Competitiveness Strategies and Technical Innovations in Light-Water Small Modular Reactor Projects

Abstract

It is widely recognized that economies of scale enhance the competitiveness of large-scale nuclear reactors compared to light-water small modular reactors (SMRs). As such, choosing an appropriate strategy to enhance competitiveness is crucial for the future of SMRs. Their development is still in the early stages, and among the leading projects, two distinct approaches to technical innovation can be observed. In some projects, technical innovations are rejected because they are perceived as triggers for risky, costly, and long-term processes. In short, this means that the competitive advantage is based primarily on modular design and the benefits of long production runs, which might require at least a few successful implementations. Examples of this approach include the Westinghouse AP300 and Rolls-Royce SMR designs. In other projects, technical innovations are viewed as a means to achieve substantial cost reductions. Here, the initial challenge is to prove that the proposed solutions are safe. Next, it must be demonstrated that their implementation and operation meet the designers’ expectations. These goals can be achieved with the first implementation. Such an approach is exemplified, for instance, in the NuScale and GEH BWRX-300 projects. Currently, available economic analyses show that it is challenging not only to identify the most promising SMR projects but also to determine which approach to technical innovation will ultimately be more effective. Therefore, it is worth examining how leading SMR projects have improved their competitiveness. Additionally, it is important to remember that, even if light-water SMRs are not deployed, it is likely that some of their innovative solutions will be incorporated into other advanced nuclear power plant designs and potentially applied beyond the nuclear industry.

1. Introduction

The nuclear energy sector in Euro-Atlantic countries has been stagnant for more than a quarter of a century. Any hopes to overcome this stagnation are, among other factors, linked to SMRs. There are many indications that the first light-water SMR could be operational in the Euro-Atlantic region in the early or mid-2030s. This conclusion is based on information provided by SMR designers, nuclear power plant operators, government agencies, including regulators, and scientific publications. Maturity assessments of leading projects, including cost analyses, are particularly valuable, as seen, for example, in Stewart’s recent publications [1,2,3]. Without a doubt, all the publications cited by Stewart are also worthy of attention. It is evident that cost analyses are fraught with significant uncertainties, as demonstrated in [4] and the subsequent discussion. The examination of potential applications of SMRs is the main focus of review articles like [5,6]. Currently, the available analyses and reviews show that the maturity of all leading SMR projects developed in Euro-Atlantic countries is low, and it is challenging to identify the most promising ones. This article focuses on the strategies adopted by leading light-water SMR projects in Euro-Atlantic countries to increase the competitiveness of their designs.

Table 1. Selected light-water SMR designs.

	EDF NUWARD	GEH BWRX-300	Holtec SMR-300	NuScale	Rolls-Royce SMR	Westinghouse
Reactor type	PWR	BWR	PWR	PWR	PWR	PWR
Gross electrical output (MW)	170	300	320	77	470	300
Number of reactors per block	2	1	2	4–12	1	1
References	[7]	[8]	[9]	[10]	[11]	[12]

Source: EDF NUWARD—Électricité de France S.A., Paris, France; NUWARD—consortium led by EDF, GEH BWRX-300—GE Hitachi Nuclear Energy, Marlborough, MA, USA; BWRX-300—reactor name, Holtec SMR-300—Holtec International, Marlton, NJ, USA, SMR-300—reactor name, NuScale—NuScale Power, LLC., Corvallis, OR, USA; NuScale—reactor name, Rolls-Royce SMR—Rolls-Royce SMR Limited, Derby, UK. Westinghouse AP300—Westinghouse Electric Company, LLC., Cranberry Township, PA, USA, AP300—reactor name.

presents a list of selected projects, including basic details about each one. Five are pressurized water reactors (PWRs), while one is a boiling water reactor (BWR).

The selected projects are based on proven, large-scale light-water reactors. In particular, the fuel design, reactor core, control systems, and emergency shutdown mechanisms have been adapted from these large-scale reactors. Additionally, the steam parameters generated by the reactors to drive the turbines are similar to those used in larger nuclear power plants. As a result, the core aspects of light-water reactor technology are not part of the innovation. Rather, the main innovation lies in reducing the scale and adopting a modular design, which aims to simplify financing and project organization, as well as to open up nuclear energy to new markets. However, implementing an effective cost-saving strategy is crucial for any SMR project due to the absence of economies of scale. The most basic model of economies of scale, which aligns with advanced models [13], suggests that the power output of a nuclear power plant is proportional to the volume of the reactor vessel. Meanwhile, the cost is linked to the quantity of material used, which corresponds to the surface area of the reactor vessel. This means that the cost of a nuclear power plant is proportional to its power raised to the two-thirds power. In particular, this simple model shows that an eight-fold increase in power only results in a four-fold increase in cost.

