Nuclear Engineering Research Articles

Synergistic effects between potassium bubbles and high-energy-rate forging enabled ultrahigh strength and ductility of tungsten alloy

The intrinsic brittleness of tungsten (W) significantly restricts its application as the primary material for plasma-facing components. In this study, we propose a novel approach to improve both the strength and ductility of W-based alloys based on the synergistic effects between potassium (K) bubbles and high-energy-rate forging. K doping was introduced into W, followed by a two-step high-energy-rate forging (HERF) process. This leads to laminated matrix grains with refined sizes and deformation textures, as well as an increase in the density of low-angle grain boundaries and smaller size K bubbles along the grain boundaries. As a result, the prepared W alloys exhibit a substantially reduced ductile-to-brittle transition temperature within the range of room temperature to 50 °C, along with a notable ultimate tensile strength of up to 1393 MPa. Impressively, these alloys also demonstrate remarkable elongation at 200 °C, reaching a value as high as 33.12%. The remarkable mechanical strength and exceptional ductility exhibited by these alloys highlight their considerable potential for commercial application in the field of nuclear fusion engineering.

Sub-micrometer real-time imaging of trajectory of alpha particles using GAGG plate and CMOS camera

High-resolution and real-time imaging of the trajectories of alpha particles is desired in nuclear medicine and nuclear engineering. Although an imaging method using a scintillator plate combined with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera is a possible method of obtaining high-resolution trajectory images, the spatial resolution of the system is limited to ∼2 μm. To overcome the spatial resolution limitations of this method on trajectory imaging, we used a cooled complementally metal oxide (CMOS) camera in which the sensor had a much larger number of pixels, which were also smaller. Using the CMOS camera based imaging system, we could measure the trajectories of alpha particles in real time with the spatial resolution of 0.34 μm FWHM. With smoothing of the images to reduce image noise, spatial resolution was still kept to less than 0.75 μm. We conclude that this CMOS camera-based alpha-particle trajectory-imaging system is promising for alpha-particle or other particles imaging where ultrahigh spatial resolution is required.

Development of Direct Laser Deposition Technology for Large-Scale Products of Nuclear Power Engineering

Development of Direct Laser Deposition Technology for Large-Scale Products of Nuclear Power Engineering

Mechanical Properties of Experimental SiC/SiC Pipe Samples for Application in Nuclear Power Engineering Devices

Mechanical Properties of Experimental SiC/SiC Pipe Samples for Application in Nuclear Power Engineering Devices

Assessing the weaponability of enriched uranium trade in the geopolitics of nuclear energy: The EU-Russia interrelations

Russia's invasion of Ukraine in 2022 revived the debates over Moscow's grip on the nuclear fuel market. European and American governments had since planned for policies to diminish their reliance on Russian supplies, motivated by fear of the Kremlin using it as a coercive diplomatic tool, drawing parallels with experiences of fossil fuels exportation disruptions. While global interest for atomic energy is on the rise again, this article aims at assessing the weaponability of nuclear fuel trades, i.e., the conditions in which they can be used by suppliers to politically constrain importing nations. Geopolitics scholarship had until recently paid little attention to nuclear power and the few existing works overlooked the supply issue. In this paper, we bridge existing literature on the “energy weapon” to build a renewed analytical framework to identify the conditions in which fuel trade interdependencies can be coercively used. We then applied it to the case of enriched uranium trade between Russia and European Union's member states. Data were gathered through analysis of a textual corpus consisting of articles from three main magazines focused on nuclear power—Nuclear Engineering International, World Nuclear News and NucNet — (n = 439), 14 semi-structured interviews and three international conferences observations. Results show that Russia's weaponization capacity of enriched uranium trades against Europe in low, but not inexistent, thanks to supply diversification strategies, existing inventories, ongoing production overcapacity, transport fluidity and partial dependence of Rosatom on exports. However, countries' vulnerability isn't homogenous through Europe, and the low weapon ability of nuclear fuel is largely dependent on the fragile equilibrium in the supply and demand balance. Finally, this paper identifies the limits of applying weaponization theories developed in the context of fossil fuel trades to the case of nuclear power.

