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Segmented gamma scanning (SGS) is a fast and effective method for measuring radioactive waste drum. The efficiency calibration is directly related to the accuracy of reconstructed radioactivity. An efficiency function model and SGS efficiency calibration method are proposed for solving existing SGS efficiency calibration problems such as time lag, limited by experimental sources or difficult to effectively combine with SGS system. The SGS system model is established by the Geant4 to calculate the segment efficiency under different linear attenuation coefficients of medium and gamma energies. The efficiency calibration function is established with the function model and parameters. Waste drum samples are constructed with the polyethylene and point sources 137Cs/60Co to complete SGS experimental measurement, efficiency calibration and radioactivity reconstruction. The result shows that the relative deviation of the reconstructed activity of a single point source at different locations in the drum is −50.48% to 43.69% and it of multi-point sources in a segment or a drum is −27.88% to 3.57%. Experimental results verify the effectiveness of this efficiency function model and SGS calibration method. • An efficiency function model is proposed for the SGS efficiency calibration. • The relative deviation of reconstructed activity is −50.48% to 43.69% for a single point source placed in the drum. • This method can conveniently and quickly calculate the SGS efficiency. [ABSTRACT FROM AUTHOR]

An algorithm based on moment estimation is presented to determine the initial parameters of the particle spectrum peak shape function for the iteration fitting procedure. The algorithm calculates the mean value, variance, and third-order central moment by using the spectrum peak data, solves the parameters of the fitting function, and then provides them as the initial values to the Levenberg–Marquardt algorithm to ensure convergence and optimized fitting. The effectiveness of the proposed algorithm was tested by gamma and alpha spectra. The algorithm can be used in automated peak curve fitting and spectral analysis. [ABSTRACT FROM AUTHOR]

An improved lossless group compression algorithm is proposed for decreasing the size of SEG-Y files to relieve the enormous burden associated with the transmission and storage of large amounts of seismic exploration data. Because each data point is represented by 4 bytes in SEG-Y files, the file is broken down into 4 subgroups, and the Gini coefficient is employed to analyze the distribution of the overall data and each of the 4 data subgroups within the range [0,255]. The results show that each subgroup comprises characteristic frequency distributions suited to distinct compression algorithms. Therefore, the data of each subgroup was compressed using its best suited algorithm. After comparing the compression ratios obtained for each data subgroup using different algorithms, the Lempel-Ziv-Markov chain algorithm (LZMA) was selected for the compression of the first two subgroups and the Deflate algorithm for the latter two subgroups. The compression ratios and decompression times obtained with the improved algorithm were compared with those obtained with commonly employed compression algorithms for SEG-Y files with different sizes. The experimental results show that the improved algorithm provides a compression ratio of 75–80%, which is more effective than compression algorithms presently applied to SEG-Y files. In addition, the proposed algorithm is applied to the miniSEED format used in natural earthquake monitoring, and the results compared with those obtained using the Steim2 compression algorithm, the results again show that the proposed algorithm provides better data compression. [ABSTRACT FROM AUTHOR]

To the chemical behavior of Pu on backfill material for high-level radioactive waste repository. Adsorption and desorption of Pu on Natural bleaching earth, Na-bentonite, GMZ-bentonite, Ca-bentonite, acid-Ca-bentonite and alk-Ca-bentonite are discussed in this paper. Data analysis shows that adsorption abilities of Ca-bentonite, alk-Ca-bentonite, Ca-bentonite are greater than GMZ-bentonite, Natural bleaching earth, Na-bentonite, and in which Na-bentonite is relatively minimal. Desorption abilities of Na-bentonite, acid-Ca-bentonite are greater than alk-Ca-bentonite, Ca-bentonite, GMZ-bentonite, Natural bleaching earth, and in which GMZ-bentonite and Natural bleaching earth are relatively minimal. When the pH of the water phase is 1 or 13, the adsorption ability of Ca-bentonite is changed obviously. One reason is that the degree of surface complex reaction has been changed. Another reason is that the compositions and structure of Ca-bentonite have been also changed after acidizing or alkalosis by H + or OH − in the water phase. [ABSTRACT FROM AUTHOR]

