Vol.29,

Molecular dynamics (MD) simulations were conducted to investigate the structural and chemical environment of aluminum in aluminophosphate glasses. Such glasses have the potential for application in the disposal of radioactive fluoride waste from molten salt reactors (MSR). Due to the risks of studying these materials and the limitations of realistic research conditions, MD simulations were used as an alternative method to study the vitrification of radioactive fluoride waste. In the past decades, aluminophosphate glasses have been studied, and they exhibit certain favorable properties for high-level radioactive waste (HLW) management. This work focuses on the effects of fluorine addition on structural changes in the glass. We observed that glass with composition P₂ O₅ –Al₂ O₃ –Na₂ O–CaO exhibited a good performance in immobilizing fluoride at low F concentrations (approximately under 25 mol%). Significant changes were observed where PO₃ F₂ units replaced PO₃ F units in the glass. The four-coordinated AlO₄ units were increasingly converted into five-coordinated [AlO_x F_y ] with the increasing F content. The radionuclide Sr in the simulation had the tendency to form six-coordinated octahedrons in the glass. We conclude that the structural changes resulting from the fluoride waste added to aluminophosphate glasses does not adversely affect their chemical stability at relatively low F concentrations, i.e., under 25 mol%. Hence, the use of phosphate glasses is a potential alternative method of fluoride waste disposal.

474

This paper presents the results of a radiological risk assessment arising from the presence of naturally occurring radionuclides in sand samples from three riverbanks in Muzaffarabad. The mean values obtained for ²³²Th, ²²⁶Ra, and ⁴⁰K were found to be 44.58 ± 3.34, 48.25 ± 1.77, and 239.92 ± 22.73 Bq.kg^-1, respectively. To assess the uniformity of exposure, the radium equivalent activity (Ra_eq) was calculated and was found to be 130.47 ± 8.29 Bq.kg^-1. The current reported value for Ra_eq is lower than the maximum permissible value, that is, 370 Bq.kg^-1, and equivalent to a gamma dose of 1.5 mSv y^-1. To investigate the possible contribution to health risks of alpha particle exposure, the radon exhalation rate (RER) from the sand samples was determined. The mean RER for all the samples was found to be 335 mBq.m^-2 h^-1. About 43% of the samples were found to have an indoor excess lifetime cancer risk value slightly higher than recommended safety limit of 1, as proposed by the ICRP. A normalized parameter, the equivalent multiplicative factor (EMF), was defined and used to compare the current results with the findings of studies performed in other countries. Our findings are relevant to both human health and future environmental radiation monitoring.

414

In this study, the activity concentrations of the fallout radionuclide ¹³⁷Cs in 150 soil samples collected from 13 districts of Manisa province were determined using a gamma-ray spectrometer with a NaI(Tl) detector. The health risks to people resulting from external exposure were evaluated by estimating the outdoor absorbed gamma dose rate and annual effective dose rate (outdoor and indoor). The activity concentration of ¹³⁷Cs varied from 3.6 ± 2.0 Bq kg^-1 to 124.1 ± 11.0 Bq kg^-1, with an average value of 43.3 Bq kg^-1. The average values of the outdoor absorbed gamma dose rate and annual effective dose (outdoor plus indoor) were found to be 1.3 nGy h^-1, and 8.0 µSv y^-1, (6.38µSv y^-1 + 1.59 µSv y^-1), respectively. The results were compared with internationally recommended values.

501

Attaining tritium self-sufficiency is indispensable in a Z-pinch driven fusion-fission hybrid reactor (Z-FFR). In this paper a conceptual design is presented in which the Z-FFR tritium cycle system was divided into eight subsystems. A theoretical analysis of tritium inventory based on the mean residence time was performed to quantitatively obtain the tritium distribution in each subsystem. Tritium self-sufficiency judgment criteria was established using a tritium mass flow analysis method. The dependency relationships between the burning rate, tritium breeding ratio, extraction efficiency, and tritium self-sufficiency were also specified for the steady state.

