Vol.34,

Helium–xenon cooled microreactors are a vital technological solution for portable nuclear reactor power sources. To examine the convective heat transfer behavior of helium–xenon gas mixtures in a core environment, numerical simulations are conducted on a cylindrical coolant channel and its surrounding solid regions. Validated numerical methods are used to determine the effect and mechanisms of power and its distribution, inlet temperature and velocity, and outlet pressure on the distribution and change trend of the axial Nusselt number. Furthermore, a theoretical framework that can describe the effect of power variation on the evolution of the thermal boundary layer is employed to formulate an axial distribution correlation for the Nusselt number of the coolant channel, under the assumption of a cosine distribution for the axial power. Based on the simulation results, the correlation coefficients are determined, and a semi-empirical relationship is identified under the corresponding operating conditions. The correlation derived in this study is consistent with the simulations, with an average relative error of 5.3% under the operating conditions. Finally, to improve the accuracy of the predictions near the entrance, a segmented correlation is developed by combining the Kays correlation with the aforementioned correlation. The new correlation reduces the average relative error to 2.9% and maintains satisfactory accuracy throughout the entire axial range of the channel, thereby demonstrating its applicability to turbulent heat transfer calculations for helium–xenon gas mixtures within the core environment. These findings provide valuable insights into the convective heat transfer behavior of a helium–xenon gas mixture in a core environment.

491

The accurate modeling of depletion, intricately tied to the solution of the neutron transport equation, is crucial for the design, analysis, and licensing of nuclear reactors and their fuel cycles. This paper introduces a novel multi-group Monte-Carlo depletion calculation approach. Multi-group cross-sections (MGXS) are derived from both 3D whole-core model and 2D fuel subassembly model using the continuous-energy Monte-Carlo method. Core calculations employ the multi-group Monte-Carlo method, accommodating both homogeneous and specific local heterogeneous geometries. The proposed method has been validated against the MET-1000 metal-fueled fast reactors, using both the OECD/NEA benchmark and a new refueling benchmark introduced in this paper. Our findings suggest that microscopic MGXS, produced via the Monte-Carlo method, are viable for fast reactor depletion analyses. Furthermore, the locally heterogeneous model with angular-dependent MGXS offers robust predictions for core reactivity, control rod value, sodium void value, Doppler constants, power distribution, and concentration levels.

435

Monte Carlo simulations are frequently utilized in radiation dose assessments. However, many researchers find the prevailing computing platforms to be intricate. This highlights a pressing need for a specialized framework for phantom dose evaluation. To address this gap, we developed a user-friendly radiation dose assessment platform using the Monte Carlo toolkit, Geant4. The Tsinghua University Phantom Dose (THUDose_PD) augments the flexibility of Monte Carlo simulations in dosimetric research. Originating from THUDose, a code with generic, functional, and application layers, THUDose_PD focuses predominantly on anatomical phantom dose assessment. Additionally, it enables medical exposure simulation, intricate geometry creation, and supports both three-dimensional radiation dose analysis and phantom format transformations. The system operates on a multi-threaded parallel CPU architecture, with some modules enhanced for GPU parallel computing. Benchmark tests on the ICRP reference male illustrated the capabilities of THUDose_PD in phantom dose assessment, covering the effective dose, three-dimensional dose distribution, and three-dimensional organ dose. We also conducted a voxelization conversion on the polygon mesh phantom, demonstrating the method’s efficiency and consistency. Extended applications based on THUDose_PD further underline its broad adaptability. This intuitive, three-dimensional platform stands out as a valuable tool for phantom radiation dosimetry research.

494

Micro mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power generators and can be flexibly deployed in remote places to meet increasing electric power demands. However, previous steady-state simulations and experiments have deviated significantly from actual micronuclear system operations. Hence, a transient analysis is required for performance optimization and safety assessment. In this study, a hardware-in-the-loop (HIL) approach was used to investigate the dynamic behavior of scaled-down heat pipe-cooled systems. The real-time features of the HIL architecture were interpreted and validated, and an optimal time step of 500 ms was selected for the thermal transient. The power transient was modeled using point kinetic equations, and a scaled-down thermal prototype was set up to avoid modeling unpredictable heat transfer behaviors and feeding temperature samples into the main program running on a desktop PC. A series of dynamic test results showed significant power and temperature oscillations during the transient process, owing to the inconsistency of the rapid nuclear reaction rate and large thermal inertia. The proposed HIL approach is stable and effective for further studying of the dynamic characteristics and control optimization of solid-state small nuclear-powered systems at an early prototyping stage.