Abstract: The previous radon migration experimental research object is for the most of radon gas in underground migration or the migration of air interface. By using the method of active carbon accumulated measuring radon, this thesis adjusts air pressure to study the migration regularity of radon. The paper measures the concentration distributions of radon in airtight vertical glass tube under the same temperature, humidity, different cumulative times and different pressure in vacuum (respectively for -0.06MPa, -0.05MPa, -0.04MPa, atmospheric conditions).Basing on the migration equations of radon gas in the air and the concentration distribution of radon under different gas pressure, the paper estimates the average speed of radon gas under different pressures. Through series experiments, following conclusions can be obtained: the migration velocity of radon in the air is related with the air pressure: with greater air pressure, the conveyance speed is faster. Especially at low-pressure state the downward migration is more apparent. The average speed of radon in different pressures cases are estimated that compliance of the calculation results and the actual measurement was good results. [Copyright &y& Elsevier]

Abstract: The paper studies the adsorption features of 239Pu in phyllitic slate and clay media through static experiment method. The two different geo-media were collected from a site for disposing very low level waste (VLLW) as experimental samples. Experimental results have shown that an adsorption equilibrium time of 239Pu in phyllitic slate and clay is approximately 10 days, and the adsorption coefficient (Kd) B Bvalues of phyllitic slate and clay are about 6000ml/g and 2700ml/g, respectively. The experimental result of particle size effect indicates when adsorption of plutonium in particle samples increases, the KBdB values of these two geo-media increase while the particles decrease in size. And the experimental impact on aqueous phase pH value reveals that Kd of 239Pu in creases at higher aqueous phase pH value, illustrating stronger adsorption capacity. Experimental data are also measured through the curve fitting, KBdB values are thus obtained theoretically. [Copyright &y& Elsevier]

Abstract: An online automatic Ti-grade analyzer (OATGA), consisting of a 238Pu source and a proportional counter, is designed for assuring product quality. The advantage of this system was its time-effectiveness; the entire monitoring process can be finished within approximately 5min. This system has successfully solved some key analysis issues in titanium ore concentrate production process. The results obtained by feature measurements and chemical analysis were in agreement with each other. After two-year usage of OATGA at PANGANG, southwestern China, it was proved as a reliable method for online quality control in the production process of titanium ore concentrate. [Copyright &y& Elsevier]

Neutrons produced by cosmic rays comprise the main factor in radiation hazards for astronauts and spacecraft during space exploration. A silicon-photomultiplier- (SiPM-) array-coupled Cs 2 LiYCl 6 : Ce 3 + (CLYC) detector was proposed to measure neutrons onboard spacecraft. Since both light-collection efficiency and thermal noise rate are proportional to a SiPM's size, it is necessary to compare CLYC's characterization when coupled with SiPM arrays of different sizes. In this paper, a 4 × 4 array and an 8 × 8 array, both of which are composed of 3 × 3-mm2 SiPM elements, were coupled to a Φ 38 mm × 38 mm cylindrical CLYC detector. The energy resolution, pulse-shape-discrimination (PSD) performance, and temperature dependence were tested with two gamma-ray sources and a neutron source. Results indicate that both energy resolution and PSD performance mainly benefit from the higher light-collection efficiency of the large array. The peak centroids of 137Cs varied by ∼ 20% in the testing temperature region from -35 °C to +55 °C. [ABSTRACT FROM AUTHOR]

Neutron activation analysis is a highly sensitive non-destructive testing technique with important applications in industry, geoscience, medical therapy, etc. This work designed and optimized a thermal neutron device that utilized a portable D-D neutron generator, and the Monte Carlo method with the Geant4 toolkit was applied to simulation. The objective of the optimized design is to maximize the thermal neutron flux at the output surface and increase the utilization efficiency of the neutron generator. A parameter K was defined as a measure of the device's slowing capacity for neutrons and was used to determine the optimized device geometry. The simulation considered the contribution of different types and sizes of moderators and reflectors to the thermal neutron intensity to obtain the optimal size. The shielding protection of the device was then designed. The effectiveness of shielding with different thicknesses was evaluated using three dose reference points. The results indicated that the optimized device can achieve a maximum thermal neutron flux of 1.97 × 105 n∙cm−2∙s−1 at the output surface by using high-density polyethylene (HDPE) as the moderator and nickel as the reflector. It was determined that using 45 cm of HDPE and 9 cm of lead protection in sequence along the neutron head axis would reduce the dose rate at the reference point, located 5 cm from the surface of the device, below the safety limit of 2.5 μSv/h. • Geant4 was used to optimize the design of a thermal neutron activation analysis setup based on a DD neutron generator. • A maximum thermal neutron flux of 1.97 × 105 n∙cm−2∙s−1 at the output surface. • The reference point dose rate is reduced to below the safe limit of 2.5 μSv/h. [ABSTRACT FROM AUTHOR]

