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The growing attention to naturally occurring radionuclides in building materials has a significant societal impact. This impact is apparent in recent research studies and the latest European Council directives, where reference levels for indoor radon concentrations and gamma radiation levels are reported. This paper studies black sand samples from the Estonian coast, mainly from Kihnu island. The results are discussed from various aspects to determine if utilization of these sands as a building material component is viable. For this reason, this paper focuses on the mineralogical and radiological characterization of these samples with special attention to radon emanation and exhalation. Furthermore, a detailed correlation study of mineralogical components against emanation and exhalation factors and the levels of 226Ra, 232Th and 40K was performed. It is found that the sand samples are composed of very high heavy mineral content as compared to the rest of Estonia; the black sands studied here include a heavy fraction dominated by garnets and a light fraction characterized by quartz and feldspars. The analysis also indicates that the higher 232Th and 226Ra content in the samples is correlated with an increase in zircon, ore minerals and garnets; on the other hand, the 40K content is connected to amphiboles. A strong correlation was also found between the 226Ra activity concentration and the measured massic exhalation rates.

The effect of vacuum degradation in cryostat of a gamma spectrometer on the steady-state temperature of thermal shield and its efficiency are analyzed in this study. Considering the thermal load du...

The behavior of radionuclides in the bauxite residue valorization chain has been analyzed, and accumulation ratios have been measured for secondary residues produced after recovery of valuable metals. Key analysis outcomes are valid specifically for the processes and raw materials in use at the Aluminium of Greece plant and are as follows: the processing of bauxite residue is unlikely to create secondary residues that would be hazardous from the radiological perspective, even if bauxite residue is processed successively multiple times to recover different metals. From a radiological perspective, there are no considerable limitations for the exploitation of specific BR for metal recovery. As some conclusions may be raw material or process dependent, future research could assess the possibility of applying these outcomes to other bauxite plants.

The activity concentrations of 238U, 226Ra and 210Pb were modelled in Pinus sylvestris (Scots pine trees) on a uniform CaF2 sludge heap in Belgium. The aim of this work is to enhance the knowledge of how transfer factors behave in NORM landfills. The simplest possible model in radioecology is used, which is based on Concentration Ratios (CR-s) measured in equilibrium and activity concentrations of the above-mentioned radionuclides measured in the substrate where pine trees grow. Two alternative CR-s were used: (1) international CR compilations by the IAEA (2014) and (2) CR-s specifically determined for pine trees studied in British Columbia (Mahon and Mathews, 1983). Both CR-s were applied assuming lognormal distributions fitted from data reported in the literature. The results were compared with activity concentrations measured in trees sampled on-site. Modelled concentrations match the measured ones best in the case of 238U. For the studied NORM waste site, the approach using generic IAEA concentration ratios does not fulfill the conservatism requirement in the cases of 238U and 226Ra, as the concentration of radionuclides in trees is underestimated. On the other hand, the ratios from Mahon and Mathews, (1983) produce wide distributions, ensuring conservatism due to larger CR-s. The measured concentrations are narrowly distributed in general, which can be expected on a small sampling site on a uniform substrate. The generic approach outlined here is practical but, as a result of the uniqueness of the site considered, should be applied cautiously in other NORM situations.

Two of the world's largest oil shale-fired power plants (PPs) in Estonia have been operational over 40 years, emitting various pollutants, such as fly ash, SO x , NO x , heavy metals, volatile organic compounds as well as radionuclides to the environment. The emissions from these PPs have varied significantly during this period, with the maximum during the 1970s and 1980s. The oil shale burned in the PPs contains naturally occurring radionuclides from the 238 U and 232 Th decay series as well as 40 K. These radionuclides become enriched in fly ash fractions (up to 10 times), especially in the fine fly ash escaping the purification system. Using a validated Gaussian-plume model, atmospheric dispersion modelling was carried out to determine the quantity and a real magnitude of fly ash and radionuclide deposition fluxes during different decades. The maximum deposition fluxes of volatile radionuclides ( 210 Pb and 210 Po) were around 70 mBq m −2 d −1 nearby the PPs during 1970s and 1980s. Due to the reduction of burned oil shale and significant renovations done on the PPs, the deposition fluxes were reduced to 10 mBq m −2 d −1 in the 2000s and down to 1.5 mBq m −2 d −1 in 2015. The maximum deposition occurs within couple of kilometers of the PPs, but the impacted area extends to over 50 km from the sources. For many radionuclides, including 210 Po, the PPs have been larger contributors of radionuclides to the environment via atmospheric pathway than natural sources. This is the first time that the emissions and deposition fluxes of radionuclides from the PPs have been quantified, providing the information about their radionuclide deposition load on the surrounding environment during various time periods.

