Small Reactor Research Articles

Lunar Power Sources: An Opportunity to Experiment

This paper presents a systematic analysis of power generation technologies for a lunar outpost supporting six astronauts. Based on a detailed power budget analysis requiring 65 kWe for life support, scientific equipment, and in situ resource utilization (ISRU), a comparative analysis of solar and nuclear power solutions is conducted. Nuclear fission is identified as the most promising technology based on key criteria, including mass efficiency, reliability, and power density. A parametric study is then conducted to optimize the nuclear reactor design, with particular focus on radiation shielding using lunar regolith and its impact on safety distances. The analysis demonstrates that proper shielding can reduce the required safety distance from over 2.5 km to approximately 90 m while maintaining radiation exposure within acceptable limits. Finally, leveraging insights from existing reactor designs, an optimized configuration is proposed that combines multiple small reactors to meet the unique challenges of lunar power generation while ensuring crew safety and operational redundancy.

Experimental research on heat transfer characteristics of a two-layer corium pool based on a three-dimensional ellipsoidal lower plenum

To better understand the application of IVR (In-Vessel Retention), extensive experiments have been conducted on the heat transfer characteristics of molten pool. However, most research mainly focuses on hemispherical lower heads, and the research on ellipsoidal lower head suitable for small pressurized water reactors is relatively lacking. In order to provide some reference for the implementation of IVR with ellipsoidal lower head, this paper conducted the experimental study on the heat transfer characteristics of a three-dimensional double-layer molten pool based on the design of a small pressurized water reactor. The test section consists of two parts: ellipsoidal and cylindrical, with a span of 1150 mm and a total height of 700 mm. The molten material is simulated by nitrate mixture (20mol%NaNO3-80mol%KNO3), and electric heating wire is chosen to simulate the oxide layer decay heat. The effects of heating power, oxide layer height and layered partition thickness on heat transfer characteristics of two-layer molten pool under static conditions were studied. The results show that the thermal stratification phenomenon mainly occurs in the lower and middle regions of the oxide layer, with a smaller dimensionless temperature gradient in the upper region; with the similar volumetric power densities, the height of the oxide layer has little effect on the wall heat flux density; the layered partition increases the thermal resistance between the two layers and reduces the upward heat transfer to the ceramic pool. In addition, the heat transfer relationships in the oxide layer, both downward and upward, are fitted for the internal Rayleigh number range of 3.43 × 1012 to 1.54 × 1013.

Small and advanced nuclear reactors: Closing the fuel cycle?

ABSTRACT Small and advanced nuclear technologies are viewed as key to meeting future low-carbon dioxide energy demands. Big Tech companies are even planning to build their own nuclear reactors to power the digital revolution, including those that are yet to leave the drawing board. Building disposal solutions for the radioactive waste that these mainly novel reactors, which come with novel fuel, is essential too. Experience from 70 years of nuclear energy generation tells us that focusing on the cradle, and not adequately considering the grave of nuclear reactors, leads to significant and unconstrained costs that investors and governments might prefer to avoid.

A multi-molecular beam/infrared reflection absorption spectroscopy apparatus for probing mechanisms and kinetics of heterogeneously catalyzed reaction from ultrahigh vacuum to near-ambient pressure conditions.

A novel multi-molecular beam/infrared reflection absorption spectroscopy (IRAS) apparatus is described, which was constructed for studying mechanisms and kinetics of heterogeneously catalyzed reactions following a rigorous surface science approach in the pressure range from ultrahigh vacuum (UHV, 1 × 10-10mbar) to near-ambient pressure (NAP, 1000mbar) conditions. The apparatus comprises a preparation chamber equipped with standard surface science tools required for the preparation and characterization of model heterogeneous catalysts and two reaction chambers operating at different pressure ranges: in UHV and in the variable pressure range up to NAP conditions. The UHV reaction chamber contains two effusive molecular beams (flux up to 1.1 × 1015 molecules cm-2s-1), a quadrupole mass spectrometer, a Fourier-Transform (FT) IRA spectrometer, and a molecular beam monitor for beam aligning. This combination of the methods allows us to independently dose different reactants on the surface in a highly controlled way while simultaneously monitoring the evolution of gaseous products by QMS and recording the evolution of the surface species by FT-IRAS. The second reaction chamber operating in the variable pressure range is equipped with polarization-modulation-IRAS and three gas dosers and is designed as a small reactor, which can be operated in a continuous flow mode. The sample prepared under well-controlled UHV conditions can be in situ transferred between all chambers, thus allowing for investigations of structure-reactivity relationships over model surfaces. In this contribution, we provide a detailed description of the apparatus and the test measurements of the different crucial parts of the apparatus in the variable pressure range.

