Water Activity Content Research Articles

Y-90 SPECT ML image reconstruction with a new model for tissue-dependent bremsstrahlung production using CT information: a proof-of-concept study

While the yield of positrons used in Y-90 PET is independent of tissue media, Y-90 SPECT imaging is complicated by the tissue dependence of bremsstrahlung photon generation. The probability of bremsstrahlung production is proportional to the square of the atomic number of the medium. Hence, the same amount of activity in different tissue regions of the body will produce different numbers of bremsstrahlung photons. Existing reconstruction methods disregard this tissue-dependency, potentially impacting both qualitative and quantitative imaging of heterogeneous regions of the body such as bone with marrow cavities. In this proof-of-concept study, we propose a new maximum-likelihood method that incorporates bremsstrahlung generation probabilities into the system matrix, enabling images of the desired Y-90 distribution to be reconstructed instead of the ‘bremsstrahlung distribution’ that is obtained with existing methods. The tissue-dependent probabilities are generated by Monte Carlo simulation while bone volume fractions for each SPECT voxel are obtained from co-registered CT. First, we demonstrate the tissue dependency in a SPECT/CT imaging experiment with Y-90 in bone equivalent solution and water. Visually, the proposed reconstruction approach better matched the true image and the Y-90 PET image than the standard bremsstrahlung reconstruction approach. An XCAT phantom simulation including bone and marrow regions also demonstrated better agreement with the true image using the proposed reconstruction method. Quantitatively, compared with the standard reconstruction, the new method improved estimation of the liquid bone:water activity concentration ratio by 40% in the SPECT measurement and the cortical bone:marrow activity concentration ratio by 58% in the XCAT simulation.

The distribution of tritium in aquatic environments, Lithuania

The aim of this study is to investigate mobile radionuclide tritium (3H or T) activity dynamics in aquatic environments related to Ignalina NPP (INPP) site and water bodies located in remote areas unaffected by the INPP. The 3H excess in the INPP environment was analyzed and compared to the variable 3H background level over the period of operation of the INPP (end of 1983 – end of 2009) and during the initial stage of decommissioning (2010–2017). 3H in the INPP vicinity has been studied in the water of artificial channels related to operation of the INPP and site drainage, in natural surface water bodies and, at a smaller scale, in unconfined groundwater. This study presents an extensive 3H data set extending back to 1980, i.e. before INPP operation started. To assess the contribution of global sources to 3H dynamics, monthly precipitation was also studied, along with water from the Baltic Sea, Curonian Lagoon and Nemunas River were studied as well, all three of these located in the Lithuanian maritime zone. The 3H activity concentration in water was measured using liquid scintillation counting (LSC) techniques (direct counting and counting after enrichment). During the period of INPP operation, 3H from liquid effluent could be clearly observed in discharge channels, occurring in rather low diluted conditions, as well as in Lake Druksiai, the cooling basin, at an even more diluted level. The highest 3H activity concentration in Lake Druksiai was observed in 2003 and reached 201.3 ± 1.3 TU at a time when 3H activity concentrations in background water bodies was 9.2 ± 3.5 TU. After the closure of the INPP, the 3H liquid effluent rate reduced by approximately two orders of magnitude (from 1012 Bq in 1991 to 1010 Bq in 2016) and when decommissioning activity commenced then the 3H activity concentration fell to that approaching the background level (19–27 TU) that can still be observed in industrial discharge and rainwater drainage channels. 3H as a result of leakage from the INPP can be observed in groundwater only in direct proximity to the INPP site near the radioactive waste storage zone.

Optimization of the liquid scintillation counting technique for the European interlaboratory comparison on gross α/β activity concentrations in water

A liquid scintillation counting (LSC) measurement method optimization for the gross α/β activity analysis in drinking waters with different chemical and radionuclide composition was performed. The optimized method was suitable to provide gross radioactivity results in drinking waters with the levels of the accuracy and precision similar to those obtained using other radioactivity screening techniques. Robust LSC results contributed to the calculation of gross α/β activity reference values of EC-JRC interlaboratory comparison water samples in 2012. Some of the most common errors in the determination of the gross radioactivity using the LSC are presented.