Historically, it is also known that no investor has undertaken the construction of the AP600, whereas six AP1000 reactors have been built in China and the United States (AP300, AP600, and AP1000 are reactor designs developed by Westinghouse Electric Company, Cranberry Township, PA, USA). Since 2022, China has initiated the construction of eight additional similar reactors under the name CAP1000, a design based on the AP1000 and developed by China National Nuclear Corporation (CNNC), Beijing, China. It is important to note that the three Westinghouse designs—AP300, AP600, and AP1000—use the same technology, with differences primarily in scale. As the AP300 design progresses, it will demonstrate how modular concepts allow SMRs to penetrate markets that large-scale reactors cannot access or face significant challenges in reaching. In the UK, Rolls-Royce’s 460 MW SMR design draws on decades of nuclear experience, with reactors of similar capacity having been constructed and integrated into the energy market. Some of these reactors are still in operation. This boosts the prospects for Rolls-Royce, a renowned company with extensive experience in nuclear power, to bring its SMR design to market. It is also worth noting that the nuclear expertise of the French company EDF and the U.S.-Japanese company GE Hitachi ensures that their designs, NUWARD and BWRX-300, respectively, are built on solid foundations from the outset. On the other hand, it is well documented that over the last twenty-five years, only a few large-scale reactors have been built in Euro-Atlantic countries, and all investments have experienced significant delays and cost overruns. This situation creates opportunities for SMRs while simultaneously challenging them to compensate for the loss of economies of scale and avoid investment delays and cost overruns.

This brief outline of the current state of nuclear energy in Euro-Atlantic countries clearly shows that achieving competitiveness with SMRs is possible, but it requires innovation in all SMR projects. However, it should be emphasized that the potential market for SMRs is broader than the power sector and includes energy-intensive industries whose energy demands align with the capabilities of SMRs. Specifically, the market includes the chemical, petrochemical, fertilizer, mining, desalination, and metallurgical industries, both in terms of electricity supply and process heat. In the future, it may expand to zero-emission hydrogen production. There are also opportunities to use SMRs in district heating. Entry into these potential markets will depend on the profitability of SMRs. Currently, it can only be ensured that the best SMR projects have the potential to offer a level of safety that is unattainable for large-scale reactors. As a result, their locations can be planned near industrial facilities, as well as in the vicinity of urban areas. It is also worth noting that the dynamically growing data center investments, necessary for the development of artificial intelligence, will consume huge amounts of energy. It is possible that, in a decade or so, they will constitute a noticeable part of the energy-intensive industry in the world’s most developed economies. As a result, SMRs have the potential to establish a strong market presence, even if their competitiveness is slightly lower than large-scale reactors.

2. Approaches to Enhancing Competitiveness

The key innovation in all SMR designs is their modular construction. This approach divides the project into independent modules and then mass-producing standard modules in the factories. The Westinghouse AP300 and Rolls-Royce SMR projects contain no groundbreaking technical innovations. The only way to ensure that these projects remain competitive is by constructing a large fleet of standardized power plants with a modular design. However, the modularization of designs is also being implemented in large-scale nuclear power plants, as exemplified by the AP1000 project [14]. It can be expected that Westinghouse will leverage the experience gained from the AP1000 in developing the AP300.

The Rolls-Royce SMR design is based on the concept of deep modularity. This approach permeates every aspect of the design, as demonstrated by the designers [11] and a recent publication by Wrigley [15]. However, in this context, the modularity is based on the project’s theoretical assumptions and examples from other sectors, including chemical industry construction. Therefore, the project’s business validation will only be possible once the first investments are well advanced.

