Three-dimensional metal halide perovskites (3D-MHPs) have emerged as potential semiconductors for direct-conversion X-ray detectors. However, excessive ion migration in 3D-MHPs compromises device stability, hindering practical deployment. While perovskite heterojunctions have been explored to suppress ion migration, their effectiveness are often limited by challenges in fabricating high-quality heterojunctions, resulting in suboptimal charge collection compared to individual perovskite crystals. In this work, a liquid-phase interfacial array-epitaxial growth method was developed to construct high-quality MAPbBr3/MAPbI3 heterojunctions for direct X-ray detectors. The heterojunction crystal exhibit a serrated, ultrathick transition region that enhances X-ray response by increasing the interfacial contact area between MAPbBr3 and MAPbI3. Consequently, the fabricated detectors demonstrate stable operational performance, a high sensitivity of 0.99 x 106 mu C Gyair -1 cm-2, and an ultralow detection limit of 0.56 nGyair s-1. Furthermore, the built-in electric field enables self-powered X-ray detection at 0 V bias, achieving a sensitivity of 1.16 x 103 mu C Gyair -1 cm-2.

Due to the strong X-ray attenuation coefficient, high carrier mobility-lifetime product, remarkable detection efficiency, and high-resolution imaging capability, metal halide perovskites have attracted increasing attention in the field of X-ray detection, known as promising candidates for next-generation high-performance radiation monitoring semiconductor materials. However, critical challenges, such as high dark current and pronounced ion migration, particularly in 3D perovskites, hinder their practical applications. Here, a unique 3D/1D perovskite heterojunction is presented as an effective strategy to address these limitations, where a distinctive, crisscross-structured 1D perovskite crystal with a planar and smooth surface is synthesized to form a robust interface with the 3D perovskite crystal. Benefiting from the synergistic effects of the heterostructure and 1D quantum wells, the resulting 3D/1D heterojunction exhibits a high ion migration activation energy, significantly suppressing ion migration and reducing the dark current. Consequently, the fabricated direct X-ray detector demonstrates exceptional operational and storage stability, achieving a high detection sensitivity of 1.03 × 105 µC Gyair -1 cm-2 and a low detection limit of 4.9 nGyair s-1. Furthermore, X-ray imaging experiments confirm the superior imaging quality and spatial resolution of the 3D/1D perovskite heterojunction device, highlighting its potential for high-performance, stable, and reliable X-ray detection applications.

Metal halide perovskites offer exceptional sensitivity for direct x-ray detection through direct current (DC) signals, but the DC bias-induced ion migration poses substantial challenges to their signal consistency and operational stability. In this work, we propose a capacitance signal-based imaging strategy that uses an alternating current (AC) bias to suppress ion migration and eliminate nonlinear responses. A quantitative correlation between capacitance changes and x-ray dose rate is established, enabling stable, high-resolution imaging. Using this method, we achieve three-dimensional internal structure reconstruction with a simple single-pixel detector. This approach overcomes intrinsic material limitations and enhances signal reliability, providing a promising pathway toward the commercialization of low-cost, high-performance perovskite-based x-ray imaging and computed tomography systems.

Metal halide perovskites have emerged as promising materials for X-ray detection due to their high X-ray attenuation coefficients, defect tolerance, and suitability for large-area, low-temperature fabrication. However, the intrinsic high ion conductivity of these materials presents challenges, such as high dark current density and current drift, which impair the stability and sensitivity of perovskite X-ray detectors. This study introduces an approach to mitigating these issues by incorporating 2,2,3,3,3-pentafluoropropylamine hydrochloride (PFH) into polycrystalline MAPbI3-xClx films using a one-step blade-coating method. PFH aggregates at grain boundaries, raising local vacuum energy levels and passivating surface defects, thereby reducing ion conductivity without affecting electron conductivity. As a result, this approach significantly reduces the dark current and enhances sensitivity, achieving a low detection limit of 14.7 nGyair/s. Additionally, it improves signal stability, consistency, and response speed of the detector. These findings suggest that PFH is a promising additive for advancing the performance and practical application of polycrystalline metal halide perovskite-based X-ray detectors.

Organic-inorganic halide perovskites, which integrate organic and inorganic elements, hold great potential for direct X-ray detection. Economical production methods, such as slurry blade coating, enable the manufacture of large-area X-ray detectors based on these materials. However, numerous pores and pinholes in the resulting polycrystalline thick films lead to detrimental effects like non-radiative recombination and ion migration, compromising detection performance. To overcome this challenge, we promote the growth of oriented crystal domains to assist in the fabrication of high-quality and thick perovskite X-ray photoconductor films. This approach leverages the synergistic effects of enhanced hydrogen bonding and A-site incorporation by carefully controlling the amount of guanidinium iodide. As a result, the film exhibits larger grains and fewer grain boundaries, leading to lower trap state densities and a higher carrier mobility-lifetime product. The resulting detector achieves a sensitivity of 7.6 x 104 mu C Gyair- 1 cm-2 and a limit of detection of 28 nGyair s-1. The devices also demonstrate improved stability by effectively eliminating ion migration pathways. This study proposes a methodological strategy for producing high-quality polycrystalline thick films, pivotal for advancing large-area flat-panel X-ray detection systems.

