Search Results (13)

There has been increasing interest in deploying Small Modular Reactors (SMRs) due to their simplicity, enhanced safety features, and economic advantages, which may facilitate the transition from coal to nuclear energy. However, the revival of nuclear power today depends on reactors meeting long-term operational security requirements, which can lead to optimized costs for nuclear energy and greater public acceptance. Therefore, it is crucial to demonstrate best practices in the operation, reliability, and stability of the systems and materials used in construction to ensure that nuclear power plants can operate safely over extended periods. Corrosion remains a critical factor affecting the safe operation of these plants. While corrosion issues have been extensively studied in traditional nuclear reactors that use water as a coolant, advanced reactors employing non-water coolants—such as liquid metals or molten salts—present new corrosion challenges. This work aims to present the various sources of corrosion in different SMR cooling systems, along with the results of corrosion processes. It also discusses the challenges related to materials used in multiple SMR designs and highlights advancements in the development of new materials suitable for use in SMRs. Full article

Combining energy storage with base-load power sources offers an effective way to cover the fluctuation of renewable energy. This study proposes a nuclear–solar hybrid energy system (NSHES), which integrates a small modular thorium molten salt reactor (smTMSR), concentrating solar power (CSP), and thermal energy storage (TES). Two operation modes are designed and analyzed: constant nuclear power (mode 1) and adjusted nuclear power (mode 2). The nondominated sorting genetic algorithm II (NSGA-II) is applied to minimize both the deficiency of power supply probability (DPSP) and the levelized cost of energy (LCOE). The decision variables used are the solar multiple (SM) of CSP and the theoretical storage duration (TSD) of TES. The criteria importance through inter-criteria correlation (CRITIC) method and the technique for order preference by similarity to ideal solution (TOPSIS) are utilized to derive the optimal compromise solution. The electricity curtailment probability (ECP) is calculated, and the results show that mode 2 has a lower ECP compared with mode 1. Furthermore, the configuration with an installed capacity of nuclear and CSP (100:100) has the lowest LCOE and ECP when the DPSP is satisfied with certain conditions. Optimizing the NSHES offers an effective approach to mitigating the mismatch between energy supply and demand. Full article

Nuclear power plants have the lowest life-cycle greenhouse gas emissions intensity and produce more electricity with less land use compared to any other low-carbon-emission-based energy source. There is growing global interest in Generation IV reactors and, at the same time, there is great interest in using small modular reactors. However, the development of new reactors introduces new engineering and chemical challenges critical to advancing nuclear energy safety, efficiency, and sustainability. For Generation III+ reactors, water chemistry control is essential to mitigate corrosion processes and manage radiolysis in the reactor’s primary circuit. Generation IV reactors, such as molten salt reactors (MSRs), face the challenge of handling and processing chemically aggressive coolants. Small modular reactor (SMR) technologies will have to address several drawbacks before the technology can reach technology readiness level 9 (TRL9). Issues related to the management of irradiated graphite from high-temperature reactors (HTR) must be addressed. Additionally, spent fuel processing, along with the disposal and storage of radioactive waste, should be integral to the development of new reactors. This paper presents the key chemical and engineering aspects related to the development of next-generation nuclear reactors and SMRs along with the challenges associated with them. Full article

Marine sources contribute approximately 2% of global energy-related CO₂ emissions, with the shipping industry accounting for 87% of this total, making it the fifth-largest emitter globally. Environmental regulations by the International Maritime Organization (IMO), such as the MARPOL (International Convention for the Prevention of Pollution from Ships) treaty, have driven the exploration of alternative green energy solutions, including nuclear-powered ships. These ships offer advantages like long operational periods without refueling and increased cargo space, with around 200 reactors already in use on naval vessels worldwide. Among advanced reactor concepts, the molten salt reactor (MSR) is particularly suited for marine applications due to its inherent safety features, compact design, high energy density, and potential to mitigate nuclear waste and proliferation concerns. However, MSR systems face significant challenges, including tritium production, corrosion issues, and complex behavior of volatile fission products. Understanding the impact of marine-induced motion on the thermal–hydraulic behavior of MSRs is crucial, as it can lead to transient design basis accident scenarios. Furthermore, the adoption of MSR technology in the shipping industry requires overcoming regulatory hurdles and achieving global consensus on safety and environmental standards. This review assesses the current progress, challenges, and technological readiness of MSRs for marine applications, highlighting future research directions. The overall technology readiness level (TRL) of MSRs is currently at 3. Achieving TRL 6 is essential for progress, with individual components needing TRLs of 4–8 for a demonstration reactor. Community Readiness Levels (CRLs) must also be addressed, focusing on public acceptance, safety, sustainability, and alignment with decarbonization goals. Full article