Our previous studies indicated the suitability of tobacco plants for biomonitoring remediated depositories, due to their 210Po and 210Pb accumulation ability. The methods and requirements of testing 210Pb uptake by leaf-surface adsorption was investigated and implemented in the construction of a controlled environment. Uranium ore (theoretical Rn concentration 638 Bqm−3) was the main source of radon and progeny. Rn concentrations were measured by RAD7, AlphaGUARD, EQF 3220, RTM 2100 and CR-39 SSNTDs (411–516 Bqm−3). Activity concentrations of the attached and unattached fractions were determined by EQF 3220. The results are indicative of good measurement setup for tracking 210Po(Pb) uptake pathways.

Naturally occurring radionuclides were studied through the Bayer process by calculating their mass flows. Aluminium of Greece (AoG) provided sample materials and plant data from several process stages. Measurements of radionuclide concentrations were carried out by gamma-ray spectroscopy. The performed measurements show that in the specific case of the AoG plant, the majority of the natural radionuclides were introduced with karst bauxites, which showed higher activity concentrations for nuclides compared to lateritic bauxites. Most of these nuclides accumulated in the bauxite residue, while only a minor portion of uranium isotope 238U was found in alumina, corresponding to 3% of its input value. Uranium was observed to partially dissolve in the process liquors similarly to 40K, whereas the latter was not associated with aluminium hydroxide. All the materials studied in the current research work had radionuclide concentrations well below the exemption limits set by EURATOM Basic Safety Standard, indicating that these naturally occurring radionuclides do not pose a radiological hazard for workers of the AoG plant or the public., https://doi.org/10.1016/j.mineng.2019.04.016

This research describes methods for the sequential determination of 210Pb and 210Po activity concentrations in Ca-rich ash samples collected from oil shale-fired power plants in Estonia. The procedure involves digestion of Ca-rich ash samples in a microwave digestion system, radiochemical separation of 210Pb and 210Po and their measurements. All samples, blanks and standards were measured by liquid scintillation counting (Quantulus 1220). The method was tested using IAEA (International Atomic Energy Agency) RGU-1 and IAEA-444 reference materials. Spectral calibration/peak identification which included the optimization of α/β discrimination system (pulse shape analyser), and recovery have been made by 209Po and 210Pb standard solutions.

Total lead and (210)Pb concentrations were determined in various ash fractions (collected from two of the world's largest oil shale-fired power plants) by inductively coupled plasma mass-spectrometry (ICP-MS) and gamma spectrometry. Results show a clear increase in total lead (values up to 193 ppm in filter ashes) and (210)Pb (values up to 148 Bq kg(-1) in filter ashes) concentrations in the ash fractions from the furnace towards the filter ashes. A strong positive linear correlation (Pearson's bivariate correlation remained between 0.86 and 0.99) was determined between total lead concentration (ppm) and (210)Pb activity concentration (Bq kg(-1)) within all the boilers under observation. The constant concentration ratio between total lead and (210)Pb remained around one (with minor exceptions), independent of the sampling location and the used combustion technology. The determined concentration ratio can be applicable as an indicative tool in waste material characterization. It also provides multiple additions to the general material characterization approach, by integrating radiological and elemental studies and providing an option to rapidly obtain initial indicative information about the residues. This in turn helps to generate the initial information to work out the next steps in waste material management.

This paper presents the design of an easily portable spectrometer using high purity germanium (HPGe) detector – HandSpec. The key challenge in the design of a lightweight spectrometer is to minimize its heat losses so that efficient electric cooling could be used instead of bulky dewars. The design process has been largely based on experimental investigations. In this study, a digital twin of the HandSpec cryostat using computational fluid dynamics (CFD) method is developed to support the design and optimization of the physical prototype.