Coded-aperture imagers typically have a smaller field-of-view (FOV) than in un-collimated gamma imaging systems. However, sources out of the fully coded field-of-view (FCFOV) can cause pseudo hotspots on the wrong side of an image reconstructed using the cross-correlation method. In this work, we propose a neural network method to identify and localize the sources within the partially coded field-of-view (PCFOV). The model was trained using Monte Carlo simulation data and evaluated with both simulation and experimental data. The results showed that the proposed model can identify and localize sources with good classification accuracy, low positioning error, and strong robustness to the statistical noise. • Sources localization within a partially coded field-of-view was investigated. • A neural network model was proposed to identify and localize sources. • The model was trained using Monte Carlo simulation data. • Both simulation and experimental results demonstrate the feasibility of the method. [ABSTRACT FROM AUTHOR]

• This paper analyzed the differences between SE and DE trapezoidal shaping algorithm in detailed. • Peak probability estimation formula based on the area of photopeak and pulse resolution time is proposed. • HPGe detector, fast SDD and NaI(Tl) detector are chosen are built, experiment results show that the probability estimation formula is suitable for system with high detection efficiency and less counting loss. Nuclear signal will pile up seriously at the condition of high counting rate when using semiconductor detectors because of its high resolution and wide output signal. In order to solve the problem. Dual-exponential trapezoidal shaping algorithm with fixed pulse width discrimination is used to eliminate partial pile-up pulses at first. Then this paper proposes characteristic peak probability estimation formula based on the calculation of characteristic peaks area and pulse shaping time. And then systems based on High Purity Germanium (HPGe) detector, high performance Silicon Drift Detector (fast SDD) and NaI(Tl) detector are chosen are built, experiment results show that the probability estimation formula is suitable for system with high detection efficiency and less counting loss. [ABSTRACT FROM AUTHOR]

Structure is a crucial factor to decide the selectivity and sensitivity of chemosensors. In this work, a diacylhydrazone 2a and its congeneric derivatives 2b-2d were synthesized and their applications for Al 3+ detection were investigated. Except 2d , all the other compounds exhibit notable turn-on fluorescence toward Al 3+ over 15 other metal ions and the sensitivities of 2b and 2c are even higher after modification, illustrating ortho -OH indispensability in their structures for sensing. Reversibility investigation shows that the sensors all have regeneration ability. Meanwhile, the sensor-Al 3+ systems show selective fluorescence turn-off for Cu 2+ , providing a potential platform for tandem recognition of Al 3+ and Cu 2+ . 2a as a standard, shows a 1:2 molar ratio to Al 3+ confirmed by Job’s plot, 1 H NMR spectra and mass spectra, and its detection limit for Al 3+ is 7.63 nM in ethanol. It has relevant sensitivity over pH 3-9, with the highest sensitivity at around pH 4. Apart from Al 3+ detection, anion selectivity was also explored and it shows that 2a , 2b and 2c all have selectivity toward CN − evidenced by UV-vis spectra. [ABSTRACT FROM AUTHOR]

The fluorapatite-type Ca 8 Sm 1 Na 1 (PO 4 ) 6 F 2 ceramic was successfully fabricated by hot uniaxial pressing (HUP) sintering process. The effects of sintering temperature and holding time on the relative density and Vickers hardness of the ceramic were investigated. The surface microstructure, weight loss rate and surface composition of Ca 8 Sm 1 Na 1 (PO 4 ) 6 F 2 ceramic before and after the leaching experiment were examined. The influences of leaching temperature and pH value on the chemical durability of the ceramic were also studied. The results showed that the ceramic sintered by HUP at 1100 °C for 2 h obtained the highest relative density (99.46%) and maximum Vickers hardness (3.704 GPa). The largest weight loss rate (0.578%) and the highest normalized elemental leaching rates of Sm, Ca, P, Na and F were obtained in the media (pH = 3) at 90 °C. The surface of ceramic in the media (pH = 3) appeared obvious corrosion with plenty of intergranular and intragranular pores. The small weight loss rates (0.003%–0.008%) and the low normalized elemental leaching rates of Ca (7.44 × 10 −3  g m -2  d -1 - 8.22 × 10 −4  g m -2  d -1 ) and Sm (9.11 × 10 −6  g m -2  d -1 - 1.07 × 10 −6  g m -2  d -1 ) were acquired in the media (pH = 7, 9 and 11), indicating that the Ca 8 Sm 1 Na 1 (PO 4 ) 6 F 2 ceramic possessed high chemical durability in the neutral and alkaline media at 90 °C. [ABSTRACT FROM AUTHOR]

