Nuclear Systems Research Articles

Missed prediction of the neutron halo in 37Mg

Halo phenomena have long been an important frontier in both experimental and theoretical nuclear physics. 37Mg was identified as a halo nucleus in 2014 and remains the heaviest nuclear halo system to date. While the halo phenomenon in 37Mg was not predicted before the discovery, its description has been still challenging afterwards. In this Letter, we report a microscopic and self-consistent description of the neutron halo in 37Mg using the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) that was developed in 2010. The experimental neutron separation energies and empirical matter radii of neutron-rich magnesium isotopes as well as the deformed p-wave halo characteristics of 37Mg are well reproduced without any free parameters. In particular, the orbital occupied by the halo neutron in 37Mg, exhibiting p-wave components comparable to those suggested in experiments, remains consistent across various employed density functionals including PC-F1, PC-PK1, NL3*, and PK1. The DRHBc theory investigated only even-even magnesium isotopes in previous works and for that reason missed predicting 37Mg as a halo nucleus before 2014. Although the core and the halo of 37Mg are both prolate, higher-order shape decoupling on the hexadecapole and hexacontatetrapole levels is predicted.

A hybrid multi-objective optimization method for nuclear essential service water system design

Evolutionary algorithms have proven to be very successful in solving multi-objective optimization problems (MOPs). However, their performance often deteriorates when constraints are introduced. This paper proposes a hybrid heuristic intelligence (HHI) approach to remedy this issue. First, a classification operator is designed to sort individuals by their relative constraint values, which enlarges the size of feasible solutions in the early process. Then, by combining constraints with the non-dominated sorting method, we define a new selection operator to increase the probability of selecting individuals who have low constraint values but high objective values. Finally, we use hybrid optimized operations to simultaneously enhance the convergence and diversity performance by performing different operators in a certain domain. The proposed method achieves state-of-the-art performance on test functions ZDT1, Binh2, and OSY, with a remarkable decrease of 24% in the inverted generational distance (IGD) on OSY. For further applications, our method is also tested with an engineering model established for the design of the nuclear essential service water system (SEC). The final result shows that without taking hundreds of hours, the final solution of HHI has met all constraints and reduced the total cost by 8.9%© YEAR The Authors. Published by Elsevier Ltd.

Thermodynamic performance evaluation and power/cooling energy trade-off estimation of an isolated system driven by nuclear energy

The wide temperature range requirement of components in an isolated system offers the possibility for power regulation for combined cooling and power system by adjusting the cooling energy supplement amount. To achieve the flexible operation and combined energy output for the independent nuclear power system, this paper proposes an isolated combined cooling and power system driven by nuclear energy to track power load by making an energy trade-off between net power output and cooling capacity by combing the steam Rankine cycle with the ammonia-water mixture cycle. Parametric analysis and single objective optimization are carried out to explore the effect of the key parameters on system performance. Multi-objective optimization is presented to obtain the optimal parameters group. The regulation capacity of power and cooling is analyzed by trade-off strategy for the proposed system based on the design condition. Results show that the optimal thermal efficiency of the proposed system is 31.60 % based on the single objective optimization. The rated thermal efficiency is 32.8 % with 2229.7 kW power energy and 1045.7 kW cooling energy output based on multi-objective optimization. In addition, the power load can be regulated from 78.1 % to 111.8 %, and the corresponding cooling load is adjusted from 176.1 % to 58.7 %. Furthermore, the improvement of the component performance should focus on the steam turbine and evaporator. The trade-off strategy offers an original conception of the regulation method for an isolated system.

