Jérôme Fagelson is an energy expert and consultant, having served in a number of energy trading roles in different European markets.

The narrative surrounding a new generation of nuclear power in the West often emphasizes high costs, protracted timelines, and complex regulatory hurdles. However, this perspective overlooks a pragmatic and cost-effective alternative: enhancing the capacity of existing nuclear reactors through upgrades. As utilities and investors grow increasingly cautious about committing to capital-intensive new-build projects, uprating offers a compelling pathway to expand nuclear capacity with significantly lower financial and temporal burdens. By leveraging existing infrastructure, uprates enable rapid increases in clean energy output—aligning with urgent decarbonization and electrification goals.

A view of the nuclear power plant in Jaslovské Bohunice, Slovakia | Source: Guliver Image

The Current State of Nuclear Stagnation

The current state of nuclear energy in Western nations presents a paradox: a growing recognition of nuclear’s crucial role in decarbonizing energy systems juxtaposed with the stark realities of aging infrastructure and the significant hurdles hindering the deployment of new power plants. A substantial portion of the existing nuclear fleet in the West, constructed during the latter half of the twentieth century, is nearing the end of its theoretical and planned operational lifespan, requiring either substantial investments in lifespan extensions or eventual decommissioning. While life extensions offer a near-term solution, they are not without their own economic implications. The prospect of constructing new nuclear power plants, frequently highlighted as essential for achieving ambitious climate goals, encounters a formidable array of interconnected challenges. A primary obstacle is the inherent complexity of nuclear projects. These large-scale, technologically intricate endeavors require highly specialized engineering, procurement, and construction expertise.

Decades of limited nuclear construction activity in many Western nations have resulted in a significant erosion of this specialized knowledge and a weakening of the associated supply chain. This deficit of recent experience consequently elevates the risk of delays, cost overruns, and compromised quality control. The cost factor is particularly significant, driven by several converging forces. The substantial upfront capital investment necessary for nuclear power plants is inherently sensitive to interest rates; elevated borrowing costs significantly inflate overall project financing. Furthermore, protracted construction timelines—frequently extending well beyond initial projections—contribute to cost escalations stemming from inflation, regulatory changes, and unforeseen technical difficulties. The Flamanville 3 EPR project in France, beset by years of delays and a quadrupling of its initial budget, serves as a stark cautionary example illustrating the considerable financial risks inherent in complex nuclear construction.

The difficulties in realizing new nuclear projects in the West are starkly highlighted by several prominent examples. The Olkiluoto 3 (OL3) project in Finland, an EPR design akin to Flamanville 3, has been afflicted by extensive delays and substantial cost overruns, requiring nearly two decades from groundbreaking to commercial operation—a clear indication of the complexity and decline in construction expertise. Similarly, the Hinkley Point C project in the UK has encountered significant obstacles, with projected costs escalating and timelines extending considerably. The financial risks associated with this project were so considerable that the then-CFO of EDF (Électricité de France), Thomas Piquemal, reportedly resigned due to apprehensions regarding its potential to jeopardize the company's financial stability.

Across the Atlantic, the expansion of the Vogtle Electric Generating Plant in the United States, involving the addition of two new AP1000 reactors, has also endured years of delays and multi-billion-dollar cost increases. These examples illustrate a recurring pattern: advanced reactor designs, while offering the promise of enhanced safety and efficiency, have grappled with first-of-a-kind engineering challenges, intricate supply chains, and stringent regulatory oversight—collectively contributing to schedule slippage and budget overruns.

Beyond the technical and economic challenges, social and regulatory factors exert significant influence. Public perception of nuclear energy remains polarized, frequently influenced by historical accidents and concerns regarding radioactive waste disposal, leading to strong local opposition (“NIMBYism”) that can impede or even derail projects. The regulatory environment in many Western nations, while understandably prioritizing safety and environmental protection, can be exceptionally stringent and bureaucratic, thereby imposing additional layers of complexity, cost, and time on licensing and construction processes. This stands in contrast to some nations outside the West, where regulatory frameworks may be more streamlined, facilitating more rapid project deployment. In response to these challenges, many Western operators are increasingly focusing on significant power uprates of their current well-performing reactors as a more pragmatic and economically viable strategy for increasing nuclear electricity generation into the future. Uprates capitalize on existing infrastructure, benefit from established regulatory frameworks, and generally involve lower capital costs and shorter implementation timelines compared to greenfield projects.

Uprating, the process of increasing a reactor’s power output, is frequently pursued discreetly by reactor operators and often in tandem with investments in plant lifetime extensions. This approach not only maximizes the value of existing assets but also capitalizes on proven technologies and established regulatory frameworks. In a global energy landscape where the dual imperatives of reducing carbon emissions and meeting rising electricity demand are increasingly challenging, uprates represent low-hanging fruit with substantial untapped potential. Industry stakeholders, from utilities to policymakers, recognize uprates as a strategic tool to bridge the gap between current capabilities and future energy needs, delivering reliable, low-carbon power without the complexities of greenfield projects.