744

This study presents a probabilistic safety analysis (PSA) method for the external event of extreme snowfall on a floating nuclear power plant (FNPP) deployed in the Bohai Sea. We utilized the Weibull and Gumbel extreme value distributions to fit the collected meteorological data and obtained a hazard curve for the event of an extreme snowfall where the FNPP is located, providing a basis for the frequency of extreme snowfall-initiating events. Our analysis indicates that extreme snowfall primarily affects the ventilation openings of the equipment, leading to the failure of devices such as the diesel generators. Additionally, extreme snowfall can result in a loss of off-site power (LOOP). Therefore, the developed extreme snowfall PSA model is mainly based on the LOOP event tree, considering responses such as snowfall removal by personnel. Our calculations indicate a core damage frequency (CDF) of 1.13E-10 owing to extreme snowfall, which is relatively low. The results of the cut-set analysis indicate that valve failures in the core makeup tank (CMT), passive residual heat removal system (PRS), and in-containment refueling water storage tank (IRWST) significantly contribute to the CDF.

409

The NaI:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low ⁶Li concentration. To achieve real-time n/γ discrimination, a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was developed. The algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/γ discriminator based on a feld-programmable gate array (FPGA). The discriminator and NaI:Tl,⁶Li detector were tested in a neutron-gamma mixed field produced by an ²⁴¹Am-Be neutron source to evaluate the performance of the algorithm. The Figure of Merits (FoM) was measured as 2.88 at a sampling rate of 50 MHz, indicating that the discriminator with its embedded algorithm has a promising n/γ discrimination capability. Efficient discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.

399

Considering the R&D for upgrading the KL0 and μ detectors in the Belle II experiment using a scintillator and silicon photomultiplier (SiPM), we designed a compact high-speed and low-noise preamplifier. The preamplifier demonstrated a good gain stability, bandwidth of 426 MHz, baseline noise level of σ≈0.6 mV, dynamic range of up to 170 mV of the input signal amplitude, good time resolution of 20 ps, and it can be comprehensively applied to SiPMs. Adopting pole-zero-cancellation in the preamplifier reduces both the rise and fall times of the SiPM signal, which can significantly improve the time resolution and reduce the pile-up when using a large SiPM or an array of SiPMs. Various combinations of the preamplifier and several types of SiPMs demonstrated time resolutions better than 50 ps for most cases; when the number of detected photons was larger than 60, a time resolution of approximately 25 ps was achieved.

567

Gamma-ray polarimetry is a new and prospective tool for studying extremely high-energy celestial objects and is of great significance for the field of astrophysics. With the rapid development of microsatellite technology, the advantages of space exploration have become increasingly apparent. Therefore, we simulated a soft-gamma-ray polarimeter for a microsatellite based on the Compton scattering principle. We performed detailed Monte Carlo simulations using mono-energetic gamma-ray linear-polarization sources and Crab-like sources in the energy range of 0.1–10 MeV considering the orbital background. The polarimeter exhibited excellent polarization detection performance. The modulation factor was 0.80±0.01, and the polarization angles were accurate within an error of 0.2◦ at 200 keV for on-axis incidence. For the Crab-like sources for on-axis incidence, the polarization degrees were consistent with the set values within the error tolerance, the modulation factor was 0.76±0.01, and the minimum detectable polarization reached 2.4% at 3σ for an observation time of 10⁶ s. Additionally, the polarimeter exhibited recoil electron tracking, imaging, and powerful background suppression in a large field of view (FoV; ∼2π sr). The proposed polarimeter meets the requirements of a space soft-gamma-ray polarization detector and has promising research prospects.

