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This contribution describes the synthesis of robust extractive scintillating resin and its use in a flow-cell detector for the direct detection of uranium in environmental waters. The base poly[(4-methyl styrene)- co -(4-vinylbenzyl chloride)- co -(divinylbenzene)- co -(2-(1-napthyl)-4-vinyl-5-phenyloxazole)] resin contains covalently bound fluorophores. Uranium-binding functionality was added to the resin by an Arbuzov reaction followed by hydrolysis via strong acid or trimethylsilyl bromide (TMSBr)-mediated methanolysis. The resin was characterized by Fourier-transform infrared spectroscopy and spectrofluorometry. Fluorophore degradation was observed in the resin hydrolyzed by strong acid, while the resin hydrolyzed by TMSBr-mediated methanolysis maintained luminosity and showed hydrogen bonding-induced Stokes' shift of ∼100 nm. The flow cell detection efficiency for uranium of the TMSBr-mediated methanolysis resin was evaluated at pH 4, 5 and 6 in DI water containing 500 Bq L −1 uranium-233 and demonstrated flow cell detection efficiencies of 23%, 16% and 7%. Experiments with pH 4, synthetic groundwater with 50 Bq L −1 uranium-233 exhibited a flow cell detection efficiency of 17%. The groundwater measurements show that the resins can concentrate the uranyl cation from waters with high concentrations of competitor ions at near-neutral pH. Findings from this research will lay the groundwork for development of materials for real-time environmental sensing of alpha- and beta-emitting radionuclides. [ABSTRACT FROM AUTHOR]

This contribution characterizes the stability of scintillating resins for ionizing radiation detection that were synthesized with 2-(1-naphthyl)-5-phenyloxazole (α-NPO) or 2-(1-naphthyl)-4-vinyl-5-phenyloxazole (v-NPO) fluor in polystyrene (PS) or poly(4-methyl styrene) (PVT) matrices. Leaching studies of the PS and PVT resins with methyl acetate show a 60 % reduction in luminosity and 80 % reduction in detection efficiency for α-NPO samples; while v-NPO resins retained detection properties. Degradation studies indicate the nitration of PS resins and the fluors after nitric acid exposure, resulting in a 100 % reduction in optical properties; whereas PVT resins with v-NPO fluor maintained 20 % detection efficiency. Heuristics are reported for designing stable scintillating resins. [ABSTRACT FROM AUTHOR]

Traditional radiochemistry approaches for the detection of trace-level alpha-emitting radioisotopes in water require lengthy offsite sample preparations and do not lend themselves to rapid quantification. Therefore, a novel platform is needed that combines onsite purification, concentration, and isotopic screening with a fieldable detection system. This contribution describes the synthesis and characterization of polyamidoxime membranes for isolation and concentration of uranium from aqueous matrices, including high-salinity seawater. The aim was to develop a field portable screening method for the rapid quantification of isotopic distribution by alpha spectroscopy. Membranes with varying degree of modification were prepared by chemical conversion of nitrile groups to amidoxime groups on the surface of polyacrylonitrile ultrafiltration (UFPAN) membranes. Attenuated total reflectance Fourier-transform infrared spectroscopy was used to analyze changes in surface chemistry. Flow through filtration experiments conducted using deionized (DI) water and simulated seawater solutions indicated that the modified membrane was effective in capturing more than 95% of the uranium in the solution prior to breakthrough even in the presence of salt ions. Batch uptake experiments were conducted and compared with the flow through experimental data to elucidate likely binding mechanisms. Alpha spectra of uranium loaded membranes were analyzed, and the effects of solution matrix and degree of modification on peak energy resolution were studied. Peak energy resolutions of 24 ± 2 keV and 32 ± 6 keV full width at half maximum (FWHM) were obtained by loading uranium from DI and seawater solutions onto modified membranes. Full width at 10% maximum of the same spectra were calculated to be 63 ± 9 keV and 160 ± 34 keV to quantify differences seen in peak tailing. Calculations performed based on the results show that it would take less than 3 h of analysis time to screen a sample provided enough volumes of solution are available. This work offers a facile method to prepare polyamidoxime-based membranes for uranium separation and concentration at circumneutral pH values, enabling the rapid, onsite screening of unknown samples. [Display omitted] • New functionalized membrane enables selective separation of uranium from water. • Approach results in high percent removal of uranium at near neutral pH solutions. • High-throughput technique allows rapid processing of large volumes of solution. • Study reveals effects of solution matrix and flow rate on uranium detection. [ABSTRACT FROM AUTHOR]

This contribution details the application of extractive scintillating resin with covalently bound fluorophore, v-NPO, and ligand, methyl phosphonic acid, in flow-cell experiments utilizing varying column diameters, resin diameters and diffusion times. The detection efficiency was evaluated by standard offline liquid scintillation counting methods. Diffusion experiments were conducted to determine the effect of the location of the alpha decay on detection efficiency, and the data were compared to a diffusion model to assess the feasibility of relying on diffusion-enhanced detection efficiency in an online measurement. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations were used to investigate the correlation between luminosity parameters and pulse shape discrimination (PSD) and subsequently compared with experimental results from CsI:Tl. Luminosity intensity parameters Af, As (fast and slow initial luminosities) and temporal luminosity parameters \tauf, \taus (fast and slow decay time constants) of a dual decay mode scintillator were applied to create a dynamic model with Crystal Ball simulation system. The simulated pulses were analyzed with charge comparison (CC) and constant time discrimination (CTD) PSD methods followed by quantification of the histogrammed pulse data with Figure of Merit (FoM) and spillover (pulse misclassification). Performance in terms of FoM and spillover is compared with that of fixed reference pulses set at (Af \tauf/As \taus)\gamma = 1 and (Af \tauf/As \taus)\gamma = 0.1. For the CC method, independent of the reference pulse characteristics [(Af \tauf/As \taus)\gamma = 1\ {\or} = 0.1], \taus is the most influential parameter for PSD as compared with Af, As, and \tauf. For the CTD method, Af and As are seen to have less influence over the PSD compared to \tauf and \taus when (Af \tauf/As \taus)\gamma = 1 and \tauf is the most influential parameter for both reference pulses. Using both methods with either reference pulse applied, the scintillator having luminosity parameters such that 0.1 < (Af \tauf/As \taus)\alpha/\gamma < 2 is classified as having poor PSD. Excellent correlation is observed between the simulation and the experimental results with CsI:Tl, which is known for very good \alpha/\beta (\gamma) pulse shape discrimination. This study is useful for describing how the luminosity parameters affects PSD. [ABSTRACT FROM PUBLISHER]

