Hasil untuk "Nuclear engineering. Atomic power"

Jianwen Huo, Minghua Luo, Tujiu Li et al.

This paper addresses the problem of multi-agent collaborative radioactive source localization using multi-agent deep reinforcement learning (MADRL). In this problem, agents need to learn collaborative search and collision-avoidance behaviors. Therefore, we propose a source search strategy, abbreviated as PSOPF-MATD3, that combines the particle swarm optimized particle filter (PSOPF) algorithm with the multi-agent twin delayed deep deterministic policy gradient (MATD3) algorithm. Specifically, the PSOPF algorithm is used to estimate the state of the source, and the key features of the source items are extracted using the Gaussian mixture model as inputs to the neural network. The MATD3 algorithm is used to find the optimal source search strategy based on the estimated status of the source terms. Experimental results show that the proposed PSOPF-MATD3 algorithm outperforms two multi-agent reinforcement learning algorithms (MADDPG and MASAC) in general and difficult scenarios. The proposed algorithm demonstrates a higher average group reward during the evaluation phase, completes the multi-agent collaborative target detection task in a shorter time, and exhibits superior convergence performance.

S. Panda, P. Netrakanti, S. Behera et al.

In this work, we present results for discrimination of neutron and $\gamma$ events using a plastic scintillator detector with pulse shape discrimination capabilities. Machine learning (ML) algorithms are used to improve the discriminatory power between neutron and $\gamma$ events at lower energy ranges which otherwise are not addressed by the conventional pulse shape discrimination techniques. The use of a multilayer perceptron with Bayesian inference (MLPBNN) and support vector machine (SVM) algorithms are studied using the recorded waveforms from the detector. Input variables are constructed for the ML algorithms, which captures the essence of the differences in the head and tail part of the neutron and $\gamma$ waveforms. A new variable, which utilizes the product of kurtosis and variance calculated from the waveform gives better ranking in terms of separation of neutron and $\gamma$ events. The training and the testing of the ML algorithms are done using an AmBe neutron source. In the lower energy region, the results obtained from the ML predictions are compared with the results obtained from a time of flight (ToF) technique to benchmark the overall performance of the ML algorithms. A reasonable agreement is observed between the results obtained from ML algorithm and the ToF experiment in the studied energy range. The MLPBNN gives better discriminatory power for the neutron and $\gamma$ events than the SVM algorithm.

CUI Chunsheng, CHEN Ran, WANG Chuangao, PANG Hongchao, LUO Zhiping, HUANG Xin

Styrene-acrylate emulsion fixation agent is used in control of radioactive aerosols of integrated fast reactors. In integrated fast reactor design, radioactive aerosol control represents a critical safety requirement. To mitigate hazards from sodium aerosols and other radioactive particles generated during potential sodium fire accidents in sodium processing compartments, while facilitating post-accident residue management, effective suppression of aerosol resuspension and dispersion becomes imperative. This study developed a film-forming aerosol fixing agent through emulsion polymerization using styrene (St) and butyl acrylate (BA) as primary monomers, with acrylic acid and methacrylic acid as functional monomers, specifically for sodium aerosol capture. Conditional experiments first established optimal dosages of initiator and emulsifier at 1.25wt% and 1.5wt% of total monomer mass and emulsion mass, respectively. Three fixing agent samples with varying monomer ratios (St∶BA = 1∶1, 1.75∶1, and 2∶1) were subsequently synthesized and aerosol natural settling experiments and aerosol capture experiments were designed to characterize the aerosol capture performance of the three fixative samples. An experimental setup was constructed, consisting of an aerosol capture test bench, an aerosol generator, an aerosol particle size spectrometer, and a fixed agent atomization device. The above experiment was conducted based on experimental design and experimental setup. Comparative aerosol capture experiments revealed the St∶BA=1.75∶1 formulation demonstrated superior performance, achieving 99.43% capture efficiency within 6 hours, significantly exceeding the 78.32% natural sedimentation rate observed in control trials. Resuspension tests further confirmed the agent’s effectiveness, showing aerosol resuspension rates reduced from 16.15% in natural sedimentation scenarios to merely 0.19% following aerosol fixation treatment. Microstructural analysis through SEM revealed the optimized formulation formed continuous polymer films that effectively encapsulated aerosol particles, while FTIR characterization verified successful copolymerization of functional groups enhancing interfacial interactions. The results show that the styrene-acrylate emulsion fixing agent enables superior radioactive aerosol control in sodium fire scenarios compared to passive sedimentation, with capture efficiency improvements exceeding 20 percentage points. The film-forming mechanism provides durable suppression of aerosol resuspension, reducing post-deposition particle remobilization by two orders of magnitude. The 1.75∶1 St/BA ratio optimizes the balance between polymer film flexibility and adhesion strength required for effective particle encapsulation. This research demonstrates the technical feasibility of applying polymeric fixation agents for enhanced radioactive aerosol management in advanced reactor systems, offering significant safety improvements over conventional passive containment strategies.

