Natural Radioisotopes Research Articles

SGSD: A novel Sequential Gamma-ray Spectrum Deconvolution algorithm

A novel approach for analyzing complex gamma-ray spectra using a sequential algorithm is introduced. The developed Sequential Gamma-ray Spectrum Deconvolution (SGSD) algorithm produces a sequence of spectra converging to the best estimation of output spectrum of a gamma-ray detector. In each point of sequence, an isotope of unknown gamma-ray source is identified and the respective response of the detector to unknown source is reconstructed. Effectiveness of the developed algorithm is demonstrated by two empirical and simulation studies. In the case of empirical study, a number of recorded gamma-ray spectra related to a mixed gamma-ray source including different combinations of 5 isotopes (Co-60, Cs-137, Na-22, Eu-152 and Am-241) are analyzed using whole information of spectra. Furthermore, a number of simulated gamma-ray spectra related to a mixed gamma-ray source including different combinations of 30 isotopes are analyzed in simulation study. Both man-made and natural radioisotopes like Ba-133, Co-60, Ir-192, Cs-137, K-40, Th-232 series, U-238 series, Ac-227 series, etc. are used for Monte Carlo simulations. The numerical results of the SGSD algorithm are compared with those of the conventional Non-Negative Least Squares (NNLS) algorithm. Based on the results, the identification procedure of the SGSD algorithm has a remarkable superiority over the NNLS algorithm.

Radioactivity of waste materials coming from the largest power plants in Poland

The Central Laboratory of Radiological Protection together with 30 other laboratories in Poland is involved in the analysis of radioactivity among indirect products of combustion (ashes and slags) coming from polish power plants and thermal power station. Systematic studies are conducted on the concentrations of natural radioactive isotopes in waste materials obtained from the power industry, and their results are recorded in a database. This database is supervised by the Central Laboratory for Radiological Protection. The database already contains 46300 by now and the oldest results come from the eighties. In this article the results of studies on radioactive concentration of natural radioisotopes 40K, 226Ra and 228Th in waste materials coming from the largest power plants in our country are presented. Furthermore an analysis was carried out on the possibility to use the selected waste materials (ashes and slags) in housing construction, road construction and in public facilities buildings, considering the values of activity indexes f1 and f2.

Considerable radioactivity levels in the granitic rocks of the central areas of the Eastern Desert, Egypt.

The distribution of the natural radioisotopes 238U, 226Ra, 232Th, and 40K in addition to their radiological parameters in granitic rock samples from five different localities (Gebel El-Missikat, Gebel El-Gidamy, Gebel Ria El-Garra, Gebel El-Aradiya, and Gebel Kab Amira) in the central area of the Eastern Desert, Egypt, was measured using high purity germanium (HPGe) detector-based γ-spectrometry. The average activity concentrations of 238U, 226Ra, 232Th, and 40K in all five studied areas are higher than the corresponding global average values. The highest average activity concentrations of 238U and 226Ra were observed in Gebel El-Missikat, whereas the highest average value of 232Th activity concentration was found at Gebel El-Gidamy, and the highest concentration of 40K was obtained at Gebel El-Aradiya. The radiological hazard parameters radium equivalent (Raeq), external hazard index (Hex), internal hazard index (Hin), absorbed dose rate (ADR), annual effective dose rate (AEDR) outdoors, annual gonadal dose equivalent (AGDE), and excess lifetime cancer risks (ELCR) were calculated to assess the radiation hazards associated with the rock samples. The average values of these parameters are higher than the recommended reference levels. The obtained data provide a valuable future database for estimating the impact of radioactive contamination in the studied area and in the places where the rocks are used.

