Vol.29,

Boron carbide/natural rubber latex (B₄ C/NRL) flexible films were prepared via dip-molding with B₄ C content in the range of 5–55 wt.% for thermal neutron (0.0253 eV) shielding. B₄ C was well dispersed in NRL according to microscopic observation. Both the inside and outside surfaces of the film were smooth. For B₄ C/NRL flexible films, the minimum elongation at break was greater than 600%, the minimum tensile strength was greater than 12 MPa, and the hardness was in the range of 35–55 HA, which were suitable for preparing flexible wearable products. The attenuation efficiencies of the B₄ C/NRL flexible films for thermal neutrons were also calculated. The B₄ C/NRL flexible films exhibit good attenuation effect for thermal neutrons.

395

Backscattering of gamma photons from a material is of fundamental importance in radiation shielding, industrial and medical applications, radiation dosimetry, and non-destructive testing. In Compton scattering, incident photons undergo multiple scatterings within the material (target) before exiting. Gamma photons continue to soften in energy as the number of scatterings increases in a thick target, in other words the energy of gamma photons decreases as the scatterings increase in case of a thick target and results in the generation of singly and multiply scattered events. In this work, the energy distribution of backscattered gamma photons with backscattering intensity and energy probabilities were calculated by using the Monte Carlo method for metallic, biological, and shielding materials with various thicknesses of slab geometry. The materials under study were targeted with gamma photons of 0.279, 0.662, 1.250, and 2.100 MeV energies. In addition, the energy distributions of multiply scattered gamma photons were studied for materials with infinite geometry. The results are presented and discussed in detail by comparing with other Monte Carlo calculations.

425

Water molecules could form a liquid droplet on the water monolayer on a specific solid surface, which has been referred to as "ordered water monolayer that does not completely wet water" at room temperature. In contrast to the water molecules, the family of alcohol molecules have the same OH polar head and various lengths of their hydrophobic nonpolar tail; the length of the hydrophobic tail can affect the hydrophobic effect. In this study, using molecular dynamics simulations, we investigated the wetting behaviors of methanol, ethanol, and propanol molecules adsorbed on a SiO₂ surface. The results showed that the methanol, ethanol, and propanol molecules could form an ordered monolayer on the SiO₂ surface and a droplet on top of this monolayer, with different contact angles. The differences of the contact angles were attributed to the differences of the interactions between the alcohol monolayer and droplet.

749

A two-dimensional axisymmetric finite element model based on an improved cohesive element method was developed to simulate interfacial debonding, sliding friction, and residual thermal stresses in SiC composites during single-fiber push-out tests to extract the interfacial bond strength and frictional stress. The numerical load–displacement curves agree well with experimental curves, indicating that this cohesive element method can be used for calculating the interfacial properties of SiC composites. The simulation results show that cracks are most likely to occur at the ends of the experimental sample, where the maximum shear stress is observed, and that the interfacial shear strength and constant sliding friction stress decrease with an increase in temperature. Moreover, the load required to cause complete interfacial failure increases with the increase in critical shear strength, and the composite materials with higher fiber volume fractions have higher bearing capacities. In addition, the initial failure load increases with an increase in interphase thickness.

507

Muon tomography is a capable imaging technique to measure the geometry of high-Z objects. However, most existed algorithms used in muon tomography have obscured the effects of angular distribution and momentum spectra of cosmic ray muons and reduced the spatial resolution. We present a modified multi-group model that takes into account these effects and calibrates the model by the material of lead. Performance tests establish that the model is capable of measuring the thickness of a Pb slab and identifying the material of an unknown slab on a reasonable exposure timescale, in both cases of complete and incomplete angular data. Results show that the modified multi-group model is helpful for improvements of image resolution in real applications.

442

Ion cyclotron wave resonance heating (ICRH) is one of the most important auxiliary methods to heat plasma in the Experimental Advanced Superconducting Tokamak (EAST). Several megawatts of power is transmitted through separate coaxial lines, and coupled with the plasma through arrays of loop antennas. The parameters of the ICRH system, including the injected power and phasing between antenna straps, are critical to the coupling efficiency of the power as well as the resulting impact on the heating efficiency. In this paper, we present a system for feedback control of the phase between the current straps and the ICRH power on EAST. The feedback control system was tested using both a matched dummy load and a plasma load, and it successfully maintained stable operation in the 2016 EAST campaign. Good control of the injected power and wave phases were achieved during edge localized mode operation.

