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Presented is an application of wave potential formulation (WPF) together with domain reduction method (DRM) to modeling earthquake soil structure interaction (ESSI) behavior in horizontally layered ground under inclined incident seismic waves. Wave potential formulation is used to develop a spatially varying, inclined seismic wave field from incident Primary (P) and Secondary (S) waves that propagate through layered ground. Developed seismic wave field is then used to develop effective forces for Domain Reduction Method that are then used for analyzing ESSI response of a soil structure system. Developed methodology, called WPF-DRM, is verified using analytic solution for a free field response of layered ground subjected to inclined incident waves. Developed WPF-DRM methodology is illustrated through analysis of an ESSI response of a deeply embedded structure, a small modular reactor (SMR) subjected to incident S wave polarized in vertical plane (SV) with variation in inclinations and frequencies. Presented example highlights the influences of incident wave inclination and frequency on ESSI response of analyzed SMR.

The publication is devoted to the basics of calculating the economic effect of providing electric energy storage systems with the service of compensating the surplus of electric energy generation by nuclear power plants with small modular reactors at night. The main components of the mathematical model for calculating the service tariff for the accumula-tion of a surplus of electric energy generation are considered. A simulation model of the operation of the electric en-ergy storage system is given. A mathematical model was developed for calculating the minimum tariff for the service of compensation for the surplus of electric energy generation by nuclear power plants with small modular reactors at night with the help of electric energy storage systems. Bibl. 13, fig. 3.

The use of nuclear energy can contribute to achieving positive socio-economic and environmental benefits, but nuclear power plants are one of the most water-intensive industries in the world. The use of Small Modular Reactor (SMR) technologies is increasing due to their interesting advantages such as reduction of construction costs and use in remote areas, which favors distributed generation. Hygroscopic Cycle Technology (HCT) can be of great interest for power generation in nuclear power plants, due to the potential improvement in terms of energy efficiency and water savings. This study presents the benefits of implementing HCT in an existing SMR, the HTR-10, based on the classical Regenerative Rankine Cycle (RRC). The HTR-10 is used to produce electricity and thermal energy for District Heating (DH). Analytical models of both cycles have been developed to compare them in terms of energy production and water consumption. Sensitivity analyses of the influence of the main variables have been performed. The results show that by varying the condensing pressures, the thermal power for DH and the net mechanical power production of the HCT increase up to 2.5 % and 1 %, respectively, with respect to the RRC. The maximum tolerable ambient temperature for the plant with the HCT is 43.12 °C, increasing the availability of the plant and avoiding water consumption between 70000 and 88000 m3/year, depending on the operating conditions. Extrapolation of the results suggests that HCT can improve the energy production of nuclear power plants in a more sustainable way, contributing significantly to the energy transition.

Abilene Christian University (ACU) is developing a 1-MW(thermal) molten salt research reactor that will be built on the ACU campus. A conceptual reactor core model was developed to facilitate the safety analysis required for a construction permit. A series of scoping studies were performed seeking to define the reactor core design parameters subject to a variety of design requirements. A Pareto curve identifying the tradeoff between uranium and LiF-BeF2 was determined. Within this curve, at least 250 kg of uranium and 700 kg of LiF-BeF2 are needed, albeit for different reactor configurations and fuel salt compositions. The cylindrical reactor vessel associated with the best-performing fuel salt composition is ~130 cm in diameter, ~170 cm tall, and contains ~2.5 tons of graphite. The conversion ratio of the reactor is low and will require regular refueling. The shift in neutron spectrum observed with the changing fuel salt composition does not significantly impact reactivity loss with respect to burnup. [ABSTRACT FROM AUTHOR]

An experiment was conducted that demonstrates a novel core power distribution reconstruction method based on ex-core detectors using time-dependent measurement at the University Teaching and Research Reactor of Kindai University (UTR-KINKI). Although the proposed method PHOEBE was able to identify the power distribution change caused by control rods under static conditions in a previous experiment, time-dependent experiments were not conducted. Hence, the present study measured time-dependent neutron counts using ex-core detectors to reconstruct the power distribution based on PHOEBE. Extraction of the control rods was expected to cause a shift in the reactor power distribution from the north side to the south, and the results of the power distribution reconstruction also demonstrated this power shift. This result experimentally and qualitatively demonstrated the detection of time-dependent power shifts based on PHOEBE. However, quantitative verification was difficult in this study because there are no verified time-dependent three-dimensional neutronics codes available. This issue will be addressed in a future study when a code becomes available. [ABSTRACT FROM AUTHOR]

One of the well-known technologies that fit well into the goal of reduction of greenhouse gas emissions is nuclear energy. In particular, the change in approach to the design and construction of nuclear power plants led to the development of small modular reactors (SMRs), which are characterized by a broader range of possible applications than large nuclear reactors and the ability to flexibly operate as per load demand. This paper presents an analysis of the thermal loads of a steam turbine rotor operating in a power plant with SMR. Steam-water cycle and turbine train of a 300 MW unit are presented. High-pressure steam turbine rotor and its thermal loading due to varying steam conditions are investigated for a cold startup designed with consideration of the thermal characteristics of nuclear reactors. It was shown by numerical simulations that steam condensation on rotor surfaces plays a crucial role in determining its thermal behaviour. Comparison with conventional rotors has shown that the thermal loading of nuclear turbine rotors is lower and more stable than that of conventional turbines. [ABSTRACT FROM AUTHOR]