Isotopic determination of trace-level Pu in water requires time-consuming concentration and sample preparation steps, and the samples routinely must be prepared off-site from the contamination source. An analytical method that combines on-site Pu concentration with spectroscopic screening would be a valuable tool for environmental monitoring and nuclear forensics. This contribution describes the development of extractive polymer thin-film composite (e-TFC) membranes for the rapid concentration and isotopic determination of Pu from water. The e-TFC membranes were prepared by spin coating Pu-extractive copolymers on the surface of an ultrafiltration membrane. The copolymers were synthesized from methyl methacrylate or 4-methylstyrene and a Pu-reactive monomer. Three Pu-reactive monomers were evaluated for their ability to create copolymers that were suitable for casting and capable of extracting Pu from water at trace levels. Copolymers containing 5% (w /w) ethylene glycol methacrylate phosphate (EGMP) had distribution coefficients of 92.7 ± 18.5 L/kg for 242Pu at pH 6.8. e-TFC membranes prepared with an EGMP-based copolymer active layer were effective for concentrating 242Pu from a 4.53 Bq/mL (1.26 × 10−8 M) solution at pH 6.8. The resulting alpha spectra of Pu-loaded e-TFC membranes achieved energy resolutions (full-width at half-maximum, FWHM) of 71.7 ± 8.7 keV, allowing for the isotopic discrimination of 242Pu from 238Pu/241Am also present in the solution. [Display omitted] • Phosphate-based copolymers exhibit high uptake of waterborne Pu at different pH. • Extractive copolymer thin-film composites (e-TFCs) allow for rapid capture of Pu. • Alpha spectroscopy enables isotopic screening of Pu captured on the e-TFC surface. • High alpha spectroscopy peak energy resolutions achieved with e-TFC samples. [ABSTRACT FROM AUTHOR]

The objective of this research was to develop a method suitable for the determination of aqueous concentrations of radioactive iodine as I2, I-, and IO3-. As one of the primary risk-drivers and contaminants of concern at nuclear waste repositories, the accurate determination of 129I in aqueous systems is of significant concern. The redox-active nature of iodine makes its mobility and fate in the environment difficult to predict, thus underscoring the importance of species-specific determination of iodine concentrations. The developed method couples solid phase extraction with liquid scintillation counting, and scintillating anion exchange with a flow-cell detection system for a sequential measurement of each iodine species. Solid phase extraction disks were impregnated with polyvinylpyrrolidone for the selective extraction and stabilization of I2 with subsequent analysis by liquid scintillation counting. Aqueous I- was concentrated and measured by a previously developed flow-cell system utilizing scintillating anion-exchange resin. A subsequent chemical reduction of IO3- to I- in the effluent was used to quantify IO3- by the same flow-cell system. Nearly quantitative results were found for standardized single-species samples of I2 (95%), I- (101%), and IO3- (91%), respectively, while consistent measurements were obtained for multispecies samples using the developed method and algorithm. [ABSTRACT FROM AUTHOR]

Abstract: A prototype gas-filled proportional counter (PC) based on micro-scale tungsten wire and carbon fiber, and nano-scale carbon nanotube (CNT) anodes was built and tested with a 90Sr source. Tungsten anodes of 500μm down to 4μm diameter were used to observe the gradual decrease in operating voltage for the proportional region with a decreasing anode diameter. The 40nm diameter CNTs anodes ranged in length from 35 to 105μm. The absolute detection efficiency was measured at ∼10−6%. An electrostatic computer model was used to predict the resulting electric field associated with a single CNT in the coaxial configuration. For a single anode coaxial design the model predicted that the electric field was insufficient for secondary ionizations which contributed to a low amplitude signal and that the small volume of the ionization region resulted in the low absolute detection efficiency. To overcome the problems of low absolute detection efficiency and operational issues with the single anode, CNT arrays were investigated. Electrostatic modeling of 100nm×40μm long CNTs in an array with a 50μm pitch conducted for a parallel plate configuration indicated that each anode functioned independently. [Copyright &y& Elsevier]

The objective of this research was to develop a scintillating anion exchange resin selective for monitoring 129I at concentrations at or below ~0.4 Bq/L. One of the primary long-term risk-drivers and contaminants associated with nuclear waste sites is 129I. Synthesis of scintillating anion exchange resin consisted of diffusing a fluor, 2-(1-naphthyl)-5-phenyloxazole (α-NPO), into a polymeric resin. The resultant scintillating resin was further modified by amination with N-methyldi-n-octylamine (MDOA) to serve as an anion exchange group. Radiochromatography columns were prepared with the synthesized resin for use in a variety of flow-cell experiments utilizing a standard 129I solution in a synthetic groundwater to determine the properties (selectivity, interferences, loading efficiency, kinetics, capacity, and detection efficiency) of the resin. Column effluents were quantified by liquid scintillation. Average loading and detection efficiencies have been measured at 91 ± 9% and 50 ± 4%, respectively. Finally, batch sorption studies indicated fast iodide sorption rates (90% loading in ~10 min) for the resin, and dynamic sorption tracer studies indicated an iodide capacity of approximately 7800 μg/g at 10% breakthrough. [ABSTRACT FROM AUTHOR]