805

Multilayer interference mirrors play a pivotal role in spectroscopic diagnostic systems, which probe electron temperature and density during inertial confinement fusion processes. In this study, aperiodic Mo/B₄C multilayer mirrors of varied thicknesses were investigated for X-ray plasma diagnostics at the 9.67-keV W-Lβ line. The thickness distribution of the aperiodic multilayers was designed using the 1^st Bragg diffraction condition and then optimized through a simplex algorithm to realize a narrow bandwidth and consistent spectral response. To enhance spectral accuracy, further refinements were undertaken by matching the grazing incidence X-ray reflectivity data with actual structural parameters. X-ray reflectivity measurements from the SSRF synchrotron radiation facility on the optimized sample showed a reflectivity of 29.7% ±2.6%, flat-band range of 1.3 keV, and bandwidth of 1.7 keV, making it suitable for high-temperature plasma diagnostics. The study explored the potential of predicting the 9.67 keV reflectivity spectrum using the fitting data from the Grazing incidence X-ray reflectivity (GIXRR) curves at 8.05 keV. Additionally, the short-term thermal stability of an aperiodic multilayer was assessed using temperature-dependent in situ X-ray measurements. Shifts in the reflectivity spectrum during annealing were attributed to interdiffusion and interfacial relaxation. The research team recommends the aperiodic Mo/B₄C multilayer mirror for operations below 300 ℃.

545

To correct spectral peak drift and obtain more reliable net counts, this study proposes a long-short memory (LSTM) model fused with a convolutional neural network (CNN) to accurately estimate the relevant parameters of a nuclear pulse signal by learning of samples. A predefined mathematical model was used to train the CNN–LSTM model and generate a dataset composed of distorted pulse sequences. The trained model was validated using simulated pulses. The relative errors in the amplitude estimation of pulse sequences with different degrees of distortion were obtained using triangular shaping, CNN-LSTM, and LSTM models. As a result, for severely distorted pulses, the relative error of the CNN-LSTM model in estimating the pulse parameters was reduced by 14.35% compared with that of the triangular shaping algorithm. For slightly distorted pulses, the relative error of the CNN-LSTM model was reduced by 0.33% compared with that of the triangular shaping algorithm. The model was then evaluated considering two performance indicators, the correction ratio and the efficiency ratio, which represent the proportion of the increase in peak area of the two characteristic peak regions of interest (ROIs) to the peak area of the corrected characteristic peak ROI and the proportion of the increase in peak area of the two characteristic peak ROIs to the peak areas of the two shadow peak ROI, respectively. Ten measurement results of the iron ore samples indicate that approximately 86.27% of the decreased peak area of the shadow peak ROI was corrected to the characteristic peak ROI, and the proportion of the corrected peak area to the peak area of the characteristic peak ROI was approximately 1.72%. The proposed CNN-LSTM model can be applied to X-ray energy spectrum correction, which is of great significance for X-ray spectroscopy and elemental content analyses.

526

The Electron Cyclotron Resonance (ECR) ion source is a critical device for producing highly charged ion beams in various applications. Analyzing the charge-state distribution of the ion beams is essential, but the manual analysis is labor-intensive and prone to inaccuracies due to impurity ions. An automatic spectrum recognition system based on intelligent algorithms was proposed for rapid and accurate chargestate analysis of ECR ion sources. The system employs an adaptive window-length Savitzky-Golay (SG) filtering algorithm, an improved automatic multiscale peak detection (AMPD) algorithm, and a greedy matching algorithm based on the relative distance to accurately match different peaks in the spectra with the corresponding charge-state ion species. Additionally, a user-friendly operator interface was developed for ease of use. Extensive testing on the online ECR ion source platform demonstrates that the system achieves high accuracy, with an average root mean square error of less than 0.1 A for identifying charge-state spectra of ECR ion sources. Moreover, the system minimizes the standard deviation of the first-order derivative of the smoothed signal to 81.1846 A. These results indicate the capability of the designed system to identify ion beam spectra with mass numbers less than Xe, including Xe itself. The proposed automatic spectrum recognition system represents a significant advancement in ECR ion source analysis, offering a rapid and accurate approach for charge-state analysis while enhancing supply efficiency. The exceptional performance and successful implementation of the proposed system on multiple ECR ion source platforms at IMPCAS highlight its potential for widespread adoption in ECR ion source research and applications.