An analysis of the platforms of information and control systems (ICS), the impact of the features of SMR projects on the digital infrastructure (DIS) comprising a complex of ICSs for various purposes, monitoring systems, and physical security. Structure of modern SMR DIS is suggested. The requirements for DISs/ICSs in view of these features, as well as the tasks that must be solved by DIS/ICS providers in order to realize the benefits of SMR are formulated. [ABSTRACT FROM AUTHOR]

Neutron thermalization leads to the complexity of the scattering cross-section calculation, which influences the accuracy of the neutron transport calculation in the thermal energy range. The higher precision of thermal scattering data is demanded in the small modular reactors (SMRs) design, especially for small-sized PWRs and SCWRs. Additionally, the thermal neutron scattering problems in supercritical water have not yet been solved. In this study, the thermal neutron scattering problems in subcritical water are tested. Based on thermal neutron scattering theory, the GA model and IKE model were analyzed. This work selected the corresponding input parameters, such as the frequency spectrum, the discrete oscillator energy, weight parameters and so on, as well as preliminary studies on how to calculate the thermal scattering data for HinH2O to accomplish the calculation at various temperatures by developing LIPER code. The deviation between the calculated and reference results, which were both obtained by the Monte Carlo code, COSRMC, was below 0.2 pcm. The deviation of the scattering cross-section between the calculation results and reference was below 0.1%, indicating the reasonability of this study’s thermal scattering data calculation.

Hydraulic performance and flow resistance tests were performed to confirm the main parameters of the hydraulic instrumentation that can affect the pump performance of the reactor coolant pump. The flow resistance test offers important experimental data, which are necessary to predict the behavior of the primary coolant when the circulation of the reactor coolant pump is stopped. Moreover, the shape of the hydraulic section of the pump, which was considered in the test, was prepared to compare the mixed-flow- and axial-flow-type models, the difference in the number of blades of the impeller and diffuser, the difference in the shape of the impeller blade and its thickness, and the effect of coating at the suction bell. Additionally, five models of the hydraulic part were manufactured for the experiments. In this study, the differences in performance owing to the design factors were confirmed through the experimental results.

In this study, impacts of an enhanced-moderation Fuel Assembly (FA) named Truly Optimized PWR (TOP) lattice, which is modified based on the standard 17 × 17 PWR FA, are investigated in a natural circulation Soluble-Boron-Free (SBF) Small Modular Reactor (SMR). Two different TOP lattice designs are considered for the analysis; one is with 1.26 cm pin pitch and 0.38 cm fuel pellet radius, and the other is with 1.40 cm pin pitch and 0.41 cm fuel pellet radius. The NuScale core design is utilized as the base model and assumed to be successfully converted to an SBF core. The analysis is performed following the primary coolant circulation loop, and the reactor is modelled as a single channel for thermal-hydraulic analyses. It is assumed that the ratio of the core pressure drop to the total system pressure drop is around 0.3. The results showed that the reactor power could be increased by 2.5% and 9.8% utilizing 1.26/0.38 cm and 1.40/0.41 cm TOP designs, respectively, under the identical coolant inlet and outlet temperatures as the constraints.

Small modular reactors represent a promising technology for power generation, offering solutions to the energy crisis and mitigating greenhouse gas emissions. As Ukraine considers the deployment of NuScale, UK SMR, and SMR-160, it is crucial to address the safe management of spent nuclear fuel. This study focuses on evaluating the radiological characteristics of spent nuclear fuel from the selected small modular reactors and for comparison, from the VVER-1000 reactor. Using the Monte Carlo code Serpent, depletion calculations were performed for an assembly in an infinite 2-D geometry, and the activity, decay heat, and inhalation toxicity of the spent nuclear fuel were assessed. We determined the main nuclides contributing to the radiological characteristics and quantified the mass content of these nuclides. The total number of spent nuclear fuel assemblies produced during the entire life of each small modular reactor type was estimated. The radiological characteristics assessed for the three small modular reactors do not exceed those observed for VVER-1000 reactors currently operating in Ukraine. So, spent nuclear fuel generated by the selected small modular reactors will introduce no new challenges to Ukraine's radioactive waste management system. The results of this work provide valuable insights for identifying the optimal small modular reactor technologies for Ukraine concerning safe spent nuclear fuel management.