Sequential probability ratio test (SPRT) of scaled time-interval data (time to record N radiation pulses), SPRT_scaled, was evaluated against commonly used single-interval test (SIT) and SPRT with a fixed counting interval, SPRT_fixed, on experimental and simulated data. Experimental data were acquired with a DGF-4C (XIA, Inc) system in list mode. Simulated time-interval data were obtained using Monte Carlo techniques to perform a random radiation sampling of the Poisson distribution. The three methods (SIT, SPRT_fixed and SPRT_scaled) were compared in terms of detection probability and average time to make a decision regarding the source of radiation. For both experimental and simulated data, SPRT_scaled provided similar detection probabilities as other tests, but was able to make a quicker decision with fewer pulses at relatively higher radiation levels. SPRT_scaled has a provision for varying the sampling time depending on the radiation level, which may further shorten the time needed for radiation monitoring. Parameter adjustments to the SPRT_scaled method for increased detection probability are discussed. [ABSTRACT FROM AUTHOR]

False positive and false negative incidence rates of radiological monitoring data from classical and Bayesian statistical process control chart techniques are compared. The on-line monitoring for illicit radioactive material with no false positives or false negatives is the goal of homeland security monitoring, but is unrealistic. However, statistical fluctuations in the detector signal, short detection times, large source to detector distances, and shielding effects make distinguishing between a radiation source and natural background particularly difficult. Experimental time series data were collected using a 1″ × 1″ LaCl3(Ce) based scintillation detector (Scionix, Orlando, FL) under various simulated conditions. Experimental parameters include radionuclide (gamma-ray) energy, activity, density thickness (source to detector distance and shielding), time, and temperature. All statistical algorithms were developed using MATLAB™. The Shewhart (3-σ) control chart and the cumulative sum (CUSUM) control chart are the classical procedures adopted, while the Bayesian technique is the Shiryayev–Roberts (S–R) control chart. The Shiryayev–Roberts method was the best method for controlling the number of false positive detects, followed by the CUSUM method. However, The Shiryayev–Roberts method, used without modification, resulted in one of the highest false negative incidence rates independent of the signal strength. Modification of The Shiryayev–Roberts statistical analysis method reduced the number of false negatives, but resulted in an increase in the false positive incidence rate. [ABSTRACT FROM AUTHOR]

Aqueous tritium enrichment parameters of a commercially available Iridium/Platinum (Ir/Pt) polymer electrolyte membrane (PEM) cell were determined after electrolysis of tritium aqueous standards, and compared to those of a conventional Nickel/Iron (Ni/Fe) electrochemical cell. Lower aqueous enrichment is seen in the Ir/Pt PEM electrolyzer in comparison to the conventional Ni/Fe electrolytic cell. This is explained by the values found for the PEM cell fractionation factor βIr/Pt and electrolytic fractionation factor β eIr/Pt values determined to be 4.7 ± 0.3 ( βNi/Fe = 26), and 6.6 ± 0.7 ( β eNi/Fe = 37), respectively. A direct consequence of the Ir/Pt β e value is the richer tritium gas phase produced relative to the conventional cell, which is advantageous for direct reduction of HTO to HT gas. [ABSTRACT FROM AUTHOR]

Characterization of SuperLig® 620 solid phase extraction resin was performed in order to develop an automated on-line process monitor for 90Sr. The main focus was on strontium separation from barium, with the goal of developing an automated separation process for 90Sr in high-level wastes. High-level waste contains significant 137Cs activity, of which 137mBa is of great concern as an interference to the quantification of strontium. In addition barium, yttrium and plutonium were studied as potential interferences to strontium uptake and detection. A number of complexants were studied in a series of batch Kd experiments, as SuperLig® 620 was not previously known to elute strontium in typical mineral acids. The optimal separation was found using a 2 M nitric acid load solution with a strontium elution step of ~0.49 M ammonium citrate and a barium elution step of ~1.8 M ammonium citrate. 90Sr quantification of Hanford high-level tank waste was performed on a sequential injection analysis microfluidics system coupled to a flow-cell detector. The results of the on-line procedure are compared to standard radiochemical techniques in this paper. [ABSTRACT FROM AUTHOR]

The combination of an Ir/Pt PEM electrolyzer with a 1 L flow-through gas proportional counter was characterized for the quantification of tritium in water. The goal of the detection system is to quantify at concentrations below the Environmental Protection Agency (EPA) primary drinking water standard (740 Bq/L) with minimal expendables. The detector operating voltage, efficiency, background count rate of the passively shielded counter were measured in order to calculate the minimum detectable concentration of the detection system. The electrolyzer fractionation factor β e value deduced from the measurement of gas phase activity concentrations generated from tritium aqueous standards was found in good agreement with literature values. [ABSTRACT FROM AUTHOR]

Abstract: The absolute total and absolute peak detection efficiencies of gamma ray detector materials NaI:Tl, CdZnTe, HPGe, HPXe, LaBr3:Ce and LaCl3:Ce were simulated and compared to that of polyvinyltoluene (PVT). The dimensions of the PVT detector were 188.82cm×60.96cm×5.08cm, which is a typical size for a single-panel portal monitor. The absolute total and peak detection efficiencies for these detector materials for the point, line and spherical source geometries of 60Co (1332keV), 137Cs (662keV) and 241Am (59.5keV) were simulated at various source-to-detector distances using the Monte Carlo N-Particle software (MCNP5-V1.30). The comparison of the absolute total detection efficiencies for a point, line and spherical source geometry of 60Co and 137Cs at different source-to-detector distance showed that the absolute detection efficiency for PVT is higher relative to the other detectors of typical dimensions for that material. However, the absolute peak detection efficiency of some of these detectors are higher relative to PVT, for example the absolute peak detection efficiency of NaI:Tl (7.62cm diameter×7.62cm long), HPGe (7.62cm diameter×7.62cm long), HPXe (11.43cm diameter×60.96cm long), and LaCl3:Ce (5.08cm diameter×5.08cm long) are all greater than that of a 188.82cm×60.96cm×5.08cm PVT detector for 60Co and 137Cs for all geometries studied. The absolute total and absolute peak detection efficiencies of a right circular cylinder of NaI:Tl with various diameters and thicknesses were determined for a point source. The effect of changing the solid angle on the NaI:Tl detectors showed that with increasing solid angle and detector thickness, the absolute efficiency increases. This work establishes a common basis for differentiating detector materials for passive portal monitoring of gamma ray radiation. [Copyright &y& Elsevier]

