Development Of Small Modular Reactors Research Articles

Numerical investigations of transient thermal loading of steam turbines for SMR plants

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.

Review on High-Energy Beam Based Processing Technologies for Fabrication of Small Modular Reactor

The development of small modular reactors (SMRs) has attracted significant attention owing to the increasing interest in energy security and carbon neutrality worldwide. An SMR is an advanced nuclear reactor with a power capacity of up to 300 MWe per unit. To fabricate the SMR, innovative manufacturing technologies such as powder metallurgy hot isostatic pressing (PM-HIP), electron beam welding (EBW), and diode laser cladding (DLC) were introduced to reduce the fabrication cost and time. Particularly, this replaced arc-based welding and cladding with high-energy beam-based EBW and DLC. The EBW could provide one pass welding for extremely thick specimens. In addition, in the case of using the DLC, only one layer cladding was acceptable for corrosion protection owing to its low dilution rate. However, studies on the innovative manufacturing technologies were less reported because of technology security. In this study, recently reported research articles regarding the EBW and DLC were reviewed. In particular, local vacuum and reduced pressure electron beam studies were discussed by comparing their the arc welding results. Process parameter studies on the DLC were also reviewed to introduce appropriate optimized conditions for the industry application.

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.

Review on the Recent Progress in Nuclear Plant Dynamical Modeling and Control

Nuclear plant modeling and control is an important subject in nuclear power engineering, giving the dynamic model from process mechanics and/or operational data as well as guaranteeing satisfactory transient and steady-state operational performance by well-designed plant control laws. With the fast development of small modular reactors (SMRs) and in the context of massive integration of intermittent renewables, it is required to operate the nuclear plants more reliably, efficiently, flexibly and smartly, motivating the recent exciting progress in nuclear plant modeling and control. In this paper, the main progress during the last several years in dynamical modeling and control of nuclear plants is reviewed. The requirement of nuclear plant operation to the subject of modeling and control is first given. By categorizing the results to the aspects of mechanism-based, data-based and hybrid modeling methods, the advances in dynamical modeling are then given, where the modeling of SMR plants, learning-based modeling and state-observers are typical hot topics. In addition, from the directions of intelligent control, nonlinear control, online control optimization and multimodular coordinated control, the advanced results in nuclear plant control methods are introduced, where the hot topics include fuzzy logic inference, neural-network control, reinforcement learning, sliding mode, feedback linearization, passivation and decoupling. Based upon the review of recent progress, the future directions in nuclear plant modeling and control are finally given.

Neutronic analysis of silicon carbide Cladding-ATF fuel combinations in small modular reactors

With more attention being paid to the development of small modular reactors (SMR), the intrinsic safety issues have reached a critical point. Accident-tolerant fuel (ATF), such as the U3Si2, UO2-BeO, silicon carbide cladding etc. can maintain or improve fuel performance under normal reactor operating conditions and can maintain core integrity for a long period after the design-basis accident scenarios, providing a sufficient time margin to take measures. Therefore, applying the ATF to the SMR also enables the possibility of operating the SMR more safely. Most neutronic analyses of the ATF, however, have focused on the large-scale commercial pressurized water reactor. In this study, we adopted a given ATF design (the combination of U3Si2 and silicon carbide cladding) and compared it with other combinations of fuel and three different types of silicon carbide claddings in one single-fuel assembly and the full core of the mPower. We evaluated and analyzed the aspect of neutronic physics with Serpent-2 and OpenMOC computational codes. The results for the full core showed that the core life of U3Si2-SiC could be increased by 3.1% which feasibly could be used in the SMR from the neutronic point of view. The U3Si2, however, had a lower effect on neutron absorption than the UO2 when using the burnable poison rod in the full core. The neutronic penalties of different types of silicon carbide cladding were not significant in the SMR. Overall, the silicon carbide cladding-ATF fuel combinations were feasible for use in the mPower SMR.

A comparative study of alternative power cycles for small modular reactors

To combat safety concerns and poor economics, research and commercialization of new nuclear power plants has focused on the development of small modular reactors. NuScale Power has developed a small modular reactor design based on natural convection cooling inside the reactor core. The energy conversion is provided by a regenerative Rankine cycle. This comparative study provides a research review of alternative power cycles designs suited for small modular pressurized water reactors. The candidate cycles are analyzed for overall thermal efficiencies (1st law) and their primary exergy destruction sources. To compare with the baseline regenerative Rankine cycle, key design variables for each cycle are optimized using a penalty method. Results reveal that the two alternative cycles of regenerative reheat Rankine and transcritical ethanol have promise as potential alternative replacements. The regenerative reheat Rankine cycle would be the simplest cycle to integrate into the current small modular design due to being similar to the current regenerative Rankine cycle. Conversely, the transcritical ethanol cycle shows higher thermal efficiency but would requires more research to assess the viability through better understanding of its cycle design, component development and costs, and safety implications.

Current Status of Reactors Deployment and Small Modular Reactors Development in the World

Abstract Due to emerging climate change concerns coupled with increased global energy demand, eventually the world needs to move to low-carbon-emission electricity-generating sources—nonrenewables, such as nuclear power, and renewables, as hydro, wind, geothermal, solar, and tidal. The only source is nuclear power that is reliable, concentrated, and can be of large installed capacity and operate with high capacity factors. This paper updates and presents the current status of nuclear-power deployment and small modular reactors (SMRs) development in the world. Unfortunately, within last 9 years, electricity generation with nuclear power has decreased from ∼14% before the Fukushima Nuclear Power Plant (NPP) severe accident in March of 2011 to about ∼10%. Therefore, it is important to follow up with and understand the latest trends in nuclear power including SMRs development.

Development of AC2 for the simulation of advanced reactor design of Generation 3/3+ and light water cooled SMRs

Abstract The transition from Generation 2 to Generation 3/3+ and 4 reactors, as well as the development of small modular reactors (SMR), place new demands on computational programs designed to simulate conditions of normal operation, operational occurrences, design basis accidents and severe accidents. On the one hand, most passive safety systems of advanced and innovative plants operate at low pressures even down to vacuum conditions and the driving forces are low compared to active systems. On the other hand, the containment is no longer just a barrier to retain radioactive material in the event of leakage of the cooling system, but it is an important link in the passive cooling chain. This requires an expansion and improvement of the existing simulation programs for the cooling circuit and containment, as well as the realization of a coupling between these simulation programs. The new AC2 program package combines the proven simulation codes ATHLET/ATHLET-CD and COCOSYS in one software suite to hit this target. The individual components of the suite are continuously extended and validated for their application to novel safety systems. This makes it possible to simulate the entire spectrum of accidents for Generation 3/3+, 4 and light water cooled SMR systems with just one program package. This publication gives an overview of the current state of development of AC2 and its individual modules.

Necessary improvements of the GRS simulation chain for the simulation of light-water-cooled SMRs

Abstract Small modular reactors (SMRs) are one interesting option for new builds in almost all countries worldwide continuing to use nuclear energy for commercial power generation. For asserting of legitimate nuclear safety and/or security interests German authorities require in this context own and independent expertise for the safety assessments. The Gesellschaft für Anlagen und Reaktorsicherheit (GRS) mbH, which is the main technical support organization in nuclear safety for the German federal government, has among others performed a study on Safety and International development of Small Modular Reactors (GRS-376) to identify essential issues of SMR safety as well as needs for adaption, improvement and validation of nuclear evidence tools developed and applied by GRS. For the light-water-cooled SMRs, which have (at least according to GRS) the best prospects for realization, selected results of this study will be presented.