Study of the formation of the primary 137Cs vertical profile in the organic matter-rich sediments

A laboratory study of the formation of the primary vertical profile of the 137Cs activity concentration in the anaerobic organic matter-rich sediments was carried out. The incubation was performed using sediment baths method (initial thickness of the water layer over the sediments ∼40 cm, initial radiocesium activity concentration in water ∼14.53 Bq·L−1). An exponential profile (R2∼0.999) with the half-height width of ∼0.65 cm was formed after ∼32 days of the incubation. A further course of the experiment (sediments were sampled after 64, 130 and 293 days of the incubation) revealed deviations in the form of the radiocesium activity concentration profile related to the appearance of the additional Gauss factor with the increasing half-height width of ∼1.2, ∼1.3 and ∼3 cm, respectively. In spite of the evident growth of the half-height width, the radiocesium migration rate decreased from 0.02 cm·day−1 for the first 32 days of incubation down to 0.009 cm·day−1 at the end of the incubation experiment. Such a time-dependent decrease in the radiocesium migration is possibly related to the beginning of the second radiocesium migration phase depending on the retardation factor. Besides diffusion, the formation of vertical profiles of radiocesium activity concentrations in sediments was additionally induced by effects of buoyancy of the upper sediment layer due to the seepage of the above lying water into sediments.

Internal Dose from Food and Drink Ingestion in the Early Phase after the Accident

Activity concentrations in food and drink, represented by water and vegetables, have been monitored continuously since the Fukushima Daiichi Nuclear Power Plant accident, with a focus on radioactive cesium. On the other hand, iodine-131 was not measured systematically in the early phase after the accident. The activity concentrations of iodine-131 in food and drink are important to estimate internal exposure due to ingestion pathway. When the internal dose from ingestion in the evacuation areas is estimated, water is considered as the main ingestion pathway. In this study, we estimated the values of activity concentrations in water in the early phase after the accident, using a compartment model as an estimation method. The model uses measurement values of activity concentration and deposition rate of iodine-131 onto the ground, which is calculated from an atmospheric dispersion simulation. The model considers how drinking water would be affected by radionuclides deposited into water. We estimated the activity concentrations of water on Kawamata town and Minamisouma city during March of 2011 and the committed effective doses were 0.08 mSv and 0.06 mSv. We calculated the transfer parameters in the model for estimating the activity concentrations in the areas with a small amount of measurement data. In addition, we estimated the committed effective doses from vegetables using atmospheric dispersion simulation and FARMLAND model in case of eating certain vegetables as option information.

Preliminary results of radon survey in thermal spas in V4 countries

Abstract Radon concentration was measured in 11 thermal spas in Visegrad countries (Czech Republic, Hungary, Poland, and Slovakia). The results showed that in 84% of spas radon activity concentration is less than 400 Bq·m−3. However, areas with radon activity concentration exceeding 1000 Bq·m−3 were found in the Czech Republic and Slovakia as well. Preliminary analyses indicated that the highest radon activities in spas were found in places with thermal pools. Radon concentration in waters used in spas ranged from 0.5 Bq/l to 384 Bq/l. The influence of radon activity concentration in water on radon activity in the air inside the spa was observed. It was found to increase indoor radon with increasing radon in the waters. Correlation with indoor radon and radon in water was more significant for baths and less significant for pool waters. In the cases filling of the bath from water taps, significantly contribute to the increased radon was observed in the pool and bath areas of the spa.

Natural radioactivity content in groundwater of Mt. Etna’s eastern flank and gamma background of surrounding rocks.

<p>Waters of Mt. Etna are the main source of drinking water for the local population and are also distributed in municipal supply systems to neighbouring areas. Radioactivity in underground waters and surrounding rocks from the eastern flank of Mt.Etnawas investigated on the basis of 9 water and 8 rocks samples from 12 localities altogether. Three samples were from water drainage galleries and six from water wells. All water intakes are used for consumption. Activity concentration of uranium isotopes <sup>234,238</sup>U, radium isotopes <sup>226,228</sup>Ra and radon <sup>222</sup>Rn were determined with the use different nuclear spectrometry techniques. The determination of uranium isotopes was carried out with the use of alpha spectrometry. The measurements of radium and radon activity concentration in water were performed with the use of a liquid scintillation technique. Additionally, rocks surrounding the intakes were examined with gamma spectrometry. All water samples showed uranium concentration above Minimum Detectable Activity (MDA), with the highest total uranium (<sup>234</sup>U + <sup>238</sup>U) activity concentration equal to 149.2±6 mBq/L. Conversely, all samples showed radium isotopes activity concentrations below MDA. Radon activity concentration was within the range from 2.91±0.36 to 21.21±1.10 Bq/L, hence these waters can be classified as low – radon waters. Gamma natural background of the rocks surrounding the water sampling sites was found on the same levels as other volcanic rocks of Italy.</p>