The development of perovskite direct X-ray detectors shows potential for advancing medical imaging and industrial inspection precision. To ensure the optimal energy conversion efficiency of X-rays for reducing radiation doses, it is necessary for perovskites with thicknesses reaching hundreds of micrometers or even several millimeters to be utilized. However, the nonlinear current response becomes uncertain with such high thicknesses. For instance, the prevailing theory regarding the rapid trapping and release of charges by shallow-level defects falls short in explaining the nonlinear current response observed in high-quality single-crystal samples. Moreover, a significant nonlinear current response can degrade the detection performance. Here, we elucidate peculiar parasitic and drift capacitance-induced nonlinear current responses in perovskites, which arise from bulk structural deficiencies and interface junction width variation in addition to shallow-level defects. Both theoretical analysis and experimental findings demonstrate the effective suppression of nonlinear current responses by establishing bulk heterojunctions and refining interface junctions. Consequently, we have successfully developed highly linear current-responsive detectors based on polycrystalline MAPbI(3) thick films. Notably, these detectors achieve a record sensitivity of 2.3 x 10(4) mu CGy(air) (-1)cm(-2) under 100 kV(p) X-ray irradiation with a low bias of 0.1 V/mu m, enabling enduring and high-resolution X-ray imaging for high-density objects. Successful fabrication and testing of a 64 x 64-pixel flat-panel prototype detector affirm the widespread applicability of these strategies in rectifying nonlinear current responses in perovskite-based X-ray detectors.

Direct X-ray detectors represent a transformative technology in the realm of radiography and imaging. The double halide-based perovskite cesium silver bismuth bromide (Cs2AgBiBr6) has emerged as a promising material for use in direct X-ray imaging, owing to its nontoxic composition, strong X-ray absorption, decent charge mobility lifetime product (mu tau), and low-cost preparation. However, formidable issues related to scalability and ion migration, stemming from intrinsic factors such as halogen vacancies and grain boundaries, have presented significant impediments. These issues have been associated with substantial noise, baseline instability, and a curtailment of detection performance. In response to these multifaceted challenges, we propose a slurry-based in situ treatment technique for fabricating robust Cs2AgBiBr6 thick films. This novel approach adeptly mitigates halogen vacancies, actively passivates grain boundaries, and concurrently elevates the ion migration activation energy, thus effectively suppressing ion migration. Consequently, the obtained X-ray detector exhibits excellent operating stability with minimal signal drift of 8.5 x 10(-9) nA cm(-1) s(-1) V-1 and achieves a remarkable 385% increase in sensitivity with a limit of detection as low as 7.8 nGy(air) s(-1). These results mark a significant step toward the development of high-performance and long-lasting lead-free perovskite direct X-ray detectors.

The multi-modular reactor, which connects multiple reactor units to drive a single turbine, is considered to be an innovation in the nuclear power system. The load factors of reactor units need to be adjusted in the event of load changes and module scram, which can cause fluctuations in numerous parameters and affect the stability of the reactor. This paper discusses the effective matching operation problem between reactors. To realize an orderly adjustment of load factors, an automatic power controller incorporating two operational strategies "extreme first" and "equal change" is designed. The feedforward-feedback control method is introduced to regulate the average temperature of the secondary circuit in order to reduce the control delay error caused by the thermal inertia of the system. An operation and control simulation of the multi-modular lead-based reactor based on the China lead-based research reactor (CLEAR-I) is performed. The numerical results show that the system parameters are well controlled, and the effective coordination of each module is realized.

Small Modular Lead-cooled Fast Reactor (SMLFR) is characterized by high safety, high efficiency, adaptability and versatility. The integrated system design adapts to more site conditions. Cogeneration is an advanced form of energy utilization based on the principle of energy cascade utilization, in which energy is mainly used to produce electricity and waste heat is used for heating at the same time. In this paper, the preliminary design of cogeneration system for SMLFR with the extraction-condensing and back-pressure cogeneration (EBC) type is proposed based on mathematical modeling and thermodynamically analysis. Based on a 35 MWth SMLFR, the effects of the main parameters and mass flow rate of heating steam on the power generation and efficiency are analyzed. A certain urban area in northern China with about 800,000 m(2) heating area is chosen to analyze the heating capacity, power generation capacity and economy under different cogeneration types by thermodynamic calculation. The work aims to point out the optimization direction of system integration for the Lead-cooled Fast Reactor (LFR) cogeneration system by the thermodynamic analysis. This cogeneration system can provide a reference for the secondary loop design of Generation-IV (GEN-IV) reactors.

