A Forecast for the Future of GEN IV Reactors ~ A 50/50 Chance of Success for Three Types

Note to readers: This blog post is based on an article originally prepared for and published online by NucNet in Brussels, Belgium, in February 2020.  David Dalton, an editor at NucNet, collaborated on it.  Due to the length of this article, you may also download the complete text as a PDF file.


nuclear imageDesigners of advanced nuclear reactors that are moving beyond the conceptual phase and are now deeply invested in hardware design are seeking to bridge the gap between design concept and working prototype.

The problem for developers of Generation IV nuclear power plants in western industrialized countries is that it may still be too early in the development process for investors and potential customers to bet significant money on the winners from an increasingly crowded field.

New patterns of investment could help. Public-private cost sharing partnerships with the US Department of Energy (DOE), for reactor development, of the type formed by NuScale, a light water small modular reactor and TerraPower, which is a sodium-cooled 1,100 MW design, are creating similar opportunities for entrepreneurial developers who can harness the know how and get access to government funds which is also a confidence builder for investors. A working prototype for any of the Gen  IV designs built by any of the developers would attract the interest of potential customers. As yet, no one has gotten that far.

Examples of new patterns of funding include vouchers for technical assistance from the DOE’s Gateway for Accelerated Innovation in Nuclear (GAIN) which operates at the Idaho National Laboratory.  In 2018 Congress passed an ambitious plan for nuclear energy R&D. The 2020 appropriation for the Department of Energy’s nuclear energy program got a boost to historic levels from this legislation.

However, Hal Harvey, CEO of the policy firm Energy Innovation, a San Francisco-based energy and environmental policy firm, told the Morning Consult, in response to the passage of the legislation, that he is skeptical that lawmakers would direct as much funding toward nuclear energy as the new generation of reactors requires.

“The private sector’s not going to invest in nuclear power in a meaningful way,” Harvey said because the operating costs of existing plants are not cost-competitive. With a nod to the failure of the V C Summer project he noted a key barrier is that the financing, construction, and operational risks are very high.

Where the billions of dollars will come from to move new reactor designs from the drawing table to commercial success is a big problem Harvey said.

“I appreciate the gall with which people do private sector startups, but they’re all going to go off a cliff without public support,” he said.

Harvey’s agnostic views on how things might turn out for the current crop of nuclear energy entrepreneurs should be taken seriously. The experience of Transatomic may not be the last in this category.

The challenge for U.S competitiveness related to Gen IV designs in global markets is that while the DOE is spending in the tens to hundreds of millions per cost sharing partnership, countries like China and Russia have made multi-billion dollar bets on GEN IV designs.

Recent Developments in Russia and China

Russia BN-800 fast reactor, which burns advanced uranium fuels, has been in commercial service since 2016. In October 2016 the Beloyarsk-4 BN-800 fast neutron reactor began commercial operation. It is fueled by a mix of uranium and plutonium oxides arranged to produce new fuel material as it burns. However, Russia has pushed back work on the BN-1200 to the mid-2030s citing costs and uncertainties about the design.


BN-800 conceptual design. Image and translation from Russian: Alcheton

In Russia in December 2019 the Siberian Chemical Combine (SCC) signed a $412M contract with engineering company Titan-2 for construction and installation work for the Brest-OD-300 lead-cooled fast-neutron reactor. The unit, to be built at SCC, near the city of Seversk in central Russia. is scheduled for completion at the end of 2026.

The Brest plant is part of Russia’s Breakthrough project for the development of closed fuel cycle technology. The start date for construction had been postponed several times because of the need for additional testing of key reactor structural elements.

China produced a working prototype of an HTGR, but it hasn’t put multiple units of its 250 MWe design into commercial electricity generation service. Mark Hibbs, an expert on China’s commercial nuclear energy program, said that SNPTC dropped plans to manufacture 20 of the HTGRs solely for use in electricity generation when the LCOE rose to levels higher than a 1000 MW PWR, such as the Hualong One.

China’s State Nuclear Power Technology Corp (SNPTC) says the design has an outlet temperature of 750C. The firm says the reactor’s heat output is also suitable for use in steel making and hydrogen production. SNPTC is working on a plan to provide the reactor for export to Saudi Arabia for desalinization, but has not slated it for these other uses in terms of its heat output.



While China has had to take a step back in the commercialization of its 230 MW HTR-PM reactor under construction at Shidaowan, it is also is investing $300M/year over the next decade in molten salt designs including R&D efforts with thorium fuels.