Radiation-Resistant Electrical Insulation Materials for Superconducting Magnet Applications

To develop radiation-resistant electrical insulation materials suitable for cryogenic temperatures and applications that require radiation resistance such as future nuclear fusion energy systems, a United States Department of Energy Fusion Energy Sciences funded study was undertaken collaboratively by InnoSense LLC (ISL) and the Center for Advanced Power Systems. The goals for the new electrical insulation materials were low gas generation under irradiation, long pot life, high mechanical strength, good flexibility, and high dielectric strength. The development of proprietary metal oxide nanoparticle incorporated organic polymer composites (MOPOC) and their properties are reported. MOPOC consists of organic polyurethane (PU)-polyimide (PI) copolymers, ISL's proprietary and patented phenylated bipyridinium ionic polymers, and metal oxide nanoparticles. The results show the promise of the materials with the desired characteristics of mechanical, thermal, and pot life. Dielectric strength of 44 kV/mm and the suitability for cryogenic temperature application was demonstrated by room temperature and 77 K measurements. Preliminary gamma radiation exposure tests are promising. Further systematic investigations with larger doses on multiple compositions are planned in the next phase of the development with the extension of funding from the Department of Energy Fusion Energy Sciences and the established extended collaboration with the University of California Davis for neutron and proton beam exposure of the insulation samples.

Study on low cycle fatigue of ferritic-martensitic steel at high temperature

In 2011, a serious nuclear accident occurred in Fukushima, Japan, and one of the major causes was the destruction of the cladding material mainly made of Zr alloy due to a violent chemical reaction with high-temperature water vapor. Since then, scholars in various countries have been trying to find a better nuclear fuel cladding material. Because of its high temperature strength, ferritic/martensitic(F/M) steel is used in thermal power units. Over the past hundred years, the high temperature performance of ferritic/martensitic steel has developed simultaneously with the operating temperature of thermal power system. F/M steel is widely used in nuclear power system as well as thermal power, The fatigue life of nuclear fuel cladding material is an important parameter to study its service life, due to the special shape of the cladding material, especially for the pipe with a thickness of less than 0.5mm, it is difficult to directly measure its mechanical properties, this paper through special experimental materials and fixtures F/M pipe steel at room temperature and high temperature tensile test, as well as low cycle fatigue performance test, and its fracture port, surface crack analysis. Through the analysis and processing of experimental data, typical stress-cycle life curves, total strain amplitude-life curves, elastic strain amplitude-life curves, hysteresis curves with different strain amplitudes, and fatigue life prediction curves were obtained.

Cost assessment of selected nuclear driven hybrid thermochemical cycles for hydrogen production

This article presents compared cost assessment of selected nuclear-driven hybrid thermochemical cycles using International Atomic Energy's (IAEA) Hydrogen Economy Evaluation Program (HEEP). Cost estimations are made and evaluated for capital, fuel, decommissioning, O&B, and consumables, in addition to thermal energy and electricity cost details. Thanks to the data obtained with these cost estimates, 4 different nuclear hydrogen production systems were evaluated comparatively. Hybrid thermochemical cycles are expected to decrease operational expenses for hydrogen production. However, the capital expenses might be higher than pure electrolysis since they require more components for balance of plant components (BoP). The results obtained indicated that the levelized cost of hydrogen is 10%–30% less in the case of selected hybrid thermochemical cycles than that of pure electrochemical cycle.

Modern technologies to produce radionuclides for nuclear medicine

We discussed nuclear technologies to produce radioactive isotopes, with a focus on radionuclides used as radiopharmaceuticals in novel methods of cancer diagnosis and radionuclide therapy—theranostics. New target materials and nuclear reactions to produce these radionuclides were considered. The experimental and theoretical results of excitation functions of reactions (p, xn) studies in energy range 6–80 MeV for medium mass nuclear systems to produce radionuclides: scandium, technetium, antimony, terbium are presented. These radionuclides are promising for their use in nuclear medicine methods for diagnostics, therapy and theranostics.

