Low Levels Of Radioactivity Research Articles

Photopeak Efficiency and Coincidence Summing Factors for HPGe Detectors Using Bulk Sources.

In the field of gamma-ray spectroscopy with high-purity germanium detectors, used to measure the activity when the sample to be measured has low radioactivity, volumetric sources are widely used. To determine the sample activity, the full-energy peak efficiency is needed. Bulk sources are very common for low-level radioactivity measurements in activation analysis and environmental samples. The main problem with these measurements is that coincidence effects are large for close source-detector geometries. Ignoring these effects can lead to an error typically of a factor of 2 in the determination of Co and Y activity, which was used in this work in the calibration process. Extensive experimental readings have been carried out, and bulk gamma aqueous sources containing several radionuclides covering the energy range from 60 to 1,840 keV were used. By comparison, the experimental (present work) and theoretical (published) full-energy peak efficiency values are in good agreement; the overall percentage error is less than 6%.

Radiohalogenated Neopentyl Derivatives: A Novel Scaffold for Radioiodinated and astatinated Compounds of High Stability to In Vivo Dehalogenation

Astatine-211 (211At) is an α-emitting radionuclide appropriate for medical use. To expand the application of 211At-labeled compounds to radiotheranostics, we developed neopentyl derivatives as a novel scaffold for radioiodination and astatination. The stability, biodistribution, and metabolism of 125I-labeled neopentyl derivatives were evaluated. The biodistribution of a 211At-labeled compound was compared with its 125I-labeled counterpart. Two iodinated neopentyl derivatives with a nitroimidazole group were synthesized; N-[2,2-bis(hydroxymethyl)-2-(iodomethyl)ethyl]-2-nitroimidazole (BHIN) and N-[2,2-diethyl2-(iodomethyl)ethyl]-2-nitroimidazole (DEIN). The radioiodination was conducted by reacting their sulfonyl precursors with Na[125I]I. The stability to the nucleophilic substitution was evaluated in a 10 mM glutathione solution at pH 7.4 for 24 h. The biodistribution of [125I]BHIN or [125I]DEIN was evaluated in normal male mice. Urine samples collected for 6 h after injection were analyzed by a reversed-phase HPLC. [211At]N-[2,2-bis(hydroxymethyl)2-(astatomethyl)ethyl]-2-nitroimidazole ([211At]BHAN) was prepared under the procedure similar to [125I]BHIN and was subjected to biodistribution study in normal male mice. Both 125I-labeled compounds were obtained in 40 to 90% radiochemical yields and over 98% radiochemical purities after HPLC purification. Both 125I-labeled compounds remained stable after incubation in a glutathione solution for 24 h (>95%), indicating that the two radioiodinated compounds possess high stability to the nucleophilic substitution reaction. In biodistribution study, while [125I]DEIN showed high radioactivity levels in the neck (10.60 ± 0.03 %ID at 24 h), such radioactivity was hardly observed with [125I]BHIN (0.03 ± 0.02 %ID at 24 h). Both radioiodinated compounds were mainly excreted into urine. The analysis of urine samples indicated that while the majority of the radioactivity was present as [125I]I- for [125I]DEIN, [125I]BHIN showed the majority of the radioactivity as the glucuronide-conjugate. [211At]BHAN was obtained in about 14% radiochemical yields and over 98% radiochemical purities after HPLC purification. [211At]BHAN exhibited the pharmacokinetics similar to [125I]BHIN with low radioactivity levels in the neck and the stomach. Both 125I-labeled compounds possessed high stability to the nucleophilic substitution. The presence of the hydroxyl groups in BHIN provided further stabilization to the enzymatic dehalogenation reaction. [125I]BHIN and [211At]BHAN exhibited similar pharmacokinetics each other with dehalogenation being hardly observed. These findings indicate that the neopentyl derivatives would serve as a useful scaffold to develop a radiotheranostic pair consisting of radioiodinated and 211At-labeled compounds.