Nuclear reactors are very complex units in which many physical processes occur simultaneously. Efficient heat removal from the reactor core is the most important of these processes. Heat is removed from the reactor core via heat conduction, radiation, and convection. Thus, convective heat transfer and its conditions play a crucial role in the operation and safety of nuclear reactors. Convective heat transfer in nuclear reactors is a very complex process, which is dependent on many conditions and is usually described by different correlations which combine together the most important criteria numbers, such as the Nusselt, Reynolds, and Prandtl numbers. The applicability of different correlations is limited by the conditions of heat transfer in nuclear reactors. The selection of the proper correlation is very important from the reactor design accuracy and safety points of view. The objective of this novel review is to conduct a comprehensive analysis of the models and correlations which may be applied for convective heat transfer description and modeling in various types of nuclear reactors. The authors review the most important research papers related to convective heat transfer correlations which were obtained by experimental or numerical research and applied calculations and heat transfer modeling in nuclear reactors. Special focus is placed on pressurized water reactors (PWRs), boiling water reactors (BWRs), CANDU reactors, small modular reactors (SMRs), and molten salt reactors (MSRs). For each type of studied reactor, the correlations are grouped and presented in tables with their application ranges and limitations. The review results give insights into the main research directions related to convective heat transfer in nuclear reactors and set a compendium of the correlations that can be applied by engineers and scientists focused on heat transfer in nuclear reactors. Prospective research directions are also identified and suggested to address the ongoing challenges in the heat transfer modeling of present and next-generation nuclear reactors. Full article

The lifespan of core graphite under neutron irradiation in a commercial molten salt reactor (MSR) has an important influence on its economy. Flattening the fast neutron flux (≥0.05 MeV) distribution in the core is the main method to extend the graphite irradiation lifespan. In this paper, the effects of the key parameters of MSRs on fast neutron flux distribution, including volume fraction (VF) of fuel salt, pitch of hexagonal fuel assembly, core zoning, and layout of control rod assemblies, were studied. The fast neutron flux distribution in a regular hexagon fuel assembly was first analyzed by varying VF and pitch. It was demonstrated that changing VF is more effective in reducing the fast neutron flux in both global and local graphite blocks. Flattening the fast neutron flux distribution of a commercial MSR core was then carried out by zoning the core into two regions under different VFs. Considering both the fast neutron flux distribution and burnup depth, an optimized core was obtained. The fast neutron flux distribution of the optimized core was further flattened by the rational arrangement of control rod channels. The calculation results show that the final optimized core could reduce the maximum fast neutron flux of the graphite blocks by about 30% and result in a more negative temperature reactivity coefficient, while slightly decreasing the burnup and maintaining a fully acceptable core temperature distribution. Full article

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. Full article

The SM-MSR (small modular molten salt reactor) has a good prospect for development with regards to combining the superiority of the molten salt reactor and modularization technologies, showing the advantages of safety, reliability, low economic cost and flexibility of site selection. However, because its internal structural parts are not easily replaced, and the outer shielding structure is limited, the lifespan of the reactor vessel and its in-reactor shielding design needs to be addressed. In order to find an optimal shielding model with both high fuel efficiency and strong radiation shielding capability, five different design schemes were proposed in this work, which varied in thickness and boron concentration in inner-shielding materials. The neutron/gamma flux and DPA (displacements per atom)/helium production rates were evaluated to obtain an appropriate scheme. Several beneficial results were obtained. Considering the above factors and the actual manufacturing process, 20 cm-thick boron graphite with a 5 wt% Boron-10 concentration combined with a 1 cm-thick Hastelloy barrel was chosen as the in-reactor shielding structure. Outside the reactor, the neutron flux was reduced to 8.33 × 10¹⁰ cm⁻² s⁻¹, and the gamma flux was decreased to 1.13 × 10¹¹ cm⁻² s⁻¹. The vessel/barrel material could maintain a lifespan of more than 10 years, while the burnup depth was 6.25% lower than that of a model without inner-shielding. The conclusions of this research can provide important references for the shielding design and parameter selections of small molten salt reactors in the future. Full article

In the first months of 2022, there was a sharp turn in the energy policy of the European Union, initially spurred by increasing energy prices and further escalated by Russia’s invasion of the Ukraine. Further transformation of the energy system will likely be accompanied by the gradual abandonment of natural gas from Russia and an increase of renewable and nuclear energy. Such a transition will not only increase energy security, but also accelerate the pace at which greenhouse gas emissions are reduced in Europe. This could be achieved more effectively if some of the new nuclear energy capacity is optimized to play an increased balancing role in the energy system, thus allowing for deeper market penetration of intermittent renewable energy sources with a reduced need for flexible fossil backup power and storage. A double effect of decarbonization can be achieved by investments in nuclear repowering of coal-fired units, with the replacement of coal boiler islands with nuclear reactor systems. Repowered plants, in turn, operate flexibly via integration with thermal energy storage systems using molten salt. This paper presents the results of a technoeconomic analysis for three cases of nuclear repowering of a 460 MW supercritical coal-fired unit in Poland. The first reference case assumes that three reactors are replacing the existing coal boilers, while the second reference leverages two reactors. The third uses two nuclear reactors equipped with a molten salt thermal energy storage system as a buffer for the heat produced by the reactor system. The analysis of the third case demonstrates how the TES system’s capacity varies from 200 to 1200 MWh, highlighting the possibility of obtaining a high degree of flexibility of the nuclear unit due to TES system without significant drops in the efficiency of electricity production. The economic analysis demonstrates that integration with TES systems may be beneficial if the current levels of daily variation in electricity prices are maintained. For current market conditions, the most attractive investment is a case with two reactors and a TES system capacity of 800 MWh; however, with the increasing price volatility, this grows to a larger capacity of 1000 or 1200 MWh. Full article

