Load following with Small Modular Reactors (SMR): A real options analysis

Small modular reactors (SMRs) are factory-built transportable nuclear power plants (NPPs) that can generate up to 300 MWe and support new applications for nuclear energy such as hydrogen production, industrial heat generation, and water desalination. SMRs are poised for near-term deployment in the United States and offer improvements over existing NPPs such as passive safety features, greater plant site flexibility, reduced construction costs, load-following operations, and extended refueling cycles. However, in order to realize the benefits of SMRs, there are several challenges related to instrumentation and control (I&C) system components that must be addressed. The I&C systems of an SMR ensure its safe and efficient operation. I&C sensors measure process parameters such as temperature, pressure, level, flow, and neutron flux and provide input to the Reactor Protection System (RPS) to initiate a rapid shutdown if necessary. The performance of these safety-related I&C sensors and systems must be periodically verified to ensure they meet the plant technical specifications for accuracy and response time. In addition, the associated I&C cabling (which includes low-voltage cable assemblies for sensors, Control Rod Drive Mechanisms (CRDMs), and Rod Position Indication (RPI) Systems) is tested as part of normal plant maintenance activities or in support of aging management programs. Over time, exposure to harsh environmental conditions in the plant can result in degradation and failure of I&C sensors and cables. This is especially true for the I&C sensors and cables in SMRs which will be subjected to elevated temperatures, high radiation, and a vacuum atmosphere within the containment vessel during normal plant operation. These conditions lead to excessive Ohmic heating within the cables which further accelerates damage to the cable insulation material and results in premature failure. Frequent cable replacement due to premature degradation is not practical or economical for SMR plant owners. To combat these environmental stressors, the ampacity of the cable must be derated. However, there is limited experience to date with cable derating in vacuum, and no experience with cable derating in vacuum at high temperature and radiation. As a result, Analysis and Measurement Services Corporation (AMS) is conducting a study on several common NPP I&C cables to determine how various insulation materials perform at conditions that emulate those anticipated in the containment of an SMR. The on-going effort is funded under a research and development (R&D) grant awarded to AMS by the U.S. Department of Energy (DOE). In addition, AMS is partnering with the Oak Ridge National Laboratory (ORNL) to conduct specialized testing in support of this study under a separate initiative called the Gateway for Accelerated Innovation in Nuclear (GAIN). The goal of this R&D is to develop technical guidance and technologies to support initial startup and subsequent operation of SMRs through specialized testing services and condition monitoring technologies. Preliminary results of this R&D are provided in this paper. AMS will continue to investigate challenges associated with I&C systems for SMR applications in support of the timely deployment of the first U.S.-based SMR by the mid-2020s.

The paper describes the characteristics of small modular reactors (SMR), their differences from existing nuclear power plants and the features of their use in modern hybrid electric power systems in combination with renewable energy sources and Nuclear Renewable Hybrid Energy System (NRHES) electricity storage, their advantages and problems of use in the future power system of Ukraine. Prospects for cooperation in this area with companies from the United States of America were considered. Small modular SMR reactors are suitable for electrical systems of various capacities, their modular system allows flexibility and speed of construction, reduces capital investment needs and eases financing requirements. The smaller size and variety of reactors can also mean that they can be built in locations not traditionally suitable for large nuclear power plants and, importantly, near energy-intensive industries or remote communities, i.e. as elements of distributed generation. They can ensure a reliable supply of not only electricity, but also heat. SMRs can also be deployed at decommissioned coal-fired power plants. Taking advantage of existing infrastructure, including switchgear and coal-fired turbines, could reduce SMR construction costs and avoid the need to add new transmission lines from these facilities. Problems with the implementation of such networks are revealed. Attention was drawn to the increased complexity of the system in connection with the use of various sources of generation and processes of distribution and consumption of electricity. The main technical characteristics, features of the reactor design, the station building, safety systems and control systems are given. The study concludes that SMRs have significant advantages for use in modern networks, due to their modular design and modular deployment, to meet a variety of power switching and scaling requirements.