Natural radioactivity of barite concrete shields containing commonly used supplementary materials

The recycling of hazardous materials within new composites has a sustainable importance as it contributes on the reduction of high radionuclide concentrations. In this study, the effect of cementitious materials i.e. viscosity modifier, silica fume and fly ash on the 226Ra, 232Th and 40K activity levels of barite concrete shields was researched by using different mixing compositions in terms of binder content, w/b ratio and the amount of supplementary cementitious materials. In comparison to cement, silica fume and fly ash used in the production of concrete shields were found to have significantly higher activity levels of 40K, as well as 226Ra, 232Th and 40K, respectively. The 226Ra, 232Th and 40K activity levels of concrete shields range between 2.2 and 20.7 Bq kg−1; 2.6 and 7.0 Bq kg−1; 51.5 and 89.3 Bq kg−1, respectively. These activity values were found similar or less than those of building materials in the world. These satisfactory results are mostly caused by the barite source which has lower radioactivity levels. The concrete mixture details used in the study caused significant variation in the natural radioactivity of barite concrete shields. The introduction of silica fume which has high 40K activity levels and fly ash with high 226Ra, 232Th and 40K activity levels compared to cement and barite aggregate, significantly increased the radiological hazard parameters, although all results were found to be below the limits recommended by international reports. In conclusion, 226Ra activity levels of the concrete shields were significantly increased (up to 8.4 times) by the variation of mix design parameters used in comparison with concrete mixtures that have the least 226Ra activity level. The 232Th and 40K activity levels were as well increased in relatively less amounts (1.7 and 0.73 times higher, respectively).

High radioactivity levels of radium isotopes in groundwater of the Disi aquifer

Elevated levels of groundwater radioactivity found in fifteen wells from the Disi aquifer in Jordan and in the main collection reservoir were investigated. The estimated annual doses in the studied wells and the reservoir are 0.53 ± 0.02 mSv yr−1 and 0.62 ± 0.02 mSv yr−1, respectively. These values are higher than the 0.1 mSv yr−1 recommended by the World Health Organization and 0.5 mSv yr−1 recommended in the Jordanian standard. However, the measured dose after mixing with surface water has decreased. Filtered tap water is recommended for drinking since the analyzed samples showed extremely low levels of radioactivity.

EVALUATION OF RADIATION DOSES AND HAZARD INDICES IN CRUSHED ROCKS FROM SOME QUARRIES IN IBADAN SOUTHWESTERN NIGERIA.

The radiological assessment of rock samples from four quarry sites in Ibadan have been carried out. The mean activity concentrations of 40K, 226Ra and 232Th were 377.0±37.9, 17.7±3.6 and 4.98±2.1Bqkg-1, respectively, for Ratcon Quarry (RQ); 408.0±28.7, 16.6±1.6 and 10.6±2.3Bqkg-1, respectively, for Dekit Quarry; 388.0±26.6, 15.7±1.9 and 9.85±3.9Bqkg-1, respectively, for Hajaig Quarry; and 388.084±55.9, 16.2±3.9 and 12.1±3.8Bqkg-1, respectively, for NSCE Quarry (NQ). The highest mean outdoor effective dose of 0.038±0.005mSvy-1 and the minimum of 0.033±0.004mSvy-1 were obtained at NQ and RQ, respectively. The radiological hazard indices recorded in each site were <1.0. The results show lower radioactivity levels than the world average values; therefore, no serious radiological health effect is expected when the crushed rocks from the quarries are used for buildings construction.

A multi-channel beta–gamma coincidence counting system using well-HPGe and plastic scintillation detectors for radioactive Xenon measurements

Abstract A new type of multi-channel beta–gammacoincidence counting system was developed for the analysis of radioactive Xenon samples with low-level radioactivity . The proposed system consists of a state-of-the-art well-HPGe detector with a large well volume ( ∅ 28 mm × 40 mm) and a cylindrical plastic scintillation detector with an interior volume of 8.8 cm3. A two-dimensional beta–gamma coincidence histogram was obtained, and the beta–gamma coincidence counting efficiency was estimated using gaseous radioxenons and Monte Carlo simulation with the MCNP code. The energy resolution of the plastic scintillation detector for the 129.4 keV internal conversion electron was 29%, and the minimum detectable concentration for 131m Xe, 133Xe, 133m Xe, and 135Xe was calculated as 0.27 mBq/m3, 0.23 mBq/m3, 0.16 mBq/m3 and 0.24 mBq/m3 under the assumed conditions of a 20000 s measurement and a 10 m3 air sample with the beta–gamma​ coincidence mode, respectively.