Small modular reactors with power below 300 MW have the advantages of small specific mass, long lifetime, and flexible power supply, and they are suitable for providing power support for small and medium-sized towns with small populations and remote areas without grid coverage. In this paper, a small modular S-CO2-cooled molten salt reactor is proposed, and the design of a 10 MW small modular chlorine salt fast reactor (sm-MCFR) with 20 years of operation without refueling is presented. The neutron feasibility of the S-CO2-cooled small modular chlorine fast reactor is analyzed in terms of neutron energy spectrum, reactivity control, temperature reactivity coefficient, and power distribution. A distinctive feature of the sm-MCFR is the use of chlorine salts with high heavy metal solubility and a hard energy spectrum, allowing the core size to be minimized while maintaining the maximum lifetime. The designed core is about 2.44 m in diameter and 2.24 m in height. Meanwhile, the sm-MCFR uses control drum control as the control system, which can effectively achieve reactivity control without increasing the reactor size. The final optimized sm-MCFR has a negative temperature reactivity coefficient, which is necessary to ensure the safe operation of the reactor. [ABSTRACT FROM AUTHOR]

The main aim of the natural circulation of the primary coolant in a nuclear reactor is to reject heat from the reactor core to the steam generator without using a circulation pump. In this work, a vertical heater–vertical cooler, high-temperature, high-pressure, nonuniform-diameter, single-phase natural circulation loop is proposed. The rig contains a spacer grid assembly of electrical heaters in a core with a conical section in its upper plenum and a double helical coil steam generator. The proposed loop is analyzed using RELAP5 and various analytical models. First, these models are benchmarked with experimental data from the Facility to Investigate Natural Circulation in SMART or FINCLS. The model results are found to be in good agreement with the experimental data. The same models are then employed to investigate the proposed natural circulation facility, named the Integral PWR-type SMR Test Rig (iPSTR), to investigate the mass flow rate as a function of geometric and process parameters. Core power input was varied from 5 to 82.5 kW at a maximum system pressure of 10 bar and a maximum elevation difference of thermal centers of 3400 mm. Elevation differences of the thermal centers and diameter of core are found to be important parameters that affect thermal-hydraulic performance significantly. However, cone angle, spacer grid, and system pressure are found to have no significant effect on the performance of the iPSTR. Moreover, the proposed iPSTR is found to possess higher Reynolds number compared with the existing facilities. [ABSTRACT FROM AUTHOR]

Neutron thermalization leads to the complexity of the scattering cross-section calculation, which influences the accuracy of the neutron transport calculation in the thermal energy range. The higher precision of thermal scattering data is demanded in the small modular reactors (SMRs) design, especially for small-sized PWRs and SCWRs. Additionally, the thermal neutron scattering problems in supercritical water have not yet been solved. In this study, the thermal neutron scattering problems in subcritical water are tested. Based on thermal neutron scattering theory, the GA model and IKE model were analyzed. This work selected the corresponding input parameters, such as the frequency spectrum, the discrete oscillator energy, weight parameters and so on, as well as preliminary studies on how to calculate the thermal scattering data for HinH2O to accomplish the calculation at various temperatures by developing LIPER code. The deviation between the calculated and reference results, which were both obtained by the Monte Carlo code, COSRMC, was below 0.2 pcm. The deviation of the scattering cross-section between the calculation results and reference was below 0.1%, indicating the reasonability of this study's thermal scattering data calculation. [ABSTRACT FROM AUTHOR]

Nuclear energy sources, in particular the small modular reactor (SMR), are being recognized as low-emission clean energy sources. The development of SMRs has focused on minimizing their carbon footprint while ensuring that energy is generated in a safe and cost-competitive manner, which leads to a worldwide growing interest in SMR deployments. In addition, there is a strong demand for renewable energy sources; however, their output can be influenced significantly by weather and location. Therefore, integration of renewable energy sources with SMRs and an energy storage system, which results in a nuclear renewable hybrid energy system (NR-HES), is required to improve power generation reliability. NR-HES represents a promising energy system solution for off-grid communities and industries, especially those involving remote mining sites. In the present study, an off-grid NR-HES to meet electrical and thermal demands is considered for the Victor mine site in northern Ontario, Canada. Off-grid remote mines in Canada primarily rely on diesel generators. The proposed NR-HES is composed of SMR units with a thermal capacity of 15 MWth each, two wind turbines with a capacity of 2.3 MWe each, a two-tank molten salt thermal storage system, a hydrogen storage facility, and peaking diesel generators. To achieve a near-zero-emission mining site, electric vehicles are proposed in the mining site energy demand structure. A transient thermodynamics model is developed to simulate the NR-HES and generate hourly variation of sustainability performance parameters that include power cycle efficiency, SMR capacity factor, round-trip efficiency of the storage systems, thermal storage state of charging, and greenhouse gas emissions. In addition, an economic analysis is performed to determine the additional annualized cost of the system relative to a baseline site. The simulation has a test matrix of 16 runs with various combinations of design input parameters, namely SMR thermal power, storage duration (e.g., daily, seasonally, or monthly), and thermal storage system volume. Grey relational analysis (GRA) is used as a level-based multi-objective optimization technique to determine the nearest optimal design parameter (e.g., decision variable) combination within the test matrix and thus the optimal configuration. In addition, the GRA ranks the design input parameters based on how significantly each parameter can affect the overall performance of the NR-HES. Results revealed that optimal sustainable perspectives have a significant influence on the overall system parameters and performance. For instance, the results showed that there is an opportunity to achieve a reduction in greenhouse gas emissions by 94.8% with a minimal impact to system annualized cost if the cost and environmental effect objectives were prioritized over other sustainability performance parameters.

