Vol.31,

In this study, COMSOL v5.2 Multiphysics software was utilized to perform coupled neutronics and thermal-hydraulics simulations of a molten salt fast reactor, and the SCALE v6.1 code package was utilized to generate the homogenized cross-section data library. The library’s 238 cross-section groups were categorized into nine groups for the simulations in this study. The results of the COMSOL model under no fuel flow conditions were verified using the SCALE v6.1 code results, and the results of the neutronics and thermal-hydraulics simulations were compared to the results of previously published studies. The results indicated that the COMSOL model that includes the cross-section library generated by the SCALE v6.1 code package is suitable for the steady-state analysis and design assessment of molten salt fast reactors. Subsequently, this model was utilized to investigate the neutronics and thermal-hydraulics behaviors of the reactor. Multiple designs were simulated and analyzed in this model, and the results indicated that even if the wall of the core is curved, hotspots occur in the upper and lower portions of the core’s center near the reflectors. A new design was proposed that utilizes a flow rate distribution system, and the simulation results of this design showed that the maximum temperature in the core was approximately 1032 K and no hotspots occurred.

434

This paper presents a corrosion assessment of copper spent nuclear fuel (SNF) disposal canisters in crystalline rock, using hydrogeological modeling. A simplified approach is considered, to avoid complex and time-consuming computer simulations. This simplified case is presented as a Base Case, with changes in the hydrogeological parameters presented as Variant Cases. The results show that in Taiwan's Base Case, decreasing the hydraulic conductivity of the rock or decreasing the hydraulic conductivity of dikes results in a shorter transport path for sulfide and an increase in corrosion depth. However, the estimated canister failure time is still over one million years in the Variant Cases.

373

The key issue in accelerating method of characteristics (MOC) transport calculations is in obtaining a completely equivalent low-order neutron transport or diffusion equation. Herein, an equivalent low-order angular flux nonlinear finite difference equation is proposed for MOC transport calculations. This method comprises three essential features: (1) the even parity discrete ordinates method is used to build a low-order angular flux nonlinear finite difference equation, and different boundary condition treatments are proposed; (2) two new defined factors, i.e., the even parity discontinuity factor and odd parity discontinuity factor, are strictly defined to achieve equivalence between the low-order angular flux nonlinear finite difference method and MOC transport calculation; (3) the energy group and angle are decoupled to construct a symmetric linear system that is much easier to solve. The equivalence of this low-order angular flux nonlinear finite difference equation is analyzed for two-dimensional (2D) pin, 2D assembly, and 2D C5G7 benchmark problems. Numerical results demonstrate that a low-order angular flux nonlinear finite difference equation that is completely equivalent to the pin-resolved transport equation is established.

405

The BL19U2 at the Shanghai Synchrotron Radiation Facility is a small-angle X-ray scattering beamline dedicated to structural studies pertaining to biological macromolecules in solution. The beamline has been officially opened to users in March 2015, and since then, a series of technological innovations has been developed to optimize beamline performance, thereby significantly improving the data collection efficiency and broadening the application scope of biological small-angle X-ray scattering. BL19U2 is ideal for the high-throughput screening of weakly scattered proteins, protein assemblies, nucleic acids, inorganic nanomaterials, and organic drug molecules. This paper describes the design and overview of the BL19U2 beamline. Versatile sample environments at the experimental station and some recent scientific highlights are presented.

656

Systematic CR-39 bulk etching experiments were conducted over a wide range of concentrations (2-30 N) of NaOH based etchant. Critical analysis and a deep discussion of the results are presented. A comprehensive nuclear track chemical etching data bank was developed. Three regimes of CR-39 bulk etching were identified. Regime I spans etchant concentrations from 2 to 12 N. Regime II spans concentrations from 12 to 25 N. We call this the dynamic bulk etching regime. Regime III is for concentrations greater than 25 N. In this regime, the bulk etch rate is saturated with respect to the etchant concentration. This classification is discussed and explained. The role of ethanol in NaOH-based etchants is explored and discussed. A parameter called the "reduced bulk etch rate" is defined here, which helps in analyzing the dependence of bulk etching on the amount of ethanol in the etchant. The bulk etch rate shows a natural logarithmic dependence on the density of ethanol in the etchant.

383

This study presents a benchmark evaluation of the new ENDF/B-VIII.0 nuclear data library for the Organization for Economic Co-operation and Development/Nuclear Energy Agency Medium 1000 MWth sodium-cooled fast reactor (SFR). The study presented herein covers both SFR core types i.e., metallic fueled (MET-1000) and oxide-fueled (MOX-1000), simulated using the continuous-energy Monte Carlo Serpent2 code. The neutronics performances of the ENDF/B-VIII.0-based simulations were compared mainly to two libraries: ENDF/B-VII.1 and JENDL-4.0. The comparison includes several neutronics parameters evaluated for the beginning and end of the cycle conditions. These parameters include the effective multiplication factor k_eff, total effective delayed neutron fraction β_eff, sodium void reactivity (∆ρ_Na), Doppler constant (∆ρ_Doppler), and control rod worth (∆ρ_CR). In addition, a sensitivity study was used to reveal the major isotope/reaction pairs contributing to the discrepancy observed in the performance of the three libraries using 33 and 44 energy-group structures.