Superparamagnetic γ -Fe 2 O 3 nanoparticles (5 nm diameter) were synthesized in water. The bare particles exhibit good colloidal stability at ∼pH 2 because of the strong electrostatic repulsion with a surface charge of +25 mV. The polyacrylic acid (PAA)-coated particles exhibit remarkable colloidal stability at ∼pH 7 with abundant free carboxyl groups as reactive sites for subsequent functionalization. In this work, we used zeta potential analysis, transmission electron microscopy, small angle X-ray scattering, and Inductively coupled plasma mass spectrometry to investigate the adsorption behavior of U (VI) on bare and coated colloidal superparamagnetic nanoparticles at pH 2 and pH 7. At pH 2, uranyl ion (UO 2 2+ ) absorbed on the surface of the bare particles with decreasing particle surface charge. This induced particle agglomeration. At pH 7, uranyl ion (UO 2 2+ ) hydrolyzed and formed plate-like particles of uranium hydroxide that were ∼50 nm in diameter. The PAA-coated iron oxide nanoparticles absorbed on the surface of these U (VI) hydroxide plates to form large aggregates that precipitate to the bottom of the dispersion. At both pH 2 and pH 7, the resulting U (VI)/nanoparticle complex can be easily collected and extracted from the aqueous environment via an external magnetic field. The results show that both bare and polymer-coated superparamagnetic γ -Fe 2 O 3 nanoparticles are potential absorbents for removing U (VI) from water. [ABSTRACT FROM AUTHOR]

The ability of bentonite and montmorillonite pillared by Al-oxide and mixed (Ln-Al)-oxides (Ln = La, Ce) to remove 239 plutonium solution species from water is comparatively investigated at pH 7 and pH 4. Small-angle scattering and neutron contrast variation with H 2 O/D 2 O mixtures is used to verify the ingress of water in the calcined products after hydrophilicity was introduced by an NH 3 -H 2 O vapor treatment. The size and shape of the (La/Ce)-Al oxo-hydroxy pillaring cations (2 nm spheres) is determined by small-angle x-ray scattering from the pillaring solutions. Not all of the oxide pillars improved Pu uptake compared with sodium montmorillonite. At neutral and acidic pH only (Ce-Al)-oxide pillared clays showed the ability to remove Pu over the concentration range studied (1.35 × 10 −8 –8 × 10 −8  mol dm −3 ) with distribution coefficient ( K D ) values >10 4 . XPS analysis of the (Ce-Al)-oxide pillared clays indicates the presence of Ce 4+ as cerium dioxide. The progressive improvement in sorption performance in the order of pillar type Al 2 O 3  < La 2 O 3 -Al 2 O 3  << CeO 2 -Al 2 O 3 reflects the increasing access of Pu solution species to the clay mineral layers by changes to the basal spacing and specific surface area, and also to the higher stability of the (Ce-Al)-oxide pillars. [ABSTRACT FROM AUTHOR]

This study proposes a novel natural environment background model by modeling brief environment conditions. It uses Geant4 program to simulate decays of 238 U, 232 Th, and 40 K in soil and obtains compositions of different-energy gamma rays in the natural environment background. The simulated gamma spectrum of the natural environment background agrees well with the experimental spectrum, particularly above 250 keV. The model is used in the simulation of anticoincidence measurement, indicating that the natural environment background can be decreased by approximately 88%, and the Compton attenuation factor is 2.22. The simulation of anticoincidence measurement can improve the minimum detectable activity (MDA) of the detection system. [ABSTRACT FROM AUTHOR]

The detection speed of the tomographic gamma scanning (TGS) system with a detector array is faster than the single detector system. The NaI(Tl) detector is inexpensive and can work at room temperature, making it ideal for use in the TGS system with a fan-shaped detector array. The collimator of the TGS system is one of the critical elements to ensure the reconstructed image's quality. In addition to providing good detection efficiency of the detector while improving the system's spatial resolution, a proper collimator structure may also reduce cross-interference between segments. We propose a collimator design method for the TGS system with a fan-shaped NaI(Tl) detector array and combine it with the Monte Carlo method to optimize the collimator. We get the collimator aperture size and shape of the TGS system through the simulation results. Simultaneously, according to the detectors' equiangular sector arrangement limitation, we propose setting up a fan-shaped shield with adjustable depth and height at the detector collimator's front. The cross-interference between segments is effectively reduced without reducing the current segment's detection efficiency. The transmission image reconstruction shows that the collimator designed by this method can be used in the TGS system with the fan-shaped NaI(Tl) detector array. • The collimator of the TGS system with the fan-shaped NaI(Tl) detector array is optimized with the Monte Carlo method. • The fan-shaped shield effectively reduces the cross-interference between segments. • A TGS system with a fan-shaped NaI(Tl) detector array is adopted to reconstruct transmission tomography. [ABSTRACT FROM AUTHOR]