Comparison of four pulse shape discrimination (PSD) methods was performed on the same digitized pulses from two different detector configurations. Beta/gamma discrimination of 90Sr and 137Cs was performed using a phoswich detector made of BC400 and BGO scintillators. Alpha/gamma discrimination. of 210Po and 137Cs was performed using a CsI:Tl scintillation crystal. The pulse waveforms were digitized with a DGF-4C and analyzed offline with IGOR Pro software. The four pulse shape discrimination methods that were compared include: constant fraction discrimination (CFD), rise time discrimination (RTD), constant time discrimination (CTD), and charge comparison (CC). The CTD method resulted in a spillover of 9.2% (Figure. of Merit, FOM = 3.9) and 0.25% (FOM = 3.2), while the CC method resulted in a spillover of 9.9% (FOM = 3.3) and 0.033% (FOM = 3.7) for the phoswich and CsI:Tl detectors, respectively. Although the CTD results in the lowest spillover for high signal-to-noise pulses, the optimized CC method, as implemented here, appears to be the best PSD method overall. Analysis of the reciprocal of the pulse shape data typically resulted in a significantly higher FOM than conventional methods with no reduction in spillover. This simple mathematical transformation of the pulse shape data illustrates that the FOM may not be a good scheme for the quantification of PSD. [ABSTRACT FROM AUTHOR]

Flow cell detectors were developed for simultaneous concentration and scintillation detection of technetium- 99 in water. Evaluated flow cell geometries consisted of a coil and a fountain flow cell design; the latter is based on radial solution flow through a resin bed interfaced with a photomultiplier tube through a polycarbonate window. The sorptive scintillating media investigated were (1) an extractive scintillator combining a porous polystyrene resin with the extractant Aliquat-336 and fluor 2-(1- naphthyl)-5-phenyloxazole, (2) a mixed bed of organic scintillator (BC-400) and Tc-selective resin (TEVA), and (3) a mixed bed of inorganic scintillator particles (CaF2-Eu) with either TEVA resin or strong base anion-exchange resin (Dowex 1 × 8-400(Cl). Depending on flow cell geometry and medium, the detection efficiencies for 99Tc ranged from 7.26 (BC-400/TEVA in coil geometry) to 50.20% (CaF2(Eu)/Dowex 1 × 8-400(Cl) in fountain flow cell geometry). The configuration with the highest sensitivity, CaF2(Eu)/Dowex 1 × 8-400(Cl) in coil geometry, can detect 99Tc as low as 3.78 Bq L-1 for a 100-s count interval and a 200-mL sample, which is below the current regulatory level of 33 Bq L-1. The issue of sensor reusability was addressed in this research, and its potential application at near neutral pH was demonstrated. The optimal sensor design was evaluated with a 99Tc-spiked synthetic groundwater matrix. [ABSTRACT FROM AUTHOR]

A ZnS(Ag) scintillating disc coupled to a photomultiplier window tube was used to quantify the experimental detection efficiency of thick alpha sources and compare it with the theoretical detection efficiency. The experimental detection efficiencies were determined to be ∼l7%-18% for 233U and 237Np positioned 5.4 mm below the ZnS(Ag). The theoretical detection efficiency was calculated using an analytical model for an infinitely thick alpha source and was within 7% of the experimental values. In addition to these static measurements, online flow experiments were conducted. In these flow experiments, 233U wastewaters at three concentrations (14.19-53.65 Bq/mL) were quantified using the experimental detection efficiency and determined to be within 17%-18% of the expected concentrations. Pulse height analyses were performed for 233U spiked wastewater and for a 3700-Bq 90Sr solid point source. For a very low discriminator setting, the 90Sr/90Y detection efficiency was about 3.5 %, which was reduced to essentially zero by raising the discriminator level by a minimal amount that did not effect the alpha detection efficiency. Additional experiments, which included 233U (34.66 Bq/mL) on MnO2 -coated glass fiber filter resulted in a detection efficiency of 22%-23%. [ABSTRACT FROM AUTHOR]

Manganese dioxide coated polyvinyltoluene (PVT) scintillating and extractive scintillating (ES) resins, which can be used to simultaneously separate and quantity radioactivity in aqueous solutions, were applied toward environmental screening applications. Off-line screening, utilizing a commercially available liquid scintillation counter (LSC) and on-line screening using a modified hand-held survey meter was evaluated in the laboratory for quantification of 99TcO4− and uranium in groundwater. The detection efficiencies for uranium with the MnO2 coated PVT resin were determined to be 17–37% and 7–27% for the LSC and survey instrument, respectively. The loading efficiency of the uranium out of groundwater ranged from 16% to 26%. In contrast, the detection efficiencies for 99Tc with the ES resin were determined to be 2–14% and 2–3% for LSC and hand-held survey meter, respectively, while the loading efficiency of the 99TcO4− in groundwater acidified to pH 2 was nearly 100%. [Copyright &y& Elsevier]