Using ex-core detectors and deep neural networks for monitoring power distribution in small space reactors

Ex-core detectors have the potential to monitor the power distribution in small space reactors. However, there are still considerable challenges remain in their practical implementation. To address this gap, this paper proposes a novel method to monitor power distribution utilizing ex-core detectors and deep neural networks. A small space reactor model simplified from TOPAZ-II was constructed based on the assumption that 12 ex-core detectors could be applied. New neural network models were established to consider the differences of pin power at different positions in the core by independently modeling the inner and outer fuel pins. This method was extensively validated across a wide range of operational conditions. The deep neural network method also exhibits reduced sensitivity to noise. By training on datasets containing noisy signals, the neural network method can handle signals containing ± 1 % noise while the accuracy of power distribution predictions is maintained. In addition, the deep neural network method is capable of monitoring asymmetric power distribution. By learning the characteristics of signals from asymmetric detectors, this method can accurately predict core power distribution even under abnormal operational conditions.

Constructing Chiral Core–Shell–Satellite Superstructures for Highly Efficient Antenna–Reactor Hot Electron Generation

AbstractIn hot electron (HE)‐driven photocatalysis, plasmonic metal nanocrystals with small size, or even nanoclusters, are preferrable. Antenna–reactor mechanism has been utilized to further boost the photocatalytic performance of the small reactor nanoparticles. The construction of a metal–semiconductor–metal core–shell–satellite (CSS) superstructure is demonstrated for highly efficient HE generation of the entire CSS architecture, where a mesoporous TiO2 (mTiO2) shell spatially separates the Au nanohelicoid (AuNH) antenna core and Au nanocluster (AuNC) reactor satellites. Individual AuNH@mTiO2@AuNC CSS superstructures are optically characterized using dark field scattering and circular differential scattering spectroscopies. The HE and circular differential HE photocurrent responses of the CSS superstructures are measured using a photoelectrochemical cell, where 12.4‐ and 8.3‐fold enhancements are respectively achieved with respect to that of the AuNHs. Electromagnetic simulations reveal that the contribution from the satellites with a small accumulative volume is almost equal to that from the core. Therefore, the specific‐volume HE rate of the satellites exhibit a high amplification ratio, 350, with respect to that of the core, being attributed to the antenna–reactor mechanism in the CSS architecture. Key factors are optimized, which includes small size of the plasmonic satellites, E‐field enhancement, and mesoporous semiconductor shell for efficient separation and collection of hot carriers.

Fuel Behavior Implications of Reactor Design Choices in Pressurized Water SMRs

Small pressurized water reactors can feature boron-free operation, natural circulation mode, reduced-height assemblies, and/or long refueling cycles. This paper attempts to explore core design optimization for each of these design evolutions. In consequence, five core design layouts are developed incorporating boron-free operation with continuous control rod insertion, natural circulation with low burnup/low power density design, natural circulation with high burnup/low power density design, forced circulation with standard core power density design, and forced circulation with high power density design. These cores’ performance is compared to a standard four-loop pressurized water reactor. The design process aims to improve the fuel cycle cost under safety constraints through core design optimization using the CASMO4E/SIMULATE3 reactor physics codes and the FRAPCON4.1 fuel performance assessment tool. Core modeling assumes standard 17×17 PWR fuel assemblies loaded with low enriched uranium up to 5 wt% or low enriched uranium plus (i.e. below 10 wt% enrichment) pellets with gadolinium oxide as the burnable poison. Satisfactory core and fuel performances are obtained for all the designed cores under steady state and considered overpower transients. For low power density operation, long cycle lengths are achieved reaching 2.5-year and 5-year cycles, and peak rod-average burnup is pushed to 83 MWd/kgU. Other cycle lengths are maintained at 18 months. Boron-free operation exhibits the ability to achieve longer cycle lengths at the cost of higher peaking factors leading to high local power and fuel temperatures, which prevents sizable power uprates and is deemed uneconomical. Fuel assembly height reduction allows coolant velocity retrofit, which enables higher core power density without violating the structural integrity of the fuel assembly. As a result, a core power density of 123 kW/L is reached where total cladding hoop strain becomes the limiting parameter.