Forensic Aspects in Polonium-210 Poisoning

The human body is exposed to radiation resulting from the presence and degradation in the environment of natural radionuclides like uranium and thorium. In laboratories, several radioactive isotopes are being used: uranium-235, iodine-131, cobalt-60, and carbon-14. These radioactive isotopes are useful in scientific (dating human skeletal remains) and medical purposes (radiotherapy/radiodiagnosis), but they are also used in criminal context. Polonium 210 (Po-210) is a natural radioisotope occurring in the natural environment as consequence of uraniu-238 decay chain. The current paper presents a less known subject of lethal poisoning with Po-210 radioisotope, in order to underline the methods used for Po-210 identification in forensic samples. The authors performed a literature review of the scientific researchers published in the last years concerning polonium sources and its use as a poison. Polonium�s effectiveness as a poison relies on its chemical characteristics only to the extent that they determine the isotope�s distribution and retention in organs and tissues; the alpha particles are responsible for the lethal effect. Po-210 poisoning is particular, as it doesn�t leave traces, it can be easily transported, and is not detected by airport scanners. Identifying this compound during a medico-legal autopsy is very difficult, as the post-mortem examination will not yield characteristic aspects, the forensic pathologist being forced to consider this as a potential cause of a rapid death, with significant visceral damage.

Fast in situ gamma spectroscopy using hand-held spectrometer with NaI probe

In this work a hand-held spectrometer InSpector 1000 with NaI (Tl) 2″ x 2″ detector has been adapted to fast in situ gamma-ray spectroscopy. Two specially designed mounting stands with shielding have been built, allowing conducting measurements in different geometries. Three particular geometries (NW, IS50, IS00) have been chosen for efficiency calibration and further study. The first one (NW) is intended for small environmental samples (volume ca 140 cm3) collected on site. IS50 geometry is a typical in situ geometry meant for radioactivity measurements in soil with detector pointed towards the ground. In this geometry the probe is shielded and mounted 50 cm above the soil surface. The new proposed geometry IS00 is designed in the way that the detector is inserted directly into the soil in order to increase the counting efficiency. The methods of efficiency calibration involved using calibration standards (in NW geometry) and the results obtained in previous in situ measurements with InSpector 2000 portable spectrometer with HPGe detector and ISOCS™ Shield Systems, which is routinely used in environmental measurements.NW geometry turned out to be useful for natural radioisotopes concentrations (K-40, U-238 and Th-232), which significantly exceed typical values of those concentrations observed in Poland. Both IS50 and IS00 geometries are applicative for quick (2 h long measurement) evaluation of typical concentrations of K, U and Th in soils. The newly proposed geometry IS00 is superior as it showed lower detection limits and uncertainties as well as its handling was far easier than of IS50. Authors have proven that hand-held spectrometer InSpector 1000, together with mounting stands and shielding, can be successfully used for fast in situ gamma-spectroscopy. Its relatively small weight and good mobility are additional assets. Moreover, detailed procedures for measurements in each geometry have been developed to conduct such analyses properly.

Performance comparison of finely pixelated LYSO- and GAGG-based Si-PM gamma cameras for high resolution SPECT

Although Lu-based scintillators, including Ce-doped Lu1.8Y0.2SiO5 (LYSO) scintillators, are often used for positron emission tomography (PET) detectors, they are not commonly used in gamma cameras for single-photon emission computed tomography (SPECT) because background counts due to contamination of the natural radioisotope in Lu are detected. However, several studies report that deterioration in image contrast due to background counts of the natural radioisotope is not critical and thus LYSO is promising for use in SPECT detectors. Meanwhile, a new scintillator, the Ce-doped Gd3Al2Ga3O12 (GAGG) with a high light yield and no natural radioisotope, has been developed and is also thought to be a promising scintillator. Thus, we compared the performance of LYSO with that of GAGG to determine which is more appropriate for a silicon photomultiplier (Si-PM)-based high-resolution small field-of-view (FOV) gamma camera for SPECT. We used finely pixelated LYSO and GAGG plates that were optically coupled to Si-PM arrays to form gamma cameras and measured the basic performance for 122-keV gamma photons. The energy resolutions of the LYSO- and GAGG-based Si-PM gamma cameras were 30% and 23% full width at half maximum (FWHM), respectively. The intrinsic spatial resolution of the GAGG (∼0.5mm FWHM) based gamma camera was better than that of the LYSO (∼0.6mm FWHM). The background counts of the LYSO-based gamma camera were 28 times larger than that of the GAGG. Based on these results, we conclude that GAGG is more appropriate than LYSO for the development of a Si-PM based gamma camera for high resolution SPECT.