Extractive scintillating resins, which are used to simultaneously separate and quantify radioactivity in aqueous solutions, were developed for low-level alpha radiation monitoring of natural waters. Resins were investigated with bis(2-ethylhexyl)methane-diphosphonic acid (H2DEH[MDP], Dipex®) extractant, which has a strong affinity for tri-, tetra- and hexavalent actinides in dilute acids. Extractive scintillating resins were manifested (1) as a mixed bed of scintillating resin and extraction chromatographic resin and (2) by diffusing the organic fluor 2-(1-naphtyl)-5-phenyloxazole into macroporous polystyrene chromatographic resin, then coating with H2DEH[MDP], or by coating H2DEH[MDP] on scintillating polyvinyltoluene beads. The scintillation light was detected with a modified Hidex Triathler to allow for continuous flow measurements. The average detection efficiencies were 51.7±2.6% and 65.8±10.1% for natural uranium and 241Am, respectively, for the extractant coated scintillator. The resin was stable for solution flow of up to 1000 ml resulting in rapid real-time quantification of natural uranium in groundwater down to 30 μg/ml. [Copyright &y& Elsevier]

Provides information on a study that developed a flow-cell detector for quantification of alpha radiation in aqueous streams. Factors used in the development of the flow-cell detector; Composition of the radiation detector; Way of processing signals from the PIN-photodiodes; Result of setting an appropriate region of interest for alpha events in a dual parameter histogram.

• First application of DGA resins in analytical flow systems. • Achieved ppt limit of detection allows environmental and technological applications. • Fast computer controlled procedure with on-line preconcentration for determination of 239Pu. The monitoring of the presence of plutonium isotopes is a very important issue in both nuclear energy industry and environmental protection for human health risk assessment. The developed method for the determination of 239Pu isotope with ICP-QMS detection is based on the use of sequential injection analysis (SIA) system for the pretreatment of samples to be analyzed with the use of a commercial sorbent called diglycolamide (DGA-b) for the analyte preconcentration and separation from 238U, which is the source of the most significant isobaric interference 238U1H+. Optimizing the size of the sorbent bed and the conditions of analyte sorption and elution of plutonium and uranium provides the analytical procedure for 239Pu determination, where at total analysis time of 45 min (at flow rate 10 mL min−1) the evaluated method detection limit (MDL) for 100 mL sample volume was 88 mBq L−1. This is satisfactory detectability for applications in both technological and environmental samples. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Diglycolamide ligands are widely applied in the analysis of radionuclides, especially lanthanides and actinides. They are used in liquid-liquid extraction procedures or in solid-phase extraction sorbents where they are adsorbed on the surface of hydrophobic polymers. The main objective of this study was to synthesize the N , N , N'N ′-tetrahexyl diglycolamide with one vinyl terminating group (vTHDGA) for further covalent immobilization on the polystyrene-divinylbenzene polymeric support. The obtained complexing resin (THDGA) was employed for the mechanized sample pretreatment in the Sequential Injection Analysis - Lab-on-Valve (SIA-LOV) flow system for the determination of 239Pu using ICP-MS detection. The analytical procedure was optimized in terms of selectivity towards several other radionuclides and elements forming potentially isobaric interferences in mass spectrometry. For 100 mL volume of sample to be analyzed, the method detection limit (MDL) was 96 mBq L−1 (42 pg L−1). The developed method was employed for the determination of 239Pu in real samples of a nuclear reactor coolant and spent fuel pool water from a nuclear reactor. Image 1 • Computer-controlled SIA-LOV setup with an exchangeable sorbent bed • New complexing sorbent for actinides • ICP-MS detection with examination of numerous interferences • Pu-239 determination in samples from nuclear industry [ABSTRACT FROM AUTHOR]

The research presented here is the development of sensor materials that are applicable for real-time in situ quantification of radiostrontium in aqueous solutions. Two different approaches were applied to prepare highly selective structures for simultaneous extraction and detection of radiostrontium using online detection methods. Online data were acquired with a flow scintillation analyzer IN/US β-Ram model 5 (LabLogic Systems, Inc) with a 30-s dwell time. Both approached utilized the commercially available SuperLig620 solid-phase extractant (IBC Technologies, Inc.) to concentrate the strontium in combination with a scintillator to quantify the radioactivity. [ABSTRACT FROM AUTHOR]

We explored two approaches to recover uranium and plutonium from aqueous solutions at pH 4 and pH 7 using water-soluble star-like polyacrylamide polymers with a dextran core. In the first approach, a solution comprising a neutral or ionomer polymer was mixed with a radionuclide solution to form polymer–metal complexes that were then retained by ultrafiltration (UF) membranes under applied pressure. The same polymers were first deposited on the membrane in the second approach using pressure-driven flow. The applied polymers had an overall diameter of gyration of 120 nm, which exceeded the nominal diameter of the UF membrane pores. The polymers showed a high affinity to uranyl but could also be used to extract Pu from neutral or near-neutral pH solutions. Direct-flow single-step filtration and alpha spectrometry demonstrated that the UF membranes containing star-like copolymers could recover 99% of U and up to 60% of Pu from deionized water after filtering 15 mL solutions containing 25 ppm and 33 ppb of the actinides, correspondingly. The sorption capacity of the polymers for uranium could be measured as 1mg U per mg of the polymer after six subsequent filtration steps. Alpha spectroscopy of the deposited actinides revealed peculiarities of the structural organization of polymers and their complexes with U or Pu, depending on the approach. Though both approaches were efficient, the second approach (deposition of the polymer on the membrane followed by filtration) has an additional advantage of protecting the membrane pores from capillary collapse by filling them with the polymer chains. Therefore, these polymer-modified membranes could be used either in continuous or multi-step filtration process with drying after each step without deterioration of their sorption characteristics. [ABSTRACT FROM AUTHOR]