Gamma emitters in atmospheric precipitation in Krakow (Southern Poland) during the years 2005–2015

The results of the sum of dry and wet activity deposition for naturally occurring 7Be, 210Pb, 40K, 22Na and anthropogenic 137Cs radionuclides in Krakow (Southern Poland) for the samples collected over 10 years (from August 2005 to July 2015) are presented and discussed. The radionuclides were determined using low background gamma spectrometry with HPGe detectors. Additionally, in this paper there are shown the results of activity concentrations in water from air precipitation for 7Be, 210Pb, 22Na, 40K and 137Cs radioisotopes from the period of 7 years (from August 2008 to July 2015). For all these series the statistical analysis including Spearman correlations, effects of seasonal variation and multiple regression models were conducted. After excluding two months from 2011 affected by the Fukushima accident, high Spearman correlation factors (R > 0.5) for activity deposition were noticed for the pair of the cosmogenic radionuclides 7Be and 22Na (R = 0.508) and between 210Pb and 7Be (R = 0.570). High correlation was noted between activity deposition and amount of precipitation for 7Be (R = 0.677). The seasonal correlations between 7Be–22Na, 40K–137Cs, 210Pb–137Cs and 7Be–210Pb were investigated and the highest correlation coefficient R = 0.731 for the 40K–137Cs pair was in the spring season. High correlations were observed also between 210Pb and 7Be for autumn (R = 0.594), 40K–137Cs in summer (R = 0.582), 7Be–22Na in spring (R = 0.635) and 210Pb–137Cs in autumn (R = 0.672). The multiple regression approach showed the interesting difference in scavenging mechanisms of cosmogenic and terrestrial radionuclides. According to that model, the deposition of cosmogenic nuclides was noticeably related to the amount of precipitation, while the deposition of terrestrial radionuclides did not show such dependence.

Gross α and β activity concentrations in various water from Karaman, Turkey

Natural activity concentrations in water sources are necessary to assess the effects of exposure to environmental radiation. The purpose of this study is to determine the activity concentrations of gross α and β in various water samples collected from 30 different locations in Karaman province, Turkey. The estimated values of activities of gross α and β obtained from water samples vary from 0.006 to 0.125 Bq L−1and from 0.001 to 0.667 Bq L−1, respectively. The gross β activities have been found always higher than the corresponding gross α activities for all samples. The obtained values indicated that concentration levels of α and β emitting radionuclides in samples have not exceeded WHO recommendations. The results represented here that the AED values are below of recommended reference level (0.1 mSv year−1) by the WHO for all water samples in this study.

Stochastic and deterministic models to evaluate the critical distance of a near surface repository for the disposal of intermediate and low level radioactive wastes

The aim of this paper is to present the stochastic and deterministic models developed for the evaluation of the critical distance of a near surface repository for the disposal of intermediate (ILW) and low level (LLW) radioactive wastes. The critical distance of a repository is defined as the distance between the repository and a well in which the water activity concentration is able to cause a radiological dose to a member of the public equal to the dose limit set by the regulatory body. The mathematical models are developed based on the Richards equation for the liquid flow in the porous media and on the solute transport equation in this medium. The release of radioactive material from the repository to the environment is considered through its base and its flow is determined by Darcy's Law. The deterministic model is obtained from the stochastic approach by neglecting the influence of the Gaussian white noise on the rainfall and the equations are solved analytically with the help of conventional calculus (non-stochastic calculus). The equations of the stochastic model are solved analytically based on the Ito stochastic calculus and numerically by using the Euler–Maruyama method. The impact on the value of the critical distance of the Abadia de Goiás repository is analyzed, taken as a study case, when the deterministic methodology is replaced by the stochastic one, considered more appropriate for modeling rainfall as a stochastic process.

Natural environmental radioactivity and the corresponding health risk in Johor Bahru District, Johor, Malaysia

This study aims to obtain the baseline data on environmental terrestrial radiation and to assess the corresponding health risk in Johor Bahru District, Johor, Malaysia. The mean activity concentrations of 232Th, 226Ra and 40K were 119 ± 6, 51 ± 4 and 158 ± 21 Bq kg−1, respectively. Primordial radionuclide 232Th is the main contributor to gamma dose rate and the mean found to be 135 nGy h−1. Gross alpha and gross beta activity concentrations in water were 0.012 ± 0.003 and 0.234 ± 0.018 Bq L−1, respectively.