Emerging small modular nuclear power reactors: A critical review

7 - Human–system interfaces (HSIs) in small modular reactors (SMRs)

Nuclear power plants play a significant role in global electricity generation, offering a reliable and low-carbon energy source. Maximizing the efficiency of nuclear power plants is crucial for optimizing energy output and reducing operational costs while ensuring safety and environmental sustainability. This paper presents a comprehensive review of the efficiency analysis conducted on nuclear power plants, covering various aspects such as thermal efficiency, conversion efficiency, fuel utilization, and overall plant performance. The review synthesizes the existing literature, discusses key factors influencing efficiency, and highlights potential areas for future research and improvements. It is revealed from the present review that the efficiency of the Boiling Water Reactor (BWR) of the Nuclear Power Plant is 32% and which can be increased to 33% by using advanced BWR. Also, the efficiency of the Pressurized Water Reactor (PWR) of the Nuclear Power Plant is 33% and which can be increased to 36.5% by using the PWR with Gas Burner and Reheating. On the other hand, the efficiency of the Small Modular Reactor (SMR) of the Nuclear Power Plant is 33.4% and which can be increased to 35.5%, 37.4% and 45% by using SMR with Gas Burner, SMR with Reheating and SMR with CCGT, respectively. Therefore, it is predicted that the Small Modular Reactor (SMR) is the most economic Nuclear Power Plant as it has higher thermal efficiency when it is incorporated with Combined Cycle Gas Turbine (CCGT).

The small modular reactor (SMR) class core design concept of once-through SuperCritical light Water-cooled Reactor (SCWR) with fast neutron spectrum (Super FR) is being developed at Waseda University. The preceding studies revealed that SMR class Super FR core can be designed, whose performance is compatible to large Super FR core with respect to average power density and average coolant outlet temperature with small core pressure drop, which is favorable from the viewpoint of achieving natural circulation cooling after reactor shutdown. However, consequences of severe accident of such SMR class Super FR has never been considered. Two major issues need to be addressed. The first issue is the fundamental issue for a water-cooled reactor, which is the possibility of the whole core meltdown as the coolant boils off at low temperature under depressurized condition. Second issue is the fundamental issue for a fast spectrum core, which is to avoid re-criticality of molten core as the reactivity increases with core compaction. With the above described background, this study proposes In-Vessel Retention (IVR) of SMR class Super FR, which can avoid re-criticality even if the whole core relocates to the lower plenum of the Reactor Pressure Vessel (RPV). The debris coolability may be a subject for the future study. The core characteristics with a given set of design specifications and criteria are evaluated based on fully coupled neutronics and thermal-hydraulics core burnup calculations. The neutronics calculations are based on interpolation of macroscopic cross sections with neutron diffusion approximation (SRAC and COREBN codes with JENDL-4.0 nuclear data library). The thermal-hydraulics calculations are based on in-house code that adopts single channel model with Watts’ correlation for evaluating supercritical water heat transfer. The batch fuel shuffling pattern is considered to evaluate the equilibrium core characteristics. The debris criticality is evaluated based on Monte-Carlo based method (MVP) to consider the RPV lower plenum and debris configurations. The fuel debris are assumed to be homogeneous. Firstly, for a given discharge burnup, quantitative relationship between the core criticality and the debris criticality is evaluated. The results show that downsizing the core increases the debris criticality when relocated to the RPV lower plenum, because the Pu enrichment needs to be raised to attain the same discharge burnup with larger neutron leakage. The results also show that some measures are necessary to prevent re-criticality of the debris if the whole core is assumed to relocate to the lower plenum. Then, the new “debris dispersion IVR” concept is proposed. In this concept, heat resistant structure (tentatively ZrO2), which contains some neutron absorbing material (tentatively, B4C) is placed at the center of the lower plenum to disperse the debris and gain neutron leakage and absorption. Then, the trade-off relationships between the core discharge burnup and the size of the debris dispersion structure are evaluated with considerations of core design specifications such as average Pu enrichment, operation cycle length, and fuel shuffling patterns.