Evaluation of A Novel GLP-1R Ligand for PET Imaging of Prostate Cancer.

Glucagon-like peptide 1 receptor (GLP-1R) is an important biomarker for diagnosis and therapy of the endocrine cancers due to overexpression. Recently, in human prostate cancer cell lines the receptor was also observed, therefore it may be a potential target for the disease. 18F-Al-NOTA-MAL-Cys39- exendin-4 holds great promise for GLP-1R. Therefore, the feasibility of the 18F-labeled exendin-4 analog for prostate cancer imaging was investigated. New probe 18F-Al-NOTA-MAL-Cys39-exendin-4 was made through one-step fluorination. Prostate cancer PC3 cell xenograft model mice were established to primarily evaluate the imaging properties of the tracer via small animal PET studies in vivo. Pathological studies and Western Blots were also performed. PC-3 prostate xenografts were clearly imaged under baseline conditions. At 30 and 60 min postinjection, the tumor uptakes were 2.90±0.41%ID/g and 2.26±0.32 %ID/g respectively. The presence of cys39-exendin-4 significantly reduced the tumor uptake to 0.82±0.10 %ID/g at 60 min p.i. Findings of ex vivo biodistribution studies were similar to those of in vivo PET imaging. The tumors to blood and muscles were significantly improved with the increase of time due to rapid clearance of the tracer from normal organs. Low levels of radioactivity were also detected in the GLP-1R positive tumor and normal organs after coinjection with excessive unlabeled peptides. Immunohistochemistry and Western Blots results confirmed that GLP-1R was widely expressed in PC-3 prostate cancers. 18F-Al labeled exendin-4 analog might be a promising tracer for in vivo detecting GLP-1R positive prostate cancer with the advantage of facile synthesis and favorable pharmacokinetics. It may be useful in differential diagnosis, molecularly targeted therapy and prognosis of the cancers.

Evaluation of elemental concentrations of uranium, thorium and potassium in top soils from Kuwait

Abstract Top soil samples across the state of Kuwait numering ninety were collected and analysed using gamma-ray spectrometry, to evaluate the elemental concentration of 238U, 232Th and 40K and their depletion/enrichment. Results of elemental concentration ranges from 0.48 to 2.61 mg/kg, 0.87–5.23 mg/kg, and 0.24–2.23%, with a mean values of 1.39 mg/kg, 3.47 mg/kg, and 1.18%, for the 238U, 232Th and 40K, respectively. Further analysis was conducted amongst the five identified soil types, i.e. Aquisalids (S1), Calcigypsids (S2), Petrocalcids (S3), Petrogypsids (S4), and torripsamment (S5). The highest radioactivity concentrations from both uranium and thorium were recorded in the S2 (Calcigypsids) soil, with a value of 1.71 (mg/kg) and 4.45 (mg/kg), respectively. Minimum and maximum values of 40K are 1.1(%) and 1.27(%) and is prevalent in Aquisalids (S1) and Petrocalcids (S3) soil types, respectively. Ratios of elemental concentration for 232Th/238U, 40K/238U, 40K/232Th across the soil types are 2.53, 0.09 and 0.03, with a correlation coefficient of 0.92, 0.34, and 0.38, respectively. A progressively higher 232Th/238U ratio is observed moving south-wards, indicating lower 238U content in soils from the south relative to the northern part. Overall results indicate Kuwait to be relatively an area with low level of natural radioactivity.