Z. Shen, T. Schwarz-Selinger, A. Manhard et al.

A systematic investigation was carried out to study the effects of ion energy and flux during deuterium (D) exposure of self-ion damaged tungsten (W) at a sample temperature of 570 K. Experimental conditions included combinations of 5 and 38 eV/D ions and fluxes of 6×1019 and 5×1020D/m2/s. The depth distribution of deuterium at the topmost 7.4 μm was determined by 3He Nuclear Reaction Analysis (NRA), while its total inventory was evaluated using both NRA and Thermal Desorption Spectroscopy (TDS). Morphological modifications at the surface were analyzed by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) together with focused ion beam cutting (FIB). The experimental results show that already a flux of 5×1020D/m2/s leads to the formation of blisters on the W surface even for 5 eV/D. With 38 eV/D ions additional defects are created that trap deuterium exceeding a depth of 7.4 μm. All blisters in this study were very shallow with widths in the micrometer range and heights of only few tens of nanometers. The study revealed that blisters with a low height-to-diameter ratio are difficult to detect using scanning electron microscopy (SEM). These features could only be clearly identified through CLSM applying the differential interference contrast (DIC) mode.

Yiqin Wang, Qingmei Xiao, Yang Liu et al.

Quantifying deuterium (D) retention in plasma-facing components (PFCs) with minimal material impact is critical for fusion reactor operation. This study employs laser-induced desorption coupled with quadrupole mass spectrometry (LID-QMS) for in situ D-retention analysis on HL-3 graphite tiles. As an auxiliary strategy, laser-induced breakdown spectroscopy (LIBS) is implemented under optimized low-fluence conditions to intermittently evaluate LID-QMS desorption efficiency during operation. Laboratory experiments demonstrate > 80 % deuterium release in the first LID pulse (laser fluence > 570 MW/m2), validated via cross-calibrated QMS measurements; LIBS provides rapid efficiency assessment by correlating D/H spectral results with QMS-resolved H, HD and D2 desorption signals. The integrated LID-QMS-LIBS framework permits: real-time optimization of LID parameters during material analysis, direct efficiency validation without destructive sampling. This methodology is currently being implemented on HL-3 tokamak for in situ wall-D monitoring, demonstrating potential to replace ex situ post-mortem analysis in future fusion devices.

Heewon Aneka Choi, Cheonho Park, JuHyeon Lee et al.

Cyberattacks on nuclear facilities can cause unauthorized information leakage and critical impacts on nuclear safety, making an effective cyber incident response system essential. The International Atomic Energy Agency (IAEA) emphasizes the protection of computer-based systems for physical security, nuclear safety, and nuclear material control from cyber threats. Nuclear facility operators must possess the capability to detect and respond to cyber incidents, and this capability can be evaluated through cyber incident response exercises. This study proposes a framework for evaluating nuclear operators' incident response capabilities. The framework analyzes and builds upon IAEA's cyber incident response phases, breaking them down into six phases, defines key activities and evaluation requirements for each phase, and incorporates existing cyber response evaluation technologies. It also presents criteria and performance indicators to evaluate whether these requirements are met. To examine the applicability and practical relevance of the framework, a cyberattack scenario tailored for nuclear facilities is applied to a simulator replicating real-world conditions. The findings of this study provide a systematic and objective way to evaluate response exercises, offering a foundation for effective cyber incident management and minimizing impacts on nuclear facilities.