Institute for Safety Problems of Nuclear Power Plants (NPP) of the National Academy of Sciences of Ukraine at a meeting of the National Commission for Radiation Protection of Ukraine on June 1, 2020. It is described the crisis in the nuclear industry due to approval of the new energy balance for 2020 by the Ministry of Energy and Environmental Protection of Ukraine. According to this balance, the volume of electricity production by NPP decreased and at the same time the share of thermal power plants and “green energy”, which produce much more expensive electricity, increased in the energy market. The situation is analyzed and recommendations are given for the implementation of measures to improve it. It is shown that the main task of the Ukrainian energy sector will be to continue the course of market relations and to abandon excessive market regulation. Market relations will lead to the fact that generating companies with cheaper energy will be able to sell it not at the cost level price, but at tariffs that have formed in the market. The price of nuclear energy will be brought up to the level of the price of energy produced by thermal power plants. Consumption costs will increase, but government generation will receive more funds, and the state will decide where to direct them: to subsidies for the population or to the development of nuclear or renewable energy. It is proposed to make the necessary changes to the legislation on “green energy”; establish a reasonable tariff for energy produced at NPPs; to introduce technical and organizational measures to ensure the operation of NPP power units in shunting modes. It is concluded that the optimal solution for the future from the standpoint of the both environmental and economic policy of Ukraine is the gradual replacement of NPP power units, which have “exhausted” project resource, with modern new ones with a higher level of safety. This will support the share of NPPs in the energy balance of Ukraine at 40−50%, as well as contribute to the fulfillment of its commitments to increase the use of low-carbon technologies in energy. As for solving energy problems of Ukraine on the basis of promising technologies — small modular reactors (SMR), this strategy does not yet have a proper feasibility study and is not confirmed by the necessary proven practice, as in the world such reactors are still being developed. Observations on the construction of the Central Spent Fuel Storage Facility (CSFSF) for long-term storage of spent fuel from the power units of Rivne, Khmelnytskyi and South-Ukraine NPPs were made. The construction of the CSFSF is under threat because already at the final stage of construction it was decided to liquidate the division of NNEGC “Energoatom”, which was engaged in the construction. Such an incomprehensible decision will not lead to anything positive, but will only delay the commissioning period of the storage facility by 1−2 years. It is shown that the construction of a New Safe Confinement (NSC) over the Shelter object of the Chornobyl NPP is just an intermediate stage in the transformation of the Shelter object into an ecologically safe system. In the near future, it is necessary to perform dismantling of building structures of the Shelter object, the term of operation of which ends in 2023. This is prompted by cases of destruction and collapse of building structures of this object, which occurred last year, and therefore this issue requires immediate solution. The critical state of nuclear science in Ukraine is reflected and it is warned that if the financial support does not change properly, in the coming years the country will be left without a unique scientific institution that conducts research on the safety of nuclear facilities, including the most dangerous in the world Shelter object. Emphasis is placed on the complete absence of a safety culture at the highest level of the country’s leadership, the lack of which is manifested in violations of national norms and international standards, the absence of some leaders in nuclear industry and dangerous enterprises, as well as the attitude of government agencies to the nuclear industry.

One of the most promising concepts for replacing the conventional power plants in the clean energy transition is the conversion of Coal-Fired Power Plants (CPP) to Nuclear Power Plants (NPP) or Hybrid Power Plants (HPP). This approach has the advantage that it not only replaces CPPs with clean energy sources but also could take their role in the energy system compared to the option of replacing with Renewable Power Plants. The conversion of CPPs into NPPs (C2N) could be done in different ways: repowering, retrofitting, revamping or replacement. The focus of this work is to explore and evaluate different variants for combining pressurized water small modular reactor (SMR) with a subcritical steam turbine of CPP, resulting in C2N or different options of CPP conversion into HPPs. The difficulties arise from the fact that the turbine is designed with high live steam parameters and the SMR produces slightly superheated steam with low temperature and pressure. Also, the temperature and pressure of the feed water for the steam generator in SMR and in a CPP are very different which in the best case scenario leads to additional losses. Despite the obstacles, successful combinations are achieved, but which of them would be the most economically feasible depends on the specific conditions of the CPP and the regulations in the country, in which it is located.