Steady-state and transient investigation of a small pressurized water reactor ACPR50S for different ATFs based on Bamboo-C code

Steady-state and transient investigation of a small pressurized water reactor ACPR50S for different ATFs based on Bamboo-C code

A Factorial Fractional Chance-Constrained Programming Model for Regional Electricity Systems Management under GHG Emission Mitigation — A Case Study of Saskatchewan, Canada

In this study, a factorial fractional chance-constrained programming model (FFCC) is developed for managing Saskatche- wan’s electricity systems under the pressure of greenhouse gas (GHG) emissions reduction. Through integrating multiple programming methods (i.e., linear fractional, mixed-integer linear, and chance-constrained) with factorial analysis into an optimization framework, FFCC could effectively (1) tackle multi-objective problems; (2) manage stochastic features of system parameters expressed as probability distributions and facilitate constraint-violation analysis; (3) reflect the impacts of various economic and environmental factors and their interactions on system response. Optimal electricity generation schemes, capacity expansion plans, and electricity import/export strate- gies under different policy scenarios and risk levels are explored with the objective of maximizing low-carbon power generation per unit of system cost. Results find that small modular nuclear reactor power would have the potential to replace fossil fuel-fired technologies and aid Saskatchewan in achieving net-zero carbon emissions by 2050. It is expected that the modelling results can support regional ef- forts in proposing effective power generation capacity expansion plans and relevant environmental policies.

Scale-Up of Continuous Metallaphotoredox Catalyzed C-O Coupling to a 10 kg-Scale Using Small Footprint Photochemical Taylor Vortex Flow Reactors.

We report the development and optimization of a scalable flow process for metallaphotoredox (Ir/Ni) C-O coupling, a mild and efficient approach for forming alkyl-aryl ethers, a common motif in medicinal and process chemistry settings. Time-resolved infrared spectroscopy (TRIR) highlighted the amine as the major quencher of the photocatalyst triplet excited state, along with the formation of an Ir(II) species that, in the presence of the Ni cocatalyst, has its lifetime shortened, suggesting reductive quenching of Ir(III)*, followed by reoxidation facilitated by the Ni cocatalyst. TRIR and batch reaction screening was used to develop conditions transferrable to flow, and many processing benefits of performing the reaction in flow were then demonstrated using a simple to construct/operate, small-footprint FEP coil flow reactor, including short (<10 min) space times and reduced catalyst loadings (down to 0.1 mol % Ir, 1 mol % Ni) while retaining good yield/conversion. Scalability was demonstrated by increasing the length or diameter of the FEP coil flow reactor tubing, however, due to suspected mass transfer/mixing limitations, the yield decreased upon scale-up in some cases. Therefore, we applied a modified version of our previously reported photochemical Taylor Vortex Flow Reactor (PhotoVortex), where Taylor vortices and a short-irradiated path length allow photochemical reactions to be performed efficiently via excellent mixing. In a small PhotoVortex (8 mL irradiated volume), we have demonstrated projected productivities around 1 kg day-1 and >10 kg day-1 in a large PhotoVortex (185 mL irradiated volume) with good product yields (>90%) and low catalyst loadings (0.1 to 0.5 mol % of [Ir{dF(CF3)ppy}2dtbbpy]PF6), enabled by excellent mixing ensuring sufficient mass transfer between short-lived photoexcited and other transient species.