Most power plants, particularly those that burn fossil fuels such as coal, oil, and gas, create CO2, a greenhouse gas that contributes to climate change. By 2060, the Indonesian government has committed to reach net zero emissions. With the lowest CO2 emissions, nuclear power plants are dependable sources of energy. Small modular reactors (SMRs) are a particular kind of nuclear power plant that has the potential to be Indonesia's first commercial nuclear power plant because of their small size, low capacity, uncomplicated design, and modular characteristics. The purpose of this study is to examine the economics and technological feasibility of SMRs. In this analysis, the levelized cost of electricity (LCOE) comparative method and the technology readiness level (TRL) approach are both applied. The SMRs with a minimum TRL value of 7 were CAREM-25 (TRL7), KLT-40S (TRL8), and HTR-PM (TRL 8), according to the results of this research. Although CAREM-25 and KLT-40S are still in the demonstration stage and have not yet entered the market, their LCOE estimates are greater than 0.07 USD/kWh with a 5% discount rate. Whereas CAREM 100 MW is an economy scale from CAREM-25 and VBER 300 MW is a commercial size from KLT-40S, HTR-PM is already an economy scale. With discount rates between 5% and 10%, the LCOE values of HTR-PM, CAREM 100 MW, and VBER 300 MW range from 0.06 USD to 0.12 USD per kWh. Other than hydropower and coal-fired power plants, these LCOE figures can compete with the local LCOE in Indonesia and the LCOE of a variety of other types of power plants. [ABSTRACT FROM AUTHOR]

This scientific paper discusses the importance of reducing greenhouse gas emissions to mitigate the effects of climate change. The proposed strategy is to reach net-zero emissions by transitioning to electric systems powered by low-carbon sources such as wind, solar, hydroelectric power, and nuclear energy. However, the paper also highlights the challenges of this transition, including high costs and lack of infrastructure. The paper emphasizes the need for continued research and investment in renewable energy technology and infrastructure to overcome these challenges and achieve a sustainable energy system. Additionally, the use of nuclear energy raises concerns, such as nuclear waste and proliferation, and should be considered with its benefits and drawbacks. The study assesses the feasibility of nuclear energy development in Latvia, a country in Northern Europe, and finds that Latvia is a suitable location for nuclear power facilities due to potential energy independence, low-carbon energy production, reliability, and economic benefits. The study also discusses methods of calculating electricity generation and consumption, such as measuring MWh produced by power plants, and balancing supply and demand within the country. Furthermore, the study assesses the safety of nuclear reactors, generated waste, and options for nuclear waste recycling. The transition to a carbon-free energy system is ongoing and complex, requiring multiple strategies to accelerate the transition. While the paper proposes that nuclear energy could be a practical means of supporting and backing up electricity generated by renewables, it should be noted that there are still challenges to be addressed. Some of the results presented in the paper are still based on studies, and the post-treatment of waste needs to be further clarified. [ABSTRACT FROM AUTHOR]

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The once-through steam generator used in the small modular reactor needs to consider the stability of the outlet steam pressure and steam superheat of the secondary circuit to achieve better operating efficiency. For this reason, this paper designs a controllable operation scheme for the steam pressure and superheat of the small reactor once-through steam generator. On this basis, designs a variable universe fuzzy controller, first, design the fuzzy control rules to make the controller adjust the PI controller parameters according to the change of the error; secondly, use the domain adjustment factor to further subdivide the input and output domain of the fuzzy controller according to the change of the error, to improve the system control performance. The simulation results show that the operation scheme proposed in this paper have better system performance than the original scheme of the small reactor system, and controller proposed in this paper have better control performance than traditional PI controller and fuzzy PI controller, what's more, the designed control system also showed better anti-disturbance performance in lifting experiment between 100% and 80% working conditions. Finally, the experimental platform formed by connecting the digital small reactor with Matlab/Simulink through OPC(OLE for Process Control) communication technology also verified the feasibility of the proposed scheme.

This study explores how sector coupling via Integrated energy systems (IES) can improve the operational flexibility of the power grid, while hydrogen is gaining traction as a versatile energy carrier. Specifically, we have evaluated the operational benefits of integrating two electrolytic processes for hydrogen generation, namely low-temperature electrolysis (LTE) and high-temperature steam electrolysis (HTSE), into a nuclear-renewable IES using a 3-cycle power system operation framework. Detailed steady-state models of the electrolytic hydrogen generating facilities are constructed, with the HTSE process represented using standard transient models to account for the steam-bypass scheme from the nuclear reactor. These models are then integrated into a renewable-intensive power network model (specifically, the NREL 118-bus system). To simulate the operation of the integrated system across multiple timescales, a multi-timescale scheduling and dispatch tool is employed. Results indicate that while both electrolytic processes contribute to significant flexibility enhancement and renewable energy curtailment reduction (3 MWh and 16 MWh), the LTE process offers more operational benefits than the HTSE process across multiple timescales. • Evaluate the benefits of integrated nuclear, renewables, and hydrogen systems. • Construct steady-state models of electrolytic hydrogen generating facilities. • Compare low-temperature electrolysis and high-temperature steam electrolysis. [ABSTRACT FROM AUTHOR]