The situation is somewhat different in SMR projects based on technical innovations. In such cases, the modularity of the design is an integral part of the entire new design. However, technical innovations offer the potential for a competitive advantage but also carry the risk of delays and substantial cost increases, particularly when constructing first-of-a-kind units. On the other hand, abandoning technical innovations can provide an advantage by shortening the permitting process, leveraging the existing market of key component manufacturers, and utilizing the pool of experienced contractors. In this context, it becomes evident that making any decision regarding technical innovation is very challenging. The history of the circulation pumps in the AP1000 reactor illustrates this challenge well. By integrating the circulating pump motors into the primary cooling system (using canned motor pump technology), the design was significantly simplified by reducing the thermohydraulic systems. While these pumps worked well in submarine reactors, adapting them for the large-scale AP1000 reactor proved difficult [16], and a pump failure caused an almost year-long shutdown of one of the Chinese AP1000 reactors [17]. The difficulties in implementing innovative pumps caused notable delays in the construction of AP1000 reactors. However, the designers of the AP1000 met the challenge successfully, and it is now clear that the canned motor pump technology enhances the competitiveness of the AP1000.

Such determination is not common, and within the realm of light-water SMR projects, a notable withdrawal from technical innovation occurred in June 2024, when EDF pulled out of the NUWARD project [18]. At the same time, it was announced that the revised NUWARD would solely rely on proven solutions. For example, the innovative plate steam generators will be excluded [19]. Since the new NUWARD concept has not yet been unveiled, further analysis of the project is not possible.

A similar innovation crisis occurred with the SMR-160 project, which was renamed SMR-300 in December 2023 [20]. Holtec abandoned the direct connection of the reactor vessel to the steam generator because it could not provide satisfactory answers to the U.S. regulator’s questions regarding the fulfillment of nuclear safety requirements by this innovative solution. The aim of directly connecting these two vessels was to eliminate the risk of a large break loss of coolant resulting from a rupture of the pipes connecting the reactor vessel with the steam generator. At the same time, this solution involved eliminating the circulation pumps. Abandoning this innovation meant returning to the classic system with traditional circulation pumps in the design and doubling the power from 160 to 320 MW while keeping the reactor dimensions almost unchanged.

Undoubtedly, even with extensive experience in modular design and the use of well-established technical solutions, demonstrating the benefits of implementing such a strategy to enhance the competitiveness of SMR designs will require the successful execution of several projects. There is a risk that the time and cost saved by foregoing technical innovations may be lost during the execution of pioneering projects.

Among the leading selected light-water SMR projects, significant technical innovations are primarily found in the NuScale and BWRX-300 projects. The power output of a single NuScale module is the smallest among the considered SMR projects, leading to the greatest loss of economies of scale but offering the highest potential for gains from series production. Concurrently, the NuScale project incorporates the most extensive technical innovations, primarily focusing on system integration, as illustrated in Figure 1. It must be pointed out that a detailed description of the full functionality of the NuScale modules, including safety and control systems, is not possible on the basis of Figure 1 and requires an analysis of the documentation provided by NuScale.

Circulating pumps have been eliminated, and the steam generator is installed within the reactor vessel, which is housed in a compact, vacuum-sealed, cylindrical steel containment vessel. This integrated module is placed in a pool, remaining submerged in water, ensuring that the containment vessel is effectively cooled under any emergency conditions. Such a design has the potential to significantly lower costs due to the small size of the containment vessel. In conventional PWR reactors, the containment building must be much larger than the reactor vessel since it is surrounded by air, making cooling during emergencies far less efficient and more complicated. The implementation of this innovation, which is essential for NuScale, in large-scale reactors is at least questionable due to the scale effect. While the scale effect positively impacts the economy, it also makes it increasingly difficult to safely dissipate heat through the reactor vessel’s external surface during emergency situations as reactor power increases. Furthermore, there is no doubt that as reactor power increases, placing the reactor vessel inside the confined steel containment will become increasingly challenging. In the NuScale design, four to twelve integrated modules, each with an output of 77 MW, are to be placed in isolated sections of a common water pool, providing a total gross capacity of 308 to 924 MW. There is also a common spent fuel storage area and shared use of other facilities, including a common control room where a small group of operators will control all the modules. The U.S. regulator’s certification process for the initial 50 MW module design spanned six years. Understanding the scope and significance of these innovations is crucial for evaluating whether the certification process could have been carried out more efficiently. The U.S. regulator issued the certification in January 2023 but noted that it does not cover three specific issues, including the helical coil steam generator, due to insufficient information provided by NuScale. Efforts to approve the missing elements are ongoing as part of the certification process for the 77 MW modules, which is expected to be completed by mid-2025 [21].

