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The ability of the autoradiographic device BeaQuant™ is evaluated herein to quantitatively map the ultratrace element 226 Ra distributed spatially in celestine (SrSO 4 ) grains/crystals. 226 Ra doped celestines have been obtained from coprecipitation and recrystallization experiments, and have been characterized with high purity germanium gamma detector (HPGe), giving specific activities ranging from 3251 to 32523 Bq.g -1 . Alpha autoradiographs of polished sections from doped celestines have been obtained using BeaQuant™. These alpha maps have been compared to the celestine grains/crystals arrangement observed with a scanning electron microscope (SEM). At the sample scale, celestine grains are responsible of an alpha signal, indicating that 226 Ra is detectable in celestine from its alpha emissions. 226 Ra distribution has also been investigated at the celestine grains/crystals scale: the crystal/grain properties do not allow to decide if the distribution process is homogeneous or not, i.e. if there is a chemical zoning into the crystal/grain. The counting of alpha particles by autoradiography has been compared with the total activity of the 226 Ra doped celestines by gamma counting (HPGe technique). This comparison was performed by standardizing the measured activities to the same celestine volume, which has been determined by performing a threshold on SEM grey level images to assess to the celestine surface and using Geant4 Monte Carlo simulation toolkit to assess to the emission depth of the particles in celestine. A very good linear correlation between gamma activity and alpha counting from autoradiographs is obtained for all the samples, demonstrating the ability of BeaQuant™ to quantify 226 Ra in any points of the millimetric section samples, at a resolution of 20 μm., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

We compared radioactivity scanning, film autoradiography, and digital photostimulated luminescence (PSL) autoradiography (phosphoimaging technique) in detection of radioactivity on thin-layer chromatography (TLC) plates. TLC combined with radioactivity detection is rapid, simple, and relatively flexible. Here, (18)F-labelled synthesis products were analyzed by TLC and the radioactivity distribution on the plates determined using the three techniques. Radioactivity scanning is appropriate only with good chromatographic resolution and previously validated scanning parameters. Film autoradiography exhibits poor linearity if radioactivity varies greatly. PSL provides high sensitivity and resolution and superior linearity compared with the other methods.

Radioactive particles often contain very high radioactivity concentrations and are widespread. They pose a potential risk to human health and the environment. Their detection, quantification, and characterization are crucial if we are to understand their impact. Here, we present the use of a real-time autoradiography gaseous detector (using parallel ionization multiplier) to expedite and improve the accuracy of radioactive particle screening in complex environmental samples. First, standard particles were used to assess the detector capabilities (spatial resolution, spectrometry, and artefact contributions), then, we applied the technique to more complex and environmentally relevant samples. The real-time autoradiography technique provides data with a spatial resolution (≲100 µm) suitable for particle analysis in complex samples. Further, it can differentiate between particles predominantly emitting alpha and beta radiation. Here, the technique is applied to radioactive cesium-rich microparticles collected from the Fukushima Daiichi nuclear exclusion zone, showing their accurate detection, and demonstrating the viability of real-time autoradiography in environmental scenarios. Indeed, for more complex samples (radioactive particles in a less radioactive heterogeneous background mix of minerals), the technique permits relatively high selectivity for radioactive particle screening (up to 61.2% success rate) with low false positive percentages (~ 1%). [ABSTRACT FROM AUTHOR]

Summary: STED nanoscopy (Stimulated Emission Depletion). which can resolve details far below the diffraction barrier has been applied hitherto preferentially to life sciences. The method is however also ideal for the investigation of geological matrices containing transparent minerals, an application tested here, to our knowledge, for the first time. The measurements on altered granitic rock and sedimentary clay rock, both containing very fine‐grained phases, were conducted successfully. The STED fluorophore was dissolved in C‐14‐labelled methylmethacrylate (C‐14‐MMA) monomer which was polymerised within the rock matrix, thereby labelling the pore space in the geomaterials. Double labelling provided by the C‐14‐labelled MMA enables autoradiography and scanning electron microscopy (SEM), providing necessary complementary information for characterisation and quantification of porosity distributions and mineral and structure identification. Promising perspectives for further investigations of geological matrices by using different fluorophores and the optimisation of measuring procedures or even higher resolution are discussed. The combination of these different methods enlarges the observation scale of porosity from nanometre to centimetre scale. [ABSTRACT FROM AUTHOR]

Radon emanation from intact samples of fresh (“BG”), altered (“Fract”) and disturbed (“EDZ”) Finnish granitic rock from Kuru (Finland) and its dependence on humidity and rock structural factors was studied. The pore network of the rock was characterized by microscopy and impregnation with 14 C-PMMA (polymethylmethacrylate) resin and autoradiography. The radon emanation factor was increasing linearly with the relative humidity. 14 C-PMMA autoradiography of the altered zones and the EDZ indicated significant, mineral-specific increase of porosity and porosity gradients towards the fracture surfaces (Fract) and microcracks within the EDZ. For small samples in the cm-scale emanation was not diffusion, but source term controlled. [ABSTRACT FROM AUTHOR]