 

Technical Overview of Reactor Uprates

A reactor’s electric power output is a function of the core’s thermal output and its conversion efficiency. Uprates target either or both of these variables—thermal output and conversion efficiency—through a combination of advanced measurement techniques, fuel management strategies, and hardware upgrades. These methods are not only technically robust but also synergistic, amplifying the overall impact of uprate initiatives. In general, there are three primary approaches to achieving power uprates:

The first is Measurement Uncertainty Recapture (MUR). Typically limited to a 2 percent increase in power output, MUR uprates rely on advanced instrumentation and calculation methods to reduce uncertainties in reactor power measurements. By employing precise assessments of feedwater flow—a critical parameter in determining reactor power—operators can more accurately gauge the reactor’s operational limits. This enhanced precision ensures that safety margins are maintained for hypothetical accident scenarios, allowing regulators to approve modest power increases without compromising plant safety.

The second is Increased Fuel Burn-Up and Enrichment. A more substantial uprate can be achieved by increasing the fuel burn-up rate, often through higher enrichment levels in the reactor fuel. This approach boosts the thermal output of the core but requires comprehensive safety analyses and licensing amendments to verify that reactor systems, including cooling and containment structures, can handle the elevated power levels. While this method offers significant capacity gains, it demands rigorous regulatory oversight to ensure compliance with safety standards.

The third is Hardware Modifications for Enhanced Conversion Efficiency. Efficiency improvements here often involve upgrading key components in the steam cycle, such as modern steam generators equipped with axial economizers, which enhance steam production in the secondary circuit for a given thermal input. This increases the amount of energy transferred from the reactor core to the turbine. High-efficiency turbines also allow more electricity to be generated from the same steam flow, thereby boosting electrical output.

These hardware upgrades are synergistic: improved thermal efficiency not only increases electricity production but also creates additional cooling capacity, enabling safe operation at higher core power levels. A notable example is the FREJ uprate project at Sweden’s Ringhals 4 reactor, led by Areva and Vattenfall from 2007 to 2011. By replacing steam generators and turbines with cutting-edge technologies, the project achieved a remarkable 20 percent increase in reactor power output, demonstrating the transformative potential of integrated uprate strategies.

Optimizing plant power consumption should also be mentioned as an alternative approach. Beyond increasing gross power output, uprates can enhance net electricity delivery by reducing the plant’s internal power consumption. Upgrading components such as cooling pumps and auxiliary systems to more energy-efficient designs allows a greater share of generated electricity to be sold to the grid, thus effectively increasing the plant’s commercial output without altering its thermal capacity.

 

Strategic and Economic Implications

The appeal of uprates lies not only in their technical feasibility but also in their economic and strategic advantages. Compared to new-build projects—which often face costs exceeding $10 billion and construction timelines spanning a decade or more—uprates typically require investments in the range of hundreds of millions and can be completed within a few years. This makes them an attractive option for utilities seeking to maximize returns on existing assets while contributing to national and global climate goals. Moreover, uprates leverage the operational history and regulatory familiarity of existing plants, reducing the risk of delays and cost overruns.

In the broader context of energy policy, uprates offer a pragmatic solution to the challenges of scaling nuclear capacity in a carbon-constrained world.

 

Historical Evolution of Nuclear Reactor Uprates

The history of nuclear reactor uprates reflects the nuclear industry’s ongoing efforts to optimize performance, adapt to technological advancements, and respond to evolving energy demands. From the 1970s to the early 2000s, uprates primarily focused on achieving the “true” design capacity of newly commissioned reactors. Many first-of-a-kind (FOAK) projects required extensive post-commissioning testing to validate design assumptions—a process now streamlined by advanced simulations. During this period, reactors typically saw power output increases of up to 6 percent as they transitioned from initial operation to their stabilized reference unit power, ensuring alignment with original design specifications.

In the 1990s, the focus shifted toward improving operational reliability, particularly in the United States, where the nuclear fleet’s average capacity factor surged from 60 percent in 1990 to 90 percent by 2000. This trend was mirrored across most OECD countries, with the notable exception of France, which grappled with overcapacity following its rapid nuclear expansion in the 1970s and 1980s. The post-Chernobyl era—marked by a decline in new-build projects after the 1986 disaster—prompted Western reactor operators to seek alternative strategies to maximize the value of their existing fleets. Uprates emerged as a practical and cost-effective solution, leveraging operational experience and technological innovation to enhance output without the need for new construction.