• Proposed a small modular chloride salt fast reactor design for TRU burning. • Evaluated different fuel salt options and reprocessing rates. • Optimized the TRU incineration capacity of the sm-MCFR. • Assessed radiotoxicity of optimized the sm-MCFR. • Evaluated temperature feedback coefficient of optimized the sm-MCFR. The management of radioactive waste poses a significant challenge to the sustainable development of nuclear energy. Efficient transmutation of nuclear wastes is crucial to minimize their accumulation. A small modular chloride salt fast reactor (sm-MCFR) capable of transmuting transuranic elements (TRU) is proposed in this paper, combining the advantages of the small modular reactor (SMR) and the molten salt reactor (MSR). The sm-MCFR is characterized by a high fuel loading and a compact core structure that can be quickly deployed around large commercial reactors to achieve TRU transmutation. To evaluate the TRU burnup capability of the sm-MCFR, several fuel salts and reprocessing modes were analyzed using the internally developed TRITON MODEC Coupled Burnup Code (TMCBurnup) tool. NaCl-MgCl 3 with 98 % enrichment in 37Cl is chosen as carrier salt for the sm-MCFR, which can achieve 76.7 % TRU transmutation rate in average and 355 kg·GW−1·a−1 TRU transmutation quality at a continuous reprocessing rate of 10 L/d for 50 operation years. The optimized sm-MCFR reduced the radioactive toxicity of TRU by 84 %, thereby simplifying waste reprocessing. In addition, the sm-MCFR has a negative temperature feedback coefficient of −7.195 pcm/K, favoring safe reactor operation. [ABSTRACT FROM AUTHOR]

Helical petal-shaped fuel rods have the characteristics of increased heat transfer area and self-supporting positioning, which makes them have great potential for application in small modular reactors. By employing the multi-scale coupled numerical model, the flow and heat transfer characteristics of the petal-shaped bundle in hexagonal arrangement were obtained under natural circulation conditions. The results indicated that the spatial structure of flow channel exhibited a centrally symmetric distribution. Consistent flow and heat transfer behaviors were obtained at symmetric positions. Additionally, fluid viscosity exerted the most significant influence on flow resistance coefficient. Meanwhile, vortices that develop in the opposite direction resulted in flow losses, which induced variations in the resistance coefficient along the channel. Finally, the applicability of existing flow and heat transfer correlations was evaluated under natural circulation conditions. This study has provided significant theoretical guidance for engineering application of the petal-shaped fuel rods. • Flow channels in petal-shaped rod bundle channels satisfy centrally symmetric. • Effects of viscosity and secondary flow on the flow resistance have been analyzed in detail. • Both the existing resistance coefficient and Nusselt number correlations have been evaluated. [ABSTRACT FROM AUTHOR]

• Uncertainty analysis of source term reflected latent peaks of release starting time. • Release starting time is classified to support a flexible SMR emergency plan via GMM. • Dose level for SMR main emergency action is limited to 1 mSv zone within 6 km radius. • Chance of late release starting time is used to set backup emergency plans for SMR. Due to the interest in SMR reactors in newcomer countries, the understanding of the risk of source term release and dose exposure of SMR technology is important scientific data for communicating between the government and people. This study aims to extend the application of release starting time classification of level 2 PSA in SMR technology to inform strategic planning for nuclear consequences and determine size requirements for the emergency planning zones in level 3 PSA. The SBO accident scenario of iPWR at the location in the Ubon Ratchathani province, Thailand, was investigated in this study. The GMM is used to classify the probability density of uneven distributions of release starting times into the two groups. The higher probability density and maximum radioactive release in Group (1) were used to suggest the main plan for emergency response. In the main plan, the local government needs to evacuate the people outside 6 km to avoid dose exposure if source term release is monitored within 8–21 h. The impact of source term release in Group (2) was set as a backup plan for considering an emergency planning extension if the time delay to later than 21 h. Finally, the nuclear consequences of SMRs are compared with large NPPs in the same accident scenarios. SMR technology has the potential to support flexible emergency planning zones for sheltering and evacuation without significant dose exposure to neighboring countries. [ABSTRACT FROM AUTHOR]

• Helical coil steam generator flow stability tests with a facility modelling iSMR. • Stability map using the homogeneous equilibrium model. • Strong dependency of stability on the secondary side pressure. • Core power/feedwater mass flow rate ratio of 40 kW/l/min for the onset of DWOs. • MOTEL steam generator heat transfer capacity 250–300 kW for stable operation. Small modular reactors (SMRs) are under extensive development globally. Some SMR concepts have design features that are rare in traditional pressurized water reactors (PWRs). One such feature is a helical coil steam generator which differs from traditional horizontal and vertical inverted U-tube steam generators in several ways. The helical coil steam generator is a once-through design where the primary side flow runs in the shell side and the secondary side flow runs inside the tubes and can generate superheated steam. Boiling instabilities in helically coiled tubes are a crucial research question due to their potentially negative impact on steady plant operation. The MOTEL (MOdular TEst Loop) facility at LUT University is a model of an integral SMR with a helical coil steam generator representing an integral pressurized water reactor. A large variation of core power and feedwater flow values were tested to map MOTEL operating conditions in which the steam production in the helical coil steam generator is stable. [ABSTRACT FROM AUTHOR]

