Small Reactor Research Articles

Activation analysis of the lead coolant in SUNRISE-LFR

A lumped, zero-dimensional, mass transport model is combined with a depletion matrix solver to study the influence of coolant circulation on radionuclide build-up in a small lead-cooled fast reactor. It is shown that the addition of coolant circulation results in a lower activity for a minority of studied nuclides, and it is thus recommended to consider stagnant coolant when licensing a reactor. Activation analysis of three different lead qualities potentially used in SUNRISE-LFR is performed, and the result shows that a low silver content is desirable to simplify maintenance and decommissioning.

Dynamic Model of a Virtual Air Gap Reactor

Variable reactors have been a vital component of power networks for decades, where they have been used as fault-current limiting devices or for reactive power compensation. Traditionally, modifying the inductance of predominantly mechanically operated variable reactors requires seconds to minutes. In contrast, virtual air gap (VAG) reactors can change the inductance within milliseconds, potentially improving power system stability. Existing dynamic models of VAG reactors cannot capture the entire system dynamics, limiting their applicability for simulations in the time-domain. This research presents two dynamic VAG reactor models, one with and one without core losses. The models capture all significant system dynamics using electromagnetic principles and VAG reactor flux linkage behavior. The proposed models were experimentally validated using a small VAG reactor. Over a broad operating range, both models accurately reproduce the dynamic behavior, transient response, and dominant harmonics of the small VAG reactor. Consequently, the models may be used for a variety of applications, such as time-domain simulations, harmonic analysis, and the development of suitable controllers for VAG reactors. In addition, engineers may use the core loss omitting model as a VAG reactor design tool, as the actual reactor is not required for modeling.

Review of the Structural Behavior of the KSTAR TF Magnet

The TF coil structures are the main structural components in the magnet system, and consist of TF coil cases, inter-coil structures, gravity support and interface structures. The structures enclose the TF coils to protect the CICC from mechanical, electrical and thermal loads, and support 7 pairs of PF coils. The structural behavior of TF magnet has been monitored during cool-down and plasma operation for over 10 years. High stress and large displacement regions are investigated through the review of the TF magnet structure design. The measured structural behaviors are compared with the estimated behavior from the design analyses. The discrepancy between measured and estimated behaviors has to be analyzed and a correction method will be introduced. The study will be helpful to monitor exactly the safety operation of the KSTAR superconducting magnet system as well as to develop a small fusion reactor for DEMO.

On the performance of the United States nuclear power sector: A Bayesian approach

Concerns over climate change and global emissions has again placed attention on clean energy sources. Nuclear power plants are one of many sources of clean energy and yet few studies have examined the structure of technology exclusively in this area. We utilize Bayesian empirical likelihood methods to estimate a stochastic frontier model to examine scale economies, technical efficiency and technological change in the United States nuclear energy generation sector. We find decreasing scale economies, a fact consistent with the recent decline of the industry. Our results suggest that small nuclear reactors may benefit the sector as a whole.

A solid-liquid mixing reactor based on swirling flow technology

Solid-liquid mixing is often applied in the chemical industry to keep solids in suspension for, amongst others, crystallization, adsorption, heterogeneous catalysis, etc. The most widely used technology to obtain a good degree of mixing is the mechanically stirred tank reactor. However, this technology is limited to small reactor volumes in case of high pressure/temperature processes due to sealing issues. An alternative for solid-liquid mixing is the application of swirling flow. This work studies the mixing capacities of a specially designed reactor geometry, the Swirling Flow Reactor (SFR). Computational Fluid Dynamics (CFD) is used to simulate the flow field and particle distribution in the SFR, where the RNG k−ϵ model and the Eulerian-Eulerian (E-E) multi-phase approach with a Kinetic Theory of Granular Flow (KTGF) model are applied for their proven effectiveness in the study of dense solid-liquid mixing problems. The effectiveness of mixing in the SFR is assessed by the axial particle distribution and homogeneity H. The mechanism of particle recirculation in the SFR is also identified, in which a Coanda jet flow (CoJF) formed by a specially designed inlet nozzle plays an important role in washing the reactor bottom surface. Additionally, Spectral Proper Orthogonal Decomposition (SPOD) is used to identify and reconstruct the coherent structures in the swirling flow. The results indicate that precessing coherent flow structures are present, which include the dominant double layer double helical vortex core and its second order harmonic, the double layer quadruple helical vortex core.