Radiohalogenated Neopentyl Derivatives: A Novel Scaffold for Radioiodinated and astatinated Compounds of High Stability to In Vivo Dehalogenation

Astatine-211 (211At) is an α-emitting radionuclide appropriate for medical use. To expand the application of 211At-labeled compounds to radiotheranostics, we developed neopentyl derivatives as a novel scaffold for radioiodination and astatination. The stability, biodistribution, and metabolism of 125I-labeled neopentyl derivatives were evaluated. The biodistribution of a 211At-labeled compound was compared with its 125I-labeled counterpart. Two iodinated neopentyl derivatives with a nitroimidazole group were synthesized; N-[2,2-bis(hydroxymethyl)-2-(iodomethyl)ethyl]-2-nitroimidazole (BHIN) and N-[2,2-diethyl2-(iodomethyl)ethyl]-2-nitroimidazole (DEIN). The radioiodination was conducted by reacting their sulfonyl precursors with Na[125I]I. The stability to the nucleophilic substitution was evaluated in a 10 mM glutathione solution at pH 7.4 for 24 h. The biodistribution of [125I]BHIN or [125I]DEIN was evaluated in normal male mice. Urine samples collected for 6 h after injection were analyzed by a reversed-phase HPLC. [211At]N-[2,2-bis(hydroxymethyl)2-(astatomethyl)ethyl]-2-nitroimidazole ([211At]BHAN) was prepared under the procedure similar to [125I]BHIN and was subjected to biodistribution study in normal male mice. Both 125I-labeled compounds were obtained in 40 to 90% radiochemical yields and over 98% radiochemical purities after HPLC purification. Both 125I-labeled compounds remained stable after incubation in a glutathione solution for 24 h (>95%), indicating that the two radioiodinated compounds possess high stability to the nucleophilic substitution reaction. In biodistribution study, while [125I]DEIN showed high radioactivity levels in the neck (10.60 ± 0.03 %ID at 24 h), such radioactivity was hardly observed with [125I]BHIN (0.03 ± 0.02 %ID at 24 h). Both radioiodinated compounds were mainly excreted into urine. The analysis of urine samples indicated that while the majority of the radioactivity was present as [125I]I- for [125I]DEIN, [125I]BHIN showed the majority of the radioactivity as the glucuronide-conjugate. [211At]BHAN was obtained in about 14% radiochemical yields and over 98% radiochemical purities after HPLC purification. [211At]BHAN exhibited the pharmacokinetics similar to [125I]BHIN with low radioactivity levels in the neck and the stomach. Both 125I-labeled compounds possessed high stability to the nucleophilic substitution. The presence of the hydroxyl groups in BHIN provided further stabilization to the enzymatic dehalogenation reaction. [125I]BHIN and [211At]BHAN exhibited similar pharmacokinetics each other with dehalogenation being hardly observed. These findings indicate that the neopentyl derivatives would serve as a useful scaffold to develop a radiotheranostic pair consisting of radioiodinated and 211At-labeled compounds.

Disposal of very low-level radioactive waste: Lithuanian case on the approach and long-term safety aspects

Decommissioning of nuclear power plants typically requires management of hundreds of thousands of cubic meters of waste with very low levels of radioactivity. Such very low-level waste (VLLW) is suitable for disposal in simple landfill type facilities.The only nuclear power plant in the Republic of Lithuania, the Ignalina NPP, was finally shut down at the end of 2009. Final management of the existing operational radioactive waste and that arising during the decommissioning will require the disposal of 60,000 m3 of very low-level short-lived solid waste. An overview of the implementation of the landfill disposal facility for very low-level radioactive waste at the Ignalina NPP site and the main aspects of long-term safety assessments based on national regulations as well as the IAEA's recommendations including the siting process are presented in this paper as well as a short description of the disposal concept and the characteristics of the waste intended for disposal in the landfill. Water pathway scenarios as well as intrusion scenarios have been investigated following an IAEA methodology. It has been defined that 14C is the greatest contributor to the total dose in the case of water pathway scenarios. In the case of intrusion scenarios, the main contribution to the total dose is from radionuclides 94Nb and 137Cs. In all the considered cases, the total value of the annual effective exposure dose remains quite well (orders of magnitude) below the value of the dose constraint established by regulations of Lithuania. Uncertainty analysis is carried out to define the influence of various factors on the obtained results of the safety assessment.