Digital autoradiography (DA) based on phosphor plate imaging was tested for porosity quantification using C-PMMA method, and was compared to the classical film autoradiography (FA) method. Validation was undertaken by characterizing porosity evolution of moraine deposits of Lamarck granodiorite (eastern Sierra Nevada, USA). The connected porosities obtained with FA and DA are comparable to density measurements. Using adapted exposure times, DA is more accurate than FA for analysing large variations of porosity within a given sample, and is faster than FA. [ABSTRACT FROM AUTHOR]

In the framework of dismantling of nuclear facilities, there is a strong need to obtain analytical results on residual radioactivity especially on concrete but also on metal surfaces. Since investigation of hundreds of m areas by the standard Wipe test method is difficult, a semi quantitative digital autoradiography (DA) technique was developed. The DA technique is sensitive to all types of radiation and therefore it is advantageous in dismantling investigations. Recent developments on the DA technique were investigated on concrete floor of an old laboratory in which research had been carried out using H and C beta emitters. The results showed that the DA technique was a powerful tool in localization and quantification of residual radioactivity on concrete floor. [ABSTRACT FROM AUTHOR]

Spent nuclear fuel repository safety evaluation today requires both laboratory and in situ field work in order to assess the parameters affecting the sorption and diffusion of radionuclides. Recent investigations at the Grimsel test site suggest that non-conservative errors in transport properties derived from laboratory scale experiments can lead to over-conservative estimates of matrix diffusion depths. As a result, the geosphere's capability to retain radionuclides may be underestimated. In this study the in situ diffusion and the sorption of Cs and Na into granodiorite were determined using gamma spectroscopy. Autoradiography was used to reveal the minerals into which the radionuclides were sorbed. A rock sample was obtained from the Grimsel underground in situ diffusion test site in Switzerland. In the in situ test, a solution containing several different radionuclides was circulated continuously in a packed-off injection hole for two years and three months in order to study diffusion of the radionuclides into the surrounding bedrock. The gamma measurements show that in the course of the experiment Cs diffused 2.5 cm and Na 10 cm into the rock matrix, respectively. Caesium was found to have sorbed on mafic minerals biotite and chlorite. Results of this study were used in order to calculate an in situ effective diffusion coefficient for caesium and sodium in Grimsel granodiorite. [ABSTRACT FROM AUTHOR]

The aim of our study was to develop a sensitive analytical technique to investigate tritium traces on concrete floor, ceiling and walls of a laboratory under dismantling process. In dismantling process, the behaviour of tritium must be followed very closely and in particular releases to atmosphere and exposure to public must be prevented. The investigations were carried out using liquid scintillation counting (LSC) and digital autoradiography techniques. The LSC investigations were carried out using wipe tests. It was concluded that even though LSC technique provided accurate information on the level of contamination, the loss of exact localisation of contamination spots was considered to be a major disadvantage in this application. The digital autoradiography was shown to provide both quantitative information and localisation of contamination spots. The exposure time on the digital autoradiography films were optimized, the matrix effect and the selectivity of the films were studied using polymethylmethacrylate standards. The studies showed that the digital autoradiography technique can give quantitative results, especially if standards of the investigated material (concrete) are used. [ABSTRACT FROM AUTHOR]

Spent nuclear fuel from the Finnish and Swedish nuclear power plants will be permanently disposed of in deep geological disposal facilities located on the coast of the Baltic Sea. As a part of the disposal's safety case, the migration properties of the safety-relevant spent nuclear fuel-borne radionuclides, such as the radionuclide progeny of the waste component 238U, 226Ra, need to be assessed in the lithosphere surround the facility. To this end, the sorption of Ra on disposal-relevant rock and groundwater types was studied in batch sorption experiments in a wide Ra and Ba concentration isotherm (2.6 × 10−9 M to 1 × 10−3 M). The experimental results of the batch sorption experiments were further interpreted using a PHREEQC geochemical model with ion exchange and surface complexation reactions considered. Additionally, the sorption of Ra was studied with thin section sorption studies where autoradiography analysis was combined with mineralogical data obtained in SEM/EDX to establish spatial distribution and mineral specific sorption of Ra on the studied rocks. In the study, it was observed that Ra sorbs well on all tested rock types and water conditions of low ionic competition, regardless of the rock type's projected sorption affinity based on its highly sorbing mica mineral content. In conditions of high ionic competition, Ra tends to stay in the sorption solution, facilitating migration in the disposal context. The obtained experimental and modeled Ra sorption data will be used in the safety case calculations and modeling of the Finnish and Swedish spent nuclear fuel disposal. • Radium gets strongly retarded on rock in conditions of low ionic competition. • Spatial distribution of radium sorption can be used to study its sorption mechanism. • Radium sorption can be modeled accurately in deep geological disposal context. [ABSTRACT FROM AUTHOR]