Analysis of Dynamic Characteristics of Attached High Rise Risers

The exhaust chimney of third-generation nuclear power units is a typical attached high-rise riser structure. In this paper, the simplified mechanical model and dynamic model of China’s third-generation nuclear power Hualong-1 VNA system, including multiple nonlinear factors, are established for the first time. The DTM (differential transformation method) was first applied to solve the natural vibration characteristics of a multi-point constrained variable cross-section riser structure, and the effects of variable cross-section, variable mass, variable axial force, and different elastic constraint parameters on the natural vibration characteristics of the system were studied. The dynamic behavior of the VNA system under the combined action of internal flow velocity, vortex excitation, and foundation excitation was studied. The results show that the outer diameter function of the VNA system pipeline should be designed as a quadratic function or a near quadratic multi-segment constant value function. The “limiting” effect of constraining large stiffness can force low-order vibration modes with high constraint stiffness to jump to high-order vibration modes with low constraint stiffness. The elastic constraint arrangement scheme with near center symmetry can make the system vibration mode present a half stable and half-curved form. A new optimization design scheme has been proposed regarding the layout and stiffness parameters of the VNA system guide bracket. This can enable the VNA system pipeline to avoid severe oscillations near the response extreme values caused by multiple frequency excitations of seismic loads under design and accident conditions and ensure the service life of the equipment.

Synthesis of Elements in Compact Stars in Pycnonuclear Reactions with Carbon Isotopes: Quasibound States vs. States of Zero-Points Vibrations

(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact stars with new calculations of quasibound spectra and spectra of zero-point vibrations. (3) Results: Peculiarities of the method are analyzed for reaction with isotopes of Carbon. The developed method takes into account continuity and conservation of quantum flux (describing pycnonuclear reaction) inside the full spacial region of reaction, including the nuclear region. This gives the appearance of new states (called quasibound states) in which compound nuclear systems of Magnesium are formed with the largest probability. These states have not been studied yet in synthesis of elements in stars. Energy spectra of zero-point vibrations and spectra of quasibound states are estimated with high precision for reactions with isotopes of Carbon. For the first time, the influence of plasma screening on quasibound states and states of zero-point vibrations in pycnonuclear reactions has been studied. (4) Conclusions: The probability of formation of a compound nucleus in quasibound states in pycnonuclear reaction is essentially larger than the probability of formation of this system in states of zero-point vibrations studied by Zel’dovich and followers. Therefore, synthesis of Magnesium from isotopes of Carbon is more probable through the quasibound states than through the states of zero-point vibrations in compact stars. Energy spectra of zero-point vibrations are changed essentially after taking plasma screening into account. Analysis shows that from all studied isotopes of Magnesium, only 24Mg is stable after synthesis at an energy of relative motion of 4.881 MeV of the incident nuclei 12C.

Cost Optimization and Reliability Parameter Extraction of a Complex Engineering System

Nowadays, the transformation of the various energy system is the core objective of the dedicated sustainable development goal related to energy sustainable world within the new United Nations development agenda. Different nuclear regulatory authorities around the globe, sets Technical Specifications (TSs) for ensuring the human and environmental safety of various highly volatile and complex Nuclear Power Generation Plants (NPGPs). TSs define numerous measures and limitations related to safety and sustainability that must be followed by all NPGPs around the world. Reliability, availability and cost components associated with a NPGPs form important bases for the setting of TSs. In this work, a framework based on few recent metaheuristics like Cuckoo Search Algorithm (CSA), Grey Wolf Optimizer (GWO), Hybrid PSO GWO algorithm (HPSOGWO) has been presented for cost optimization and reliability parameter extraction of a complex engineering system named Heat Removal System (HRS) of a nuclear power generation plant safety system (NPGPSS). A multi-criteria decision-making (MCDM) method named Weighted-Sum Method (WSM) has also been employed for prioritizing the available metaheuristics based on available beneficial and non-beneficial criteria’s.

ΔNp63 Regulates Radioresistance in Human Head and Neck Squamous Carcinoma Cells.