Radon in waterworks: dose assessment, analysis of influence parameters and improved methods of measurement

In Austria a comprehensive study on radiation exposure in waterworks was conducted. The aim of this study was to evaluate the risks for the affected employees. On the basis of geographical, geological and hydrological aspects, 21 waterworks were selected. A total of 85 passive short-term measurements and measurements with active devices for the detection of 222Rn were conducted and compared regarding their applicability to waterworks. Additionally, the results of 47 passive combined 222Rn/220Rn measurements for the detection of 220Rn are part of this paper. 222Rn was determined in row water samples. The influences of water flow rates and of the 222Rn activity concentration in water on the 222Rn activity concentration in indoor air of water supplies were investigated. On the basis of the results of radon measurements at 165 points, the annual effective doses for 74 persons of the staff were determined.

Radon Emanation from Drinking Water Samples of Nineveh Province (IRAQ)

The study include measurements of radon concentration in water samples for a total of eleven selected locations from Nineveh province. The natural exposure method using CR-39 track detector and the sealed cuptechniquewere chosen for analysis of radon concentration. Radon content in water samples of the study area ranges from 17.4Bq/l in Talskuf to 36.1 Bq/l in Sad Al-Mosul with an average value 26.37 Bq/l, all measured 222Rn activity concentrations in water are below the European Commission recommended level for radon in drinking water of 100 Bq/l.The results of the annual effective dose ranged from 64µSv/y in Talskuf to 132 µSv/y in Sad Al-Mosul, the total annual effective dose in 54.54% locations of the studied area are found to be within the safe limit (0.1 mSv/year) recommended by World Health Organization and EU Council and 45.45% locations are exceeding the annual effective dose limit of 0.1 mSv/y.

Radon concentrations in air and water in the thermal spas of Ischia Island

The aim of the paper is to give information about radon concentration in air and in water of 16 thermal spas of the Isle Ischia to assess the corresponding mean effective dose for workers. Measurements of air radon concentration were carried out by means of Electret Passive Environmental Radon Monitor (E-PERM) devices in long-term configuration, while radon activity concentration in water was measured using the same detectors in short-term configuration. In each plant, several kinds of rooms of different uses (office, muddy room, massage room, relax room, aerosol, mud pit and medical treatment room) were selected. Results show a great variability among the measurements relative to the different kinds of rooms of the spas. In some cases, the dose received by workers was higher than 3 mSv/y, which is the effective dose limit for occupational exposure imposed by Italian legislation.

Isosteric Heats of Water Vapor Sorption in Two Castor Varieties

Equilibrium moisture content-water activity data for two varieties of castor (GSS and WBS) at temperatures 30, 40, 50, 60 and 70°C and water activity range of 0.07-0.98 were determined using the static gravimetric method. A nonlinear regression programme was used to fit four sorption isotherm models (modified Halsey, modified Henderson, modified Oswin and modified Guggenheim-Anderson-de Boer (GAB)) to the experimental data. These models were then compared using standard error of estimate and randomness of residuals. The sorption isosteric heats were determined by the application of Clausius-Clapeyron equation. The modified Oswin and modified Halsey proved the best for predicting equilibrium moisture content of castor with standard error of estimate of 0.238 and 0.242 for GSS and WBS respectively. The isosteric heats decreased exponentially with increase in moisture content and approached the latent heat of pure water at a free water point of between 13 and 16% moisture content (d.b). The difference in isosteric heats of both varieties was not significant.

Exposure to radon in the radon spa Niška Banja, Serbia

Abstract There is a well-known radon spa Niska Banja in south-east of Serbia. In Niska Banja spa there is a medical complex and radon is used for therapeutic purposes for many different diseases. This paper presents elevated radon levels in the Niska Banja spa. Indoor radon and radon in water activity concentration measurements in thermal pools and therapy rooms are presented. There are also results from gamma spectrometry measurements of soil, rock and therapy mud. A special attention is paid to the medical staff exposure to radon around thermal pools. The annual effective doses from radon for staff working around the thermal pools in Niska Banja spa are very high comparing to the maximum recommendation level. The maximal radon concentration of (22.90 ± 0.57) kBq m −3 was measured in the basement of the hotel-dispensary “Radon”. This hotel is settled on “bigar” rock – travertine, which has high content of 226 Ra.