In recent years, there has been a growing interest in the design, development and commercialization of nuclear power Small Modular Reactors (SMRs). Actual SMR designs cover the full spectrum of nuclear reactor technologies, including water-, gas-, liquid-metal-, and molten-salt-cooled. Despite physical and technological differences, SMRs share some relevant design features, such as small size, modularity, inherent and passive safety systems. These features are expected to enhance availability, recoverability, promptness and robustness, thereby contributing to the resilience of power supply. Thanks to the peculiar design features of SMRs, they are likely to satisfy a number of Functional Requirements (FRs) for this objective, namely: (i) low vulnerability to external hazards; (ii) natural circulation of primary coolant; (iii) prompt, unlimited and independent core cooling under shutdown conditions; (iv) shutdown avoidance in response to variations of the offsite power supply quality and electrical load; (v) island mode operation; (vi) robust load-following; (vii) independent, self-cranking start. These make advanced Nuclear Power Plants (aNPPs) comprised of SMRs perfect candidates to withstand a broader range of natural disruptions and to recover faster from them, compared to conventional Nuclear Power Plants (cNPPs), thus rendering them a major potential asset for guaranteeing resilience and security of power supply. The review focuses on Natural Technological (NaTech) events that impact a typical Integrated Energy System (IESs) within which SMRs are embedded: IESs are, indeed, being developed to integrate different power generation plants with gas facilities, through gas and electricity infrastructures, because they are expected to bring increased security and resilience of power supply, as shown in the qualitative case study presented. Full article

The small modular dual fluid reactor is a novel variant of the Generation IV molten salt reactor and liquid metal fast reactor. In the primary circuit, molten salt or liquid eutectic metal (U-Pu-Cr) is employed as fuel, and liquid lead works as the coolant in the secondary circuit. To design the control system of such an advanced reactor, the uncertainties of the employed computer model and the physicochemical properties of the materials must be considered. In this paper, a one-dimensional model of a core is established based on the equivalent parameters achieved via the coupled three-dimensional model, taking into account delayed neutron precursor drifting, and a power control system is developed. The performance of the designed controllers is assessed, taking into account the model and property uncertainties. The achieved results show that the designed control system is able to maintain the stability of the system and regulate the power as expected. Among the considered uncertain parameters, the reactivity coefficients of fuel temperature have the largest influence on the performance of the control system. The most optimized configuration of the control system is delivered based on the characteristics of uncertainty propagation by using the particle swarm optimization method. Full article

The Small Modular Dual Fluid Reactor (SMDFR) is a novel molten salt reactor based on the dual fluid reactor concept, which employs molten salt as fuel and liquid lead/lead-bismuth eutectic (LBE) as coolant. A unique design of this reactor is the distribution zone, which locates under the core and joins the core region with the inlet pipes of molten salt and coolant. Since the distribution zone has a major influence on the heat removal capacity in the core region, the thermal hydraulics characteristics of the distribution zone have to be investigated. This paper focuses on the thermal hydraulics analysis of the distribution zone, which is conducted by the numerical simulation using COMSOL Multiphysics with the CFD (Computational Fluid Dynamics) module and the Heat Transfer module. The energy loss and heat exchange in the distribution zone are also quantitatively analyzed. The velocity and temperature distributions of both molten salt and coolant at the outlet of the distribution zone, as inlet of the core region, are produced. It can be observed that the outlet velocity profiles are proportional in magnitude to the inlet velocity ones with a similar shape. In addition, the results show that the heat transfer in the center region is enhanced due to the velocity distribution, which could compensate the power peak and flatten the temperature distribution for a higher power density. Full article

The most important target of the concept “sustainability” is to achieve fairness between generations. Its expanding interpolation leads to achieve fairness within a generation. Thus, it is necessary to discuss the role of nuclear power from the viewpoint of this definition. The history of nuclear power has been the control of the nuclear fission reaction. Once this is obtained, then the economy of the system is required. On the other hand, it is also necessary to consider the internalization of the external diseconomy to avoid damage to human society caused by the economic activity itself, due to its limited capacity. An extreme example is waste. Thus, reducing radioactive waste resulting from nuclear power is essential. Nuclear non-proliferation must be guaranteed. Moreover, the FUKUSHIMA accident revealed that it is still not enough that human beings control nuclear reaction. Further, the most essential issue for sustaining use of one technology is human resources in manufacturing, operation, policy-making and education. Nuclear power will be able to satisfy the requirements of sustainability only when these subjects are addressed. The author will review recent activities of a thorium molten-salt reactor (MSR) as a cornerstone for a sustainable society and describe its objectives and forecasts. Full article