Developmental and hemocytological effects of ingesting Fukushima\u2019s radiocesium on the cabbage white butterfly Pieris rapae

High morphological abnormality and mortality rates have been reported in the pale grass blue butterfly, Zizeeria maha, since the Fukushima nuclear accident. However, it remains uncertain if these effects are restricted to this butterfly. Here, we evaluated the effects of ingesting cabbage leaves grown with contaminated soils from Fukushima on the development and hemocytes of the cabbage white butterfly, Pieris rapae. Contaminated cabbage leaves containing various low levels of anthropogenic 134Cs and 137Cs radioactivity (less than natural 40K radioactivity) were fed to larvae from Okinawa, the least contaminated locality in Japan. Negative developmental and morphological effects were detected in the experimental groups. The cesium (but not potassium) radioactivity concentration was negatively correlated with the granulocyte percentage in hemolymph, and the granulocyte percentage was positively correlated with the pupal eclosion rate, the adult achievement rate, and the total normality rate. These results demonstrated that ingesting low-level radiocesium contaminants in Fukushima (but not natural radiopotassium) imposed biologically negative effects on the cabbage white butterfly, as in the pale grass blue butterfly, at both cellular and organismal levels.

Measurement of absolute activation cross sections from carbon and aluminum for proton therapy

This experimental study aims to measure nuclear cross sections from natC and 27Al which serve as reference targets regarding radioactivation in proton therapy. Graphite and aluminum foils were activated in broad, quasi-monochromatic proton fields generated with the pencil-beam scanning technique. The γ-emissions were analyzed subsequently in a nearby γ-ray spectrometry facility designed for low-level radioactivity measurements. The number of incident protons was measured with a Faraday Cup. A detailed evaluation of the uncertainties was performed.The cross section for the natC(p,x)11C reaction at 100 MeV is (70.2 ± 1.6 (sys.) ± 0.2 (stat.)) mb. The production cross sections from 27Al at 100 MeV are (19.9 ± 0.4 ± 0.3) mb for 22Na and (11.5±0.3±0.1) mb for 24Na. The systematic uncertainties contribute 2.0%–2.4% of the quoted uncertainties (k=1) of cross sections. Concluding, radioactivation cross sections were measured with proton fields in a clinically commissioned environment. The measured activation cross sections from aluminum used for monitoring of the proton fluence agree with the averaged values compiled in nuclear reaction data bases. For proton-induced radioactivation from carbon the chemical purity of the target strongly affects the experimental results. The cross section for the production of 11C derived from a measurement with a high-purity graphite target is in line with the largest cross section obtained in prior studies.

The electronics of the energy plane of the NEXT-White detector

This paper describes the electronics of NEXT-White (NEW) detector PMT plane, a high pressure xenon TPC with electroluminescent amplification (HPXe-EL) currently operating at the Laboratorio Subterráneo de Canfranc (LSC) in Huesca, Spain. In NEXT-White the energy of the event is measured by a plane of photomultipliers (PMTs) located behind a transparent cathode. The PMTs are Hamamatsu R11410-10 chosen due to their low radioactivity. The electronics have been designed and implemented to fulfill strict requirements: an overall energy resolution below 1% and a radiopurity budget of 20 mBq unit−1 in the chain of 214Bi . All the components and materials have been carefully screened to assure a low radioactivity level and at the same time meet the required front-end electronics specifications. In order to reduce low frequency noise effects and enhance detector safety a grounded cathode connection has been used for the PMTs. This implies an AC-coupled readout and baseline variations in the PMT signals. A detailed description of the electronics and a novel approach based on a digital baseline restoration to obtain a linear response and handle AC coupling effects is presented. The final PMT channel design has been characterized with linearity better than 0.4% and noise below 0.4mV.

Risk and regulatory considerations for small modular reactor emergency planning zones based on passive decontamination potential