The helical coil steam generator (see Figure 1) offers higher efficiency than typical steam generators used in nuclear power plants with PWR. Its small size offers the potential to reduce costs; however, in the NuScale project, it plays a key role due to the integrated design, in which the steam generator is installed inside the compact pressurized reactor vessel. It is also well known that the helical coil steam generator is subject to undesirable vibrations and the phenomenon of density wave oscillation. Maintaining a stable flow through the helical coil steam generator in the NuScale design is a key issue. Therefore, NuScale has recently conducted extensive theoretical research [22] and, in collaboration with the SITE laboratory in Italy, has intensified the experimental studies that have been ongoing there for a decade [23]. The significant interest in the stability of helical coil steam generators is also related to the possibility of their use in other SMR projects, such as the i-SMR project in South Korea [24], and several SMRs designed based on non-light-water technologies. It is possible that large-scale nuclear power plants will also implement helical coil steam generators in the future. This is why numerous studies have been conducted in recent years, as illustrated by various publications [25,26,27]. Publication [28] refers directly to the NuScale helical coil steam generator design. Based on the information provided, it seems that ensuring safe and efficient flow through the helical coil steam generator in the NuScale design remains challenging but feasible. Unfortunately, the comprehensive documentation provided by the U.S. regulator reveals little about the certification progress of the helical coil steam generator, as key information has been withheld [29].

It should be emphasized that the ongoing NuScale certification process does not cover the entire project. This concerns, for example, the refueling procedure, which in the NuScale design differs from the standard procedures used in large-scale reactors. Specifically, it is assumed that during the refueling of a given module, the other modules can continue to operate normally. The U.S. regulator does not question this concept, but approval of this procedure will only be possible at a later stage of the construction and operation permitting process.

The main challenge in the BWRX-300 project is the return to boiling water reactors, whose development has been paused since the Fukushima disaster in 2011. In Japan, only two out of about a dozen BWRs had restarted by the end of 2024 [30]. However, the future restart of other BWRs remains unclear, and plans to build several large-scale ABWRs have been canceled. In the United States, although two construction permits were granted, the construction of ABWRs never began, and both permits expired in 2018 [31]. The BWRX-300 reactor is described as a smaller and simplified version of the large ESBWR, incorporating a passive, gravity-driven cooling system. However, no investor has proceeded with the construction of an ESBWR, despite the fact that two permits were granted in the U.S. in 2015 and 2017, both of which are still valid [31]. The second point of reference for the BWRX-300 is the Dodewaard power plant, which housed a 55 MW passively cooled BWR and operated in the Netherlands from 1971 to 1997. Despite years of operation with an availability rate of 80–90%, the plant was shut down for economic reasons.

In the initial publicly unveiled BWRX-300 design by GE Hitachi, the reactor building and containment structure were closely integrated and positioned underground. GE Hitachi presented this concept in a study submitted to the IAEA in 2019 [32] (this document is currently unavailable on the IAEA website). The underground compact reactor building design aimed to minimize the use of concrete, which was highlighted as one of the key features of the BWRX-300 project, offering significant savings. However, this concept particularly prevented any external inspection of the containment vessel. It is therefore not surprising that in later versions of the BWRX-300, including the current one [33,34], the underground reactor building has a significantly larger diameter than the containment, allowing for inspection. Stewart [35] estimated that the volume of the reactor building increased more than four-fold. Consequently, the amount of concrete required to construct the BWRX-300 has significantly increased, and a significant part of the cost reduction concept from 2019 is no longer relevant.

Alongside the substantial expansion of the reactor building, GE Hitachi proposed replacing conventional reinforced concrete with an innovative composite technology. Figure 2 shows a diagram of the composite of steel plates with diaphragms. First, diaphragms with holes are welded to steel plates. Then, the assembled panels are positioned in the designated location and filled with concrete.