Direct air capture (DAC) is a key component in the transition to net-zero society. However, its giga-tonne deployment faces daunting challenges in terms of availability of both financial resources and, most of all, large quantities of low-carbon energy. Within this context, small modular nuclear reactors (SMRs) might potentially facilitate the deployment of DAC. In the present study, we present a detailed thermodynamic analysis of integrating an SMR with solid sorbent DAC. We propose different integration designs and find that coupling the SMR with DAC significantly increases the use of thermal energy produced in the nuclear reactor: from 32% in a stand-alone SMR to 76%–85% in the SMR-DAC system. Moreover, we find that a 50–MW SMR module equipped with DAC could remove around 0.3 MtCO _2 every year, while still producing electricity at 24%–42% of the rated power output. Performing a techno-economic analysis of the system, we estimate a net removal cost of around 250 €/tCO _2 . When benchmarking it to other low-carbon energy supply solutions, we find that the SMR-DAC system is potentially more cost-effective than a DAC powered by high-temperature heat pumps or dedicated geothermal systems. Finally, we evaluate the potential of future deployment of SMR-DAC in China, Europe, India, South Africa and the USA, finding that it could enable up to around 96 MtCO _2 /year by 2035 if SMRs prove to be cost-competitive. The impact of regional differences on the removal cost is also assessed.

Greenhouse gas emissions from burning fossil fuels, including the predominant energy generation method in many countries, coal power plants, face challenges resulting from the pursuit of climate policy. Modelling performed by intergovernmental organizations detailing scenarios to reach global decarbonization goals include the reduction of burning of fossil fuels and an increase in electrical demand. Replacing coal-fired power plants with technology that produces lower emissions offers a potential solution. In this paper we calculate emissions reductions available from converting coal-fired power plants to nuclear plants in both the U.S. and India, the countries having the world’s largest coal-fired power generation capacity outside of China. We consider potential timelines for the coal to nuclear conversion, and then determine the resulting emissions to help us better understand the impact that a fleet-scale nuclear conversion campaign could have on each nation’s decarbonization goals. Our results indicate that, while the U.S. and India presently have similar installed coal generation capacity and annual emissions, India’s remaining committed emissions are approximately five times greater than those of the U.S. for both a base case and a 46-plant conversion case. We conclude that converting coal-fired power plants to nuclear plants can offer emissions reductions, but that the national impact relies heavily on fleet composition. Although older fleets have the potential to offer annual emissions reductions from retirements and conversions, converting younger fleets can have a much greater impact on committed emissions, which is a better indicator of the potential of coal-to-nuclear conversion in global decarbonization.

Population growth, industrial development as well as limited fossil fuel resources have motivated the study of other energies, especially nuclear energy. Small modular reactors have been introduced as an efficient energy source due to their greater safety, easy transport, electricity generation and water desalination, even in remote areas. Optimization in the nuclear fuel management to improve performance and save energy leads to cost-effective design with higher efficiency and better safety. In this research, core loading pattern optimization of system-integrated modular advanced reactor (SMART) has been considered using the new dragonfly algorithm. In addition to the selected algorithm, the efficiency of optimizing loading pattern also depends on the definition of the objective function. Two-objective functions including flattening the power distribution and maximizing the effective multiplication factor are considered. Simulations of the reactor fuel assemblies and reactor core were performed by DRAGON lattice calculation and PARCS core calculation codes, respectively. According to the final results, the cycle length and effective multiplication factor are increased for 185 days and 582 pcm, respectively. Also the fitness function is decreased from 0.905931 to 0.194527.

This paper presents a high performance burnable absorber named as CIMBA (Cylindrically Inserted and Mechanically Separated Burnable Absorber) for the soluble-boron-free SMR. The CIMBA is the cylindrical gadolinia inserted into the annular fuel pellets. Although the CIMBA utilizes the spatial self-shielding effect of the fuel material, a large reactivity upswing occurs when the gadolinia is depleted. To minimize the reactivity swing of the CIMBA-loaded FA, two approaches were investigated. One is controlling the spatial self-shielding effect of the CIMBA as burnup proceeds by a multi-layered structure of the CIMBA (ML-CIMBA) and the other is the mixed-loading of two different types of CIMBA (MIX-CIMBA). Both approaches show promising performances to minimize the reactivity swing, where the MIX-CIMBA is more preferable due to its simpler fabrication process. In conclusion, the MIX-CIMBA is expected to accelerate the commercialization of the CIMBA and can be used to achieve an optimal soluble-boron-free SMR core design.

The small modular liquid-metal fast reactor (SMFR) is an important component of advanced nuclear systems. SMFRs exhibit relatively low breeding capability and constraint space for control rod installation. Consequently, control rods are deeply inserted at beginning and are withdrawn gradually to compensate for large burnup reactivity loss in a long lifetime. This paper is committed to investigating the impact of control rod compensation operation on core neutronics characteristics. This paper presents a whole core fine depletion model of long lifetime SMFR using OpenMC and the influence of depletion chains is verified. Three control rod position schemes to simulate the compensation process are compared. The results show that the fine simulation of the control rod compensation process impacts significantly the fuel burnup distribution and absorber consumption. A control rod equivalent position scheme proposed in this work is an optimal option in the trade-off between computation time and accuracy. The control position is crucial for accurate power distribution and void feedback coefficients in SMFRs. The results in this paper also show that the pin level power distribution is important due to the heterogeneous distribution in SMFRs. The fuel burnup distribution at the end of core life impacts the worth of control rods.