天然放射性同位元素を用いた放射化学実験法 (IV) : 園芸用過リン酸石灰から放出される ^ Rn およびその娘核種の放射能測定 (i)

天然放射性同位元素を用いた放射化学実験法 (IV) : 園芸用過リン酸石灰から放出される ^ Rn およびその娘核種の放射能測定 (i)

Experiences of radiological examinations of buildings in Hungary

Natural radioisotopes occur everywhere in the environment, being a source of exposure to the general population. Everyone is continuously exposed to terrestrial and cosmic radiations both indoors and outdoors, which are the main contributors to external exposure of individuals. There were made many ambient dose rate and indoor gamma radiation and radon concentration measurements in Hungarian by different laboratories. The main goal of the present work is the summarisation and evaluation of the latest results of the Laboratory of National Public Health Center National Research Directorate for Radiobiology and Radiohygiene. The reviewed examinations were made between 1995 and 2016. The average ambient dose rate was 103 ± 17 nSv/h and the average indoor gamma dose rate was 155 ± 47 nSv/h based on the data of 382 and 581 sampling points, respectively. The average indoor radon concentration was 108 Bq/m3 with the median value of 75 Bq/m3 based on the data of 415 sampling points. We performed an additional analysis of the results of 233 personal surveyed buildings where sophisticated gamma radiation and/or indoor radon concentration measurements were made. We were also interested in has got any affect the presence of slag to the radiation levels of the buildings? We found that usually elevated radiation can be detected in houses which contain slag compared to buildings without slag. In addition we conclude that the recommended minimum duration of short-term radon measurement shall be at least three days even if it does by closed conditions.

Measurements for Natural Radioactive Materials at the East & West banks of The River Nile

Soil samples were collected along the East and West banks of the River Nile region starting from Bait Al-mal in the West side and the second East bank of the River Nile Shambat. Gamma radiation measurements were performed using high resolution HPGe detector with low background PC multichannel spectrometer. The gamma measurements of the soil revealed the presence of the natural long-lived radioisotopes ²³⁸U, ²³²Th and ⁴⁰K. The ranges of their activity concentrations were 3.32±1.1~6.3±2.1 Bqkg^-1, 5.61±1.7~10.76±2.13 Bqkg^-1 and 180±7.77~291±11.6 Bqkg^-1 ‘respectively’. The other factors controlling the distribution of the detected natural radioisotopes have been discussed. Absorbed dose rates have been calculated for each location with range 15.27±0.82~21.07±1.53 nGyh^-1. Also, the estimated activity utilization indexes have been presented. The ratios between the detected radioisotopes have been calculated.

Applicationisotope hydrology method research aboutoriginal groundwater of Nam Bo Plain

There are two main points of view about underground water in Nam Bo Plain. These are: fossil water and groundwater formed from water meteorology. The research results about underground water using isotope hydrology techniques based on the isotope oxygen-18, Deterium and some natural radioisotopes conducted by Center for Nuclear techniques show that underground water in the aquifer ofNam Bo Plainis formed from meteorological water in different periods. They also reveal the recharge sources of some shallow aquifers. Therefore, Isotope hydrology technique is a good method for studying about recharging of the deep aquifers at Nam Bo Plain as well as to learn the environmental temperature change in the past for research climate change now.

Naturally occurring radioactivity in some Swedish concretes and their constituents – Assessment by using I-index and dose-model

The reference level for effective dose due to gamma radiation from building materials and construction products used for dwellings is set to 1 mSv per year (EC, 1996, 1999), (CE, 2014). Given the specific conditions presented by the EC in report 112 (1999) considering building and construction materials, an I-index of 1 may generate an effective dose of 1 mSv per year. This paper presents a comparison of the activity concentrations of 40K, 226Ra and 232Th of aggregates and when these aggregates constitute a part of concrete. The activity concentration assessment tool for building and construction materials, the I-index, introduced by the EC in 1996, is used in the comparison. A comparison of the I-indices values are also made with a recently presented dose model by Hoffman (2014), where density variations of the construction material and thickness of the construction walls within the building are considered. There was a ∼16–19% lower activity index in concretes than in the corresponding aggregates. The model by Hoffman further implies that the differences between the I-indices of aggregates and the concretes' final effective doses are even larger. The difference is due, mainly to a dilution effect of the added cement with low levels of natural radioisotopes, but also to a different and slightly higher subtracted background value (terrestrial value) used in the modeled calculation of the revised I-index by Hoffman (2014). Only very minimal contributions to the annual dose could be related to the water and additives used, due to their very low content of radionuclides reported.