461

The streak camera is an ultra-fast diagnostic instrument with high sensitivity, and a high temporal and spatial resolution. It is primarily employed in various scientific research, such as inertial confinement fusion (ICF), synchrotron light sources, and electron positron colliders. An automatic control system for an X-ray streak camera is presented in this paper. The output terminal of an analog-to-digital converter (ADC) was isolated from its input terminal, to reduce interference from high-voltage electrodes. Compared with traditional methods, this scheme also improved the internal electromagnetic interface (EMI) immunity. Therefore, the system stability was enhanced. With this optimized control system, some characterizations of the streak camera were measured. Static and dynamic spatial resolutions of 25 and 20 lp/mm (CTF = 20%), respectively, were obtained. In addition, a dynamic range of 552:1 and temporal resolution of 7.3 ps were achieved. The results confirmed that these characterizations are sufficient for the specifications derived from the diagnostic requirements of ICF.

417

Monte Carlo transport simulations of a full core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full core model typically includes millions of burnup areas requiring hundreds of gigabytes of memory for burnup related tallies. This paper presents the study of a parallel computing method for full-core Monte Carlo transport–burnup calculations and the development of a thread-level data decomposition method. The proposed method decomposes tally accumulators into different threads and improves the parallel communication pattern and memory access efficiency. A typical PWR(Pressurized Water Reactor) burnup assembly along with the BEAVRS(Benchmark for Evaluation And Validation of Reactor Simulations) model was used to test the proposed method. The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.

494

On-line reactivity monitoring plays an important role in operation and safety analyses of fission reactor systems. The inverse kinetics method, which is based on a point kinetics model, is the most widely used method for reactivity reconstruction of critical water reactors. However, this method is seldom applied to the reactivity reconstruction of subcritical reactors. In this study, an inverse kinetics method was employed for the reactivity reconstruction of a lead-based reactor under different initial reactivity states (ρ₀ = 0, −2786, −5486, −8367, and −12371 pcm). The results showed that the deviation in the reactivity of the lead-based subcritical reactor was greater when ρ₀ became smaller. The reactivity reconstructed using the inverse kinetics method was globally underestimated. At a given reactivity perturbation, the relative and absolute errors increased with the decrease in the initial reactivity. At a given initial reactivity, with the increase in the reactivity perturbation, the absolute error increased, whereas the relative error remained the same. This deviation is due to the variation in the external neutron source, spatial-spectral effects, and sub-diffusive effects, which require further study.

410

In this paper, we build on the concept of equivalent fundamental-mode source to propose using delayed neutrons as a neutron source in multiplication experiments to acquire the effective multiplication factor k_eff of subcritical systems, which is difficult to acquire directly from conventional neutron source multiplication method. We analyzed the difference between a fundamental-mode fission source and delayed neutron source, then adopted a factor to convert delayed neutron distribution to an equivalent fundamental-mode source distribution and employed Monte Carlo code to acquire this factor. The delayed neutron multiplication measurement method was established for the first time, and corresponding experiments were conducted in subcritical systems. The multiplication of delayed neutrons was measured based on Chinese Fast Burst Reactor-II (CFBR-II) at subcritical states, and k_eff was acquired from delayed neutron multiplication successfully (0.9921 and 0.9969, respectively). The relative difference between k_eff obtained by the new method and previous values acquired by the positive period method is less than 1% for these two studied cases.