Small modular nuclear reactors (SMRs) are an emerging technology with many potential benefits to cost, manufacturing, and safety over more traditional reactor designs. The NuScale Power Module (NPM) is a pressurized water SMR that uses natural convection to circulate its coolant. Variations of steam Rankine cycles have been the predominant design for power cycles in the nuclear energy space for decades, but ongoing research has suggested promising alternatives to be used in future designs. Previous works have suggested that a transcritical Rankine cycle with an organic working fluid like ethanol or methanol could have superior thermal efficiency compared to comparable steam Rankine cycles for mid-temperature applications. This study presents a design optimization and sensitivity analysis of an organic transcritical Rankine cycle (ORTC) with methanol as a working fluid, with a model of the NPM used as the primary cycle. Multi-objective optimization is used to analyze the trade-off between thermal efficiency and levelized cost of energy (LCOE) for this cycle design. All of the optimal designs identified in the multi-objective optimization show improvements in LCOE compared to the benchmark regenerative steam Rankine cycle at comparable thermal efficiencies, with LCOE being reduced by as much as 19.1% by using the ORTC. In the Pareto front, higher efficiency solutions use regenerative cycle designs, while lower LCOE solutions do not utilize regenerators. A sensitivity analysis of the optimal design points reveals that regenerative design points have greater sensitivity in both LCOE and thermal efficiency to the variation in the design parameters.

Micro and Small Modular Reactor (MSMR) is an emerging energy technology that meets the requirements of market demand, safety, efficiency, and sustainability. This paper summarizes the advantages, application scenarios, and advanced technologies to support MSMR. Now that the energy market is more flexible and the requirements are more complex, while MSMR can meet the market demand and has a lower cost compared with other clean energies such as wind and solar photovoltaic. The United States is vigorously developing MSMRs into residential energy markets. The MSMR developed around the world has more than three generations of safety characteristics that have adopted passive safety features. MSMR can be manufactured in the factory which reduces construction schedule, cost, and waste. The nuclear fuel supply chain for MSMR is complete and perfect, including the front end and back end. An increasing number of advanced technologies support the development of MSMR, including advanced materials (TRISO fuel and accident-tolerance fuel), advanced control knowledges (DI&C, cybersecurity, and AI), and an advanced computational platform (MOOSE framework).

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This study presents neutronic analyses of a small modular reactor utilizing transuranium and thorium. Two different fuel cases are considered in the analyses as the transuranium extracted from PWR-MOX spent fuel (a form of a mixture of minor actinide and Pu isotopes) (Case A) and 4.5 % enriched UO2 with ThO 2(the form of separate fuel rods) (Case B). The total power of the considered small modular reactor containing 69 assemblies is 450 MW thermal. In both fuel cases, the time-dependent critical burnup calculations are carried out by using MCNPX 2.7 code until their effective neutron multiplication factors decrease to 0.99. The calculations bring out that the small modular reactor can operate for quite a long time without refueling and that a new fuel with a richness of 1.05 % can be obtained from ThO as well 2 as energy production.

Summary: Rankine (steam) cycle traditionally has been the exclusive energy conversion system (the secondary side) for nuclear power plants based on light‐water reactors (the primary side). In an effort to improve the economics of nuclear as a clean, sustainable energy source, various small modular reactor designs have been developed and some have been scheduled to deploy at the end of this decade. In this work, technoeconomic analysis is conducted for three alternative power cycles for the light‐water small modular reactor by NuScale Power, which include a regenerative reheat Rankine cycle, a transcritical ethanol cycle and a recompression supercritical CO2 cycle. The results have shown the baseline regenerative Rankine cycle is a good fit for the current small modular reactor due to its attractive cycle efficiency (31.2%), low cost and relatively simple design. Using the selected first‐order cost models, the costs for the major power cycle components including turbines, compressors, pumps, and heat exchangers, as well as the levelized cost of electricity for each cycle are estimated. The results show both the regenerative reheat Rankine cycle and transcritical ethanol cycle would provide higher cycle efficiencies (33.1% and 33.9%) and a lower levelized cost of electricity (5.14% and 4.96% reduction from the baseline, respectively), while the recompression supercritical CO2 cycle has a lower thermal efficiency (29.8%) while a higher levelized cost of electricity (21.8% increase from the baseline). As the result, the recompression supercritical CO2 cycle is not suitable as the energy conversion system for light‐water small modular reactors. HIGHLIGHTS: Technoeconomic analysis of three alternative power cycles for a small modular light‐water reactor is conducted.Cost models for major components are comparatively selected for calculating levelized cost of electricity for each alternative power cycle.Supercritical CO2 cycle is not suitable for light‐water SMRs based on the technoeconomic analysis.The transcritical ethanol cycle and regenerative reheat Rankine cycle have shown higher thermal efficiency and lower levelized cost of electricity than the baseline regenerative Rankine cycle. [ABSTRACT FROM AUTHOR]