Small Reactors: The Promise and Challenges [View Point

Small Reactors: The Promise and Challenges [View Point

Integrating Small Modular Reactors and Policy Frameworks for Sustainable Energy Security in Indonesia

This study evaluates the potential of Small Modular Reactors (SMRs) as a sustainable solution for Indonesia's energy diversification. Amid Indonesia’s rising energy demands and environmental commitments, SMRs-particularly Small Modular Molten Salt Reactors (SM-MSRs)-present an alternative to conventional power sources. SMRs offer advantages like modularity, operational efficiency, and safety, making them suitable for Indonesia’s geographically dispersed landscape. Using a qualitative descriptive approach, this research examines the technical, regulatory, and societal factors influencing SMR integration. Findings reveal that while SMRs show competitive Levelized Cost of Electricity (LCOE) compared to coal, challenges remain, including stringent regulatory requirements, high initial capital costs, and limited public acceptance due to nuclear safety concerns. Policy adjustments, community engagement, and collaboration with established SMR programs globally are suggested to address these issues. Additionally, SMRs’ scalability and compatibility with renewables support Indonesia’s goals for a resilient energy mix, potentially transforming remote energy access. This comprehensive approach underscores the viability of SMRs within Indonesia’s energy transition, contributing to a cleaner, more flexible energy infrastructure

ОЦІНЮВАННЯ ЕФЕКТИВНОСТІ РОБОТИ МАЛОГО МОДУЛЬНОГО ЯДЕРНОГО РЕАКТОРА НА РИНКУ ЕЛЕКТРИЧНОЇ ЕНЕРГІЇ

A mathematical model for constructing an optimal loading schedule of a power unit with a small modular nuclear reactor is presented. The main conditions of operation of small modular nuclear reactors with constructive solutions similar to the development of NuScale are determined, and the architecture of the mathematical model for the search of optimal schedules of their operation is presented. The main attributes of the operating modes of small modular nuclear reactors and a mathematical model for simulating the control functions of the reactor operation schedules have been determined. The main components for displaying the results of purchase-lease/sale of electricity by the power-generating company have been determined. The objective function of maximizing the benefit from the operation of a small modular nuclear reactor and limiting the profitability of its operation is given. The basics of the methodology of using the model for building the optimal daily schedule of the functioning of a small modular nuclear reactor in the tasks of assessing the effect of the construction and operation of such reactors at a nuclear power plant have been formulated. Ref. 15, fig. 4, table.

Manufacturing Scale-up of ALD Onto Synthetic Graphite Powder in a Continuous Vibrating Reactor for Battery Applications

As the demand for improved performance in battery material increases, development of large-scale, high-throughput ALD processes and equipment is necessary to meet production demands. Forge Nano has previously demonstrated ALD deposition onto natural and synthetic graphite over a range of scales (50 g – 50 kg) in both rotary bed and fluidized bed reactors. This process has now been successfully scaled-up to the highest throughput system (ton scale) with a continuous vibrating reactor (CVR). The CVR (and associated product Circe) is a spatial ALD system where the substrate powder travels down a porous deck, driven by vibration. Process gases flow at atmospheric pressure perpendicularly to the powder flow, up through the porous deck, and fluidize the moving powder bed and mixing the particles with the gases top to bottom in the process. The substrate travels through zones of the precursors and purge gases of an ALD cycle (Figure 1).Reproducibility per batch and relative to successful graphite deposition criteria from smaller ALD batch systems was explored in a CVR system configured to perform 4 TMA/H2O ALD cycles. Commercial synthetic graphite was coated at a rate of 33 kg/h, in 45-50 kg batches, at 180°C. Precursor flow was controlled based on the calculated stoichiometry required to achieve 100% titration of available surface sites, as determined in experiments performed in small scale fluidized bed reactors. Samples of coated product were taken from the reactor effluent every 10 minutes. Effluent samples of replicate runs were analyzed using ICP to determine the Al loading, and to characterize the reproducibility of the coating process. An average of 84 ± 13 ppm Al was deposited for all replicate runs (each totaling 4 ALD cycles). The 1-2 initial samples for a given run comprised lower Al mass loadings, likely due to the system approaching steady state in terms of substrate and precursor flow. Additional tests with 150% of the calculated stoichiometric TMA flow rate showed the deposition to be self-limiting. Finally, the coated material was homogenized and then recycled through the CVR to demonstrate reproducibility at higher deposition levels. This material was recycled multiple times to achieve 20 TMA/H2O ALD cycles and establish an average and linear growth rate per ALD cycle. Additionally, bed height and speed conditions were explored to achieve higher material processing rates. Coated materials were tested in coin cells as anode powders for lithium-ion batteries, with performance being compared to coated graphite prepared via more traditional deposition in fluidized bed reactors under vacuum conditions. Coated materials demonstrated that increasing coating levels increased first cycle coulombic efficiency (FCE), reversible capacity, and cycle life.Figure 1. Schematic and photo of the spatial CVR ALD system Figure 1