By the late 1990s and early 2000s, as the nuclear industry achieved maturity in operational performance, uprates began to extend beyond original design specifications. This shift was driven by a convergence of technological advancements and the need to replace aging or obsolete equipment such as steam generators, turbines, and instrumentation and control systems. Three ever-evolving transformative innovations have been pivotal in enabling utilities to push 20- to 40-year-old reactors to new performance frontiers.

The first innovation in this context is advanced steam generator materials. The transition from corrosion-prone Alloy 600 tubing to more durable Alloy 690 significantly improved the reliability and longevity of steam generators, enabling higher operational efficiency and supporting uprate initiatives.

The second is enhanced fuel design. Improvements in fuel technology allowed for higher Uranium-235 enrichment levels, increasing from 2.5–3.5 percent to as much as 5 percent. These advancements enabled greater thermal output from reactor cores while maintaining safety margins, though they required rigorous licensing amendments.

The third innovation is sophisticated numerical modeling, representing advances in computational capabilities that revolutionized reactor analysis. These tools allow more precise simulations of core performance, thermal-hydraulic behavior, and safety margins. Refined calculations provided the confidence needed to pursue ambitious uprate projects.

These technological breakthroughs coincided with a critical juncture for many nuclear plants, as aging infrastructure necessitated equipment upgrades. By integrating state-of-the-art components and leveraging improved analytical tools, utilities unlocked significant capacity increases. According to the U.S. Nuclear Regulatory Commission, power uprates implemented between 2000 and 2021 added approximately 6 gigawatts-electric (GWe) to the U.S. nuclear fleet—equivalent to the output of nearly four Westinghouse AP1000 reactors, the current standard for large-scale nuclear power in the United States.

Globally, uprate programs have yielded impressive results. In Finland, the historical nuclear fleet (excluding the Olkiluoto 3 EPR) achieved an average power output increase of over 20 percent from 1997 to the present day—a feat mirrored by Sweden’s nuclear plants. Even the Soviet-designed VVER-440 reactors in Czechia, Slovakia, and Hungary saw their average output rise by approximately 15 percent during the same period, demonstrating the versatility of uprate strategies across diverse reactor designs. These examples underscore the global applicability of uprates, which have enabled aging nuclear fleets to remain competitive in modern energy markets while contributing to decarbonization goals.

 

Ongoing U.S. Efforts in Nuclear Reactor Uprates

While Canadian and European reactor operators—excluding France’s EDF—have embraced uprates as a cost-effective strategy to offset reactor closures and reduce reliance on coal, U.S. utilities have historically approached major investments with caution. This hesitancy stems from uncertainties surrounding the long-term viability of nuclear plants in a highly competitive energy market. It became particularly pronounced after the American shale gas revolution of the late 2000s, which depressed electricity prices and challenged the economic case for nuclear power. However, recent policy developments and shifting market dynamics have reinvigorated interest in uprates as a means to enhance the capacity and longevity of the U.S. nuclear fleet.

State-level initiatives, such as Production Tax Credits (PTCs) and Investment Tax Credits (ITCs), have provided a financial lifeline for nuclear operators by establishing a price floor for nuclear-generated electricity and offering long-term revenue certainty. At the federal level, the 2022 Inflation Reduction Act (IRA) further bolstered these incentives, encouraging utilities to invest in existing plants. Even if the IRA were to be repealed, surging electricity demand—driven by data centers, industrial electrification, and the broader push for decarbonization—has created a compelling case for uprate projects. As a result, many U.S. reactor owners are pursuing license extensions to operate their plants for up to 80 years, while simultaneously exploring uprates and operational optimizations to maximize output and efficiency.

A 2024 report from the U.S. Department of Energy (DOE) underscores the significant potential for uprates, estimating that up to 8 GWe could be added to the U.S. nuclear fleet in the coming years. Of this, licensees have already submitted applications for 2.5 GWe to come online by 2032, primarily through MUR uprates and turbine modernization projects. MUR uprates, which leverage advanced instrumentation to reduce uncertainties in power measurements, typically yield modest gains of up to 2 percent. Meanwhile, turbine upgrades enhance conversion efficiency, allowing more electricity to be generated from existing steam flows. These approaches are particularly attractive due to their relatively low cost and minimal regulatory hurdles compared to more extensive uprates requiring core modifications or major hardware replacements.

 

A Tricky Choice in France

France’s nuclear power fleet, one of the largest in the world, presents a unique case in the context of power uprates due to its operational and strategic characteristics. Despite its reliance on nuclear energy for over 70 percent of electricity production, the French fleet is less optimized compared to other OECD nations, with production costs ranging between €40 and €50 per MWh—nearly double the €20 to €30 per MWh seen in the United States or Finland. Historically, France has pursued minimal uprates, with efforts limited to achieving the reference capacity of its N4 reactors during commissioning. The fleet’s overcapacity since the mid-1990s has led to low-capacity factors, consistently below 75 percent, driven by short production cycles (280 to 395 days) and lengthy outages (90 to 110 days). Additionally, the use of lower enrichment fuel (below 4.2 percent U-235) and MOX fuel—which poses challenges for extending cycles or increasing power output—further constrains uprate potential.