Plastic scintillators (PS) allow design of portative lightweight devices for quantification of low‐activity radiation sources. We have recently suggested a new type of organic fluorophores based on triphenyl pyrazoline (PZ) derivatives with high fluorescence quantum yield showing high radioluminescence when combined with a polyvinyltoluene (PVT) matrix. In this publication we report on radioluminescence properties of the PZ−X family with various halogen substitution (X=F, Cl, Br, I), or having vinyl functional group (vPZ, X=vinyl). PS based on such fluorophores and PVT matrix can be prepared as bulk samples, micrometer size beads or cladding on optical fibers. Application of fluorophores with vinyl functional groups enabled their enhanced interaction with the matrix due to covalent bonding between the components. We demonstrate high performance of PZ−X fluorophores and especially vPZ fluorophore in fabrication of nanocomposites for detection of various types of radiation. Scintillators have enhanced gamma ray detection capabilities with an addition of triphenyl Bi, or Gd2O3 nanoparticles. High fluorescence quantum yield and luminosity of PZ fluorophores allows dramatical reduction of their content in PS systems. Mechanisms of energy transfer and conversion during scintillation process are discussed. Special consideration is given to enhancement of α/β and neutron/gamma (n/γ) pulse shape discrimination (PSD) function of the developed scintillators. [ABSTRACT FROM AUTHOR]

A colorimetric method was developed for the determination of uranium in groundwater. The detection limit for the method is approximately 25 μg/L uranium, which is below the maximum contaminant level for uranium in drinking water, 30 μg/L. The method is rapid and requires little technical training to conduct, allowing it to be used by consumers, in the laboratory, or in the field. The two-step technique involves preconcentrating uranium using a U/TEVA-2 extraction chromatographic resin followed by complexation with a pyridylazo indicator dye, 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. If color change is visible to the eye, the concentration of uranium in groundwater is above the detection limit. Preconcentration using U/TEVA-2 also serves to eliminate metals that may interfere with the quantification of uranium. [ABSTRACT FROM AUTHOR]

This contribution describes the development of reactive polymer films for the concentration of uranium from circumneutral pH solutions for spectroscopic analyses. These films were prepared by grafting uranium-selective polymers from polyethersulfone (PES) films via UV-initiated polymerization, and by introducing uranium-selective functional groups to polyacrylonitrile (PAN) films by chemical reaction. Ellipsometry was used to study poly(phosphoric acid 2-hydroxyethyl methacrylate ester) film growth kinetics on PES films. X-ray photoelectron spectroscopy of modified PAN films revealed conversion of nitrile groups to amidoxime groups to be as high as 40% and showed that the extent and depth of reaction could be varied precisely. Static uptake experiments with solutions of depleted uranium spiked with 233U were conducted to determine uranium binding capacities and kinetics of the modified polymer films at different pH values from 4 to 8. Sorption isotherm data were fitted to the Langmuir model, and the highest sorption capacities of 1.09 × 10−2 ± 1.03 × 10−3 mmol m−2 and 1.02 × 10−2 ± 3.00 × 10−3 mmol m−2 were obtained at pH 6 for modified PAN (M-PAN) and PES (M-PES) films. Capacities at pH 4 and 8 were lower and could be explained by differences in sorption mechanisms. Uranium batch uptake kinetics followed a pseudo-second order rate model. Equilibrium uptake was attained within 3 h for M-PAN film and 1 h for M-PES film. Alpha spectroscopy pulse height spectra were analyzed to study the role of selective layer film thickness on peak energy resolution. Full width at half maximum values from 29 to 41 keV were recorded for M-PAN film and from 26 to 45 keV for M-PES film. Whereas uranium uptake increased with selective layer film thickness and varied with polymer chemistry/extent of modification, the peak energy resolution was independent of layer thickness and polymer chemistry within the experimental measurement uncertainties. Results from this work are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of radionuclides in water for nuclear forensics investigations and environmental studies. Unlabelled Image • New polymer nanofilms enable the rapid isotopic analysis of waterborne uranium. • Films concentrate uranium from neutral pH solutions for direct spectroscopic analyses. • Nanofilm platform generates high peak energy resolution alpha-particle spectra. • Study reveals roles of film thickness and chemistry on uranium uptake and resolution. [ABSTRACT FROM AUTHOR]

Abstract The objective of this study was to synthesize extractive scintillating resins for the direct, real-time analysis of uranium in neutral pH environmental waters. In the first synthetic approach, a methyl phosphonic acid-derivatized resin was prepared by suspension polymerization to create a matrix containing a covalently bound fluorophore and 4-vinylbenzyl chloride, followed by phosphorylation and hydrolysis to add phosphonic acid functionality. In the second approach, methyl phosphate-derivatized resin was synthesized in a one-step suspension polymerization, resulting in matrix containing a covalently bound fluorophore and ethylene glycol methacrylate phosphate ligand. Uranium binding capacity and detection efficiency of the resins were evaluated in pH 4, 6 and 8 simulated ground water and compared. The ability of both resins to detect uranium from neutral pH simulated ground water was evaluated through a Shewart-3σ control statistic applied to real-time data collected in a flow-cell detector. Resins exhibited similar binding capacities (0.18 mmol g−1) and detection efficiencies; however, the methyl phosphate resin concentrated uranium more rapidly from simulated ground water than the phosphonic acid resin. The pH dependence on the volume to detection was interpreted through changes in uranium speciation and binding mechanism supported by computational simulations. [ABSTRACT FROM AUTHOR]

Abstract Water can become contaminated as a result of a leak from a nuclear facility, such as a waste facility, or from clandestine nuclear activity. Low-level on-line radiation monitoring is needed to detect these events in real time. A Bayesian control chart method, Shiryaev-Roberts (SR) procedure, was compared with classical methods, 3- σ and cumulative sum (CUSUM), for quantifying an accumulating signal from an extractive scintillating resin flow-cell detection system. Solutions containing 0.10–5.0 Bq/L of 99Tc, as T 99 cO 4 − were pumped through a flow cell packed with extractive scintillating resin used in conjunction with a Beta-RAM Model 5 HPLC detector. While T 99 cO 4 − accumulated on the resin, time series data were collected. Control chart methods were applied to the data using statistical algorithms developed in MATLAB. SR charts were constructed using Poisson (Poisson SR) and Gaussian (Gaussian SR) probability distributions of count data to estimate the likelihood ratio. Poisson and Gaussian SR charts required less volume of radioactive solution at a fixed concentration to exceed the control limit in most cases than 3- σ and CUSUM control charts, particularly solutions with lower activity. SR is thus the ideal control chart for low-level on-line radiation monitoring. Once the control limit was exceeded, activity concentrations were estimated from the SR control chart using the control chart slope on a semi-logarithmic plot. A linear regression fit was applied to averaged slope data for five activity concentration groupings for Poisson and Gaussian SR control charts. A correlation coefficient (R 2) of 0.77 for Poisson SR and 0.90 for Gaussian SR suggest this method will adequately estimate activity concentration for an unknown solution. Highlights • Shiryaev-Roberts (SR) procedure uses less volume than classical control charts. • Poisson SR uses least volume but could be confused as a false positive. • Gaussian SR has low false positive rate and continuous increasing trend. • Activity concentration can be estimated from SR control chart slope. [ABSTRACT FROM AUTHOR]