Cross-operating-condition fault diagnosis of a small module reactor based on CNN-LSTM transfer learning with limited data

Fault samples of Small Modular Reactor (SMR) are scarce and the data distribution cross operating conditions are different, resulting in poor generalization performance of fault diagnosis model. In this paper, Convolutional Neural Network (CNN) and Long Short-Term Memory (LSTM) are integrated and a novel CNN-LSTM transfer learning method is proposed for fault diagnosis of SMR at different power levels, which is used to improve the deep extraction capability of spatial and temporal features of fault data. Based on small sample data and feature visualization technology, five different feature transfer strategies are compared to obtain the best generalization performance of the cross-operating condition fault diagnosis model. In addition, the effects of different network structures and hyperparameter combination settings of the CNN-LSTM model on the convergence speed and accuracy of transfer learning are analyzed to optimize the design of SMR fault diagnosis model. The results show that the CNN-LSTM method has stronger fault feature extraction capability than other deep learning methods. The simulation results also show that the proposed transfer learning strategy and the optimized network structure and hyperparameters could significantly enhance the generalization performance and accuracy of SMR fault diagnosis under different operating conditions with few labeled samples.

National Council on Radiation Protection (NCRP) 2024 annual meeting: advanced and small modular nuclear power reactors**The authors have confirmed that any identifiable participants in this study have given their consent for publication.

On 25-26 March 2023, the U.S. National Council on Radiation Protection and Measurements (NCRP) held its 2024 annual meeting in Bethesda, Maryland, USA. The NCRP dates from 1929, and this meeting celebrated the 60th anniversary of receiving a U.S. Congressional Charter. For this annual meeting the NCRP felt it was essential to provide a briefing about advanced and small modular nuclear reactors (SMRs). The Journal of Radiological Protection is delighted to publish the following synopsis of material presented at the U.S. NCRP meeting. This synopsis is divided into five sections. The first section provides an overview of the whole meeting together with summaries of two context setting overview papers. The following four sessions of this synopsis are specific to advanced and small modular nuclear power reactors. The meeting also included keynote presentations by three of NCRP annual award recipients. The meeting topical areas were Technology Overview and Critical Issues. The individual papers laid the groundwork to understanding reactor technologies, terminology, and the fundamental concepts and processes for electrical generation. The perspectives of the U.S. Environmental Protection Agency and states, through the Conference of Radiation Control Program Directors were provided. The papers included a discussion of diverse topics including potential emergency preparedness considerations, radiological survey requirements, an evaluation of the future of nuclear power, the economics of reactors (both large and small), and the critical issues identified by the recent National Academies of Sciences' study on advanced reactors. The summary papers were developed to briefly document the major points and concepts presented during the oral papers presented at the 2024 NCRP Annual Meeting. The meeting heralded the dawn of a new era for commercial nuclear power.