516

We present a concise review of the recent development of relativistic hydrodynamics and its applications to heavy-ion collisions. Theoretical progress on the extended formulation of hydrodynamics toward out-of-equilibrium systems is addressed, with emphasis on the so-called attractor solution. Moreover, recent phenomenological improvements in the hydrodynamic modeling of heavy-ion collisions with respect to the ongoing Beam Energy Scan program, the quantitative characterization of transport coefficients in three-dimensionally expanding quark–gluon plasma, the fluid description of small colliding systems, and certain other interdisciplinary connections are discussed.

817

The isospin fractionations in ¹²⁴Sn, ¹⁰⁷Sn + ¹²⁰Sn at 600 MeV/nucleon, and ¹³⁶Xe, ¹²⁴Xe + ²⁰⁸Pb at 1000 MeV/nucleon are investigated by the isospin-dependent quantum molecular dynamics model coupled with the statistical code GEMINI. The yield ratio as a function of the binding energy difference for light mirror nuclei ³H/³He, ⁷Li/⁷Be, ¹¹B/¹¹C, and ¹⁵N/¹⁵O is applied to estimate the ratio between neutrons and protons in the gas of the fragmenting system. By comparing the estimated values resulting from the simulations with and without the GEMINI code, it was found that the secondary decay distorts the signal of the isospin fractionation. To minimize the secondary decay effects, the yield ratio of the light mirror nuclei ³H/³He as well as its double ratio between two systems with different isospin asymmetries of the projectiles are recommended as robust isospin observables.

519

The mass attenuation coefficients of the breasts, lungs, kidneys, pancreas, liver, eye lenses, thyroid, brain, ovary, heart, large intestines, blood, skin, spleen, muscle, and cortical bone were measured at different sources (i.e., 0.021, 0.029, 0.03, 0.14, 0.218, 0.38, 0.412, 0.663, 0.83, and 1.25 MeV) using various methods including the Monte Carlo N-particle transport code (MCNP), the Geometry and Tracking code (GEANT4), and theoretical approach described in this study. Mass attenuation coefficients were also compared with the values from the National Institute of Standards and Technology (NIST-XCOM). The values obtained were similar to those obtained using NIST-XCOM. Our results show that the theoretical method is quite convenient in comparison to GEANT4 and MCNP in the calculation of the mass attenuation coefficients of the human body samples applied when compared with the NIST values and demonstrated an acceptable difference.

532

This paper describes a low-cost and fast method to evaluate gross α and β^- radioactivities in natural water based on an online high-purity germanium detector gamma measurement system. The major gamma activities in natural water are provided by natural and artificial radionuclides such as ⁴⁰K, ¹³⁷Cs, and radionuclides belonging to ²³⁸U and ²³²Th series. The main α emitters related to gamma emissions in natural water are ²²⁴Ra (240.98 keV), ²²⁶Ra (186.21 keV), and the β^- emitters are ⁴⁰K (1460.85 keV), ²¹⁴Bi (609.31 keV), ²⁰⁸Tl (583.19 keV), and ²¹⁴Pb (351.93 keV). The formula for gross α and β^- activity concentration is based on these radionuclides, and the short half-life decay products are considered in the calculation. The detection efficiency of the device across energy region (0–3 MeV) are obtained through Monte-Carlo simulation, and a calibration experiment is conducted to verify the simulation results. Gamma radioactivity is measured continuously for 114 d in Pixian County and Dongfeng Canal located in the Zouma River, Chengdu, Sichuan Province, China. A comparison of the calculation results and monitoring data from the Sichuan Management & Monitoring Center Station of Radioactive Environment indicates that the percentage and absolute error of α activity concentration is lower than 53% and 0.02 Bq/L, respectively, and that of β-activity concentration is lower than 33.2% and 0.016 Bq/L, respectively. The method can rapidly determine gross α and β^- activity concentrations in natural water online.

493

To effectively replace the isotope radiation source in litho-density logging, this study presents a method for measuring the formation density and photoelectric absorption index (P_e) using a switchable X-ray tube. First, the gamma-ray litho-density logging (GLD) method for measuring formation density and P_e using chemical sources is introduced. Then, a benchmark verification based on the X-ray litho-density logging tool prototype and data published by Simon et al. [12] was carried out using Monte Carlo numerical simulations. Second, the impacts of the photoelectric effect and detector statistical error on the GLD method were analyzed. Finally, based on a theoretical analysis, the formation density and P_e measurement algorithm (double energy window (DEW) method) was improved, which was found to be suitable for X-ray litho-density logging. Moreover, the results obtained using this algorithm were compared with those obtained using the GLD method. The results indicate that owing to the impact of photoelectric effect and detector statistical error on the density energy window, the accuracy of formation density and P_e measurement using the GLD method is relatively low, with the uncertainty in formation density and P_e measurement reaching 2.620±0.047 g/cm³ and 4.090±0.580 b/e, respectively. In comparison, the DEW method can improve the accuracy of density and P_e measurement to 0.006 g/cm³ and 0.065 b/e, respectively, as the photoelectric effect in the density window is corrected using the counts in the lithology window of the energy spectrum. This study aims to provide a new theoretical foundation for processing X-ray litho-density logs in the future.

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