Metabolic multireactor: Practical considerations for using simple oxygen sensing optodes for high-throughput batch reactor metabolism experiments.

We present a system for carrying out small batch reactor oxygen consumption experiments on water and sediment samples for environmental questions. In general, it provides several advantages that can help researchers achieve impactful experiments at relatively low costs and high data quality. In particular, it allows for multiple reactors to be operated and their oxygen concentrations to be measured simultaneously, providing high throughput and high time-resolution data, which can be advantageous. Most existing literature on similar small batch-reactor metabolic studies is limited to either only a few samples, or only a few time points per sample, which can restrict the ability for researchers to learn from their experiments. The oxygen sensing system is based very directly on the work of Larsen, et al. [2011], and similar oxygen sensing technology is widely used in the literature. As such we do not delve deeply into the specifics of the fluorescent dye sensing mechanism. Instead, we focus on practical considerations. We describe the construction and operation of the calibration and experimental systems, and answer many of the questions likely to come up when other researchers choose to build and operate a similar system themselves (questions we ourselves had when we first built the system). In this way, we hope to provide an approachable and easy to use research article that can help other researchers construct and operate a similar system that can be tailored to ask their own research questions, with a minimum of confusion and missteps along the way.

Transient characteristics of typical design basis accidents in integrated small reactor NHR200-II using RELAP5 model

The development of advanced integrated small reactors is one of the most important trends in nuclear engineering nowadays, the NHR200-II reactor proposed by Tsinghua university has also undergone several iterations of improvement. The increased thermal–hydraulic parameters mean that the design-basis accidents need to be reanalyzed, of which three typical scenarios are chosen as benchmarks and simulated with the complete RELAP5-model. The small break loss-of-coolant accident, the pump-shaft-stuck accident and the heat-transfer-tube-rupture in main heat exchanger accident were assessed systematically and showed good agreement with previous research. The characteristics like the transient flow rate at the break, the moment of inertia of circuit pump and the position of the main heat exchanger were examined, different control variables mainly affect the sequence of trigger actions rather than overall thermal–hydraulic parameters. The results demonstrate that the reactor core can be cooled sufficiently throughout all transient conditions and be flooded with coolant.

Nuclear reactor at home? Public acceptance of small nuclear reactors in the neighborhood

Small Nuclear Reactors (SNR) can provide climate-neutral, stable electricity and heating if located in people’s neighborhoods close to people’s dwellings. The extensive use of SNR would reduce capacity requirements for energy transmission systems and increase the overall stability of energy grids. However, the public fear location of SNR close to their homes. This paper hypothesizes that the public acceptance of SNR in the neighborhood is contingent upon knowledge of technology, fear of nuclear energy (NE), trust in the government, the expected increase of future electricity needs and the expected ability of renewables to cover these needs, environmental and climate concerns, and media exposure. We rely upon representative survey data from the Czech Republic (N = 1,013, 51.2% female, aged 18–91, M ± SD: 47.7 ± 17.6; 19.6% with higher education). Methodologically we conduct exploratory Principal Component Analysis and a series of ordinal regressions. The results suggest that the knowledge of technology, trust in the government, the preference for NE expansion, and media exposure increased the acceptance of SNR, while fear of NE decreased SNR acceptance. The perceived replaceability of conventional energy sources with renewables decreased acceptance of SNR in most cases. Surprisingly, worries about climate change reduced the support for SNR. Women accept fewer SNRs located close to their residence compared to men. More educational effort is needed in the specifics of SNR technology and the environmental effects of SNR. Media proved to be an excellent way to start.

Modeling and control of nuclear–renewable integrated energy systems: Dynamic system model for green electricity and hydrogen production

The need for decarbonization and diversification of energy resources has led to the development of integrated energy systems (IESs), where multiple resources supply more than one energy sector. One such IES with small modular nuclear reactors and renewables (wind and solar) as generating resources, catering to the demand of the electric grid while producing hydrogen for industries, is modeled in this paper. The physics-based component models are represented using the Modelica language and interconnected to form the IES. The control and coordination of the overall system are ensured by designing a suitable control architecture composed of individual subsystem-level controls and supervisory control. The dynamic performance and the load-following capability of the IES are evaluated, while satisfying the safe operational limits of the components. Different configurations and modes of IES operation are considered, where the adaptability of the control system in the presence of varying demands and renewable generations is validated. The simulation results indicate that hydrogen as a flexible load facilitates the supply of varying grid demand. Additionally, the renewables are also accommodated into the IES owing to the flexibility of the balance of plant associated with the nuclear reactors.