It has been argued that risk and performance-based approaches to licensing would be appropriate for Small Modular Reactors (SMRs) because their risk profiles differ from large-scale reactors. This is based on several factors including their limited electrical capacity of 300 MW, the below grade reactor vessel, and passive safety features. One design feature that can significantly reduce accident severity is the larger lateral surface area-to-volume (A/V) ratio of SMRs. Following a nuclear accident, this larger A/V ratio can increase the removal of radioactive particles due to natural phenomena compared to large light water reactors (LWRs). To quantify the improvements in safety, this work estimates the airborne radioactivity within containment and environmental dose exposure in a post-accident scenario for an advanced Generation III+ LWR (AP1000), a representative Generation II LWR (Surry), and an SMR. On average, the AP1000, Surry, and SMR produces 139, 153, and 104 curies/ft3 (182, 200, and 136 terabecquerels/m3) 75 min after a Loss-of-coolant-accident (LOCA). Using Monte Carlo simulations, the SMR produces less radioactivity per volume in containment than the AP1000 and Surry 84% and 96% of the time, respectively. On average, the AP1000, Surry, and SMR produces 84, 106, and 7 thousand curies/MWth (3.1, 3.9, and 2.5 petabecquerels/MWth) 75 min after a LOCA. The larger A/V ratio of the SMR plays a substantial role in reducing the radioactivity. While it is expected that the SMR would have a lower levels of radioactivity compared to the AP1000 and Surry, the SMR produces less radioactivity after normalizing by thermal reactor power and containment volume. With respect to environmental dose exposure, the US Environmental Protection Agency 1–5 rem (0.01–0.05 sieverts) Protective Action Guide (PAG) limits for whole body exposure is not exceeded at the 10-mile (16.1-km) EPZ using the mean estimates for the AP1000 and Surry. The iPWR does not exceed the 1 rem (0.01 sieverts) lower PAG limit for whole body exposure at the 5-mile (8-km) EPZ using the mean value. These findings can be used in conjunction with the improved analytical methods, found in the SOARCA study, to provide accurate and realistic estimates for exposure. This will help create a pathway to develop a regulatory basis for technology-neutral, risk-based approach to EPZs for iPWRs.

Simplified representative models for long-term flow and advective transport in fractured crystalline bedrock

Simplified representative models (SRMs) of the hydrogeological system at radioactive-waste repository sites are presented and demonstrated to give useful predictions of the key hydrogeological factors affecting long-term safety. The SRM is constructed from complex site-descriptive models, which have been developed to be consistent with detailed site information and data from short-term (with duration of days, weeks, up to months) field experiments, by keeping elements that are important for long-term predictions into thousands of years and simplifying features of less importance. The simplified approach relies only on fundamental hydrogeological principles and the mathematics can be kept relatively simple. The purpose of SRM is to provide a means of verifying predictions from complex numerical models, with an approach that is easy to evaluate and allows transparent evaluation of factors influencing long-term results. The approach is applied to evaluations of sites for two repositories in fractured crystalline bedrock in Sweden: one for spent nuclear fuel rod assemblies and one for waste with lower levels of radioactivity. The results indicate that the SRMs are able to yield results similar to those of calculations based on much more complex models. Further, the approach allows an evaluation of additional sources of uncertainty that are difficult or expensive to conduct with the complex models. These capabilities make SRMs a very useful and transparent tool for regulatory review.

Radioactivity, radiological risk and metal pollution assessment in marine sediments from Calabrian selected areas, southern Italy

The two most significant categories of physical and chemical pollutants in sediments (radionuclides and metals) were investigated in this article, in order to evaluate pollution levels in marine sediments from eight different selected sites of the Calabria region, south of Italy. In particular samples were analyzed to determine natural and anthropic radioactivity and metal concentrations, in order to assess any possible radiological hazard, the level of contamination and the possible anthropogenic impact in the investigated area. Activity concentrations of 226Ra, 232Th, 40K and 137Cs were measured by High Purity Germanium (HPGe) gamma spectrometry. The obtained results show that, for radium (in secular equilibrium with uranium), the specific activity ranges from ( $ 14 \pm 1$ ) Bq/kg dry weight (d.w.) to ( $ 54 \pm 9$ ) Bq/kg d.w.; for thorium, from ( $ 12 \pm 1$ ) Bq/kg d.w. to ( $ 83 \pm 8$ ) Bq/kg d.w.; for potassium, from ( $ 470 \pm 20$ ) Bq/kg d.w. to ( $ 1000 \pm 70$ ) Bq/kg d.w. and for cesium it is lower than the minimum detectable activity value. The absorbed gamma dose rate in air (D), the annual effective dose equivalent (AEDE) outdoor and the external hazard index ( $ H_{\rm ex}$ ) were calculated to evaluate any possible radiological risk, mainly due to the use of marine sediments for the beach nourishment. The results show low levels of radioactivity, thus discarding any significant radiological risk. Some metals (As, Cd, Crtot, Hg, Ni, Pb, Cu, Zn, Mn and Fe), that could be released into the environment by both natural and anthropogenic sources, were investigated through inductively coupled plasma mass spectrometry (ICP-MS) measurements and compared with the limits set by the Italian Legislation, to assess any possible contamination. Experimental results show that they are much lower than the contamination threshold value, thus excluding their presence as pollutants. The degree of sediment contaminations were quantified using enrichment factor (EF) and geoaccumulation index ( Igeo) for some potential hazardous elements. Results show that EF and Igeo values of As, Pb and Mn were the greatest among the studied metals. Data of this preliminary study could be helpful in the future to obtain background levels in marine sediments of the investigated region and to develop environmental regulatory frameworks.