锂热管反应堆是空间核反应堆的主要堆型之一,而锂热管结构材料的性能直接影响着反应堆经济性与安全性.本文以美国新墨西哥大学HP-STMCs锂热管堆芯方案为研究对象,采用SuperMC程序对Nb-1Zr,PWC-11,Mo-14Re,W-4Re,T-111以及ASTAR-811C几种候选锂热管结构材料的中子经济性与掉落临界安全特性进行分析研究.结果表明,上述几种候选结构材料的中子经济性依次为:PWC-11≈Nb-1Zr>Mo-14Re>W-4Re>ASTAR-811C>T-111;其中使用PWC-11、Nb-1Zr、Mo-14Re以及W-4Re结构材料时其管壁厚度变化对反应堆的有效增殖因子无显著影响;发生掉落事故情况下,临界安全分析结果表明结构材料的谱移吸收价值为:T-111>ASTAR-811C>W-4Re>Mo-14Re>PWC-11>Nb-1Zr.综合考虑锂热管反应堆的中子经济性与安全性,推荐使用Mo-14Re合金作为热管结构材料.

燃料组件是反应堆的核心部件,冷却剂在堆芯组件内部流动的流动阻力特性是反应堆热工水力特征的重要参数之一.本文以中国铅基研究堆(CLEAR-I)燃料组件为实验模型,利用水作为工作介质,基于雷诺数Re相似准则,间接研究燃料组件在铅基合金冷却剂中的阻力特性,通过测量常温水在不同流速下流经燃料棒束产生的压降值,获得Re在4000~43500范围内摩擦因子随Re变化的关系式,并将阻力模型Rehme关系式和Novendstern关系式的理论分析与实验数值进行了对比研究,结果表明,两个阻力计算模型与实验最大相对误差分别为18.9%和35.6%.

Lead and lead-alloys are proposed in future advanced nuclear system as coolant and spallation target. To test the natural circulation and gas-lift and obtain thermal-hydraulics data for computational fluid dynamics (CFD) and system code validation, a lead–bismuth eutectic rectangular loop, the KYLIN-II Thermal Hydraulic natural circulation test loop, has been designed and constructed by the FDS team. In this paper, theoretical analysis on natural circulation thermal-hydraulic performance is described and the steady-state natural circulation experiment is performed. The results indicated that the natural circulation capability depends on the loop resistance and the temperature and center height differences between the hot and cold legs. The theoretical analysis results agree well with, while the CFD deviate from, the experimental results.

T he interface corrosion characteristics of T 91 steel , one of the candidate structural materials of lead‐based reactor ,were studied in static lead‐bismuth eutectic (LBE) with an oxygen concentration of 0.01 ppm at 500 ℃ for 500 ,1 000 and 2 000 h , respectively .The morphology at corrosion interface was examined by SEM .In addition , the product composition and element diffusion behavior were analyzed by EDX .The results show that the oxidation of T 91 steel occurs and a three‐layered oxidation film forms on the surface .The outermost layer is magnetite (Fe3O4 ) which has a porous structure penetrated by LBE ,the middle layer is (Fe ,Cr)3 O4 that is more compact and protective ,and the innermost layer is an internal oxidation zone (IOZ ) consisting of Cr‐rich oxides . With the increasing of corrosion time , the thicknesses of Fe3 O4 and (Fe ,Cr)3 O4 increase rapidly at first , w hich reach 6.5 μm and 7.4 μm at 1 000 h , respectively .Subsequently ,the thickness of Fe3O4 slightly decreases while the thick‐ness of (Fe ,Cr)3 O4 slightly increases ,but the thickness of IOZ always increases slowly with time and the grow th kinetics follow s a linear law approximately .

Based on the operation environment of China Lead-based Research Reactor (CLEAR-I),the tensile properties of filter material-sintered 316L fiber felt exposed to stagnant lead bismuth eutectic (LBE) with 1×10-6 wt% oxygen concentration was investigated at 500℃ for 500 h,1000h,1500 h.The results showed that compared to the original fiber felt,the tensile strength of the fiber felts decreased to 67%,33% and 15% after 500 h,1000 h and 1500 h,respectively.It was found that the binding strength of the joints and diameter of 316L stainless steel fibers gradually decreased with exposure time due to the compact single-layer (Fe,Cr)3O4 spinel formation on 316L fibers,which was the main cause of tensile strength of sintered 316L fiber felt dropping after LBE corrosion.