Radiation therapy is commonly used to treat head and neck squamous cell carcinoma (HNSCC); however, recurrence results from the development of radioresistant cancer cells. Therefore, it is necessary to identify the underlying mechanisms of radioresistance in HNSCC. Previously, we showed that the inhibition of karyopherin-β1 (KPNB1), a factor in the nuclear transport system, enhances radiation-induced cytotoxicity, specifically in HNSCC cells, and decreases the localization of SCC-specific transcription factor ΔNp63. This suggests that ΔNp63 may be a KPNB1-carrying nucleoprotein that regulates radioresistance in HNSCC. Here, we determined whether ΔNp63 is involved in the radioresistance of HNSCC cells. Cell survival was measured by a colony formation assay. Apoptosis was assessed by annexin V staining and cleaved caspase-3 expression. The results indicate that ΔNp63 knockdown decreased the survival of irradiated HNSCC cells, increased radiation-induced annexin V+ cells, and cleaved caspase-3 expression. These results show that ΔNp63 is involved in the radioresistance of HNSCC cells. We further investigated which specific karyopherin-α (KPNA) molecules, partners of KPNB1 for nuclear transport, are involved in nuclear ΔNp63 expression. The analysis of nuclear ΔNp63 protein expression suggests that KPNA1 is involved in nuclear ΔNp63 expression. Taken together, our results suggest that ΔNp63 is a KPNB1-carrying nucleoprotein that regulates radioresistance in HNSCC.

System-level modeling, analysis and coordinated control design for the pressurized water reactor nuclear power system

A flexible operation of the nuclear power system (NPS) over a large operating range is emphasized when it is used as marine power. The current study exposes two bottlenecks in this field: (1) lack of the system-level high-quality dynamic model whose structure is simple enough for control design limits the implementation of the model-based controller; (2) nonlinearity problem due to the large load variation poses challenges for NPS to maintain its performance over a wide operating range. For these reasons, a first-hand simplified nonlinear model is developed and validated for the pressurized water reactor nuclear power system (PWRNPS) through mixed modeling methods of mechanism analysis and data identification. An optimal 50% full-power compromise steady-state operation scheme is first proposed for PWRNPS to balance its primary coolant temperature and secondary steam pressure. Using the simplified nonlinear model as the predictive model, a novel nonlinear model predictive controller (NMPC) is designed to realize the wide-range flexible operation of PWRNPS. Especially, an integrating tracking error is innovatively added to the cost function of NMPC to achieve offset-free control. Two groups of simulations on a complex PWRNPS process developed on the MATLAB/SIMULINK platform demonstrate the effectiveness of the proposed methods.

Solving the issue of reliability data for FOAK equipment in an innovative nuclear energy system

There is a demand for the improved safety and economics of advanced nuclear energy systems. The world's first high-temperature gas-cooled reactor pebble-bed module nuclear power plant (HTR-PM Demo Project) is about to be completed in China. This power plant achieved initial full power at the end of 2022. The success of the HTR-PM Demo Project shows the importance of risk-informed initiatives throughout the project with solid support from comprehensive risk assessment. This paper focuses on a technical issue that needs to be solved when conducting risk-informed initiatives for HTR-PM, namely the issue of reliability data for first-of-a-kind (FOAK) equipment. In short, no data for the FOAK equipment are available in existing reliability databases. On the basis of the HTR-PM pilot experience, this paper proposes a process of estimating the required data for the reliability parameters of FOAK equipment. The process has five steps: (1) identification of key parts and assemblies, (2) preliminary determination of the reliability parameters and the associated reference values for the key parts and assemblies, (3) analysis of maintenance management tactics, (4) estimation of reliability parameters for the FOAK equipment using a Bayesian network, and (5) Bayesian updating with operational data. The helium circulator of HTR-PM is taken as an example to demonstrate the feasibility of the proposed process. A lack of reliability data is a common issue for innovative nuclear energy systems. The proposed process is supposed to be universal to all types of innovative design.