Small modular reactors: An assessment of workforce requirements and operating costs

Small Modular Reactors (SMRs) are gaining significant attention as nuclear power sources due to their advantages, such as compact design, enhanced safety features compared to large nuclear plants, and scalability for varying power output needs. To successfully consider this emerging technology, understanding SMR designs and their readiness levels is essential for informed decision making and effective planning. This technical review provides insights into the potential, development, and application of SMR technology. Various SMR designs were investigated to identify those in deployment, commercial operation, or nearing deployment stages. Key technical parameters of advanced-stage SMRs, with some local insights, were analyzed to establish a comprehensive set of criteria for future technical and economic assessments in the context of local applications. Additionally, this study outlines potential phases for SMR project implementation in the Philippines, referencing the IAEA Milestone Approach for nuclear power infrastructure development. Relevant policies, issues, and activities are also discussed, highlighting the status of the country’s nuclear power infrastructure, as well as its legislative and regulatory framework for supporting nuclear energy. While certain SMR technologies show technical readiness, it is important to consider that many are still under development, requiring a careful evaluation of factors such as the 19 Infrastructure Issues to ensure a successful SMR deployment in the Philippines.

Small Modular Reactors (SMRs) are becoming one of the key trends in the development of nuclear technology, offering a flexible, safe and cost-effective alternative to large nuclear power plants. This review defines the “driving force” of SMRs as their ability to enhance safety, modular scalability, and fuel sustainability through innovative design and policy integration. It aims to provide a systematic assessment of technological trends, deployment strategies, and fuel innovations that underpin the future of nuclear energy. This article provides a comprehensive overview of the main classes of SMRs, categorised by fuel type and application, ranging from Low-Enriched Uranium (LEU) and High-Assay Low-Enriched Uranium (HALEU) reactors to thorium-232, metallic fuel and reprocessed nuclear materials. The key technical advantages of SMRs are discussed—passive safety systems, extended fuel cycles (longer operational periods before refuelling compared to conventional reactors), modular production and compactness—which make such reactors particularly suitable for use in hard-to-reach regions, military facilities, in space and as part of hybrid power systems. Special attention is paid to the prospects of advanced fuel cycles, including the conversion of thorium to uranium-233 and the reuse of actinides, which contributes to waste reduction and supports the realisation of a closed nuclear cycle. The current status of SMR projects around the world is also analysed, highlighting the most promising solutions and discussing regulatory, infrastructure readiness and geopolitical factors.

In exploring the prospects for the nuclear generation of electricity supplies in Australia, the order of discussion is as follows: in Part I the writer outlines and identifies the principal economic and technical characteristics of electricity supply systems in general and nuclear power plant in particular; Part II is an empirical study of the individual Australian public electricity supply systems, to determine those characteristics relevant to the problem; while Part III applies the findings of the previous Parts, embodies essential calculations and predictions, discusses the process of decision-making and reaches a firm general conclusion. The writer then proceeds to a summing-up and concludes with a glossary of terms and bibliography. The principal findings are: (l) An electricity supply system is an arrangement of transmission and distribution lines linking power generating sources and load centres, forming a grid which normally covers a wide area, operating under central management and control: (2) The cost of supplying a unit of electricity (kWh) to any point is a function of site, fuel, labour and capacity costs; the size and thermal efficiency of generating sets and power stations; the size of the system as a whole having regard to aggregate generating capacity, capacity of transmission and distribution lines, geography and reserve capacity; the pattern of demand together with resultant plant and system load factors; and social benefits and social costs: (3) The short-run marginal fuel cost of individual generating sets is horizontal over normal loads: (4) As systems tend to include plant of a variety of ages and efficiencies, and plant is brought on load in accordance with an order-of-merit, the short-run marginal costs within system capacity increase with increasing output: (5) Technological developments have ensured a declining long-run marginal cost curve: (6) Systems are centrally operated in such a way as to minimise the fuel costs of meeting the consumption of electricity whatever the time pattern of demand happens to be: (7) Pricing policies influence both growth in demand and the incidence of demand, particularly between peak and off-peak periods: (8) The pattern of demand as expressed in the system load factor is an important factor influencing the prospects of employing high capacity cost/low energy cost generating plant, such as nuclear power plant: (9) New plant is added to a system to meet actual or prospective demand which will maximise the present worth of net benefits: (10) As the social benefits or costs of any officially approved new plant are likely to be roughly similar, the maximisation of the present worth of net benefits is obtained through the minimisation of the total system costs in the selection of new plant: (11) For two or more alternative plants which will render equal service both in terms of aggregate output in a prescribed time period and in the pattern or timing of that supply, the system savings (or costs) will be identical and the problem becomes one of comparing the present worths of direct costs (direct in the sense that they are immediately associated with or internal to a plant and here imply both capacity and energy costs): (12) The ability of a system to employ nuclear power plant to economic advantage is a function of system size in terms of aggregate generating capacity and system load factor, as well as a function of plant capacity and energy costs per se: (13) There are no unique social benefits or social costs likely to arise in a limited use of nuclear power generation, either in terms of benefits to Australian industry generally or costs associated with the hazards of nuclear radiation: (14) A penalty must be imposed on the calculated costs of nuclear power generation to take account of the uncertainty arising from the world's lack of experience of the technical life span of nuclear plant generally and its likely flexibility (or inflexibility) in a mid-load role with marked swings in output: (15) It cannot be assumed ex ante that nuclear power plant will enjoy higher lifetime plant load factors than comparable conventional plant: (16) The prospects for nuclear power are gloomy; only New South Wales and Victoria have systems large enough to accept nuclear generating sets of minimum commercial size; the other State systems will not be large enough until the 1990s; the Jervis Bay proposal is revealed as inordinately costly; nuclear power plant is unlikely to become competitive with alternative coal-fired plant before the mid- 1980s and then only in power station sizes of 1,000 MW and above; Australia should avoid a commitment to nuclear power generation for at least 10 to 15 years, there being no case for a subsidised programme; towards the end of that period more advanced types of nuclear reactor may have become available.