Simulation of a loss of flow transient of a small Lead-Cooled reactor using a CFD-Based model

The recent development of small modular reactors needs to be followed by safety analysis using the newest available tools. This work focuses on one type of reactor, SEALER, which is a small lead cooled reactor intended for remote communities in Canada. Simulations of a loss of flow transients are performed using a CFD-based model that was specifically developed for this project. The CFD geometry includes the entire primary circuit with some simplifications. The fuel channel, steam generator and pumps use a simple geometry with momentum source and heat source/sink. Free surface level is modelled with the multiphase volume of fluid (VOF) method. The CFD part of the model is coupled to a custom code for heat transfer in the fuel rods and point kinetics for neutronics. Transient results show that core temperatures do not increase significantly and stay well below coolant boiling and fuel melting points. The CFD-based model presented here is compared against a lumped-parameter model using the same transient. It is shown that the evolution of the mass flow and temperature is significantly different and more detailed with the CFD-based model. Finally, the influence of the moment of inertia of the pump flywheel on the transient is explored.

Enhancement of proton exchange membrane fuel cell net electric power and methanol-reforming performance by vein channel carved into the reactor plate

A prospective small power system that uses fuel from a small reactor to turn methanol into hydrogen is a proton exchange membrane (PEM) fuel cell (FC). This article examines the fuel conversion ability of the small methanol steam reformer (MSR) creating different vein channels with varying widths and angles on the reactor plate and PEMFC net electric power at various heated temperatures. For each channel, the catalyst quantity remains the same. The maximum hydrogen yield is 92.44%, methanol conversion 0.01187 kmole ⋅ m−3, and cell net electric power 133.86 W. The augmentation of hydrogen yield and methanol conversion from the innovative SR reactor by the vein channel of width 1.25 mm and angle 120° achieves 84.32% and 29.52% compared to the parallel-channel SR reactor under Twall of 250 °C. The novel SR reactor, having a vein channel with a width of 1.5 mm and an angle of 90°, acquires 29.09% compared to the parallel-channel SR reactor in PEM fuel cell net electric power under Twall of 250 °C, allowing low CO exhaust. The findings show that the novel SR reactor with a venous channel enhances the net electrical energy conversion of MSR and PEM fuel cells.

Algae bioreactor for biodiesel production

Biodiesel production and use are becoming more prevalent across North America and Europe as fueling stations become equipped with biodiesel pumps at a continually increasing rate. As petroleum reserves become depleted, the price of petroleum-based diesel will increase, while biodiesel prices are expected to decrease due to increased supply. Biodiesel is produced through transesterification of oils or fats and can be used in unmodified diesel engines. This makes biodiesel an ideal petroleum-based-diesel substitute as car manufacturers and consumers will not experience manufacturing cost changes. Algae are efficient for biodiesel production because they are about 50% by mass oil, which can be used to make biodiesel fuel. Algae can also grow in areas where other plants cannot be grown such as salt water or polluted areas. Additionally, algae grown near power plants will consume the emitted CO2 and use it for photosynthesis. This article reports the results of a student capstone design project, in which a small reactor for biodiesel production was built using a vertical design. It produced 1420 ml (48 fl. oz.) of algae, which resulted in a net production of 591 ml (20 fl. oz.) of lipid oil through refreezing the algae. We were able to produce 532 ml (18 fl. oz.) of biodiesel fuel in less than 11 weeks.

Strategy for the management of used nuclear fuel and radioactive waste of small water-water modular reactors

Based on the strategy of Ukraine in the energy industry for the period until 2035, advanced reactor technologies should be chosen for construction of new nuclear power units to replace the nuclear power plants that will be decommissioned. Currently, high-capacity water-water reactors AP1000 and small modular reactors NuScale -iPWR and/or SMR-160, which are highly secure and cost-effective, are considered promising. Among a number of criteria for the selection of nuclear power plant reactor technologies, the management of spent nuclear fuel and radioactive waste, which directly affect radiation and environmental safety and all stages of the existing nuclear fuel cycle in Ukraine, is of great importance. Based on published data, the author analysed and summarized prospects of development of water-water SMR technologies (NuScale -iPWR and SMR-160), their advantages and disadvantages, the evaluation criteria of the spent nuclear fuel (SNF) and radioactive waste generated during operation and decommissioning of reactors, and problems of waste disposal.