Physical interference of magnetic dipole for retardation type nanofluid with bioconvection phenomenon

The bioconvection aspect for the rate type nanomaterial under dynamic of induced magnetic force has been numerically worked out. The Oldroyd-B nonlinear model is incorporated to inspect the interesting rheological dynamic of rate type classifications. Following nonlinear models, the relaxation and retardation features are observed. The numerical proposed data is fundamentally achieved via the shooting method. After developing the dimensionless problem expressions, the shooting numerical algorithm is followed for the computations. The physical onset of parameters is graphically listed with interesting applications. It is observed that a more strong induced magnetic field profile has been observed due to the presence of bio-convective Lewis number and Rayleigh number. An enriched profile of thermal phenomenon due to Grashof number is observed. The composed reflected outcomes present importance in thermal management systems, extrusion systems, plasma physics, chemical processes, nuclear systems, extrusion mechanism, biofuels, etc.

A Comprehensive Situation Awareness Measurement Method for Analyzing the Operators’ Situation Awareness of Multi-Module High Temperature Gas-Cooled Reactor Plants

For multi-modular nuclear power plants under the scheme of multiple nuclear steam supply system (NSSS) modules driving a single steam turbine, the NSSS modules are coupled tightly with each other by the common turbine, giving more complex normal operation with respect to the single-modular plants. To limit the operation cost of multi-modular plants, one operator is assigned to monitor and control two or more modules, whose feasibility should be verified. Combined with the characteristics of multi-module control rooms and multi-module running tasks, this paper designs a comprehensive situation awareness measurement method that combines SART, NASA-TLX (NASA Task Load Index), and eye movement tracking methods. The SART, NASA-TLX, and gaze entropy are adopted to measure the operators’ SA, and a series of accident handling experiments are performed on a full-scale simulator to gain enough data for analysis. The operators’ eye trajectories on the human–machine interface (HMI) during the experiments are all recorded for calculating the gaze entropy. Both the SART and NASA-TLX scales are filled by the operators after finishing the experiments. The experiment results show that the difference in operators’ workload and SA amongst all the experimental scenarios is limited, even between the toughest and tenderest scenarios, indicating the feasibility of one operator driving two NSSS modules simultaneously.

Nuclear magnetic resonance-based solvent system selection for counter-current chromatography separation of compounds present in the same high-performance liquid chromatography peak: Flavonoids in barley seedlings as an example.

Partition coefficient is a key parameter for counter-current chromatography separation. High-performance liquid chromatography (HPLC) is the most commonly used tool for the screening of partition coefficients. However, HPLC technology is not applicable to the compounds present in the same chromatographic peak. Nuclear magnetic resonance (NMR) technology could easily distinguish compounds according to their characteristic absorption even if they exist in the same HPLC peak. In this study, two flavonoids present in the same HPLC peak were successfully purified by counter-current chromatography with a solvent system screened by NMR to show the great potential of NMR technology in the screening of the partition coefficient of co-efflux compounds. Through NMR screening, an optimized ethyl acetate/n-buthanol/water (7:3:10, v/v/v) system was applied in this study. As a result, two flavonoids, including 4.8mg of 3'-methoxyl-6'''-O-feruloylsaponarin and 9.8mg of 6'''-O-feruloylsaponarin were separated from 15mg of the mixture. There is only one methoxy group difference between the two flavonoids. This study provides a new strategy for the screening of counter-current chromatography solvent systems and broadens the application scope of counter-current chromatography.