Lead bismuth eutectic (LBE) is one of the most promising materials for coolant and spallation target for Accelerator Driven Systems (ADS). The thermal-hydraulic features in fuel assembly are one of the most important issues for development of this system. Aiming to get a deeper understanding on heat transfer behavior of wire-wrapped bundle cooled by LBE and to support the design of ADS systems, a fuel bundle simulator with 61 electrical rods spaced by helical wire was developed in KYLIN-II facility. In this paper, the preliminary heat transfer experiments with 70 kW under forced and natural circulation regimes were performed. The thermal-hydraulic behaviors including thermal entrance characteristics, heat transfer coefficients, and temperature distribution at the cross section were investigated under both regimes. The experiments depict reasonable results, and the Nu based on center sub-channel shows an agreement with empirical correlations. Besides, a special sub-channel code named SACOS-PB was employed to support the sub-channel analysis; and similar results to each other were obtained. It can be concluded that the SACOS-PB is a reliable tool for LBE system sub-channel analysis. Based on the present work the comprehensive thermal-hydraulic analysis with a detailed test matrix in terms of different flow rates and ;heating powers will be conducted in near future. (C) 2016 Elsevier Ltd. All rights reserved.

基于KYLIN-Ⅱ热工强迫循环实验回路,对CLEAR-Ⅰ单盒燃料组件1:1模型组件在铅铋介质中的流动阻力特性进行实验研究.研究表明:组件整体压降实验值与设计值吻合较好,相对偏差在6％以内.对绕丝棒束段的摩擦阻力系数与Novendstern、Rehme公式进行对比,Novendstern模型更适用于本实验棒束结构的压降计算;基于雷诺相似准则与前期水介质下的阻力系数对比,发现相同雷诺数下水介质下的阻力系数明显偏大,其原因为相同雷诺数下绕丝在水介质中引起的二次横流强度大于铅铋介质下的情况.

Measurement and control of oxygen content in liquid lead-bismuth is one of the key technologies in accelerator-driven subcritical system (ADS).It plays a vital role to resist structural material corrosion. Liquid lead-bismuth oxygen measurement and control experimental device was designed and constructed independently to study the key technology. Pt/Air reference electrode oxygen sensors were tested for the stability and veracity in the saturated oxygen concentration with the device. The results showed that in the temperature ranging from 625 ~ 786 K, it performed good stability after relaxation time less than 750 s for thermal equilibrium relaxation affect by the low heat conduction of YSZ ceramic tube. The voltage signal of Pt/Air sensor was in good agreement with the theoretical value,with absolute deviation less than 10 mV and relative deviation less than 1.5%.Reason for deviation came from thermoelectric voltages and oxide impurities.

Accurate measurement of the concentration of dissolved oxygen in liquid lead‐bismuth eutectic (LBE) is the premise to achieve oxygen control .A self‐developed Bi/Bi2 O3 oxygen sensor was used to measure oxygen concentration in LBE .The accuracy and stability tests were carried out in stagnant liquid LBE in the condition of oxygen sat‐uration .The accuracy test results show that the change of experimental electromotive force with temperature is consistent with the theoretical curve in the temperature ranging from 340 ℃ to 480 ℃ .The maximum absolute error of electromotive force is-2.6 mV .The stability test results show that the absolute error of electromotive force is -1.4 mV within 50 hours at the temperature of 450 ℃ and the fluctuation in this test is4mV .

For the purpose of investigating the thermal-hydraulic characteristics of lead-bismuth eutectic (LBE) natural circulation (NC), a LBE NC loop (NC-loop), experimental platform of the KYLIN-II facility was operated by the Institute of Nuclear Energy Safety Technology (INEST) in 2011. Experiments to characterize the thermal-hydraulic performance of HLM coolants undergoing NC were carried out at steady state to study the following issues: 1) the initiation of NC at different power levels; 2) the effects of input power and secondary loop operational characteristics on NC; 3) the capacity limits of NC and 4) a comparison of experimental data with theoretical predictions. The maximum NC capacity for LBE with a flow rate of 1.2 kg/s was obtained for a 24 kW heat pin corresponding to heating power input of 200 W/cm, which is higher than the linear power rating of the proposed China LEad Alloy Reactor-I (CLEAR-I). The experimental results at high heat pin input power were found to be in good agreement with the theoretical predictions. (C) 2014 Elsevier Ltd. All rights reserved.

The conceptual design of 10MWt China Lead-based Research Reactor(CLEAR-I)had been finished,which has critical and subcritical dual-mode operation capability for validation of ADS transmutation system and the Generation-IV lead-cooled fast reactor technology.Lead-bismuth eutectic was selected as primary coolant.The mature fuel and material technology was preferred,and the fuel assembly can be loaded by remote refueling system.CLEAR-I has excellent safety reliability,technology feasibility,experiment flexibility and technical continuity.The overview of reference scenario design,safety characteristics analysis and RD status of the CLEAR-I was presented.