Influence of polypropylene fibers on the mechanical properties of radiation shielding concrete with barite aggregates

The brittleness of barite aggregates leads to inferior strength and toughness of radiation shielding concrete with barite aggregates (RSBC), which limits its application in high-pressure and high-heat nuclear engineering. This study aims to investigate the influence of polypropylene fibers on the mechanical properties of RSBC, and the effects of fiber type (PR40 and TMA20) and fiber content (3–9 kg/m3) on the mechanical properties of RSBC with water-to-binder (w/b) ratios of 0.44 and 0.39 are discussed. The microstructure of polypropylene fiber-reinforced RSBC was analyzed through scanning electron microscopy, revealing the underlying reinforcement mechanism of polypropylene fibers. The applicability of prediction formulas from typical codes was evaluated based on experimental data, and a reliable prediction model for the mechanical properties of RSBC was established. The findings showed that incorporating polypropylene fibers can significantly improve the compressive strength, splitting tensile strength, and flexural strength of RSBC. The addition of 9 kg/m3 PR40 and TMA20 fibers increased the 28-day compressive strength of RSBC by 17.9%–19.8% and 9.5%–16.2%, respectively; the 28-day splitting tensile strength increased by 12.1%–27.7% and 9.3%–26.1%, respectively; and the 28-day flexural strength increased by 19.3%–25.0% and 7.0%–13.5%, respectively. Adding PR40 fibers with a lower slenderness ratio yielded significantly better mechanical properties. Polypropylene fibers form a three-dimensional network structure in the concrete, acting as a bridge between the aggregate and cement mortar, enhancing the stability of interfacial transition zones, thereby effectively improving the macroscopic mechanical performance of RSBC. The mechanical property prediction models of EC 2 and GB 50010 for RSBC exhibit deviations, while the ACI 318 splitting tensile strength model and the flexural strength model established in this research demonstrate good predictive performance.

Laboratory-based X-ray spectrometer for actinide science.

X-ray absorption and emission spectroscopies nowadays are advanced characterization methods for fundamental and applied actinide research. One of the advantages of these methods is to reveal slight changes in the structural and electronic properties of radionuclides. The experiments are generally carried out at synchrotrons. However, considerable progress has been made to construct laboratory-based X-ray spectrometers for X-ray absorption and emission spectroscopies. Laboratory spectrometers are reliable, effective and accessible alternatives to synchrotrons, especially for actinide research, which allow dispensing with high costs of the radioactive sample transport and synchrotron time. Moreover, data from laboratory spectrometers, obtained within a reasonable time, are comparable with synchrotron results. Thereby, laboratory spectrometers can complement synchrotrons or can be used for preliminary experiments to find perspective samples for synchrotron experiments with better resolution. Here, the construction and implementation of an X-ray spectrometer (LomonosovXAS) in Johann-geometry at a radiochemistry laboratory is reported. Examples are given of the application of LomonosovXAS to actinide systems relevant to the chemistry of f-elements, the physical chemistry of nuclear power engineering and the long-term disposal of spent nuclear fuel.

Designing and significantly improved TeO2-based glass system for nuclear engineering applications: Radiation shielding performance and optical transparency

The radiation (beta particles (β), protons (1H), α-particles (He2+), carbon ions (C6+), fast neutrons (FN), and thermal neutrons (TN)) absorption parameters of 75TeO2–10MoO3–10BaO–(5-x)Sm2O3–xBi2O3 glass system were evaluated and presented along with their optical parameters in this study. The parameters were analyzed with the objective of evaluating the role of Sm and Bi atoms in altering the optical and radiation characteristics of the glass system. Starting with high-purity chemicals, namely BaCO3, Bi2O3, MoO3, TeO2, and Sm2O3, and following the melt-and-quench procedure, 75TeO2–10MoO3–10BaO–(5-x)Sm2O3–xBi2O3 glasses were prepared as TeMoBa-Sm/Bi1, TeMoBa-Sm/Bi2, TeMoBa-Sm/Bi3, TeMoBa-Sm/Bi4, and TeMoBa-Sm/Bi5 for Bi2O3 molar concentration of 0, 2, 4, 4.5, and 5 mol %, respectively. The optical parameters were computed theoretically from measured absorption spectra. The stopping powers and ranges of β-particles, protons, and α-particles were estimated using the ESTAR, PSTAR, and ASTAR software, respectively, while the SRIM code was used to compute for heavy carbon ions. In addition, the cross-sections of fast (FN) and thermal (TN) neutrons were computed using the standard expressions. There was a positive correlation between Bi2O3 content and the molar volume of the glasses. The refractive indices vary slightly between 2.53 and 2.56. The molar refractivity (Rm) values for TeMoBa-Sm/Bi1, TeMoBa-Sm/Bi2, TeMoBa-Sm/Bi3, TeMoBa-Sm/Bi4, and TeMoBa-Sm/Bi5 are 19.769 cm3/mol, 19.730 cm3/mol, 19.689 cm3/mol, 19.656 cm3/mol, and 19.754 cm3/mol, respectively. The values of Sp for proton are highest at 0.09 MeV with values of 284.047, 281.041, 278.135, 277.434 and 276.633 MeV cm2/g for TeMoBa-Sm/Bi1, TeMoBa-Sm/Bi2, TeMoBa-Sm/Bi3, TeMoBa-Sm/Bi4, and TeMoBa-Sm/Bi5, respectively. The Bi2O3 content thus improved the CR shielding ability of the glass system slightly. The optimum Bi2O3 concentration for FN shielding is 4 mol %. In addition, Bi2O3 compromised the TN absorption ability of the TeMoBa-Sm/Bi glass system.