The Alxa region (Inner Mongolia, China) is one of the areas preselected for use as a geological repository of high-level radioactive waste in China. Radioactive waste produces radioactive rays during long-term storage, and the cumulative absorbed dose in 1000 years can significantly exceed the maximum of 0.7 MGy, thereby challenging the long-term adsorption stability of clay. This study employed 60Co gamma (γ)-rays to irradiate clay in air under a dose rate of 10 kGy/h. The changes in the internal structure and mechanisms of clay under different gamma radiation doses (1, 2, and 3 MGy) were investigated. Additionally, the adsorption properties of irradiated clay for U(Ⅵ) were tested under different conditions. The clay samples underwent minimal structural changes following high-dose irradiation, and the interlayer spacing was altered due to the fractured framework, dehydroxylation, and radiolysis of water. After irradiation, the Fe (Ⅱ) content in clay was significantly increased, unlike Fe (Ⅲ) content. The adsorption mechanisms of clay before and after the experiments were verified, revealing that the adsorption capacity of irradiated clay to U(Ⅵ) is reduced. [Display omitted] • Gamma irradiation caused H 2 O radiolysis and skeleton fracture in clay samples. • The Fe (Ⅱ) content in clay significantly increased after gamma irradiation. • The uranium adsorption capacity of clay decreased after gamma irradiation. • Uranium adsorbed on clay mainly in the form of UO 2 2+. [ABSTRACT FROM AUTHOR]

Recently, clays have been investigated for the long-term storage of spent nuclear fuel and nanominerals have been developed for the separation of radionuclides from subsurface water, but the detailed structure relating to pillaring of the sorbent is not always easily assessable by X-ray diffraction, for example, where the shift of the basal spacing to a higher value is not distinct. The purpose of this study was to gain an insight into the correlation between nanoscale structure and macroscopic sorption performance. The time dependence of 239‑plutonium sorption to Laponite, (Ce Al)-Laponite, and (Ce Al)-bentonite was studied. (Ce Al)-Laponite was characterized by TEM, XPS, XRD, N 2 adsorption/desorption isotherms, and small-angle neutron scattering. Analysis of neutron scattering from dry powder and powder dispersed in water showed that (Ce Al)-Laponite has an open pore-fractal structure described by a fractal dimension D p = 2.5, and a radius of gyration R g = 6.5 nm. In a slightly alkaline pH condition, the strength of the sorption (K d) of 239Pu by the different sorbents, from most to least, was (Ce Al)-bentonite (104) > (Ce Al)-Laponite (~104) > Laponite (103) > bentonite (103). The time it took for Pu sorption to reach equilibrium for (Ce Al)-Laponite was almost two times faster than that observed for the starting clays and the (Ce Al)-bentonite (8 days). A pseudo-second order rate expression was applied to the time-course data to describe the kinetic behavior. The enhanced rate of sorption was attributed to the connected pore system present in (Ce Al)-Laponite. • 239Pu sorption to Laponite, Ce-Al-Laponite, and Ce-Al-bentonite is investigated. • Ce-Al-Laponite has an open pore-fractal structure based on various analyses. • K d 239Pu (mild alkalinity): Ce-Al-bentonite > Ce-Al-Laponite > Laponite > bentonite. • Enhanced sorption rate is ascribed to the connected pore system in Ce-Al-Laponite. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to reject pile-up pulse continuous zone. This paper first simulates the differences between three kinds trapezoidal shaping methods of which are trapezoidal shaping without width discrimination, with fixed width discrimination or with changing width discrimination, and then carry out experiment with silicon drift detector (SDD) and 55Fe source in laboratory, and the result of the experiment is that the ratio of peak to background (P/B) increases while the characteristic peaks in high energy section are not affected. Result of the simulation and experiment shows that the method proposed in this paper makes progress in pile-up pulse continuous zone rejection under the circumstance of high-count rates. • The pulse width of the exponential signal with rising edge after the trapezoidal pulse forming increases logarithmically with the increase of the pulse amplitude. • A pile-up pulse continuous zone reject method is proposed. • To verify the simulation result experimentally, 55Fe standard source is used as the measuring object. [ABSTRACT FROM AUTHOR]