China’s thorium fuel program is called the Thorium-Breeding Molten Salt Reactor (TMSR). According to the media reports, the R&D program has two major components and both are tied to fuel types (solid and liquid) for various kinds of molten salt designs.


TMSR R&D Roadmap  ~ Image: Oak Ridge National Laboratory

According to the World Nuclear Association there are two streams of TMSR development – solid fuel (TRISO in pebbles or prisms/blocks) with once-through fuel cycle, and liquid fuel (dissolved in fluoride coolant) with reprocessing and recycle. A third stream of fast reactors to consume spent fuel actinides from LWRs is planned. The aim is to develop both the thorium fuel cycle and non-electrical applications in a 20-30 year timeframe.

The TMSR-SF stream has only partial utilization of thorium, relying on some breeding as with U-238 to produce U-233.. It is optimized for high-temperature based hybrid nuclear energy applications.

The TMSR-LF stream claims full closed Th-U fuel cycle with breeding of U-233 and much better sustainability with thorium but greater technical difficulty is involved in bringing the design to operational maturity.. It is optimized for utilization of thorium with electrometallurgical pyroprocessing. The Fluorine design is expected to follow the sodium cooled design by about a decade.  (January 2017 Gen IV Briefing – PDF file)

Another objective for China is reported to be the design and development of a first-of-a-kind 100 MW thorium molten salt reactor in 2020 in the city of Wuwei in Gansu province. Commercial development is targeted for the early 2030s.

In a separate development in December 2017 World Nuclear News reported that the CFR-600  was developed by the China Institute of Atomic Energy. The Xiapu reactor will be a demonstration of that sodium-cooled pool-type fast reactor design. This will have an output of 1500 MW thermal power and 600MW electric power. The reactor will use mixed-oxide (MOX) fuel with 100 GWd/t burnup, and will feature two coolant loops producing steam at 480°C. Later fuel will be metal with burnup of 100-120 GWd/t. The reactor will have active and passive shutdown systems and passive decay heat removal as a key safety feature.

A commercial-scale unit – the CFR1000 – will have a capacity of 1000-1200 MW. Subject to a 2020 decision to proceed, construction could start in December 2028, with operation from about 2034. That design will use metal fuel and 120-150 GWd/t burnup.

How Will Market Economies Catch Up?

If the U.S., UK, France, Japan and and other nations with market economies that have championed the Gen IV designs want to catch up to these kinds of accomplishments in Russia and China, their governments will have to radically reconsider the levels of funding they are willing to commit to achieve these results.

Private sector investors can neither support this kind of funding alone nor take on the risks of failure associated with building first of a kind Gen IV reactors. Partnership with national nuclear energy laboratories are crucial and must focus on kicking working prototypes out the door to be further developed with commercial partners.

New Revenue Model Based on Heat as the Product

One revenue model that holds promise for developers of small modular reactors based on Gen IV design s (defined by the International Atomic Energy Agency as units with electrical power ratings of less than 300MW) is to offer heat as the primary output of their plants. Heat can be used to generate electricity, but it can also be used for process heat for industry, especially for manufacturing steel, cement, chemicals, the production of hydrogen, and desalinization. The combination of revenues from these heat streams could expand the business case for advanced reactors.

With a growing realization that nuclear energy is necessary to achieve decarbonization in the electric generation utility industry, and, in major process heat applications, the 2020s decade looks like one where action, based on this concept, could see more significant developments for nuclear energy worldwide.


Conceptual image of Terrestrial Energy Molten Salt Nuclear Reactor Design and Applications: Image: vendor website

The combination of revenues from these heat streams could expand the business case for advanced reactors as a result. Investors would then be able to look beyond the levelized cost of electricity (LCOE) when evaluating the business prospects for a new reactor design.

Shorter Time Frames Needed for First of a Kind Successes

There are significant differences in the time lines and prospects for success between developers of small modular reactors (SMRs) based on conventional light water reactor technologies (sooner), and those efforts that are based on fast neutron reactors that don’t use water as a moderator or coolant (later).

To reduce the timeframe of time to market for advanced reactors, public/private partnerships with government agencies, labs, private firms, and non-profit R&D centers are the key to access to test facilities, advanced computing capabilities, and support for development of advanced materials and new types of nuclear fuels.

Creating a “culture of innovation” globally will be necessary to create the “ecosystems” of capabilities and resources needed for these new nuclear technologies to achieve market acceptance and to have an impact on decarbonizing of electrical generation.

Some reactor design efforts may stop at the stage where intellectual property can be licensed by a developer to a deep pocket reactor vendor or state-owned corporation.