Abstract: Combining extraction and scintillation properties within the same material is a relatively new approach in development of sensors for detection of radioactive elements. Structural organization of such materials at a nanoscale typically offers higher efficiency of detection and shorter response time. In this contribution, several new protocols are discussed for fabrication of stable extractive scintillating systems based on commercial Superlig 620 (SL) material with high affinity to radiostrontium. Application of hybrid organic–inorganic beads with SL particles used as core and halloysite clay nanotubes (HNT) modified with a polyvinyltoluene (PVT) brush as a permeable shell combines high‐performance extracting properties of the SL material with efficient light emission properties of the polymer scintillator. The developed SL–HNT–PVT hybrid extractive scintillating material allows real‐time detection of low‐level concentrations of radiostrontium in water. Moreover, the suggested approach is not limited to detection of Sr but can find broader application in development of chemical, biological, or radioluminescent sensors and multifunctional materials. [ABSTRACT FROM AUTHOR]

This contribution describes a rapid, fieldable alpha spectroscopy sample preparation technique that minimizes consumables and decreases the nuclear forensics timeline. Functional ultrafiltration membranes are presented that selectively concentrate uranium directly from pH 6 groundwater and serve as the alpha spectroscopy substrate. Membranes were prepared by ultraviolet grafting of uranium-selective polymer chains from the membrane surface. Membranes were characterized by Fourier-transform infrared spectroscopy before and after modification to support functionalization. Membrane performance was evaluated using uranium-233 or depleted uranium in both deionized and simulated groundwater at pH 6. Functionalized membranes achieved peak energy resolutions of 31 ± 2 keV and recoveries of 81 ± 4% when prepared directly from pH 6 simulated groundwater. For simulated groundwater spiked with depleted uranium, baseline energy resolution was achieved for both isotopes (uranium-238 and uranium-234). The porous, uranium-selective substrate designs can process liters per hour of uranium-contaminated groundwater using low-pressure (<150 kPa) filtration and a 45 mm diameter membrane filter, leading to a high-throughput, one-step concentration, purification, and sample mounting process. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) monitoring during compressive loading was employed to investigate micro-crack formation and coalescence in cement paste specimens. To establish a correlation between damage and AE activity, the data was categorized on the basis of amplitude and cumulative signal strength (CSS). Three distinct stages of crack behavior, illuminated by changes in the slope of the cumulative signal strength versus time relationship, were identified. Micro-crack initiation, crack extension, and unstable crack growth (crack coalescence) were assigned to these stages. An unsupervised pattern recognition approach was employed to separate the data into signal subsets which were then classified and assigned to differing mechanisms. To gain further insight into the crack growth network and behavior, specimens were loaded to varying levels of ultimate capacity and micro-CT scanning was employed to investigate the dimensional extent of micro-cracking and to correlate the images with AE data. [ABSTRACT FROM AUTHOR]

A dynamic 99mTc tracer experiment was performed to investigate the capabilities of combined preclinical single photon emission computed tomography (SPECT) and X-ray computed tomography (CT) for investigating transport in a heterogeneous porous medium. The experiment was conducted by continuously injecting a 99mTc solution into a column packed with eight layers (i.e., soil, silica gel, and 0.2-. mm glass beads). Within the imaging results it was possible to correlate observed features with objects as small as 2 mm for the SPECT and 0.2 mm for the CT. Time-lapse SPECT imaging results illustrated both local and global nonuniform transport phenomena and the high-resolution CT data were found to be useful for interpreting the cause of variations in the 99mTc concentration associated with structural features within the materials, such as macropores. The results of this study demonstrate SPECT/CT as a novel tool for 4D (i.e., transient three-dimensional. noninvasive imaging of fate and transport processes in porous media. Despite its small scale, an experiment with such high resolution data allows us to better understand the pore scale transport which can then be used to inform larger scale studies. [ABSTRACT FROM AUTHOR]

The effects of different processing steps and processing conditions for the fabrication of Y2O3 and Lu2O3 ceramics were investigated, particularly the effects of calcination, and sintering temperature on the content of open-volume and electronic defects. Ceramic bodies were prepared from calcined powders by sintering from 1400°C to 1700°C for 20 h. Density was determined by the Archimedes method and showed pellets reached about 99% of Y2O3 density for temperatures ≥1450°C, and reached 98% for sintering at 1700°C for Lu2O3. The content of open-volume defects was followed by positron annihilation lifetime ( PAL) measurements. For both materials, two lifetimes were obtained. The faster lifetime, 211 ps for Y2O3 and 204 ps for Lu2O3, was assigned to bulk annihilation with possible contribution of grain boundaries. The longer lifetime was assigned to positronium annihilation in open-volume defects with radii of 2-4 Å. Doppler broadening analysis revealed the same type of defect in Lu2O3 ceramics for all sintering temperatures. PAL analysis results showed that densification was achieved through the elimination and agglomeration of open-volume defects. Thermoluminescence ( TL) measurements of Y2O3 showed that sintering is beneficial in eliminating traps and/or recombination centers, and that higher sintering temperatures increase TL signal. [ABSTRACT FROM AUTHOR]