The guide to the expression of uncertainty in measurement (GUM) describes the law of propagation of uncertainty for linear models based on the first-order Taylor series approximation of Y = f(X1, X2, ..., XN). However, for non-linear models this framework leads to unreliable results while estimating the combined standard uncertainty of the model output [u(y)]. In such instances, it is possible to implement the method(s) described in Supplement 1 to GUM – Propagation of distributions using a Monte Carlo Method. As such, a numerical solution is essential to overcome the complexity of the analytical approach to derive the probability density functions of the output. In this paper, Monte Carlo simulations are performed with the aim of providing an insight into the analytical transformation of the probability density function (PDF) for Y = X2 where X is normally distributed and a detailed comparison of analytical and Monte Carlo approach results are provided. This paper displays how the used approach enables to find PDF of Y = X2 without the use of special functions. In addition, the singularity of the PDF and the nonsymmetric coverage interval are also discussed.

European industry is dependent on the import of raw materials. The European Commission has recognized that some raw materials are crucial for the function of the European economy and show a high risk of supply shortage. This communication addresses supply and substitution options for selected critical raw materials: cobalt, niobium, tungsten, yttrium, and the rare earth elements. For each element, the most relevant data concerning mining, abundance, recycling rates and possible substitutes are summarized and discussed.​

© 2018 Elsevier B.V. High bauxite residue content inorganic polymer paving blocks have the potential not only to provide a solution to the ongoing waste management issues faced by the alumina sector, but to simultaneously provide low environmental impact building materials to the construction sector. In order to realise the potential of this emerging technology, it is important to understand where the hotspots of environmental impact are likely to occur, and identify routes to reduce this impact, at an early stage of development. In this study we use anticipatory Life Cycle Assessment (LCA) to identify hotspots of environmental impact in the production of paving blocks made from inorganic polymers derived from bauxite residue. This technology has only been demonstrated at laboratory scale; however, production was modelled at industrial scale. The bauxite residue is fired in a rotary kiln in the presence of a carbon and silica source, in order to create a reactive precursor. When mixed with an alkali the precursor forms a solid block. Our results identify the firing process as the major hotspot of environmental impact, primarily due to the combustion of fossil fuels in the rotary kiln. Steps to reduce the impact of the firing step or to reduce the amount of fired precursor used in the final paving block are suggested as routes for future impact reduction. Optimisation of the environmental aspects of these building materials at an early stage in their development could lead to a promising future for high-volume bauxite residue valorisation at low environmental cost. ispartof: RESOURCES CONSERVATION AND RECYCLING vol:138 pages:87-98 status: published

Naturally occurring radionuclides are present in the Earth crust; however, their distribution is not homogeneous. When primary or secondary raw materials containing relatively low concentrations of naturally occurring radionuclides are introduced in an industrial process then the radionuclides can become more concentrated in the produced (by-)products. For example, during the production of purified metals, throughout the purification process, also other elements, such as naturally occurring radionuclides, become concentrated in the by-products. In order to assure radiation protection of the population, it is important to map the potential exposure for workers and the general public. There is an extensive literature available regarding the presence of naturally occurring radionuclides in various by-products; however, it can be hard to review and even to interpret for the regulators and members of the industry in order to assure the safe use of by-products for example in construction. To solve this problem data mining and text processing have been applied to the ever-increasing numbers of publications (More than 39,000 filtered publications have been processed up to the Jan. 6, 2017), and the NORM4Building database has been compiled based on the analysis of the collected data. Based on this database using text analysis methods the most NORM prone raw materials and industries have been identified. This chapter gives a concise overview on the parameters to be considered during the selection of NORM by-products as feedstock for the construction industry, specifically for the production of cement, concrete, and ceramics. In the frame of this chapter the technical and radiological properties of the most representative industrial processes (such as coal mining and combustion; iron and steel production; the alumina, the zirconia, and the phosphate industry; etc.) and their by-products are discussed, especially considering the needs of the construction industry and the new European Basic Safety Standards.