Core flow distribution optimization of a natural circulation reactor using genetic algorithm, simulated annealing and characteristic statistic algorithm

Optimization of core flow distribution is a critical issue in nuclear engineering, particularly for natural circulation reactors with limited driving force. By appropriately arranging the resistance at fuel assembly inlets, core flow distribution could be well matched with core power distribution, thereby reducing the non-uniformity of core outlet temperature distribution. This, in turn, could enhance the performance and safety of the reactor. However, the flow distribution optimization throughout the fuel life cycle is a complicated global optimization problem that entails a vast solution space. In this paper, the flow distribution optimization with minimizing the maximum-to-minimum outlet temperature difference as the primary optimization objective, has been carried out incorporating various meta-heuristic algorithms with the core thermal-hydraulic analysis code COBRA, for a 200 MW natural circulation light water reactor. Minimizing the maximum-to-average outlet temperature difference is also chosen as an optimization objective since a smaller maximum outlet temperature is desirable. After the parametric sensitivity analysis of the genetic algorithm, the simulated annealing, and the characteristic algorithm, a set of parameters of each algorithm for the current flow distribution optimization problem has been determined. The results show that different algorithms yield similar resistance schemes under both optimization objectives, and all exhibit satisfying optimization effects, among which simulated annealing converges to the global optimum with significantly less computational costs.

Nuclear waste Educator's workshop: What and how do we teach about nuclear waste?

A workshop was held at the Massachusetts Institute of Technology (MIT) on July 25th and 26th, 2022. The objective was to develop a blueprint for educating next-generation engineers and scientists about nuclear waste management and disposal, which requires knowledge from diverse disciplines, including nuclear, chemical, civil, environmental, and geological science and engineering. The 49 participants included university professors, researchers, industry experts, and government officials from different areas. First, we have developed a list of key fundamental knowledge on waste management and disposal across the nuclear fuel cycle. In addition, we discussed strategies on how to teach students with diverse backgrounds through innovative teaching strategies as well as how to attract students into this area. Through the workshop, we identified the critical needs to (1) develop community resources for nuclear waste education; (2) synthesize historical perspectives, including past contamination and the management of general hazardous waste; (3) emphasize a complete life-cycle perspective, including proper waste management as the key component for energy sustainability; (4) teach students how to communicate about the key facts and risks to technical and non-technical audiences; and (5) accelerate the use of the state-of-art-technologies to attract and retain a young workforce. Furthermore, we aim to build a diverse, inclusive community that supports students in developing their own narratives about nuclear waste, particularly in recognizing that antagonistic views have been important to improving safety and protecting public health and the environment.

Approximate semi-analytical technique based on eigenfunction expansion for phase change heat transfer in a cylindrical body contained within a thick multilayered annular wall

Phase change heat transfer occurs commonly in thermal management and energy storage problems. Most literature in this direction assumes direct contact between the phase change material (PCM) and the heat source/sink. However, in practical problems, the PCM is often enclosed within a non-melting wall. This work presents an approximate eigenfunction expansion-based analysis of inwards phase change propagation in a cylindrical PCM encapsulated in a multilayer annular wall. The model accounts for imperfect thermal contact between layers. The transient temperature distribution is determined by solving a transient multilayer thermal conduction problem. Evolution of the phase change front is determined by inserting the temperature distribution into the interfacial energy conservation equation. Results are shown to agree with past work for special cases of the general problem considered here. Good agreement with both experimental and numerical data from past work, and with finite-element numerical simulations is demonstrated. The role of key non-dimensional parameters on phase change characteristics, including total time to melt/freeze is quantified. Ranges of non-dimensional numbers in which the approximate method offers good accuracy are determined. This work extends the state-of-the-art of phase change modeling, with potential applications in energy storage, nuclear engineering, oil/gas transport, and in mass transport problems.