The spatial distribution of barium activity in granitic rocks was measured with two autoradiography techniques; digital autoradiography using phosphor imaging plate technique (Fuji 5100) and filmless electronic autoradiography (i.e. The BeaQuant™), which is based on a gas detector incorporated in a micromesh Parallel Ionization Multiplier (PIM). Rock cubes taken from a diffusion experiment that were in contact with 133Ba tracer were measured to determine diffusion profiles. In addition, the spatial distribution of 133Ba in the samples was determined. Polymethyl methacrylate standards for 133Ba were developed to determine the counting efficiency for electronic autoradiography. Good visual correlation between the two autoradiography methods were obtained in this study. The results of the experiments presented here can be utilized in future studies on the diffusion behavior of barium in granitic rocks. • The spatial distribution of 133Ba activity in granitic rocks was measured with two autoradiography techniques. • Digital autoradiography using phosphor imaging plate technique and filmless electronic autoradiography were compared. • 133Ba polymethylmethacrylate standards were developed to determine the counting efficiency for electronic autoradiography. • Good correlation between the two autoradiography methods were obtained in this study. [ABSTRACT FROM AUTHOR]

A new approach is proposed in order to spatially localize and determine the equilibrium state of natural decay chains on hand-scale geological samples, thanks to a combination of three techniques: 1) Elementary chemical mapping by microprobe; 2) Alpha autoradiograph by gaseous detectors and 3) bulk alpha particle spectrometry. The quantitative nature of alpha autoradiograph and its comparison with U chemical maps allows to locate radioactive equilibrium state in four samples. This equilibrium state was confirmed by alpha spectrometry analysis. [ABSTRACT FROM AUTHOR]

The distribution coefficients of barium on Olkiluoto pegmatitic granite and veined gneiss, Grimsel granodiorite and their main minerals (quartz, plagioclase, potassium feldspar and biotite) were obtained by batch sorption experiments carried out as a function of the concentration of barium. The distribution coefficients on biotite and veined gneiss were modelled with the PHREEQC computing program. In addition, the diffusion of barium into rock cubes was also studied both experimentally and computationally and the rock cubes from the diffusion experiments were studied with autoradiography and scanning electron microscopy. The results showed that the distribution coefficients of barium were largest on biotite and the sorption as a function of barium concentration on all the minerals followed a similar trend. The distribution coefficients of barium on veined gneiss, pegmatitic granite and granodiorite followed the distribution coefficient trend of their main minerals and the distribution coefficients were largest on granodiorite due to the low salinity of the groundwater simulant. The distribution coefficients of barium on veined gneiss were of the same magnitude as on granodiorite because of the high biotite content of veined gneiss and those on pegmatitic granite were a magnitude smaller. It was also discovered that the distribution coefficients in saline water were considerably smaller than the results obtained in low salinity water, which suggests that competing ions play a significant role in the sorption of barium. Finally, the concentration decrease of barium in the solution in the diffusion experiments was largest in granodiorite which can be explained with both the porous structure of all the minerals of granodiorite leading to high accessible surface area and with the sorption properties of barium. It was discovered with autoradiography that the barium was mainly sorbed on the dark minerals of the rocks, but, additionally, barium sorption on plagioclase was also concluded to be significant. In addition, the sorbed barium could be seen with scanning electron microscopy on the biotite and calcite veins in the fissures of the rock in granodiorite and veined gneiss. [ABSTRACT FROM AUTHOR]

In rocks or artificial geo-materials, radioactive isotopes emitting alpha particles are dispersed according to the mineralogy. At hand specimen scale, the achievement of quantitative chemical mapping of these isotopes takes on a specific importance. Knowledge of the distribution of the uranium and thorium series radionuclides is of prime interest to several disciplines, from the geochemistry of uranium deposits, to the dispersion of uranium mill tailings in the biosphere. The disequilibrium of these disintegration chains is also commonly used for dating. However, some prime importance isotopes, such as 226 Ra, are complicated to localize in geo-materials. Because of its high specific activity, 226 Ra is found in very low concentrations (~ppq), preventing its accurate localization in rock forming minerals. This paper formulates a quantitative answer to the following question: at hand specimen scale, how can alpha emitters in geo-materials be mapped quantitatively? In this study, we tested a new digital autoradiographic method (called the Beaver™) based on a Micro Patterned Gaseous Detector (MPGD) in order to quantitatively map alpha emission at the centimeter scale rock section. Firstly, for two thin sections containing U-bearing minerals at secular equilibrium, we compared the experimental and theoretical alpha count rates, measured by the Beaver™ and calculated from the uranium content, respectively. We found that they are very similar. Secondly, for a set of eight homemade standards made up of a mixture of inactive sand and low-radioactivity mud, we compared the count rates obtained by the Beaver™ and by an alpha spectrometer. The results indicate (i) a linearity between both count rates, and (ii) that the count obtained by the Beaver™ can be estimated from the count obtained by the alpha spectrometry using a factor of 0.82. [ABSTRACT FROM AUTHOR]