Koji Nishida, Naoki Sano, Seitaro Sakurai et al.

The cladding temperatures and axial mass distribution computed by MAAP5 were compared with their measured values in the test bundle of the Phebus Test FPT0. The computed cladding temperatures were in good agreed with the measured values in the pre-transient phase. In the transient heat-up phase, the computed temperatures were overestimated by the Baker-Just correlation in MAAP5, but the computed temperatures could simulate the subsequently measured values. The computed mass distribution in the axial direction was in qualitative agreement with the measured one for post-test fuel damage observations. The calculated flow areas of inner and outer regions in the test bundle were compared with the photographic observations. MAAP5 computed them at the height of 0.2 m where the molten pool formed was in qualitative agreement with the photographic observations. It was found that the remaining steam flow paths might be caused by the gas-liquid two-phase flow counter-current flow limitation.

LI Tianya1, 2, , LUO Qi3, , YAO Dong2, HE Caiyun1, CHAI Xiaoming2, CAI Yun2, ZHANG Bin2, ZHANG Hongbo2, LIAO Hongkuan1, DUAN Yongqiang1

Among the high-fidelity numerical calculation methods in reactor physics, the pin-by-pin two-step method may strike a balance between calculation precision and calculation cost, and is currently a practical and viable high-fidelity numerical calculation method. Different from the traditional two-step calculation, the pin-by-pin two-step method only homogenizes the heterogeneous structure within each pin, retaining the assembly heterogeneous during three-dimensional whole-core calculations. In principle, homogenized group constants can only pre-serve the neutron leakage and reaction rates for the boundary conditions under which they are formed. However, the two-step method cannot predict the exact boundary condition in advance of an assembly in the active core. Currently, the pin-by-pin two-step method continues to apply the traditional single-assembly reflective boundary condition. The size of the homogenization region in the pin-by-pin calculation is nearly equal to the averaged neutron-free path, so the pin-by-pin homogenized parameters are more dependent on the assembly environment than the assembly-homogenized parameters. The traditional single-assembly reflective boundary condition does not account for the real environment of the fuel assemblies in the active core, however, the streaming effect and spectrum interference effect between different assemblies in the active core have a significant impact on the pin-by-pin homogenized parameters. As a result, there is deviation between the pin-by-pin homogenized parameters of the real core environment and the traditional single-assembly reflective boundary condition, leading to calculation errors. To deal with the environmental effect for pin-by-pin two-step method and improve the calculation accuracy of high-fidelity numerical calculation, this paper focused on the errors of the homogenized parameters, and improving the calculation accuracy by correcting the errors of environmental effect for the homogenization parameters. Firstly, this study discovers that the traditional Colorset method will cause the phenomenon of extrapolation of the machine learning model when representing the environmental effect, introducing large biases. So, the entire assembly Colorset and zone model was proposed to evaluate the environmental effect based on research into multi-assembly models for inner core assemblies (typical checkerboard problem) and surrounding reflector assemblies (irregular checkerboard problem). Then this study focused on three types of pin feature: information about the pin’s material and location; information about the surrounding assembly; and information about energy spectrum and leakage. By analyzing the machine learning model’s feature sensitivity, the combination features of pin material, location, surrounding assembly, energy spectrum, and leakage-related information were determined. Finally, a method for predicting pin-by-pin homogenized parameters was proposed: the correction method of pin-by-pin homogenization environmental effect of PWR based on machine learning. In order to numerically analyze the performance of the method, the HPR1000 was evaluated. The results show that, as compared to the typical single-assembly reflecting technique, the suggested method achieves higher precision outcomes in reactivity and pin power dithe stribution: The calculation accuracy of reactivity is increased by about 79%, the average pin power deviation is also greatly reduced, and the calculation accuracy is increased by about 76%. As a result, the method developed in this study may be utilized to mitigate the environmental impact of pin-by-pin homogenization in PWR and increase computation accuracy.