ПРИСТРОЇ ТА СИСТЕМИ РОЗПОДІЛЕНОЇ ГЕНЕРАЦІЇ

Abstract. The article is devoted to the analysis of the features of various distributed generation systems from the point of view of their inclusion in a single distributed energy system. It is shown that the need to switch to distributed generation is associated with the need to create reliable power supply systems that can maintain their performance in the event of partial or complete destruction of any part of such a system. The devices of solar, wind and hydropower, as well as the possibility of using small modular nuclear reactors as devices for distributed generation are analyzed. It is shown that the most promising for application are environmentally friendly solar cells. Wind generation and small hydropower plants can also be used to create sustainable and reliable power supply systems. Small modular reactors can be used to power large cities and industrial consumers. The analysis of economic and energy parameters of various devices of distributed generation is carried out. It is concluded that the elements of a distributed generation system can be not only individual devices, but also systems of such devices at the level of a territorial region. Keywords: distributed generation; electrical system; solar energy; solar power plants, wind energy; modular nuclear reactors; intelligent networks.

ПРИСТРОЇ ТА СИСТЕМИ РОЗПОДІЛЕНОЇ ГЕНЕРАЦІЇ

Abstract. The article is devoted to the analysis of the features of various distributed generation systems from the point of view of their inclusion in a single distributed energy system. It is shown that the need to switch to distributed generation is associated with the need to create reliable power supply systems that can maintain their performance in the event of partial or complete destruction of any part of such a system. The devices of solar, wind and hydropower, as well as the possibility of using small modular nuclear reactors as devices for distributed generation are analyzed. It is shown that the most promising for application are environmentally friendly solar cells. Wind generation and small hydropower plants can also be used to create sustainable and reliable power supply systems. Small modular reactors can be used to power large cities and industrial consumers. The analysis of economic and energy parameters of various devices of distributed generation is carried out. It is concluded that the elements of a distributed generation system can be not only individual devices, but also systems of such devices at the level of a territorial region. Keywords: distributed generation; electrical system; solar energy; solar power plants, wind energy; modular nuclear reactors; intelligent networks.

Effect of non-uniform inflow on the internal flow and hydrodynamic characteristics of a small modular reactor coolant pump

Small reactors have broad application prospects due to their advantages of safety, economy, and portability. In the first circuit of a small reactor nuclear power plant, the steam generator is directly connected to a reactor coolant pump, and there is a non-uniform flow situation, which has not been studied. Taking the small modular reactor coolant pump as the research object, the influence of non-uniform inflow on the internal flow and hydrodynamic characteristics of the small modular reactor coolant pump was investigated using CFD numerical simulation methods, and was verified by experiment. Firstly, the basic structural parameters of key hydraulic components are determined based on the design input parameters, and the initial model of the impeller and diffuser of the small modular reactor coolant pump is modeled. The channel-head, impeller, diffuser, and casing are modeled using three-dimensional software; Secondly, the hydrodynamic performance of the small modular reactor coolant pump was experimented, and the experimental results verified the reliability of the numerical simulation; After comparing the external characteristics of the straight-pipe small modular reactor coolant pump coupling model and channel-head small modular reactor coolant pump coupling model, it was found that the head and efficiency of the straight-pipe model were better than channel-head model, indicating that non-uniform inflow had a certain impact on the performance of the small modular reactor coolant pump. Finally, the internal flow states of the straight-pipe model and the channel-head model were compared and analyzed from the perspectives of pump internal flow field, pump internal velocity and pressure distribution. The results showed that the sudden contraction of the direct connection between the channel-head and the small modular reactor coolant pump and the short length of the direct connection caused the inlet flow of the pump to be non-uniform, which adversely affected the hydrodynamic and internal flow characteristics of the pump. This study provides a certain idea for the research on the suppression of non-uniform inflow from small modular reactor coolant pumps and the improvement of non-uniform inflow from small modular reactor coolant pumps.

Preliminary Study on Alternative Reflectors for LOTUS Reactor

LOTUS reactor - a compact lead-cooled fast reactor is currently being studied to generate 200 MWth of capacity and operate for 20 years without refueling for the floating nuclear power plant (FNPP) application. Therefore, it would be a big advantage to achieve a long operation without refueling. However, a small reactor usually has a higher neutron leakage, and a good neutron reflector is essential to maintain the neutron economy. The main objective is selecting potential reflectors materials for the LOTUS reactor using Monte Carlo code, Serpent. The various candidate reflector materials, including Al2O3, BeO, MgO, PbO, SiO2, and ZrO2 are calculated from the neutronics characteristics to determine a good neutron reflector. In this work, we have investigated the parameters of neutronics characteristics, such as core neutron flux spectrum, evolution of keff due to burn-up, power distribution, and lead coolant void reactivity with each reflector. From the comparison of those parameters, MgO material was found to be a good candidate for the relector of LOTUS reactor.