Advanced small modular reactors (SMRs) have recently been developed in many designs; therefore, nuclear energy stands out as a promising alternative to sustainability and reliability in replacing fossil fuel energies in microgrids. SMRs have been shown as the best option due to the fact of their lower initial capital, greater scalability, and siting flexibility compared to large nuclear plants. Nowadays, there are several simulators able to reproduce all the safety and control mechanics of different nuclear reactors; however, there exists a lack of emulators able to put these functionalities into a real scenario to ensure the feasibility of the use of nuclear energy within energy systems, especially in nonconventional systems. This paper aims to mimic the central control system of SMRs by modeling the nuclear processes aiming to contribute to real-time simulations using SMRs integrated with renewable energy in microgrids that could be applied for different scenarios, such as cogeneration systems or fast-charging stations for electric vehicles, by considering the impact on dispatch and reliability. The simulation process of the proposed model was validated experimentally using the hardware-in-the-loop technique, which consisted of the modeling being integrated into the hardware and tested using real-time simulators. The proposed system, also denominated as SMR-in-the-Loop, was designed and adapted to be easily integrated with existing microgrid systems to represent the behavior of an SMR in nuclear-renewable hybrid energy systems, avoiding high investments and complexity in testing and implementing actual nuclear reactors. [ABSTRACT FROM AUTHOR]

An integral test facility, PILLAR, was commissioned, aiming to provide valuable experimental results which can be referenced by system and component designers and used for the performance demonstration of liquid-metal-cooled, passive small modular reactors (SMRs) toward their licensing. The setup was conceptualized by a scaling analysis which allows the vertical arrangements to be conserved from its prototypic reactor, scaled uniformly in the radial direction achieving a flow area reduction of 1/200. Its final design includes several heater rods which simulate the reactor core, and a single heat exchanger representing the steam generators in the prototype. The system behaviors were characterized by its data acquisition system implementing various instruments. In this paper, we present not only a detailed description of the facility components, but also selected experimental results of both steady-state and transient cases. The obtained steady-state test results were utilized for the benchmark of a system code, achieving a capability of accurate simulations with ±3% of maximum deviations. It was followed by qualitative comparisons on the transient test results which indicate that the integral system behaviors in passive LBE-cooled systems are able to be predicted by the code.

In this paper, the conceptual design and a preliminary study of the LUT Heating Experimental Reactor (LUTHER) for 2 MWth power are presented. Additionally, commercially sized designs for 24 MWth and 120 MWth powers are briefly discussed. LUTHER is a scalable light-water pressure-channel reactor designed to operate at low temperature, low pressure, and low core power density. The LUTHER core utilizes low enriched uranium (LEU) to produce low-temperature output, targeting the district heating demand in Finland. Nuclear power needs to contribute to the decarbonizing of the heating and cooling sector, which is a much more significant greenhouse gas emitter than electricity production in the Nordic countries. The main principle in the development of LUTHER is to simplify the core design and safety systems, which, along with using commercially available reactor components, would lead to lower fabrication costs and enhanced safety. LUTHER also features a unique design with movable individual fuel assembly for reactivity control and burnup compensation. Two-dimensional (2D) and three-dimensional (3D) fuel assemblies and reactor cores are modeled with the Serpent Monte Carlo reactor physics code. Different reactor design parameters and safety configurations are explored and assessed. The preliminary results show an optimal basic core design, a good neutronic performance, and the feasibility of controlling reactivity by moving fuel assemblies.

Because of many special benefits of the Small Modular Reactors (SMRs) and the Accelerator Driven Subcritical Reactors (ADSRs), they are subject of a large number of studies all over the world. In the present work, the ADS photoneutron target for Holos reactor was designed and optimized by using MCNPX2.6 code. The Continuous Slowing Down Approximation (CSDA) ranges of passing electrons through tantalum, tungsten, mercury, lead and lead-bismuth were investigated. The production and leakage rates for neutrons and photons, and therefore, the deposited heat from neutrons and photons were calculated considering the electron beam bombardment of tantalum, tungsten, mercury, lead and lead-bismuth targets at beam energies of 100–1000 MeV. Other factors such as the optimization of photoneutron target dimensions for 20 and 200 MeV electron beams, and choosing of the optimal energy of incident electrons for the optimized photoneutron target were examined.

• A thermodynamic-economic model for supercritical CO 2 directly cooled reactor is developed based on thermal current theory. • PCHE's model incorporating actual channel geometries is established based on ITDB thermal resistance. • Effects of PCHE types and size on cycle's thermo–economic performances are clarified. The supercritical CO 2 Brayton cycle is a potential technology in small modular reactors (SMRs), and the overall system efficiency can be significantly improved by optimizing the PCHE design parameters. This study develops a thermodynamic-economic analysis model for a supercritical CO 2 simple Brayton cycle cooled SMR, with consideration of the detailed parameters of PCHEs. The impact of the length, channel number and channel type for the recuperator and the precooler on system thermal efficiency and levelized cost of electricity (LCOE) are analyzed. A dual-objective optimization study is conducted at the system level to identify the optimal design of size parameters and types for the heat exchangers. The results indicate that the influence of PCHE size parameters variations on system performance varies across different channel types. Additionally, the selection of the recommended recuperator type is influenced by the recuperator inlet Reynolds number. At the optimum design, the recommended channel type for recuperator and precooler are both S-shaped, resulting in a system efficiency of 39.12% and LCOE of 0.0456 $/kW e. The findings are valuable for enhancing energy utilization and reducing the power generation cost of SMRs. [ABSTRACT FROM AUTHOR]