Andrew G. M. Rankin, J. Trébosc, F. Pourpoint et al.

Solid-state NMR spectroscopy is a powerful technique for the characterization of the atomic-level structure and dynamics of materials. Nevertheless, the use of this technique is often limited by its lack of sensitivity, which can prevent the observation of surfaces, defects or insensitive isotopes. Dynamic Nuclear Polarization (DNP) has been shown to improve by one to three orders of magnitude the sensitivity of NMR experiments on materials under Magic-Angle Spinning (MAS), at static magnetic field B0 ≥ 5 T, conditions allowing for the acquisition of high-resolution spectra. The field of DNP-NMR spectroscopy of materials has undergone a rapid development in the last ten years, spurred notably by the availability of commercial DNP-NMR systems. We provide here an in-depth overview of MAS DNP-NMR studies of materials at high B0 field. After a historical perspective of DNP of materials, we describe the DNP transfers under MAS, the transport of polarization by spin diffusion and the various contributions to the overall sensitivity of DNP-NMR experiments. We discuss the design of tailored polarizing agents and the sample preparation in the case of materials. We present the DNP-NMR hardware and the influence of key experimental parameters, such as microwave power, magnetic field, temperature and MAS frequency. We give an overview of the isotopes that have been detected by this technique, and the NMR methods that have been combined with DNP. Finally, we show how MAS DNP-NMR has been applied to gain new insights into the structure of organic, hybrid and inorganic materials with applications in fields, such as health, energy, catalysis, optoelectronics etc.

L. Dittrich, P. Petersson, H. Laabadi et al.

Polycrystalline (PC) and single crystal (SC) molybdenum mirrors were irradiated with 98Mo+, 1H+, 4He+, 11B+ and 184W+. Energies were chosen to impact the optically active region (up to 30 nm deep) of Mo mirrors. Some surfaces were coated by magnetron sputtering either with B or W films 4–65 nm thick. The overall objective was to simulate the neutron-induced damage and transmutation (H, He), and the impact of H, He, B, W on the optical performance of test mirrors, and on fuel retention. In parallel, a set of PC Mo mirrors irradiated with 1.6 MeV 98Mo3+ to a damage of 2 dpa and 20 dpa was installed in the JET tokamak for exposure during deuterium-tritium campaigns. Data from spectrophotometric, ion beam and microscopy techniques reveal: (i) the irradiation decreased specular reflectivity, whereby the differences between PC and SC in reflectivity are very small, (ii) He is retained in bubbles within 25–30 nm of the subsurface layer in all irradiated materials, (iii) W, either deposited or implanted, decreases reflectivity, but the strongest reflectivity degradation is caused by B deposition. Laboratory studies show the correlation of damage and H retention. Several cycles of W deposition and its removal from SC-Mo mirrors by plasma-assisted methods were also performed.

Kuo-Yuan Chu, Weng-Sheng Kuo, How-Ming Lee et al.

This study developed a quasi-monoenergetic neutron source (QMN) for the semiconductor device's soft error rate test (SER). Quasi-monoenergetic neutrons are generated by Be(p,n)B99 nuclear reaction with a 1 mm beryllium target and 30 MeV protons from a cyclotron. An 8 mm water in the back of the beryllium target is used for avoiding proton penetration. The neutron spectra simulated by MCNP showed that the peak energy was around 26.5 MeV. The heat flow and mechanical properties are numerically analyzed, and the safe operating conditions are therefore determined.