Stress-strain curve mapping by nanoindentation – a technique to qualify diffusion-bonded window assemblies for ITER

The International Thermonuclear Experimental Reactor (ITER) is an international nuclear fusion research and engineering project with the aim to prove the feasibility of nuclear fusion as a large-scale carbon-free source of energy. The reactor vessel contains several diagnostic windows that provide a line of sight to the plasma. Design and qualification of such windows is challenging due to severe in-service conditions and the necessity to combine glasses with metals. One specific window is composed of fused silica glass that is connected to an Inconel ferrule via an aluminium bonding layer, where the joint is consolidated through a diffusion bonding process. The optimization of design and production process parameters of the windows is object of continuous improvements via dedicated three-dimensional finite element model (FEM) simulations. Importantly, these FEM simulations necessarily require stress-strain curves as input parameters. Such curves are difficult to obtain, especially from complex systems with dissimilar joints. In the present paper a methodology based on dynamic spherical nanoindentation has been developed and applied to map the stress-strain characteristics across the diffusion bonded joints. The methodology takes inspiration from the well-known theory to extract stress-strain curves from spherical nanoindentation. Here, it is applied to automated large indentation mapping with more than 1000 indentations including fully automated post-processing. The results provide bulk equivalent mechanical properties including yield stress, yield strain, work hardening parameters and elastic modulus at a micrometre resolution. Results show outstanding correlation with microstructural changes across the bonded cross-section, including grain refinement and twinning at the Inconel/aluminium interface.

Research on the shielding performance of concrete in a 60Co irradiation environment

The 60Co irradiation system used in this study created a γ environmental space. A type of cylindrical concrete shielding container with a cavity was used. The ratio of γ radiation that penetrated the shielding concrete was examined and compared to the results from the straight-line penetration tests. The outcomes demonstrated that barite concrete improved the linear attenuation coefficient by 13–18% compared to normal concrete regardless of whether the environmental method or linear 60Co irradiation method was used. The environmental method was used to determine the shielding ability of concrete in three dimensions, while the linear method was used to obtain the shielding rate from γ radiation in a single direction. The environmental 60Co radiation shielding method was more consistent with the γ diffusion model of an actual nuclear engineering design. This research is beneficial to the control of γ diffusion in nuclear engineering.

Neutron transport calculation for the BEAVRS core based on the LSTM neural network

With the rapid development of computer technology, artificial intelligence and big data technology have undergone a qualitative leap, permeating into various industries. In order to fully harness the role of artificial intelligence in the field of nuclear engineering, we propose to use the LSTM algorithm in deep learning to model the BEAVRS (Benchmark for Evaluation And Validation of Reactor Simulations) core first cycle loading. The BEAVRS core is simulated by DRAGON and DONJON, the training set and the test set are arranged in a sequential fashion according to the evolution of time, and the LSTM model is constructed by changing a number of hyperparameters. In addition to this, the training set and the test set are retained in a chronological order that is different from one another throughout the whole process. Additionally, there is a significant pattern that is followed when subsetting both the training set and the test set. This pattern applies to both sets. The steps in this design are very carefully arranged. The findings of the experiments suggest that the model can be altered by making use of the appropriate hyperparameters in such a way as to bring the maximum error of the effective multiplication factor keff prediction of the core within 2.5 pcm (10–5), and the average error within 0.5266 pcm, which validated the successful application of machine learning to transport equations.

EXPERIENCE IN TRAINING SPECIALISTS IN NON-DESTRUCTIVE CONTROL IN THE NUCLEAR POWER INDUSTRY

The data on certification of specialists of non-destructive testing of nuclear power engineering. It is shown that the largest number of specialists is certified for visual and measuring, capillary and ultrasonic control. Some procedures of training specialists in terms of presenting physical principles of NDT and some provisions of normative documents are considered. Relevant recommendations are given for the purpose of full assimilation of the training material. The main points of normative documents, which should be paid special attention to when studying them, are marked. It is noted that the experience, level of training and education of the certified specialists should be taken into account when giving lectures.