NO and NH3 Distribution in a Small Scale Coal-ammonia Co-firing Reactor

NO and NH3 Distribution in a Small Scale Coal-ammonia Co-firing Reactor

Hydrogen production from ZnCl2 salt: Application of chlor-alkali method

This experimental study investigates the efficiency of hydrogen production from an aqueous ZnCl2 solution using an electrochemical method within a chlor-alkali reactor. A laboratory-scale reactor with separate anode and cathode compartments was constructed for this purpose. The compartments are separated by a Nafion 212 membrane, which prevents the mixing of the anolyte and catholyte solutions while allowing the passage of positive ions (Zn+). Each compartment is equipped with five carbon rod electrodes. The anode chamber is fed with an aqueous ZnCl2 solution, while the cathode chamber is supplied with pure water. The experiments were conducted with a constant electrolyte transfer rate of 0.3g/s into the reactor, at three different cell voltages (5.0, 7.5, and 10.0V) and two different cell temperatures (20 °C and 45 °C). Due to the small reactor dimensions and the dilution effect caused by adding pure water to the cathode compartment which decreases electrolyte density and adversely affects the current a noticeable reduction in hydrogen gas production was observed. Furthermore, the ZnCl2 electrolyte mass flow rate did not significantly impact the current or the generation of hydrogen and chlorine gases. Consequently, no changes were made to the mass flow rate of pure water or the electrolyte. The presence of active chlorine gas was found to cause the erosion of the carbon rod electrodes in the anode chamber. As a result, the amount of chlorine gas produced in the anode chamber is significantly lower than the hydrogen gas produced in the cathode chamber. At a cell temperature of 20 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 5 V with ZnCl2 aqueous solution, the minimum hydrogen production rate is 0.625 mL/min. In contrast, at a cell temperature of 45 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 10 V, the maximum hydrogen production rate is 4.97 mL/min.

Gasification of mixed plastic-biomass pellets in an updraft fixed bed reactor: A simplified dynamic model

In the context of materials recycling, updraft gasifiers are promising small and middle-scale reactors to obtain building blocks and/or energy from waste plastic and biomasses. To this aim, these kinds of materials can also be mixed and reduced into pellets, while the needed heat enters the process with a heated carrier gas. In order to preliminarily design a gasifier to check its feasibility with an available feedstock, currently available models are inadequate. Thermodynamic ones are useless for the purposes of sizing, while too detailed rate-based models (e.g. based on fluid-dynamic modelling) are too substrate specific, need detailed input data and are extremely time consuming. A dynamic model of a fixed-bed reactor for biomass gasification is presented here. The gasifier is loaded continuously from the top with solid pellets and fed with counter-current air flow. The model considers: i) a one-step gasification kinetics, yielding a product spectrum which matches experimental data from the literature; ii) dynamic gas and solid energy balances and iii) steady-state energy balance for the furnace. The model has been applied to describe a tubular furnace (Ø 40 cm) which gasifies 500–1000 kg day−1 of mixed wastes using air heated up to 1200 °C: on the basis of the produced chemicals, the energy consumption was estimated as ca. 2 MJ per kg of solid feedstock. This simplified approach proved robust in describing the overall yields and start-up dynamics, showing higher reliability than equilibrium models in addressing the temperature profiles, at the cost of a simplified reaction kinetic and pellet description with respect to more complex simulation models. The model validation was done by comparison between the calculations results and available pilot-plant data. An overall good fit of the data can be concluded. The solid-gas heat transfer and the bed packing are the main computational criticalities to achieve a reliable process description.

Numerical investigation on a novel milli-sized heat sink equipped by twisted elliptical tubes

Thermal management in some small chemical reactors is essential to achieve a final high-quality product and heat sinks can play a remarkable role in dissipating heat from such systems. In this regard, this study attends to evaluate the conjugate heat transfer problem in a heat sink equipped by twisted elliptical tubes (TETs). The effects of significant parameters such as Reynolds number (Re = 250, 350, 500, 700 and 950) and twist ratio (TR = 2.5, 5 and 10) on hydrothermal and thermodynamics performance of the novel heat sink are investigated. The swirling flow is the main reason of fluid particles migration from hot surface to cold one and vice versa, leading a better heat transfer occurs at the expense of not significant pressure loss augmentation. The results revealed that the TETs are responsible of more wall temperature uniformity and avoids generating hot spots. Compared with plain elliptical tubes, the presence of TETs inside heat sink improves the heat transfer rate and enlarges the pressure drop by 1.08–2.03 times and by 1.02–1.92 times, respectively. In addition, the TETs decrease the entropy generation rate inside heat sink and the best value of second law efficiency is about 35 %, detected at TR = 2.5 and Re = 250.