Generation IV Nuclear Reactor Designs

The Next Nuclear Renaissance?

The CATO Institute, Fall 2025 • Regulation………………………………………………………..Around the time of the previous nuclear renaissance, there was talk of the designs that would succeed Gen III+, so-called Gen IV designs. Gen III+ designs were seen as transitional technologies filling the gap until their long-term successors were developed. The Gen IV International Forum (GIF), an international intergovernmental organization funded by the governments of nearly all the nuclear-using countries, was set up in 2001 to promote development of these designs.

The GIF has stated, “The objectives set for Generation IV designs encompass enhanced fuel efficiency, minimized waste generation, economic competitiveness, and adherence to rigorous safety and proliferation resistance measures.” It identified six designs as the most promising, and these remain its focus. Some are designs that have been pursued since the 1950s and built as prototypes and demonstration plants but never offered as commercial designs. Among these are sodium-cooled fast reactors and high temperature gas-cooled reactors (HTGRs). Some, such as the lead-cooled fast reactor and the molten salt reactor, have been talked about for 50 or more years but never actually built. Others, such as the supercritical-water-cooled reactor and the gas-cooled fast reactor, do not appear to be under serious commercial development. When GIF was created, it expected some of the designs to be commercially available by 2025, but it now does not expect this to happen before 2050.

When the Gen IV initiative began, there was no expectation they would be small or modular. Gen IV designs are now sometimes known as Advanced Modular Reactors (AMRs) in an apparent attempt to profit from the positive press that LWR SMRs are receiving. However, they are very different from LWRs, with different designs and safety requirements, so the claims made for LWR SMRs compared to the large LWR designs are not relevant to AMRs.

There is particular interest in HTGRs because of the hope that they can operate at high temperatures (above 800°C /1,500°F). This would allow a plant to also produce hydrogen more efficiently than conventional electrolysis, providing the plant an additional revenue stream. However, existing HTGRs have only operated at 750°C /1,380°F, much higher than the 375°C /700°F of PWRs but not ideal for producing hydrogen. Increasing the temperature to the levels GIF anticipated originally, 950°C–1,000°C/1,750°F–1,850°F, would require new, expensive materials and would raise significant safety issues. The British government is concentrating its efforts on HTGRs, but it has said, “It is not currently aware of any viable fully commercial proposals for HTGRs that could be deployed in time to make an impact on Net Zero by 2050.” Nevertheless, the UK is still subsidizing development of HTGRs.

Overall, there are high-profile promoters of these Gen IV designs. For example, Microsoft cofounder Bill Gates is investing in sodium-cooled fast reactors through his nuclear innovation firm Terrapower. However, given the 50+ year history of these efforts, it is hard to see why these new companies would succeed now. Few of the more prominent Gen IV designs are being developed by firms with any history of supplying nuclear reactors. At most, Gen IV designs are a long-term hope.

Large Reactors

If we exclude Russia and China (see below), three large reactor designs are currently available, at least in theory: the Westinghouse AP1000, Framatome (formerly known as Areva NP) EPR, and the South Korean KHNPC APR1400. These were all also available at the time of the previous nuclear renaissance, along with the GE–Hitachi ESBWR, but it won no orders and appears to no longer be marketed.

The only work in recent decades on a new design for a large reactor is for a modified version of the EPR, the EPR2. Despite this work starting in 2010, it had not entered detailed design phase as of the start of 2025, and the first reactor using this design is not expected online before about 2038. A new version, Monark, of the Canadian heavy water reactor CANDU has been publicized, but it seems to be at an early stage of development and the only interest in it appears to be from Canada.

The lack of new designs may reflect in part the very high cost of developing a nuclear reactor coupled with the uncertainty whether such research and development will lead to sufficient (if any) sales to recover those costs. For example, in 2023 NuScale stated that work developing its SMR design had cost $1.8 billion. In 2014, Westinghouse estimated it would have to sell 30–50 SMRs to get a return on its R&D investment. The GE–Hitachi ESBWR was carried through to detailed design and successfully completed the US NRC’s design evaluation, but commercial sales failed to materialize, and the vendor appears to no longer offer it. Another factor may be that vendors have exhausted their ideas for improving the economics of large reactors. During the previous renaissance, concepts such as passive safety, modularization, and use of production-line-made components were unable to solve the financial problems associated with large reactor designs (Thomas 2019).