Hanfei Zhang, Yanyan Luo

The effects of macro-crack in plates on the characteristic of ultrasonic guided wave were studied. Using the Finite Element Model and numerical calculation method, the finite element mesh models of various macro-crack in aluminum plate were established. The single S0 or A0 mode Lamb wave was excited in plate by the wave structure loading method. The propagation time and amplitude of wave packet in the received signal were analyzed to study the phenomenon of mode transformation and the relationship between macro-crack size and signal amplitude. The simulation results show that there is mode conversion when the single mode Lamb wave interacts with an asymmetric macro-crack, and no mode conversion with a symmetric macro-crack. The energy of reflected wave increases with the increase of the depth and width of macro-crack, and the energy of transmitted wave decreases correspondingly. The size and inclined angle of macro-crack can be quantitatively estimated by the fitting function from the energies of reflected and transmitted waves. The variation of crack depth, width and angle is approximately linear with the amplitudes of reflected and transmitted wave packets. A fitting function is constructed by using the amplitude ratio of reflected wave packet or transmitted wave packet to total wave packet, which can be used to estimate the macro-crack depth, width and angle. This conclusion is helpful to the detection of macro-crack in the actual production and service of plate structures.

LIU Yue-kun, LYU Hong-bin, XIE Shu-bao et al.

The treatment and disposal of high level liquid waste(HLLW) is an important factor affecting the sustainable development of nuclear energy. The extraction separation of high-heat-release nuclide 137Cs from HLLW is not only beneficial to the safe disposal of HLLW, but also meeting the needs of 137Cs in many industry fields. In this work, the extraction process for 137Cs from HLLW was proposed with calixcrown as extractant. The process was tested with simulated and real HLLW with a recovery percentage of 99.9% for Cs(Ⅰ) and 99.95% for 137Cs, respectively. The results show that the proposed process for Sr extraction has a bright future in the treatment of commercial HLLW and the recovery of 137Cs in China.

Wen Ding, Kui Zhang, Dalin Zhang et al.

The safety injection (SI) system might be put into use, and the coolant at high temperature will mix with the supcooled water under Loss Of Coolant Accident (LOCA). The thermo-hydraulic phenomena associated with the thermal mixing of coolant and supcooled water will directly affect the judgment on core reflooding. China General Nuclear Power Group (CGN) independently developed and designed a thermal hydraulic system code named LOCUST, and the verification of thermal mixing models in LOCUST is necessary. This paper will introduce the thermal mixing tests at the T-junction based on Emergency Core Cooling System in Xi'an Jiaotong University (ECCS-XJTU) experimental facility, which were mainly conducted for the mixing between subcooled water injected from the SI pipe with a range of 25–125 kg/h in mass flow and the pure steam in the primary pipe with a range of 100–500 kg/h in mass flow. Besides, the fluid temperature and the dynamic vapor quality after mixing in tests are analyzed, and the simulations of 25 thermal mixing tests using the LOCUST 1.2 code are performed. The results show that the maximum relative error of LOCUST in mass flow of liquid is within 13.8 %, and the maximum relative error of LOCUST in temperature is within 8 %, which validates the reliability and accuracy of simulations of LOCUST for two-phase thermal mixing in LOCA.

Stepen Baxter

The project to which this paper is a contribution is a prospectus for the integrated industrial development of the Solar System. Fast transit on an interplanetary scale is a prerequisite before such a development can be established. To facilitate this freedom of movement, this study has defined a suite of fast, large-scale interplanetary ships, achievable in the relatively near term. As background, the present paper is a review of the literature on the feasibility of fast, large-scale, nuclear-powered, cargo carrying and/or crewed interplanetary craft, as explored historically from the development of atomic theory itself through to the application of modern fusion-technology high-performance propulsion systems. The study is part of the BIS SPACE (Study Project Advancing Colony Engineering) technical initiative. Keywords: BIS SPACE Project, Nuclear Powered Spaceship, Fast Interplanetary Ship, Project Daedalus, Project Icarus

R. Aminov

LIN Guang, ZHANG Dadi, ZHANG Zhen et al.

BackgroundHefei Light Source (HLS-II) is a dedicated synchrotron radiation source with featured the characteristics spectrum in vacuum ultraviolet and soft X-rays regions. The user's experiment efficiency and data processing efficiency are the principal indicators of HLS-II operation.PurposeThis study aims to develop an experimental data management system based on SciCat to improve the user's experimental and data processing efficiency.MethodsAs the core component of HLS-II experimental data management system, the metadata system was designed and developed within the framework of SciCat, an open source metadata catalog framework used to realize the unified management of the whole life cycle of experimental data of large scientific devices. Data acquisition service, metadata system, file storage system and data analysis platform were integrated into SciCat, and the hierarchical data format 5 (HDF5) was adopted as the standard experimental data format. Interface between existing user service systems and SciCat was implemented to achieve the management of the whole experiment and experimental data lifecycle, including user authentication, proposal application, expert approval, machine time schedule, data acquisition, data storage, data analysis and data publication.Results & ConclusionsThe system has been deployed and functionally tested at the soft X-ray microscopy experimental station of HLS-II, satisfying all design requirements.