Despite advances in the development of impact categories for ionising radiation, the focus on artificial radionuclides produced in the nuclear fuel cycle means that the potential impacts resulting from increased exposure to naturally occurring radioactive materials (NORM) are still only covered to a limited degree in life cycle assessment (LCA). Here, we present a potential framework for the inclusion of the exposure routes and impact pathways particular to NORM in LCA., https://doi.org/10.1007/s11367-016-1218-2

During high temperature processes in the furnace volatile and semi-volatile elements and radionuclides are partially emitted to the environment, depending on their chemical form in the original fuel, the technological set-up of the combustion system, and the prevailing combustion conditions. Two of the world's largest oil shale-fired power plants (PPs) have been operational in Estonia from the 1960s, during which time creation of significant environmental emissions and waste containing naturally occurring radionuclides has occurred. Pb-210 and 210Po are considered natural radionuclides with the highest emission rates from PPs and possess elevated potential radiation exposure risks to humans and the environment. These radionuclides have the highest activity concentration values in fine ash fractions, especially in fractions remaining below 2.5 μm. To determine the activity concentrations of 210Pb and 210Po in the PPs' outlet, sampling was conducted from boilers operating on pulverized fuel (PF) technology with novel integrated desulphurization (NID) system and bag filters as well as with electrostatic precipitators (ESPs). The 210Pb and 210Po activity concentrations remained around 300 Bq kg−1 for the NID system compared to 60–80 Bq kg−1 in the ESP system. The dominant ash fraction in both systems was PM2.5, constituting over 50% of the fly ash mass collected from the outlet. The authors estimate that the total atmospherically emitted activity for the modernized PPs remains dominantly below 1% of the activity that is inserted via fuel. The implementation of higher efficiency purifications systems has significantly reduced the negative effect of these PPs. Based on annually emitted fly ash and boilers' working hours, the 210Pb and 210Po activity released relative to energy production were up to 68.3 kBq GWhel−1 for 210Pb and 64.6 kBq GWhel−1 for 210Po. These values are 1 to 2 orders of magnitude lower compared to the situation in the 1980s. These findings represent the first publicly available quantitative results estimating the 210Po emissions from large oil shale-fired PPs.

Several multi-day samplings were conducted over a 2-year period from an oil shale-fired power plant operating with pulverized fuel type of boilers that were equipped with either novel integrated desulphurization system and bag filters or with electrostatic precipitators. Oil shale, bottom ash and fly ash samples were collected and radionuclides from the 238 U and 232 Th series as well as 40 K were determined. The work aimed at determining possible variations in the concentrations of naturally occurring radionuclides within the collected samples and detect the sources of these fluctuations. During the continuous multi-day samplings, various boiler parameters were recorded as well. With couple of exceptions, no statistically significant differences were detected (significance level 0.05) between the measured radionuclide mean values in various ash samples within the same sampling. When comparing the results between multiple years and samplings, no statistically significant variations were observed between 238 U and 226 Ra values. However, there were significant differences between the values in the fly ashes when comparing 210 Pb, 40 K, 228 Ra and 232 Th values between the various samplings. In all cases the radionuclide activity concentrations in the specific fly ash remained under 100 Bq kg −1 , posing no radiological concerns when using this material as an additive in construction or building materials. Correlation analysis between the registered boiler parameters and measured radionuclide activity concentrations showed weak or no correlation. The obtained results suggest that the main sources of variations are due to the characteristics of the used fuel. The changes in the radionuclide activity concentrations between multiple years were in general rather modest. The radionuclide activity concentrations varied dominantly between 4% and 15% from the measured mean within the same sampling. The relative standard deviation was however within the same range as the relative measurement uncertainty, suggesting that the main component of fluctuations is derived from the measurement method and approach. The obtained results indicate that representativeness of the data over a longer time period is valid only when a fuel with a similar composition is used and when the combustion boilers operate with a uniform setup (same boiler type and purification system). The results and the accompanying statistical analysis clearly demonstrated that in order to obtain data with higher reliability, a repeated multi-day sampling should be organized and combined with the registered boiler technical and operational parameters.