Despite these setbacks, there is growing interest in Europe in large reactors, not just in the well-established markets of France and the UK, but also in countries such as the Czech Republic, Poland, the Netherlands, and Sweden. Below is a more careful look at these units.

Westinghouse AP1000 / The AP1000 (Advanced Passive) 1,100MW PWR won eight orders, four for the United States (two for the Summer plant in South Carolina and two for Vogtle in Georgia) and four for China. The Summer orders were abandoned after four years’ construction, but the others have been completed. The most recent orders were placed in 2010, and all six completed reactors were late and over budget. The Vogtle project took 11 years and cost more than double the forecasted cost. Similarly, the four reactors in China each took about 10 years to complete.

The AP1000 has been chosen by Poland for its first nuclear orders, with construction supposed to begin in 2028 and first power slated for 2036. The design was excluded from the bidding process in the Czech Republic because it “did not meet the necessary conditions.” Westinghouse is competing to win orders in Sweden and the Netherlands, neither of which has made a design choice.

Framatome EPR / The French EPR design is in a sort of limbo at the moment. In 2010, Areva NP acknowledged that the EPR design needed significant modification because of construction problems faced at Olkiluoto 3 (Finland) and Flamanville 3 (France). A modified design has been under development since then, and for the last decade Framatome has claimed it will be ready to order in two or three years. The new EPR2 design has long been expected to be used for follow-on orders from Flamanville 3, leaving only the UK as a customer for the original EPR design, for Hinkley Point C (under construction since 2018) and Sizewell C (ordered this year). In 2021, the French government required EDF to build six EPR2s, one every 18 months, with the first one expected to begin construction in 2026 and be operational in 2035. This timeline cannot be met, and the earliest first power is likely is 2038. Given the record of EPR projects, export customers likely want to see an EPR2 built and in operation before they order one. That would mean the EPR2 design is not an option for new export orders before 2040.

Despite the obvious uncertainties and risks, EDF/Framatome offered a scaled-down version of the EPR2, the EPR1200, to the Czech Republic and Poland. In both cases, Framatome’s bids were unsuccessful. Ordering an EPR1200 ahead of completion of the first EPR2 would have been an extraordinary gamble given that the reactor is an untested, scaled-down version of an untested design.

KHNPC APR 1400 / Korean Hydro and Nuclear Power Company (KHNPC) is a subsidiary of the state-owned monopoly electric utility KEPCO. The design is derived from the American engineering firm Combustion Engineering’s System 80+ design that completed a full safety review by the US NRC in 1997 but has received no orders. Combustion Engineering was absorbed into Westinghouse, and KHNPC purchased a technology license for the design.

In South Korea, six reactors of this design have been completed, the first in 2016, with two under construction as of July 2025. All except one of the completed reactors took more than 10 years to build, and the two under construction are far behind schedule. South Korea’s only reactor export has been four units, all using this design and built in the United Arab Emirates. All four took nine years to build.

KHNPC has acknowledged the design that has been built in South Korea and the UAE lacks features that would be essential for it to be licensed in Europe. Besides, under a recent change to its licensing agreement with Westinghouse, KHNPC is prohibited from marketing the unit in EU countries other than the Czech Republic, and also prohibited in Britain, Ukraine, Japan, and North America. Nevertheless, KHNPC appears confident that a scaled-down version of the APR1400, the APR1000, will be ordered by the Czech Republic. As with the EPR1200, ordering this untested design would be a gamble.

Prospects for large reactors / While the large reactor options look dated and their record is poor, in Europe they appear to have better prospects for orders in the next few years than SMRs. All will depend on a national government risking large amounts of public money to make these projects happen. France and the UK seem determined to follow this path, but other countries, which do not have as much financial strength, may waver when they find the scale of the financial commitment needed……………………………. https://www.cato.org/regulation/fall-2025/next-nuclear-renaissance#