Natural radioactivity level in materials used for medieval vaulting in the territory of the central Balkan region

This work presents the results of an investigation undertaken to determine the level of natural radioactivity in the traditional building materials used for medieval indoor vaulted constructions in the territory of the central Balkan region. Indoor radiation exposure varies appreciably if it comes from the earth building materials, hence the presence of natural radioisotopes of 226Ra, 232Th, and 40K in masonry vaulted constructions was analyzed using gamma ray spectrometry. In addition, the internal health hazard index, the absorbed dose rates and the effective annual doses were calculated. The results were then compared both with the reported data from the previous studies concerning the territory of the Balkan Peninsula, as well as with the worldwide values for the materials of historic buildings. The results obtained from the materials examined in this paper all showed the radioactivity levels below the maximum permitted values.

Lead shielding efficiency from the gamma background measurements in the salt cavern of the Polkowice-Sieroszowice copper mine.

The studies of lead shielding efficiency from the gamma background measurements were performed in the salt cavern of the copper mine - a site considered for an underground laboratory. Within the energy range of 50–2700 keV, the measured gamma-ray count rates normalized to the mass of the high-purity detectors germanium crystal are 5.93 and 6.32 s−1kg−1 for the used low-background and portable spectrometers, respectively. The gamma-ray flux of 0.124 (2) cm−2s−1 connected with the natural radioisotopes was observed by the portable HPGe, including 0.026 (1) cm−2s−1 contribution of radon decay products, whereas the photon flux at the spectrum continuum was 0.18 (5) cm−2s−1.

Efficiency calculation of NaI(Tl) 2 × 2 well-shaped detector

The aim of this work to calculate the counting efficiency of NaI(Tl) 2 × 2 well-shaped scintillation detector (Canberra Inc.). The advantage of this type detector its high efficiency which used to determination the low level of radiation as natural occurring radioactive material (NORM). The gamma attenuation coefficients of natural radioisotopes and its daughters were calculated to find the three components of counting efficiency. The values of the gamma attenuation coefficients and the counting efficiencies are presented in tables and plotted the graph.

Development of GAGG depth-of-interaction (DOI) block detectors based on pulse shape analysis

A depth-of-interaction (DOI) detector is required for developing a high resolution and high sensitivity PET system. Ce-doped Gd3Al2Ga3O12 (GAGG fast: GAGG-F) is a promising scintillator for PET applications with high light output, no natural radioisotope and suitable light emission wavelength for semiconductor based photodetectors. However, no DOI detector based on pulse shape analysis with GAGG-F has been developed to date, due to the lack of appropriate scintillators of pairing. Recently a new variation of this scintillator with different Al/Ga ratios—Ce-doped Gd3Al2.6Ga2.4O12 (GAGG slow: GAGG-S), which has slower decay time was developed. The combination of GAGG-F and GAGG-S may allow us to realize high resolution DOI detectors based on pulse shape analysis. We developed and tested two GAGG phoswich DOI block detectors comprised of pixelated GAGG-F and GAGG-S scintillation crystals. One phoswich block detector comprised of 2×2×5mmpixel that were assembled into a 5×5 matrix. The DOI block was optically coupled to a silicon photomultiplier (Si-PM) array (Hamamatsu MPPC S11064-050P) with a 2-mm thick light guide. The other phoswich block detector comprised of 0.5×0.5×5mm (GAGG-F) and 0.5×0.5×6mm3 (GAGG-S) pixels that were assembled into a 20×20 matrix. The DOI block was also optically coupled to the same Si-PM array with a 2-mm thick light guide. In the block detector of 2-mm crystal pixels (5×5 matrix), the 2-dimensional histogram revealed excellent separation with an average energy resolution of 14.1% for 662-keV gamma photons. The pulse shape spectrum displayed good separation with a peak-to-valley ratio of 8.7. In the block detector that used 0.5-mm crystal pixels (20×20 matrix), the 2-dimensional histogram also showed good separation with energy resolution of 27.5% for the 662-keV gamma photons. The pulse shape spectrum displayed good separation with a peak-to-valley ratio of 6.5. These results indicate that phoswich DOI detectors with the two types of GAGGs are promising for developing a high resolution PET system.