476

Proton-rich nuclei are synthesized via photodisintegration and reverse reactions. To examine this mechanism and reproduce the observed p-nucleus abundances, it is crucial to know the reaction rates, and thereby, the reaction cross sections of many isotopes. Given the number of experiments on the reactions in astrophysical energy regions is very rare, the reaction cross-sections are determined by theoretical methods whose accuracy should be tested. In this study, given that ¹²¹Sb is a stable seed isotope located in the region of medium-mass p-nuclei, we investigated the cross sections and reaction rates of the ¹²¹Sb(α,γ)¹²⁵I reaction using the TALYS computer code with 432 different combinations of input parameters (OMP, LDM, SFM). The optimal model combinations were determined using the Threshold Logic Unit method. The theoretical reaction cross-sectional results were compared with the experimental results reported in the literature. The reaction rates were determined using the two input parameter sets most compatible with the measurements, and they were compared with the reaction rate databases, STARLIB and REACLIB.

381

Photoneutron cross-section (PNCS) data are important in various current and emerging applications. Although a few sophisticated methods have been developed, there is still an urgent need to study the PNCS data. In this study, we propose the extraction of PNCS distributions using a combination of gamma activation and reaction yield ratio methods. To verify the validity of the proposed extraction method, experiments for generating ^{62, 64}Cu and ^{85m, 87m}Sr isotopes via laser-induced photoneutron reactions were performed, and the reaction yields of these isotopes were obtained. Using the proposed extraction method, the PNCS distributions of ⁶³Cu and ⁸⁶Sr isotopes (leading to ^85mSr isotope production) were successfully extracted. These extracted PNCS distributions were benchmarked against available PNCS data or TALYS calculations, demonstrating the validity of the proposed extraction method. Potential applications for predicting the PNCS distributions of the 30 isotopes are further introduced. We conclude that the proposed extraction method is an effective complement to the available sophisticated methods for measuring and evaluating PNCS data.

413

According to the recent studies, the gravitational wave (GW) echoes are expected to be generated by quark stars composed of ultrastiff quark matter. The ultrastiff equations of state (EOS) for quark matter were usually obtained either by a simple bag model with artificially assigned sound velocity or by employing interacting strange quark matter (SQM) depicted by simple reparameterization and rescaling. In this study, we investigate GW echoes with EOSs for SQM in the framework of the equivparticle model with density-dependent quark masses and pairing effects. We conclude that strange quark stars (SQSs) can be sufficiently compact to possess a photon sphere capable of generating GW echoes with frequencies in the range of approximately 20 kHz. However, SQSs cannot account for the observed 72 Hz signal in GW170817 event. Furthermore, we determined that quark-pairing effects play a crucial role in enabling SQSs to satisfy the necessary conditions for producing these types of echoes.

350

The pseudo-rapidity distributions of the charged particles produced in the asymmetric collision systems p+Al, p+Au and ³He+Au at sNN=200 GeV are evaluated in the framework of a fireball model with Tsallis thermodynamics. The fireball model assumes that the experimentally measured particles are produced by fireballs following the Tsallis distribution and it can effectively describe the experimental data. Our results as well as previous results for d+Au collisions at sNN=200 GeV and p+Pb collisions at sNN=5.02 TeV validate that the fireball model based on Tsallis thermodynamics can provide a universal framework for pseudo-rapidity distribution of the charged particles produced in asymmetric collision systems. We predict the centrality dependence of the total charged particle multiplicity in the p+Al, p+Au, and ³He+Au collisions. Additionally, the dependences of the fireball model parameters (y_0a, y_0A, σ_a and σ_A) on the centrality and system size are studied.

483

In this article, a comprehensive study of the fission process of Th, U, Pu, and Cm isotopes using a Yukawa-folded mean-field plus standard pairing model is presented. The study focused on analyzing the effects of the pairing interaction on the fragment mass distribution and its dependence on nuclear elongation. The significant role of pairing interactions in the fragment mass distributions of ²³⁰Th, ²³⁴U, ²⁴⁰Pu, and ²⁴⁶Cm was demonstrated. Numerical analysis revealed that increasing the pairing interaction strength decreased the asymmetric fragment mass distribution and increased the symmetric distribution. Furthermore, the odd-even mass differences at symmetric and asymmetric fission points were examined, highlighting their sensitivity to changes in the pairing interaction strength. Systematic analysis of the Th, U, Pu, and Cm isotope fragment mass distributions demonstrated the effectiveness of the model in reproducing the experimental data. In addition, the effects of the zero-point energy and half-width parameter on the fragment mass distribution for ²⁴⁰Pu were explored. Thus, this study provides valuable insights into the fission process by emphasizing the importance of pairing interactions and their relationship with nuclear elongation.