11 - Licensing of small modular reactors (SMRs)

Load-following capability is one of the distinguishing features between Small Modular Reactors (SMRs) and traditional large-scale reactors in existing nuclear power plants. An SMR needs to possess load-following capability to integrate with non-dispatchable energy resources, e.g., renewable ones, to form an off-grid hybrid energy system. This paper provides a comprehensive review of different aspects of load-following operations of nuclear reactors by systemically examining early studies and some practical operating experience on existing nuclear reactors in various applications. These applications include electricity generation, marine vessel and spacecraft propulsion, and heat generation for industry applications. Considering different advanced reactor design concepts proposed for SMRs, the paper has concentrated on six representative reactor types and highlighted their unique features and feasibilities for load-following operations. Since an SMR can be considered as a combination of the reactor and the balance-of-the-plant, its power output can be regulated at the reactor power output or from the balance-of-the-plant. Different techniques to implement load-following operations have been described regarding different reactor designs and compositions of the balance-of-the-plant. Several special issues deserve special attention when performing load-following operations. These issues are rarely encountered in existing nuclear power plants for base-load operation, for example, imbalance in core power distribution, flow-induced vibration, excessive production, higher risk of fission products leaking, and flow-accelerated corrosion. The paper has provided necessary coverage of these less obvious consequences associated with load-following operations.

Current large scale, generation 3 nuclear power plants (in the western world) are mostly expensive, delayed and over budget [1] [2]. Modularisation in industrial plants has shown cost savings of between 7–20% and schedule savings between 20–50% [3]. Small Modular Reactors (SMR) defined as “shop fabricated and then transported as modules to the sites for installation” [4] might enable further cost reductions and there are over 50+ SMR designs currently in development internationally. This paper establishes the module envelope constraints for road transportable factory built SMR Modules and analyses equipment data from a Pressurised Water Reactor (PWR) reactor for these module envelope constraints. The paper found that two tanks and a pump might need to be redesigned for road transport or they may be utilised as one off logistical operations, depending on costs. The 900MWe PWR reactor equipment items were then scaled to reflect a 450MWe plant [5], [6]. If the equipment items are scaled, all equipment would fit into the 5m module space envelope at least in one direction. It may be advantageous to redesign the two tanks. Finally, a simple Mixed Integer Linear Programming (MILP) modularisation optimisation was utilised to layout equipment into a (6 × 50 × 4.5m) module. The objective function was reduced from 14661 for the original Lapp (1989) plant to 2958 for the single module.