The applicability study and validation of TULIP code for full energy range spectrum

NECP-SARAX is a neutronics analysis code system for advanced reactor developed by Nuclear Engineering Computational Physics Laboratory of Xi'an Jiaotong University. In past few years, improvements have been implemented in TULIP code which is the cross-section generation module of NECP-SARAX, including the treatment of resonance interface, considering the self-shielding effect in non-resonance energy range, hyperfine group method and nuclear library with thermal scattering law. Previous studies show that NECP-SARAX has high performance in both fast and thermal spectrum system analysis. The accuracy of TULIP code in fast and thermal spectrum system analysis is demonstrated preliminarily. However, a systematic verification and validation is still necessary. In order to validate the applicability of TULIP code for full energy range, 147 fast spectrum critical experiment benchmarks and 170 thermal spectrum critical experiment benchmarks were selected from ICSBEP and used for analysis. The keff bias between TULIP code and reference value is less than 300 pcm for all fast spectrum benchmarks. And that bias keeps within 200 pcm for thermal spectrum benchmarks with neutron-moderating materials such as polyethylene, beryllium oxide, etc. The numerical results indicate that TULIP code has good performance for the analysis of fast and thermal spectrum system.

A setup for high-energy [formula omitted]-ray spectroscopy with the ELI-NP large-volume LaBr3:Ce and CeBr3 detectors at the 9 MV Tandem accelerator at IFIN-HH

We have performed the first experimental campaign using large-volume LaBr3:Ce and CeBr3 detectors from several of the Extreme Light Infrastructure-Nuclear physics (ELI-NP) instrumental setups together with detectors and infrastructure from the ROSPHERE array at the 9 MV Tandem facility at the Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). The performance of the detectors and the digital data acquisition system is shown to give a good energy resolution at high energies, and an excellent time resolution. We, furthermore, present the possibilities to integrate the detector system and the digital electronics with various ancillary detectors for, for example, charged particles.

Verification strategy for artificial intelligence components in nuclear plant instrumentation and control systems

The application of artificial intelligence (AI) systems in nuclear power plants has the potential to facilitate significant advancements in the industry. However, nuclear system engineers and regulators have expressed concerns regarding the reliability of AI components owing to a lack of documentation and appropriate verification methods that differ from those used for traditional software. Accordingly, this study proposes a systematic approach for the verification and validation of AI components based on nuclear software regulatory guidelines. The proposed strategy includes process verification and functional testing activities specifically tailored to AI components for instrumentation and control systems. This approach serves as a foundation for fostering understanding and agreement among system engineers, operating licensees, and regulatory bodies on the use of AI components in nuclear power plants.

Identification and stabilization of faulty Boolean control networks

Fault-tolerant control is a fundamental branch in the modern control theory, and has wide applications such as aerospace, automotive technology and nuclear engineering. Particularly, the study of faulty Boolean control networks (BCNs) is meaningful to the disease treatment. This paper focuses on both stuck-at fault and bridging fault in BCNs, and investigates the identification and stabilization of BCNs subject to these two faults. The basic mathematical tool is semi-tensor product (STP) of matrices, which is used to determine the algebraic formulation of faulty BCNs. Through the construction of invariant sets corresponding to the faulty nodes, the relations between these two faults and state transition matrices are presented, which is helpful to identify the faulty nodes. In addition, the robust stabilization of BCNs subject to these two faults is discussed and several new criteria are derived. Finally, the obtained results are applied to analyze the stabilization of oxidative stress response pathways.

Comparative Study on Shaking Table Tests for a Pile–Nuclear Island Structure under Different Soil Conditions

In this paper, the shaking table tests of a Seismic–Soil–Pile–Superstructure Interaction (SSPSI) in medium-soft and hard base soil were carried out. Silted clay with a unit weight of 1.70 g/cm3 and a shear wave velocity of 175 m/s was adopted to simulate the medium-soft soil, while the composite soil obtained by adding 20% quicklime to silted clay with a unit weight of 1.75 g/cm3 and a shear wave velocity of 300 m/s was adopted to simulate the hard soil in the tests. By inputting the artificial seismic motion time history with different amplitudes synthesized by the RG1.60 response spectrum commonly used in nuclear power engineering to the models, the dynamic interaction characteristics and seismic response laws of the soil–pile–nuclear island structure in the medium-soft and hard base soil were compared, the internal force and deformation distribution characteristics of the pile foundation under different ground conditions were analyzed, and the site conditions and mechanism of seismic failure of the pile group foundation were described. The research results can provide a reference for site selection and seismic design of a nuclear power plant.