Development of a Novel Single-Channel, 24 cm2, SiPM-Based, Cryogenic Photodetector

We report on the realization of a novel SiPM-based, cryogenic photosensor with an active area of 24 cm$^2$ that operates as a single-channel analog detector. The device is capable of single photon counting with a signal to noise ratio better than 13, a dark rate lower than $10^{-2}$ cps/mm$^2$ and an overall photon detection efficiency significantly larger than traditional photomultiplier tubes. This development makes SiPM-based photosensors strong candidates for the next generation of dark matter and neutrino detectors, which will require multiple square meters of photosensitive area, low levels of intrinsic radioactivity and a limited number of detector channels.

Chemical characterization and radiation exposure from the natural radioactivity in Romanian building materials

Abstract Buildings materials contain natural primordial radionuclides of 40K, 232Th and 226Ra (238U). The research measures activity concentrations of 40K, 232Th and 226Ra in different types of raw materials with different origins: volcanic, calcareous, zirconium minerals, silico-aluminous etc., used in Romanian building industry. This is important as these materials lead to an exposure of the public and workers from their ionizing radiations. Based on these activity concentrations an estimation of the radiological hazard is also made by analyzing radiological parameters such as radium equivalent activity (Ra eq), absorbed dose (D), annual effective dose equivalent (AEDE), external hazard index (H ex), internal hazard index (H in), gamma and alpha index and dose criterion. Important conclusions can be drawn from the analysis of these indexes in respect with the radiological hazard for the population health by using these materials. Most of materials measured in this work showed fairly low levels of radioactivity.

Screening of materials with high purity germanium detectors at the Laboratori Nazionali del Gran Sasso

The Gran Sasso National Laboratories (LNGS) of the National Institute of Nuclear Physics (INFN) are equipped with an underground ultra-low background facility namely the SubTErranean Low Level Assay (STELLA), which is in first line dedicated to material screening for the fundamental physics experiments installed in the underground laboratories. The high level of performance of the ultra-low-level detector systems allows for detecting extremely low radioactivity levels in materials down to the [Formula: see text] level. The installations and experimental setups using ultra-low background techniques will be described shortly, and an example of material screening will be discussed.

Exploring atmospheric radon with airborne gamma-ray spectroscopy

222Rn is a noble radioactive gas produced along the 238U decay chain, which is present in the majority of soils and rocks. As 222Rn is the most relevant source of natural background radiation, understanding its distribution in the environment is of great concern for investigating the health impacts of low-level radioactivity and for supporting regulation of human exposure to ionizing radiation in modern society. At the same time, 222Rn is a widespread atmospheric tracer whose spatial distribution is generally used as a proxy for climate and pollution studies. Airborne gamma-ray spectroscopy (AGRS) always treated 222Rn as a source of background since it affects the indirect estimate of equivalent 238U concentration. In this work the AGRS method is used for the first time for quantifying the presence of 222Rn in the atmosphere and assessing its vertical profile. High statistics radiometric data acquired during an offshore survey are fitted as a superposition of a constant component due to the experimental setup background radioactivity plus a height dependent contribution due to cosmic radiation and atmospheric 222Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS 222Rn detection but also a (0.96 ± 0.07) Bq/m3 222Rn concentration and a (1318 ± 22) m atmospheric layer depth fully compatible with literature data.