538

The zero-degree calorimeter (ZDC) plays a crucial role toward determining the centrality in the Cooling-Storage-Ring External-target Experiment (CEE) at the Heavy Ion Research Facility in Lanzhou (HIRFL). A boosted decision tree (BDT) multi-classification algorithm was employed to classify the centrality of the collision events based on the raw features from ZDC such as the number of fired channels and deposited energy. The data from simulated ²³⁸U + ²³⁸U collisions at 500 MeV/u, generated by the IQMD event generator and subsequently modeled using the GEANT4 package, were employed to train and test the BDT model. The results showed the high accuracy of the multiclassification model adopted in ZDC for centrality determination, which is robust against variations in different factors of detector geometry and response. This study demonstrates the good performance of CEE-ZDC in determining the centrality in nucleus-nucleus collisions.

410

Gao-Le Yang，Zhen-Dong An，Wei Jiang，Xian-Kai Li，Wei-Wei Qiu，Zheng-Fa Liao，Zi-Yue Zhuang，Xiao-Ping Zhang，Sheng-Li Chen，Chen-Chen Guo，Er-Xi Xiao，Xiao Fang，Xin-Xiang Li，Xin-Rong Hu，Bing Jiang，Jin-Cheng Wang，Jie Ren，Wen Luo，Zhi-Chao Zhu，Hao-Yang Lan，Zong-Wei Cao，Xu Ma，Ying-Du Liu，Pu-Sen Wang，Yi Yang，Ping Su，Xian-Gai Deng，Wan-Bing He，Chun‑Wang Ma，Yu-Ting Wang，Zhi-Tao Dai，Peng-Qin He，Ren-Guang Tang，Tao Zhou，Jing Wang，Han Yi，Yue Zhang，Yong-Hao Chen，Rui-Rui Fan，Ke-Qing Gao，Qiang Li，Kang Sun，Zhi-Xin Tan，Min-Hao Gu，Han-Tao Jing，Jing-Yu Tang

The neutron capture cross sections (n,γ) of bromine were obtained using the time-of-flight technique at the Back-n facility of the China Spallation Neutron Source. Prompt γ-rays originating from neutron-induced capture events were detected using four C₆D₆ detectors. The pulse-height weighting technique and double-bunch unfolding method based on Bayesian theory were used in the data analysis. Background deductions, normalization, and corrections were carefully considered to obtain reliable measurement results. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in the unresolved resonance region (URR) were obtained from 10 to 400 keV. The experimental results were compared with data from several evaluated libraries and previous experiments in the RRR and URR. The TALYS code was used to describe the average cross sections in the URR. The astrophysical Maxwell average cross sections (MACSs) of ^79,81Br from kT = 5 to 100 keV were calculated over a sufficiently wide range of neutron energies. At a thermal energy of kT=30 keV, the MACS value for ⁷⁹Br 682±68 mb was in good agreement with the KADoNiS v1.0 recommended value. By contrast, the value of 293±29 mb for ⁸¹Br was substantially higher than that of the evaluated database and the KADoNiS v1.0 recommended value.

486

This paper introduces the proposed Insertion Device (ID) scheme for the Shanghai Synchrotron Radiation Facility Upgrade (SSRF-U). Based on this scheme, the influences of the ID radiation on the Intra-Beam Scattering (IBS) emittance and energy spread were evaluated. Optical distortion caused by the IDs was comprehensively examined and compensated using both local and global corrections. Subsequently, a Frequency Map Analysis (FMA) method was used to identify potentially dangerous resonance lines. In addition, the dynamic aperture, energy acceptance, and Touschek lifetime were calculated after considering high-order magnetic field errors to ensure that the ID effect did not affect the operation of the storage ring.

474