Radon survey and soil gamma doses in primary schools of Batman, Turkey

A survey was conducted to evaluate levels of indoor radon and gamma doses in 42 primary schools located in Batman, southeastern Anatolia, Turkey. Indoor radon measurements were carried out using CR-39 solid-state nuclear track detector-based radon dosimeters. The overall mean annual 222Rn activity in the surveyed area was found to be 49 Bq m−3 (equivalent to an annual effective dose of 0.25 mSv). However, in one of the districts (Besiri) the maximum radon value turned out to be 307 Bq m−3. The estimated annual effective doses are less than the recommended action level (3–10 mSv). It is found that the radon concentration decreases with increasing floor number. The concentrations of natural and artificial radioisotopes were determined using gamma-ray spectroscopy for soil samples collected in close vicinity of the studied schools. The mean gamma activity concentrations in the soil samples were 31, 25, 329 and 12 Bq kg−1 for 226Ra, 232Th, 40K and 137Cs, respectively. The radiological parameters such as the absorbed dose rate in air and the annual effective dose equivalent were calculated. These radiological parameters were evaluated and compared with the internationally recommended values.

Selected anthropogenic and natural radioisotopes in the Barents Sea and off the western coast of Svalbard

The Murmansk Marine Biological Institute (MMBI) performed high-latitude expeditions to the Barents Sea during 2007–2009 where a scientist from the Radiation and Nuclear Safety Authority (STUK) participated. The aim of the expeditions was to study and map the current radiological situation throughout the Barents Sea. In the expeditions, samples of seawater, sediment and biota were collected for radioactivity studies. The 90Sr and 137Cs isotopes were analysed from the seawater samples and no spatial distribution in the concentrations of 90Sr and 137Cs was found. The sediment samples were analysed for γ-emitting isotopes. In the statistical analysis performed only the 90Sr was found to have no spatial distribution. In the 137Cs concentrations two areas containing higher concentrations were observed: one in the western part of Svalbard and another in Franz Victoria Trough near the Franz Josef Land archipelago. The increase in the western coast of Svalbard suggests an Atlantic influence while in the Franz Victoria Trough source regions are possibly more complex. Since 137Cs in marine sediments mainly originates from terrestrial sources, finding higher concentrations in the northern part of the Barents Sea may also suggest a contribution of 137Cs carried by the ocean currents and by sea ice from the outside Barents Sea. In addition to γ spectrometric measurements, the sediment samples were radiochemically analysed for 210Pb. It was found that the unsupported fraction of 210Pb showed significant spatial variation. The fraction of unsupported 210Pb was reduced to 40–70% near Bear Island, Edge Island and in the Franz Josef Land archipelago. In these regions the sea is typically covered with sea ice during winter. The relatively low fraction of unsupported 210Pb is possibly caused by blocking of wet and dry deposition of 210Pb onto the sea by winter sea ice. In biota samples, only small traces, at the level of 0.2 Bq/kg w.w. of 137Cs, were found. When the 137Cs concentrations found in cod and in haddock were compared with studies done in the early 1990's an effective half-life of 137Cs in cod and in haddock was deduced. For cod the estimated effective half-life of 137Cs was between 5.8 and 7.5 years and for haddock between 5.3 and 9.5 years. Similarly, the concentrations of naturally occurring 210Po and 210Pb were from 0.1 to 0.3 Bq/kg w.w. The 210Po/210Pb ratio varied from 1.8 to 30 indicating a more efficient bioaccumulation of 210Po than its precursor 210Pb. The dose to humans eating Barents Sea fish was estimated. Even for people consuming large quantities of Barents Sea fish the annual dose was found to be below 20 μSv. The effective dose from anthropogenic 137Cs was found to be less than 1% compared to the dose caused naturally occurring 210Po and 210Pb.