• Star-like polyacrylamides are identified as efficient flocculants for U, Sr, and Cs. • Application of such polymers with kaolinites enables rapid purification of water. • Within 20 min >95% of U, Sr, Cs radionuclides can be removed under neutral condition. • The process can be readily scaled up for industrial applications in water treatments. We report on the mechanisms and application of dextran-graft-polyacrylamide star-like polymers as efficient flocculation aids. Demonstrated in this paper is that these polymers form complexes with three common radionuclide contaminants: uranium, strontium, and cesium. Application of these polymers as flocculant aids together with inexpensive kaolinite-like materials allows fast and efficient purification of water. The methods presented here can be easily scaled up to industrial level decontamination of wastewater or used in large scale production of potable water. [ABSTRACT FROM AUTHOR]

The present study was oriented to prepare new scintillating anion-exchange resins for measurement of 99TcO4- in natural waters. The organic fluor 2-(1-naphthyl)-5-phenyloxazole was diffused into (chloromethyl)polystyrene resin. Thereafter, a thin layer of poly[[2-(methacryloyloxy)ethyl]trimethylammonium chloride] was grafted from the resin surface by surface-initiated atom transfer radical polymerization as an attempt to overcome potential problems related to the leaching of fluor molecules during usage. The residual chloromethyl groups of the polymer-coated resin were aminated by reaction with two different tertiary amines, triethylamine (TEA) and methyldioctylamine (MDOA). Off- and on-line quantification of 99Tc was achieved with high detection efficiencies of 60.72 ± 1.93% and 72.83 ± 0.81% for resin with TEA and MDOA functional groups, respectively. The detection limit was determined to be less than the maximum contaminant level (33 Bq L-1) established under the Safe Drinking Water Act. The two functionalized resins were demonstrated to be selective for pertechnetate from synthetic groundwater containing up to 1000 ppm Cl-, SO42-, and HCO3- and up to 1200 ppb Cr2O72- in an acidic medium. [ABSTRACT FROM AUTHOR]

A preliminary investigation of the scintillation response of rare earth-doped fluoride nanoparticles is reported. Nanoparticles of CaF2 : Eu, BaF2 : Ce, and LaF3 : Eu were produced by precipitation methods using ammonium di-n-octadecyldithiophosphate (ADDP) as a ligand that controls growth and lessens agglomeration. The structure and morphology were characterized by means of X-ray diffraction and transmission electron microscopy, while the scintillation properties of the nanoparticles were determined by means of X-ray and 241Am irradiation. The unique aspect of scintillation of nanoparticles is related to the migration of carriers in the nanoscintillator. Our results showed that even nanoparticles as small as ~4nm in size effectively scintillate, despite the diffusion length of e-h pairs being considerably larger than the nanoparticles themselves, and suggest that nanoparticles can be used for radiation detection. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the spatial variability of K d on calculations of contaminant travel time in the vadose zone was determined. Depth discrete measurements of K d were made for a suite of radionuclides (109Cd, 57Co, 60Co, 85Sr, 137Cs, and 88Y) utilizing a sediment core from the E-Area at the Savannah River Site. The K d’s were ordered as 85Sr2+ < 137Cs+ < 109Cd2+ < 57Co2+ = 60Co2+ << 88Y3+ and the values generally fell below or near the lowest quartile of values reported in the literature. Correlations were generally weak between soil properties and K d values. Most importantly, all of the K d distributions could be reasonably approximated as log-normal. Deterministic and stochastic calculations of contaminant travel time to the water table were made. The deterministic calculations were based on each of three conceptual models of the vadose zone: complete stratification (17 strata, each with a different K d), two strata (two sections of the vadose zone, each characterized by a single, average K d), and unstratified (a single zone with an average K d). Stochastic calculations were based on log-normal fits to the K d data. The two strata model generally yielded travel times 2× greater than those in the completely stratified model. The unstratified model yielded travel times that were between 3 and 5 times greater than the completely stratified model. The stochastic mean travel times were comparable to those of the two strata model. [Copyright &y& Elsevier]

The article examines radionuclide sensors for α- and β-emitting radionuclides that combine some form of selective sorption with a radiometric detection method. It focuses on sensors for Tc, which is an important radionuclide to detect in environmental monitoring, as the prototypical examples for illustrating principles of detection. The article also cites selected material on preconcentrating minicolumn sensors with the use of transduction mechanisms.

Abstract: A gamma-ray survey and analysis of 16 riverbed samples from the Reedy River watershed near Simpsonville, SC were conducted and compared with national and international studies of primordial radionuclides. The study reported here follows on a recent discovery of anomalously high uranium concentrations in several private well waters in the area. An HPGe spectrometer was used for quantification of gamma emitting radionuclides in the sediments. All sediments contained radionuclides from the uranium and thorium series as well as 40K. Uranium-238 concentrations in sediment samples ranged from 11.1 to 74.2Bqkg−1. The measured radionuclide concentrations were compared with data from UNSCEAR and NURE reports. The river and stream sediment data were augmented by in situ NaI(Tl) gamma-ray spectrometer measurements. Comparisons between the ex situ and in situ measurements indicate equivalently distributed uranium in the surface soils and stream sediments, the source of which is likely attributed to the monazite belts that are known to exist in the area. [Copyright &y& Elsevier]

In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants. The participants also agreed that many such endpoints exit or are thought to exit and while many are used in ecological risk assessment currently, additional data need to be collected that link the causal mechanisms of radiological exposure to these endpoints. Finally, the participants agreed that radiological risk assessments must be designed and informed by rigorous statistical frameworks capable of revealing the causal inference tying radiological exposure to the endpoints selected for measurement. Unlabelled Image • Ecosystem endpoints can be useful for radiological risk assessment. • Ecosystem metrics provide a holistic assessment of ecosystem condition. • Statistical rigor and conceptual modelling are critical to radiological risk assessment. [ABSTRACT FROM AUTHOR]