Assessing the cost competitiveness of electrolytic hydrogen production from small modular nuclear reactor-based power plants: A price-following perspective

Small modular nuclear reactor power plants (SMNRPPs) for hydrogen cogeneration are in early development, and their cost competitiveness for low-temperature electrolysis has not been well-studied. This study combines a quadratically-constrained economic dispatch model and a levelized cost analysis model to evaluate hydrogen cogeneration from a 300 MW SMNRPP coupled with proton exchange membrane electrolyzers. The SMNRPP adjusts its power output based on fluctuating electricity market prices and a time-invariant conversion value for electricity pricing arbitrage. We evaluated the SMNRPP-electrolysis system for 20 years in two case study locations and found the hydrogen supply cost ranged from CAD$1.77–3.36/kg and CAD$2.11–2.77/kg in electricity markets with high and low fossil fuel-dependence, respectively. The SMNRPP-electrolysis system is more cost-effective than fossil fuel-based hydrogen production at CAD$1.54/kg if the SMNRPP capital cost decreases to CAD$4,700/kW. This is because the SMNRPP capital cost accounts for 75% of the hydrogen supply cost variance, while other techno-economic parameters account for less than 27% of the supply cost variance. The system can achieve the lowest cost hydrogen production in under 17 years if the global learning rate and installation growth rates for SMNRPPs exceed 10% and 15%, respectively, to reach a 4.96 GW global footprint. The study outcomes can help formulate policies for SMNRPPs adoption in the hydrogen economy.

Estimation of Near-Field and Far-Field Post-Accident Atmospheric Dispersion for Microreactors

The current study describes a simulation-based analysis of the atmospheric dispersion of radionuclide fission product particles in the near-field and far-field of a generic, conceptual microreactor, which is a small nuclear reactor with a power output typically ranging from 1 to 20 MW(thermal) and generally lower than 50 MW(electric). The near-field is a distance of up to 100 m from the microreactor while the far-field is a distance of 300 m or beyond from the microreactor. The generic microreactor operates at a pressure close to the ambient pressure. Therefore, in the event of a postulated accident that causes the leakage of radionuclide particles from the microreactor containment into the environment, the radionuclide particles are unlikely to travel too far from the reactor, as opposed to conventional nuclear reactors. The current paper provides estimates of average and 95th-percentile values of the normalized effluent concentration of the atmospheric radionuclide particle dispersion with respect to the source strength in the near-field and far-field of the conceptual microreactor. The computer code Atmospheric Relative CONcentrations in Building Wakes (ARCON96) was used to perform all simulations for the current study. It was observed that the 95th-percentile values of the normalized effluent concentration decrease by an order of magnitude as the receptor distance increases, i.e., from the near-field to the far-field. The dispersed aerosol concentration also decreases with time. A parametric study was performed to understand which input parameters affect the normalized effluent concentration values the most, and a definitive screening design was employed for this purpose. The atmospheric stability class and the distance between the reactor and the receptor were the parameters found to affect the aerosol dispersion characteristics by the greatest extent. The study recommends that the computer code RADTRAD (Radionuclide Transport and Removal And Dose Estimation) be used to estimate the actual dosage over distance using the outputs from ARCON96 as inputs, along with reactor-specific core inventories.

Dissolution of wood components during hot water extraction of spruce

The purpose of this study was to investigate the autohydrolysis of softwood, which is the main chemical operation in both hot water extraction and steam explosion. Control of the process and monitoring its course were ensured by the careful choice of experimental setup and conditions: a milled spruce material was extracted in a small flow-through reactor to minimize degradation of the dissolved material and to enable analysis of the resulting liquors extracted at selected time points. The obtained liquid and solid fractions were analyzed for sugar composition and acetic acid concentration. The results showed that partially degraded hemicelluloses were extracted; hemicelluloses side chains were cleaved off and detected as monomers, while deacetylation was limited. Chain scissions of cellulose were observed as a result of autohydrolysis.