Nevertheless, opportunities for optimization exist, with some studies indicating a fleetwide uprate potential of 4.7 GWe through turbine upgrades and the recapture of operational margins. Such an uprate program could offer a cost-effective alternative to France’s ambitious new-build program of six EPR2 reactors (10 GWe), which faces challenges due to limited demand and a weak business case. Ironically, France is a global leader in uprate-related technologies, supplying steam generators with axial economizers, advanced fuel designs, instrumentation and controls, digital twins, and Arabelle turbines to nuclear fleets worldwide. However, domestic adoption of these technologies remains limited, as the focus on maintaining construction capabilities for new reactors competes with the potential for a more economical uprate strategy to enhance the existing fleet’s efficiency and output.

 

Untapped Potential in the West and Associated Costs

The unrealized capacity of nuclear power uprates in the United States and Europe offers a compelling opportunity to meet growing demand for decarbonized baseload power amid emissions reduction goals and coal phaseouts. Boiling Water Reactors (BWRs) have seen significant progress in uprates, largely due to GE-Hitachi’s development of Licensing Topical Reports (LTRs), which are approved by the U.S. Nuclear Regulatory Commission. These LTRs provide a standardized, cost-effective roadmap for utilities, addressing technical issues generically to enhance regulatory predictability and reduce project costs and schedules. In contrast, Pressurized Water Reactors (PWRs), particularly the prevalent Westinghouse three-loop (WH-3L) designs, have lagged due to the absence of a similar standardized approach, with vendors focusing on individualized, technology-specific processes. For instance, while most WH-3L reactors operate at 900 to 950 MWe, best-in-class examples like Ringhals 4 achieve 1,150 MWe—highlighting significant untapped potential. Further studies on Westinghouse four-loop (WH-4L) reactors in the U.S. could unlock additional capacity.

Combining uprates with Long-Term Operations (LTO) investments to enable reactors to operate for 80 years or beyond presents a strong strategic opportunity. Key investments, such as replacing steam generators with advanced designs featuring axial economizers and overhauling turbines, could yield 100 to 250 additional MWe per plant at costs ranging from $500 million to $1 billion. This translates to $2,000 to $10,000 per kW—far below the $20,000 per kW for new nuclear capacity. Beyond cost savings, uprate programs would sustain critical technical expertise in industries such as on-site welding and turbine manufacturing. Excluding France, an estimated 10 to 20 GWe of additional capacity could be added in the U.S. and Europe, though this potential remains absent from public roadmaps. However, challenges such as geopolitical factors and tariffs could complicate implementation, necessitating coordinated policy and industry efforts to fully realize this cost-effective pathway to enhanced nuclear output.

 

Looking Beyond: Innovations

Innovations in nuclear technology are poised to unlock significant potential for power uprates, offering cost-effective solutions that enhance the output of current reactors while addressing technical challenges. A key tradeoff in uprates involves balancing longer production cycles (extending from 18 to 24 months) with higher enrichment fuel, which can complicate reactor operations. However, advancements in fuel technology are mitigating these challenges. For instance, Southern Company’s recent loading of 5.5 percent U-235 fuel into one of its Westinghouse reactors marks a notable increase in enrichment levels, enabling greater power output. Additionally, Enhanced Accident Tolerant Fuel (EATF), developed by Framatome, Westinghouse, and GE-Hitachi, provides improved safety margins and operational flexibility, further supporting uprate potential. These advancements—requiring only relatively modest investments in studies (around a few million dollars) and slightly higher fuel costs (currently just over $5/MWh in the U.S.)—are easily offset by the additional electricity generated, making them a cost-efficient pathway for uprates.

Beyond fuel innovations, the development of advanced digital twins offers another avenue for optimization. These digital models enable precise monitoring and analysis, facilitating Margin Uncertainty Recapture that can boost output by 1 to 2 percent. When combined, these technological leaps—higher enrichment fuel, EATF, and digital twins—could enable second-generation reactors from the 1970s and 1980s to operate at over 30 percent above their original design capacity. Synergies among these innovations further amplify their impact, potentially transforming aging nuclear fleets into highly efficient, high-capacity assets, maximizing the value of existing infrastructure.

Ultimately, for stakeholders from utilities to policymakers, uprates represent a safe bet: a proven, cost-effective, and scalable solution to maximize the value of existing nuclear assets. By prioritizing uprates alongside long-term operations, the West can unlock a reliable source of decarbonized baseload power, reinforcing nuclear energy’s pivotal role in realizing a sustainable energy future without the uncertainties of greenfield projects. In a decarbonizing world, uprates are not just an optimization strategy—they are a cornerstone for energy security and climate progress.

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