Yu Zhang, Jiang Lai, Chao He et al.

Single-orifice plate is wildly utilized in the piping system of the nuclear power plant to throttle and depressurize the fluid of the pipeline. The cavitation induced by the single-orifice plate may cause some serious vibration of the pipeline. This study aims to find the optimal designs of the single-orifice plates that may have weak cavitation possibilities. For this purpose, a new single-orifice plate with a convergent-flat-divergent hole was modeled, a multi-objective optimization method was proposed to optimize the shape of a single-orifice plate, while computational fluid dynamics method was adopted to obtain the fluid physical quantities. The reciprocal cavitation number and the developmental integral were treated as cavitation indexes (e.g., objectives for the optimization algorithm). Two non-dominant designs ultimately achieved illustrated obvious reduction in the cavitation indexes at a Reynolds number Re = 1 × 105 defined based on fluid velocity. Besides, the sensitivity analysis and temperature effects were also performed. The results indicated that the convergent angle of the single-orifice plate dominants the cavitation behavior globally. The optimal designs of single-orifice plates result in lower downstream jet areas and lower upstream pressure. For a constant Reynolds number, the higher temperature of liquid water, the easier it is to undergo cavitation. Whereas there is a diametric phenomenon for a constant fluid velocity. Moreover, the regression models were carried out to establish the mathematical relation between temperature and cavitation indexes.

Seongin Moon, Jong-Min Kim, Joon-Yeop Kwon et al.

During a severe accident, steam generator (SG) tubes undergo rapid changes in the pressure and temperature. Therefore, an appropriate creep model to predict a short term creep damage is essential. In this paper, a novel creep model for Alloy 690 SG tube material was proposed. It is based on the theta (θ) projection method that can represent all three stages of the creep process. The original θ projection method poses a limitation owing to its inability to represent experimental creep curves for SG tube materials for a large strain rate in the tertiary creep region. Therefore, a new modified θ projection method is proposed; subsequently, a master curve for Alloy 690 SG material is also proposed to optimize the creep model parameters, θi (i = 1–5). To adapt the implicit creep scheme to the finite element code, a partial derivative of incremental creep with respect to the stress is necessary. Accordingly, creep model parameters with a strictly linear relationship with the stress and temperature were proposed. The effectiveness of the model was validated using a commercial finite element analysis software. The creep model can be applied to evaluate the creep rupture behavior of SG tubes in nuclear power plants.

Sașa-Alexandra Yehia, Lavinia Gabriela Carpen, Flavian Stokker-Cheregi et al.

In this paper, we describe a method to synthesize beryllium (Be) nanoparticles (NPs) by laser ablation of a solid target immersed in a liquid medium. Beryllium dust was successfully synthesized following the irradiation of a Be bulk target, which was immersed in water, acetone or heavy water, respectively, using the first and second harmonic (1064 and 532 nm) of a Nd: YAG laser source providing ns pulses, with a repetition rate of 10 Hz. The laser fluences used for Be target ablation were 8 and 15 J/cm2. In order to argue the successful obtaining of Be dust, scanning electron microscopy (SEM) was used for surface analysis. Colloidal solutions analysis by dynamic light scattering (DLS) supports the SEM analysis in terms of NPs size, whereas chemical analysis by X-ray photoelectron spectroscopy (XPS) was used in order to investigate the chemical composition. Moreover, thermal desorption spectroscopy (TDS) was performed on Be dust synthesized in heavy water to study the retention of deuterium (D). The key parameters for obtaining much sharper and regular size distribution were identified as being the liquid medium, laser fluence, and wavelength.