OSL dating of sediments from Negro and Solimões rivers – Amazon, Brazil

In this work, the OSL dating results of Quaternary fluvial deposits from the confluence of Negro and Solimões rivers were studied. The equivalent doses (De) of sediments were obtained using a Single Aliquot Regeneration (SAR) protocol. Statistic studies were made using frequency histogram, weighted histogram and Radial plot in order to analyze the De fluctuations. Ages from 74.5 to 205 thousand of years (Pleistocene) were recorded. The gamma-ray spectroscopy was used to evaluate the natural radioisotopes concentrations of the samples and low concentrations were found with values between 0.64 and 3.71ppm for 235U and 238U; 2.01–9.77ppm for 232Th; already, for 40K, the concentration was negligible. The OSL dating of sediments has contributed to a better understanding of the evolution of Negro and Solimões rivers, in Amazon, Brazil.

Radioisotopes and Analytical Chemistry

When Periodic Chart of elements is consulted to find natural radioisotopes, one firstly finds tritium, followed by 10Be, 14C, 50V and many others. Before Bi, 12 cosmogenic radioisotopes are listed. They are those continuously produced by nuclear reactions among light elements present in earthly atmosphere and radiations coming from the outside space. Eighteen additional primordial radioisotopes are listed. They were created at the same time that the non-radioactive isotopes composing the 92 natural elements in the periodic table. From Bi on, every isotope is radioactive, up to U. Then follow the artificial elements produced by laboratory nuclear reactions from Np to element with atomic number 118. In this way, from 118 known elements, 64 are radioactive, which amount 55% of all those units forming the chemical compounds. Therefore, the complete understanding of radioactivity should be a suitable tool to advance our knowledge of Universe, and consequent applications to get better living conditions. So, this paper deals with radioisotopes as suitable instruments for chemical analysis.

Tracking suspended particle transport via radium isotopes (226Ra and 228Ra) through the Apalachicola–Chattahoochee–Flint River system

Suspended particles in rivers can carry metals, nutrients, and pollutants downstream which can become bioactive in estuaries and coastal marine waters. In river systems with multiple sources of both suspended particles and contamination sources, it is important to assess the hydrologic conditions under which contaminated particles can be delivered to downstream ecosystems. The Apalachicola–Chattahoochee–Flint (ACF) River system in the southeastern United States represents an ideal system to study these hydrologic impacts on particle transport through a heavily-impacted river (the Chattahoochee River) and one much less impacted by anthropogenic activities (the Flint River). We demonstrate here the utility of natural radioisotopes as tracers of suspended particles through the ACF system, where particles contaminated with arsenic (As) and antimony (Sb) have been shown to be contributed from coal-fired power plants along the Chattahoochee River, and have elevated concentrations in the surficial sediments of the Apalachicola Bay Delta. Radium isotopes (228Ra and 226Ra) on suspended particles should vary throughout the different geologic provinces of this river system, allowing differentiation of the relative contributions of the Chattahoochee and Flint Rivers to the suspended load delivered to Lake Seminole, the Apalachicola River, and ultimately to Apalachicola Bay. We also use various geochemical proxies (40K, organic carbon, and calcium) to assess the relative composition of suspended particles (lithogenic, organic, and carbonate fractions, respectively) under a range of hydrologic conditions. During low (base) flow conditions, the Flint River contributed 70% of the suspended particle load to both the Apalachicola River and the bay, whereas the Chattahoochee River became the dominant source during higher discharge, contributing 80% of the suspended load to the Apalachicola River and 62% of the particles entering the estuary. Neither of these hydrologic scenarios, which were moderately low flow regimes, appeared to transport particles contaminated with arsenic and antimony to Apalachicola Bay.