Peat cores were collected from a Sphagnum-dominated Selisoo bog, which is located about 40 km from the large oil shale-fired power plants (PPs) in Estonia. These PPs have been operational from the 1960's and had the largest negative impact on the surrounding environment during the 1970's and 1980's. Nearby ombrotrophic peatlands are good indicators of atmospheric pollution due to their properties of effectively adsorbing mineral matter and pollutants. Collected peat cores (S1 and S2) from Selisoo peat bog were sliced into 1 cm thick layers and measured gamma spectrometrically. In addition, spherical fly ash particles (SFAP) originating from the combustion of the PPs were counted. The maximum concentrations (particles per cm3) of the SFAP remained between 7 and 12 cm for core S1 and between 11 and 17 cm for core S2. The concentration profiles of the SFAP reflect the combustion and emission history of the PPs. Pb-210 activity concentrations have the maximum values up to 500 Bq kg−1 and 413 Bq m−2 for S1 and for the S2 the values are 441 Bq kg−1 and 535 Bq m−2 (dry weight). The unsupported 210Pb inventory is around 4250 Bq m−2. This represents a 210Pb deposition flux of 133 Bq m−2 y−1. The estimated 210Pb deposition via fly ash from the PPs at Selisoo area remains between 0.2 and 2.2 Bq m−2 y−1. Considering the annual 210Pb deposition from the atmosphere (with a precipitation rate of 600 mm y−1) between 92 and 133 Bq m−2, which is regarded as the natural background value, we show that the radiological burden due to the power plants at these distances is negligible. As the peat cores exhibit noticeable differences from each other (in terms of radionuclide concentration distribution), the SFAP can provide a good additional parameter to improve the validity of results obtained only from radiometric methods in the chronological studies. SFAP can also act as a possible tool to estimate the radionuclide deposition rate via fly ash in the vicinity of the PPs.

The criticality of raw materials has become an important issue in recent years. As the supply of certain raw materials is essential for technologically-advanced economies, the European Commission and other international counterparts have started several initiatives to secure reliable and unhindered access to raw materials. Such efforts include the EU Raw Materials Initiative, European Innovation Partnership on Raw Materials, US Critical Materials Institute, and others. In this paper, the authors present a multi-faceted and multi-national review of the essentials for the critical raw materials (CRMs) Co, Nb, W, and rare earth elements (REEs). The selected CRMs are of specific interest as they are considered relevant for emerging technologies and will thus continue to be of increasing major economic importance. This paper presents a 'sustainability evaluation' for each element, including essential data about markets, applications and recycling, and possibilities for substitution have been summarized and analysed. All the presented elements are vital for the advanced materials and processes upon which modern societies rely. These elements exhibit superior importance in 'green' applications and products subject to severe conditions. The annual production quantities are quite low compared to common industrial metals. Of the considered CRMs, only Co and REE gross production exceed 100 000 t. At the same time, the prices are quite high, with W and Nb being in the range of 60 USD kg(-1) and some rare earth compounds costing almost 4000 USD kg(-1). Despite valiant effort, in practice some of the considered elements are de facto irreplaceable for many specialized applications, at today's technological level. Often, substitution causes a significant loss of quality and performance. Furthermore, possible candidates for substitution may be critical themselves or available in considerably low quantities. It can be concluded that one preferred approach for the investigated elements could be the use of secondary resources derived from recycling. W exhibits the highest recycling rate (37%), whereas Co (16%), Nb (11%) and rare earths (similar to 0%) lag behind. In order to promote recycling of these essential elements, financial incentives as well as an improvement of recycling technologies would be required.

Bauxite and bauxite residue, a by-product of alumina production, were studied using a combination of microanalytical techniques — electron microprobe wavelength dispersive spectrometry, laser ablation inductively coupled plasma mass spectrometry and μ-Raman spectroscopy. The aim of the work was to reveal the modes of occurrence of scandium (Sc). The motivation behind this effort was to provide mineralogical insight for the support of ongoing development of Sc extraction technologies from bauxite residue. In the analyzed bauxites and residue, Sc is mainly hosted in hematite, where Sc3+ probably substitutes Fe3+. The average concentration of Sc in the hematite matrix of bauxite is about 200 mg/kg, while in the bulk sample it ranges from 42 to 53 mg/kg Sc. In bauxite residue, the average concentration of Sc in hematite matrix is about 170 mg/kg, and in the bulk sample it is 98 mg/kg. In bauxite residue, goethite was also identified to host Sc with a concentration of about two times more than in hematite — 330 mg/kg. In bauxite residue, hematite, goethite and zircon host respectively 55 ± 20%, 25 ± 20% and 10 ± 5% of the total Sc. The effect of the Bayer process to the modes of occurrences of Sc is minor. The secondary bauxite residue minerals formed during bauxite processing do not capture any or capture very low amounts of Sc. New evidences of Sc leaching behavior from bauxite residue show that Sc is first released from goethite, then from hematite and the unrecovered proportion of Sc is likely associated with zircon.