368

In this study, novel rhenium-boron neutron-shielding high-temperature-resistant materials were designed. The considered samples, Re60-B40, Re58-B42, Re50-B50, and Re40-B60, with different concentrations of rhenium and boron, were investigated to elucidate their neutron shielding performances, and compare them with well-known neutron shielding materials such as the 316LN quality nuclear steel. In addition to the experimental studies, Monte Carlo simulations were performed using the FLUKA and GEANT4 codes, where 4.5-MeV neutrons emitted by a ²⁴¹Am-Be source were employed. Experimental equivalent dose rates, simulated track lengths, energy balances, and neutron mass absorption cross-sections were discussed in detail.

551

The Xi’an Proton Application Facility (XiPAF) is a facility dedicated to the experimental simulation of the space radiation environment. The facility uses a compact synchrotron as its final stage accelerator. The synchrotron can accelerate a proton beam from 7 to 230 MeV. Physical design results show that the radio frequency (RF) acceleration system should work in the frequency range of 1–6 MHz and provide a maximum voltage of >800 V. To dilute the strong space charge effect during the injection period, we also aim to achieve multiharmonic acceleration. A compact RF acceleration system loaded with magnetic alloy cores has been designed and developed to fulfill these requirements. The preliminary test results show that the system can work normally with a gap voltage of 800 V. With a further RF power upgrade, the voltage can be improved to >1.2 kV.

377

A Monte Carlo simulation using two schemes, the discrete-energy-loss approach and the continuous-slowing-down approximation, was implemented in C++ to calculate the energy transmission coefficient and average energy loss for low-energy (1–10 keV) incident electrons passing through a thin metal layer. The simulation model uses the Ashley model for electron inelastic scattering, the electron elastic scattering cross section taken from the NIST database, and the stopping power derived from the full Penn algorithm. The results of the two schemes agree well with each other and can be used to quantitatively evaluate the shielding effect of a thin coated metal layer on incident electrons for a diamond amplified photocathode.

388

Cellulose nanofibrils (CNFs) are a type of natural nanomaterials extracted from plants and animals that have expanding applications in numerous areas benefiting from their inherent properties of renewability, biodegradability, and sustainability. For energy consumption reduction, CNFs were extracted from raw jute fibers, which were not pretreated in a hot alkali or acid solution, by TEMPO-mediated oxidation. Synchrotron radiation wide-angle scattering (SR-WAXS) was performed to realize the crystallization of the CNF crystallites, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy were used to characterize the changes in chemical groups and visualized morphology of CNFs. The simplified preparation and shortened cycle should further help the study of the structure-function relationship of jute CNFs subjected to chemical modification.

476

A very effective adsorbent for thorium has been obtained by modification of Santa Barbara Amorphous (SBA-15) using the chelating agent thenoyltrifluoroacetone (TTA). The prepared adsorbent (SBA-15-TTA) was characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), surface area, porosity, and zeta potential analyses. We investigated the factors affecting Th(IV) adsorption on TTA-SBA-15, such as initial pH, contact time, temperature, and initial metal concentration. The effective initial pH for adsorption was found to be 4. The binding sites on TTA-SBA-15 adsorbent were saturated using an initial Th(IV) concentration of 100 mg L^-1. The Dubinin–Radushkevich isotherm suggested a strong chemical interaction between adsorbent and adsorbate. Contact time and temperature had no significant effect on the adsorption. Therefore, the studies show that TTA-SBA-15 is a promising adsorbent to treat Th(IV)-contaminated effluents.

431

The fracs parameterizations, labelled as fracs-c, have been improved in order to predict the presence of isotopes near the proton drip line produced in projectile fragmentation reactions. By investigating the cross-sections for proton-rich isotopes in a series of reactions with energies ranging from intermediate to relativistic, it is shown that the fracs-c parameterizations can predict isotopes near the proton drip line considerably well. The fracs-c parameterizations are suggested to serve as an effective tool for predicting the presence of proton-rich isotopes with large asymmetry in a projectile fragmentation reaction. Different reactions have been investigated to check these results.

486

In this paper, the implantation-decay method is introduced to study the β-delayed charged particle decay. A silicon detector array was used for the implantation of the incident beams and for the detection of the emitted particles. An experimental measurement on the β-delayed particle emission from ²²Al was used to demonstrate the method. The half-life value, charged particle spectroscopy, γ ray spectrum, and γ particle coincidence for the decay process were obtained and compared with previous experimental results for ²²Al. The results show that the implantation-decay method, using a silicon detector array, is a suitable experimental method to study the β-delayed charged particle decay for proton-rich nuclei.

