABSTRACT Spectroscopic observations of massive z > 7 galaxies selected to have extremely large [O iii] + H β equivalent width (EW ∼1500 Å) have recently revealed large Ly α detection rates, in contrast to the weak emission seen in the general population. Why these systems are uniquely visible in Ly α at redshifts where the intergalactic medium (IGM) is likely significantly neutral is not clear. With the goal of better understanding these results, we have begun a campaign with MMT and Magellan to measure Ly α in galaxies with similar [O iii] + H β EWs at z ≃ 2–3. At these redshifts, the IGM is highly ionized, allowing us to clearly disentangle how the Ly α properties depend on the [O iii] + H β EW. Here, we present Ly α EWs of 49 galaxies at z = 2.2–3.7 with intense [O iii] + H β line emission (EW = 300–3000 Å). Our results demonstrate that strong Ly α emission (EW >20 Å) becomes more common in galaxies with larger [O iii] + H β EW, reflecting a combination of increasingly efficient ionizing photon production and enhanced transmission of Ly α. Among the galaxies with the most extreme [O iii] + H β emission (EW ∼1500 Å), we find that strong Ly α emission is not ubiquitous, with only 50 per cent of our population showing Ly α EW >20 Å. Our data suggest that the range of Ly α strengths is related to the observed ellipticity, with those systems that appear edge-on or elongated having weaker Ly α emission. We use these results to interpret the anomalous Ly α properties seen in z > 7 galaxies with extreme [O iii] + H β emission and discuss implications for the escape of ionizing radiation from these extreme line emitting galaxies.

Doppler imaging detects bacterial infection of living tissue

Living 3D in vitro tissue cultures, grown from immortalized cell lines, act as living sentinels as pathogenic bacteria invade the tissue. The infection is reported through changes in the intracellular dynamics of the sentinel cells caused by the disruption of normal cellular function by the infecting bacteria. Here, the Doppler imaging of infected sentinels shows the dynamic characteristics of infections. Invasive Salmonella enterica serovar Enteritidis and Listeria monocytogenes penetrate through multicellular tumor spheroids, while non-invasive strains of Escherichia coli and Listeria innocua remain isolated outside the cells, generating different Doppler signatures. Phase distributions caused by intracellular transport display Lévy statistics, introducing a Lévy-alpha spectroscopy of bacterial invasion. Antibiotic treatment of infected spheroids, monitored through time-dependent Doppler shifts, can distinguish drug-resistant relative to non-resistant strains. This use of intracellular Doppler spectroscopy of living tissue sentinels opens a new class of microbial assay with potential importance for studying the emergence of antibiotic resistance.

Actinide in Air (Rn-Progeny Rejected) Alpha Spectroscopy with Tensioned Metastable Fluid Detectors

This article discusses outcome of research for deriving a methodology and apparatus for ascertaining for the presence of ultra-trace level actinides in air from their alpha emission signatures, while remaining blind to the relatively large (1,000× higher activity) alpha emissions from Rn-progeny. Apparatus and techniques were developed to collect and characterize alpha-emitting nuclides of Rn-progeny and actinides in air on a polycarbonate 3 m pore size continuous air monitor (CAM) filter. A wet-chemistry approach was developed and validated for successfully separating the Rn-progeny alpha emitting isotopes of Po-214 and Po-218, while extracting the actinides (U, Pu, Am) in a fluid mixture that is suitable for conduct of alpha spectroscopy with a centrifugally tensioned metastable fluid detector (CTMFD). The resulting α-TMFD technology was compared against the state-of-art "Alpha-SentryTM" Continuous Air Monitor (CAM) system commonly utilized world-wide. Results indicate that the α-TMFD technology can potentially offer complementary and superior performance in multiple performance categories, and ~18× improvement in the time to detect [e.g., at 0.02 Derived Air Concentration (DAC) within ~3 h, vs ~70 h for Alpha-SentryTM] for actinides of interest while also remaining ~100% blind to ~103× higher Rn-progeny background - with the added potential for offering few keV scale energy resolution without resorting to peak shape fitting, vs ~300-400 keV for existing CAM systems.