Effect of liming on the behaviour of 90Sr and 137Cs in a lake ecosystem

Liming of lakes is considered one possible remedial action to reduce the accumulation of radionuclides into fish in the case of a radiological accident. These responses were tested in field conditions in a small acidified lake that was divided into two parts: one limed with CaCO 3 and the other half left as an unlimed control. The transfer of 90Sr from water into fish decreased on average by 50% during the first year after liming. However, at the same time the 90Sr concentration in water increased, reaching a maximum within 6 months after liming. Approximately 50% more 90Sr was detected in water in the limed part of the lake than on control side during the first year. 90Sr was most probably released from the sediment as the Ca concentration and pH of the water increased. As a result of these two processes, which counterbalanced each other (increased release of 90Sr into water from sediment and decreased transfer of 90Sr from water into fish), the 90Sr concentration in fish did not notably differ between the limed and control sides of the lake. Liming may only be suitable as a remedial action if carried out immediately after a radiological accident, before significant amounts of radionuclides have been deposited in lake sediments. In the case of 137Cs, the effect of liming was less pronounced. 137Cs activity concentration in water increased in the first year by 20% and uptake by fish decreased by 20%.

Water Content–Water Activity–Glass Transition Temperature Relationships of Spray-Dried Borojó as Related to Changes in Color and Mechanical Properties

The water content–water activity–glass transition temperature relationships of commercial spray-dried borojo powder, with and without maltodextrin, have been studied as related to changes in color and mechanical properties. The GAB and Gordon and Taylor models were well fitted to the sorption and glass transition data, respectively. The Boltzman equation adequately described the evolution of the mechanical parameter characterized in the samples with the difference between the experimental temperature and the glass transition temperature (T g) of the sample. The color of the samples showed a sigmoid change with water activity. The changes in the mechanical properties of borojo powder related to collapse development started when the sample moved to the rubbery state and began to be significant at about 10 °C above T g. The increase in the molecular mobility from this point on also favors browning reactions. Maltodextrin presence slows the caking kinetics but induces color changes to spray-dried borojo powder.

Biotic, temporal and spatial variability of tritium concentrations in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor

The results of a 21 month sampling program measuring tritium in tree transpirate with respect to local sources are reported. The aim was to assess the potential of tree transpirate to indicate the presence of sub-surface seepage plumes.Transpirate gathered from trees near low-level nuclear waste disposal trenches contained activity concentrations of 3H that were significantly higher (up to ∼700 Bq L−1) than local background levels (0–10 Bq L−1). The effects of the waste source declined rapidly with distance to be at background levels within 10s of metres. A research reactor 1.6 km south of the site contributed significant (p < 0.01) local fallout 3H but its influence did not reach as far as the disposal trenches.The elevated 3H levels in transpirate were, however, substantially lower than groundwater concentrations measured across the site (ranging from 0 to 91% with a median of 2%). Temporal patterns of tree transpirate 3H, together with local meteorological observations, indicate that soil water within the active root zones comprised a mixture of seepage and rainfall infiltration. The degree of mixing was variable given that the soil water activity concentrations were heterogeneous at a scale equivalent to the effective rooting volume of the trees. In addition, water taken up by roots was not well mixed within the trees. Based on correlation modelling, net rainfall less evaporation (a surrogate for infiltration) over a period of from 2 to 3 weeks prior to sampling seems to be the optimum predictor of transpirate 3H variability for any sampled tree at this site.The results demonstrate successful use of 3H in transpirate from trees to indicate the presence and general extent of sub-surface contamination at a low-level nuclear waste site.

Continuous and discrete on-site detection of radon-222 in ground- and surface waters by means of an extraction module

A robust and straightforward method for on-site determination of radon-222 activity concentrations in water is presented. The methodical approach is based on the principle of liquid–gas-membrane extraction. An extraction module, which consists of hollow polypropylene fibres, allows radon stripping from the water of interest into a connected closed air-loop. The resulting radon-in-air activity concentration, which can easily be reconverted into the original radon-in-water activity concentration is measured by means of a standard mobile radon-in-air monitor. The experimental set-up allows radon detection in discrete water samples as well as continuous water pump streams. The technique, covering a wide activity concentration range, is in particular advantageous for measurements of radon-in-water in the field or on research cruises.