370

A small prototype of an active-target time projection chamber detector based on the gas electron multiplier (GEM) readout technique was designed and constructed. Simulation calculations were performed to analyze the electric field distribution and optimize the design. In particular, a guard ring installed above the GEM foil may play an important role in shaping the electric field in the gas vessel and improving the overall performance of the detector. The best results were obtained at a guard-ring voltage of -950 V. By using a collimated α-particle source, an energy resolution of 3.6–4.0 keV can be achieved for deposited energies of 18–21 keV, respectively. A position resolution of less 0.2 mm was observed along the electron drift direction, whereas the resolution in the readout plane was approximately 0.45 mm. A time resolution of less than 20 ns was obtained. By using helium as the primary working gas as well as the target material, α + α elastic scattering events can be clearly imaged.

389

A bismuth oxide (Bi₂ O₃ )-dispersed carboxylated nitrile butadiene rubber (XNBR) flexible film was prepared as a flexible lead-free material for gamma ray (γ-ray) attenuation. However, obtaining a uniform and stable dispersion of Bi₂ O₃ in carboxylated nitrile butadiene rubber latex (XNBRL) is a challenge due to sedimentation induced by the remarkable density differences. Here, this challenge was approached by reducing the Bi₂ O₃ particle radius, increasing the viscosity of the latex, and adding a dispersant. The experimental results confirmed that Bi₂ O₃ was well dispersed in the XNBRL in the concentration range of 30–70 wt.%. The mechanical properties demonstrated that the Bi₂ O₃ /XNBR flexible films had a good resistance to oil, acid, alkali, and hot air. The linear attenuation coefficients of the Bi₂ O₃ /XNBR flexible films obtained from the experiments were in good agreement with the calculated values. The attenuation efficiencies of the Bi₂ O₃ /XNBR flexible films with different thicknesses and Bi₂ O₃ contents were investigated for a few different γ-ray energies. These results showed that the Bi₂ O₃ /XNBR flexible films have wide application prospects for low-energy γ-ray attenuation.

456

The effect of gamma irradiation with different doses (25-75 kGy) on TiO₂ thin films deposited by atomic layer deposition (ALD) has been studied and characterized by X-ray diffraction (XRD), photoluminescence (PL) measurements, ultraviolet-visible (UV-VIS) spectroscopy, and impedance measurements (IS). The XRD results for the TiO₂ films indicate an enhancement of crystallization after irradiation, which can be clearly observed from the increase in the peak intensities upon increasing the gamma irradiation doses. The UV-VIS spectra demonstrate a decrease in transmittance, and the band gap of the TiO₂ thin films decreases with an increase in the gamma irradiation doses. The Nyquist plots reveal that the overall charge-transfer resistance increase upon increasing the gamma irradiation doses. The equivalent circuit, series resistance, contact resistance, and interface capacitance are measured by simulation using Z-View software. The present work demonstrates that gamma irradiation-induced defects play a major role in the modification of the structural, electrical, and optical properties of the TiO₂ thin films.

552

The purpose of this paper is to propose a friendly computational framework able to investigate particles tracking through different compartments of the human being using dedicated numerical techniques. The main building blocks of this framework are: (i) Convenient X-ray spectra calculator for different filter/anode combination (ii) Realistic voxelized computational human phantom (iii) Validated Geant4-based Monte Carlo simulation and (iv) Extendable and free image processing software. We studied the multimodality SPECT/CT cardiac imaging using specific spectrum of the ^99mTc and 120kVp X-Ray beam, for internal and external exposure, respectively. The application of the framework to quantify the loss of information between combined and simultaneous coregistration was carried out. Two main objectives were addressed: (i) an ideal geometry was simulated for educational purposes (ii) a realistic case study was carried out, for research purposes, concerning the modelling of the GE Infinia II 3/8" Gamma Camera. We compared the effect of using a NaI(Tl) and CZT crystal detector, and a LEHR and MEGP collimator with different uptake values of the heart organ (1:1, 5:1 and 50:1) for both simultaneous and combined SPECT/CT images. We confirmed the usefulness of the NaI(Tl) crystal with the LEHR collimator for such kind of study.

533