Autonomous control of heat pipes through digital twins: Application to fission batteries

Fission batteries are envisioned as nuclear energy systems and associated technology that can be fully utilized in a battery-like operation, where the system is delivered as a ‘plug-and-play’ service. Several key attributes define the desired functionality of these systems: economic, standardized, installed, unattended, and reliable. The construction and operation of unattended, plug-and-play fission batteries will require sufficiently robust hardware and software technologies. Using a digital twin (DT) may reduce costs and risk associated with employing fission batteries through the integration of the disparate systems used in the design, construction, and operation of these nuclear energy systems. A DT employing machine-learning (ML) and physics-based representations to forecast future performance could potentially be used for anticipatory control. Before application of a DT in the fission domain, the DT technology should be validated in a non-fission environment. A DT of a single-heat-pipe test article in the Microreactor AGile Non-nuclear Experimental Testbed (MAGNET) was demonstrated with predictive, self-adjusting capability on 30 March 2022. The test plan stated that: (1) the operators will manually change the temperature set point of the heat pipe to an upper limit or lower limit; and (2) the DT will predict the temperature will go beyond this temperature threshold, and then will update the temperature set point to the baseline temperature without any human intervention. The DT used a two-step process including a least absolute shrinkage and selection operator (LASSO) for variable selection between the sensors followed by vector autoregressive (VAR) models for multivariate forecasting to predict future performance of the heat pipe within MAGNET. Additionally, a physics model was created within the Sockeye framework that would be applied in future tests. With controlled rates of temperature change, the DT successfully self-adjusted the heat pipe before reaching the lower limit under expected conditions. Ultimately, this DT could be leveraged as a foundational framework in future fission battery applications for continuously monitoring and actively self-adjusting a heat pipe.

Depletion chain simplification using pseudo-nuclides

This paper introduces a method for simplifying the depletion chains and reducing the number of nuclides tracked in a given nuclear system while adding pseudo-nuclides in order to preserve decay heat. Pseudo-nuclides are demonstrated to preserve the decay heat effects of fission product irradiation with fewer nuclides tracked overall than decay heat precursors. The functionality is implemented and tested in the reactor physics application Griffin. Extensive testing is performed using the comprehensive ENDF-B/VIII.0 decay data and microscopic cross-section libraries from ORIGEN and MC2-3. The impact on the number of nuclides that must be tracked based on effects such as changing cross-section data, changing energy group structure, changing neutron flux spectrum, and tracking decay energy release is explored in this work. Overall, the addition of pseudo-nuclides allows the number of nuclides tracked to be reduced from 1,700 to 400 or fewer nuclides, based on the criteria used in this work.

In-situ observation of damage evolution in Mo-SiCf/SiC heterogeneous composite

Innovative metal-SiCf/SiC heterogeneous structure composites are promising accident tolerance fuel cladding materials for the Gen IV advanced reactors. The mechanical damage of these composites is a critical issue for their safe application. In this work, the damage process and mechanism of the Mo-SiCf/SiC cladding are revealed by combining In-situ C-ring test and Finite Element Analysis. The results show that the mirco-cracks originate from the pores in the outermost side of the SiCf/SiC layer, and propagate along the fiber bundles boundaries. At the same time, the “bamboo joint”-like damage occurs in the SiCf/SiC layer during C-ring test due to the periodic pore distribution. The fact that the formation of the main crack in SiCf/SiC layer prior to the fracture of Mo layer indicate the Mo-SiCf/SiC cladding can maintain the hermeticity and structure integrity until the sample fails completely. Moreover, the C-ring strength of the Mo-SiCf/SiC cladding is 360 MPa, which is much higher than 201 MPa of SiCf/SiC cladding. Overall, the Mo-SiCf/SiC cladding structure exhibits better crack growth resistance and higher strength compared to SiCf/SiC cladding. Meanwhile this work will provide technical support and theoretical basis for the structural design of cladding materials for advanced nuclear energy systems.

Cooling of the Nuclear Spin System of a Nanostructure by Oscillating Magnetic Fields.

We propose a method of cooling nuclear spin systems of solid-state nanostructures by applying a time-dependent magnetic field synchronized with spin fluctuations. Optical spin noise spectroscopy is considered a method of fluctuation control. Depending on the mutual orientation of the oscillating magnetic field and the probe light beam, cooling might be either provided by dynamic spin polarization in an external static field or result from population transfer between spin levels without build-up of a net magnetic moment ("true cooling").