592

Data collection with microcrystals at synchrotron radiation facilities is challenging because it is difficult to harvest and locate microcrystals. Moreover, microcrystals are sensitive to radiation damage; thus, typically, a complete data set cannot be obtained with a single microcrystal. Herein, we report a new method for data collection with multiple microcrystals having a crystal size ranging from 1 to 30 µm. This method is suitable for not only low-temperature (100 K) data collection but also room-temperature data collection. Thin Kapton membranes were used to capture multiple crystals simultaneously. The microcrystals were visible under an optical microscope and easily located because the membrane was transparent and sufficiently thin. The film was fixed to a bracket that was prepared using a three-dimensional printer. The bracket was fixed on a magnetic base via screwing and employed by the goniometer system for data collection. Multiple data sets of fatty acid-binding protein 4 (FABP4) and lysozyme microcrystals were collected using this novel designed device. Finally, the structures of protein FABP4 and lysozyme were obtained from these data via the molecule replacement method. The data statistics reveal that this method provides a comparable result to traditional methods such as a nylon loop.

398

We report the design of a wide range energy material beamline (E-line) with multiple experimental techniques at the Shanghai Synchrotron Radiation Facility (SSRF). The undulators consisted of an elliptically polarizing undulator (EPU) and in-vacuum undulator (IVU), that generate the soft and hard X-rays, respectively. The beamline covered a wide energy range from 130 to 18 keV with both a high photon flux (>10¹² phs/sec with exit silt 30 μm in soft X-ray and >5×10¹² phs/sec in hard X-ray within 0.1%BW bandwidth) and promising resolving power (maximum E/∆E>15000 in soft X-ray with exit silt 30 μm and >6000 in hard X-ray). Moreover, the beam spots from the soft and hard X-rays were focused to the same sample position with a high overlap ratio, so that the surfaces, interfaces, and bulk properties were characterized in situ by changing the probing depth.

575

Acetohydroxamic acid (AHA) is a novel salt-free reagent used for the separation of Pu and Np from U in the advanced Purex process. This paper reports the γ-ray damage of AHA in HNO₃ and its radiolytic product. For 0.2 mol·L^-1 AHA in 0.2-2.0 mol·L^-1 HNO₃ irradiated at a dose of 5-25 kGy, the radiolytic rate of AHA is 6.63%-77.5%, and it increases with the HNO₃ concentration and absorbed dose. The main radiolytic gases are N₂ O and H₂, with volume fractions of (0.500-16.2) ×10^-2 and (1.30-11.8)×10^-3, respectively, and they increase with the absorbed dose; the H₂ volume fraction decreases with increasing HNO₃ concentration. The main liquid radiolytic products are CH₃ COOH and HNO_2, and their concentrations are (3.40-19.7) ×10^-2 and (0.200-4.80) ×10^-3mol·L^-1, respectively, which increase with the HNO₃ concentration. Since a significant concentration of HNO₂ is present in the irradiated AHA-HNO₃ solution, a holding reductant must be used to destroy HNO₂ and stabilize Pu (III) and Np(V) when AHA is applied for the separation of Pu and Np from U.

523

The sorption of the uranium (VI) ions from aqueous solutions by DEEA organo-volcanics (Kula-TURKEY) was investigated under different experimental conditions. Diethylethanol ammonium (DEEA) was used to modify the surface of basaltic volcanics. The characteristic of basaltic volcanic was analyzed by XRF, SEM-EDS, FTIR, and XRD. The BET surface areas of unmodified volcanics and DEEA modified-volcanics were found as 2.265 m²/g and 3.689 m²/g, respectively. The volcanic samples were treated by using different concentrations of DEEA. The adsorption of U (VI) on natural and modiﬁed volcanics was examined as a function of the contact time, initial pH of the solution, initial U (VI) concentration, and temperature. Langmuir, Freundlinch, and D-R adsorption isotherms were used to describe the adsorption. While examining the adsorption percentage and distribution coefficient, these values for unmodified volcanics were found to be 25 % ±0.76, and 10.08 mL/g for the DEEA modified-volcanics were 88 % ±1.04 and 220 mL/g, respectively. The pseudo-first-order and pseudo-second-order kinetic model were used to describe the kinetic data. In this study, it can be seen that the adsorption process is suitable for the pseudo-second-order kinetic model. Various thermodynamic parameters (ΔG^o, ΔH^o, and ΔS^o) were calculated with the thermodynamic distribution coefficients obtained at different temperatures. The sorption process was a chemical adsorption process. The results indicated that the processes are spontaneous and endothermic.

410