A recently published review article [36] shows that composite steel–concrete structures are now increasingly used in various civil engineering projects, including nuclear power plant construction [14,37,38]. Despite its potential, this technology has not yet been adopted in nuclear safety-related applications. In the BWRX-300 design, it is planned to be used for constructing the underground reactor building and containment vessel. Additionally, steel-plate composite technology with diaphragms is planned to be used, which has never been applied in nuclear power construction. In the summer of 2024, the U.S. regulatory body conducted a detailed evaluation of the concept [39], and it looks like it could take several years of intense effort to obtain the final approval including the implementation procedures. However, if the composite steel-plate technology is commonly accepted by regulators and it turns out that its use reduces costs, we can expect its widespread use in nuclear construction including large-scale nuclear power plants. It is worth noting that the AP1000 design already makes limited use of composite steel-plate technology. It is therefore worth observing work on its implementation not only in the BWRX-300 project but also in China [38], where nuclear power is developing rapidly.

Among the other innovations in the BWRX-300, one notable change is the removal of pipelines connecting the reactor vessel to the isolation valves. This design eliminates the risk of pipe ruptures by directly attaching the isolation valves to the reactor vessel. The safety relief valves are also eliminated because the large capacity of the isolation condenser system, along with the large steam volume in the reactor pressure vessel, provides overpressure protection. These approaches have not been previously used in nuclear power plant construction, meaning that their approval by regulators could be a lengthy process. Furthermore, the limited publicly available information from GE Hitachi hinders a comprehensive evaluation of the risks and potential benefits of this design [33,34]. Similarly, the simplification of the riser chimney, achieved by eliminating its channel structure, requires careful assessment. Since the introduction of the chimney concept in 1959, passively cooled BWR chimneys have been divided into channels to prevent radial flows that could disrupt reactor operations. GE Hitachi offered a detailed explanation of the chimney partition in the ESBWR design [40] but provided little information about why it was possible to omit the chimney partition in the BWRX-300 design. As a result, assessing the feasibility of this innovation remains challenging.

Implementing a strategy to enhance competitiveness through the adoption of technical innovations, such as a helical steam generator and composite steel-plate technology, requires overcoming two key barriers. First, it is essential to demonstrate the safety of these solutions, a process that is both costly and time-consuming. Second, it is crucial to show that the innovations implemented meet the expectations placed upon them, which can be achieved during the first deployment phase.

3. Conclusions

In summary, none of the light-water SMR projects in the Euro-Atlantic region have obtained construction permits yet. The designs of the Rolls-Royce SMR, Holtec SMR-300, and Westinghouse AP300 do not introduce significant technical innovations compared to large-scale PWRs, which suggests that obtaining the necessary approvals for these projects should proceed without major obstacles. On the other hand, the NuScale and BWRX-300 projects introduce significant innovative elements, and their approval processes might face delays. However, these projects offer substantial innovation potential, which could lead to cost reductions. At this stage, it is challenging both to determine the most promising SMR project and to predict which approach to technical innovation will prove most effective.

The drive towards overall modularity is evident in all SMR designs. These concepts can be at least partially applied to other fields, such as the construction of large-scale nuclear power plants. Rolls-Royce’s SMR design, in addition to its theoretical assumptions, utilizes insights gained from other sectors, including investments in the chemical industry. The AP300 design, on the other hand, relies on Westinghouse’s experience in modularizing the AP1000 reactor.

GE Hitachi’s work on the innovative implementation of steel-plate composite technology in the BWRX-300 design has the potential to be applied to other nuclear power plant projects. High expectations regarding the use of this technology in nuclear power emerged about a quarter of a century ago, but it is still in the certification process. Only after the technology has been approved by regulators will it be possible to assess its business viability, which will most likely be clarified during the construction of the BWRX-300 reactor in Canada.

The integrated design of the reactor pressure vessel, the helical coil steam generator, and the compact containment immersed in the pool may ensure business success for the NuScale project. This project has been certified by the U.S. regulator for 50 MW modules, and certification for 77 MW modules is expected by mid-2025. However, the most significant obstacle for the NuScale project will be the construction of the first-of-a-kind power plant and the assessment of the business suitability of innovative solutions. The most advanced NuScale power plant project is currently being developed in Romania. Demonstrating the stable operation of the helical coil steam generator could have important implications for the development of many other advanced reactor designs in the nuclear industry and beyond.

All the SMRs discussed in this research study carry significant potential, both commercially and technologically; however, their implementation faces a large number of challenges related to regulation and innovation. The success of the developed technologies will mainly depend on their manufacturers’ ability to properly manage the risk, speed up certification processes, and adapt to the rapidly changing world energy market.