  • The problem for a Chief Nuclear Officer at a major electric utility is that there is no center or cohesion to these innovation efforts.
  • The many different types of technologies, each with their respective technical and economic drivers, remain to be proven through testing and the rite of passage of safety review by regulatory agencies.
  • Eventually, to achieve success, the design effort must cross a gap between media hype and prototype to get on the road to completing a unit that can be sold to customers.

What is the Future of GEN IV Designs?

The Generation IV International Forum (GIF) is a co-operative international endeavor, which was set up to carry out the research and development needed to establish the feasibility and performance capabilities of the next generation nuclear energy systems.

Gen-IV-logo-onlyThe goals adopted by GIF provided the basis to identify and select six nuclear energy systems for further development. These systems are based on a variety of reactor, energy conversion and fuel cycle technologies.

Their designs include thermal and fast neutron spectrum cores, and closed and open fuel cycles. The reactors range from very small to very large.

Depending on their respective degree of technical maturity, the first Generation IV systems are expected to be deployed commercially around 2030-2040.

At the GEN IV forum, 100 experts evaluated 130 reactor concepts before GIF selected six reactor technologies for further research and development. These include the:  Gas-cooled Fast Reactor (GFR), Lead-cooled Fast Reactor (LFR), Molten Salt Reactor (MSR), Supercritical Water-cooled Reactor (SCWR), Sodium-cooled Fast Reactor (SFR) and Very High Temperature Reactor (VHTR).

Generation IV reactors offer the promise of improved safety, efficiency, and lower costs. A 2017 study by Energy Innovation Reform Project put the average levelized cost of electricity (LCOE) at $60/MWh, or 39% lower than the $99/MWh expected by the US Energy Information Agency for pressurized-water reactor (PWR) nuclear plants entering service in the early 2020s.

The LCOE is the long-term price at which the electricity produced by a nuclear plant will have to be sold at for the investor to cover all their costs including a profit.

Of the six GEN IV types, three have gotten the most attention from entrepreneurial developers: – sodium-cooled, high temperature gas cooled, and molten salt designs. A review by three U.S. national labs also rated the three designs as having the greatest likelihood of success in the next decade. Yet the challenges they face are enormous.

No one has ever built a commercial scale unit for any of these designs and put the unit into revenue service for a nuclear utility. The capital and operational costs to build and operate the first of a kind (FOAK) unit are still in a process of discovery.

Potential new coolants for Generation IV plants include liquid metal, high temperature gases, and molten salt. Third Way, a DC think tank, says nuclear reactors using these coolants can be even safer than most light-water reactors. Most are expected to operate at atmospheric pressure.


An indicator light from the control room of the Integral Fast Reactor.  Image: ANL-W.

For instance, sodium cooled reactors like the EBR-II, which operated at Argonne National Lab in Idaho for several decades, simply shuts down when the cooling system is shut off. This design became the basis for the Integral Fast Reactor, which is now the design basis for the 300 MWe GE-Hitachi Nuclear PRISM SMR that began licensing work with the NRC in 2016.

Replacing water as a coolant with liquid molten salt could tap more of the energy available in radioactive materials and reduce the risk of a meltdown by slowing the nuclear reactions automatically if they get too hot.

The higher operating temperatures of coolants like helium, liquid metals, and molten salts more readily lend themselves to industrial applications requiring high temperature process heat – exactly the kind of applications that would add value to the business model.

Safety design reviews by regulatory agencies require steep and expensive learning curves by the agencies. Recent collaboration efforts between the Canadian Nuclear Safety Commission (CNSC) and the U.S. Nuclear Regulatory Commission (NRC) are a step in the right direction.

Two firms so far – Terrestrial Energy, a developer of a molten salt based SMR, and NuScale, which has an SMR based on LWR design principles – have signed up for the process.

While disposition of spent fuel from full size commercial LWR reactors has been tangled in political disputes, the actual handling of the material in dry casks is not a key technical challenge.

Developers of advanced reactors, some of which will use spent nuclear fuel from commercial LWRs, are facing the same political head winds. Eventually, nations that have nuclear reactors will have to come to terms with the need for a deep geologic repository for the highly radioactive residuals that cannot be repurposed, reprocessed, or otherwise utilized in the fuel cycle.

Success Factors for Advanced Nuclear Reactor Developers

In the U.S. and Canada more than three dozen firms, representing more than $1 billion in investor money, are currently pursuing technological innovations in nuclear energy. These firms include large, big-name projects, with deep pockets and small startups.


While large, light water reactors will continue to be significant early players in the commercial mix in global markets, the bet is that there will also be market opportunities for reactors based on new, and as yet unproven, technologies. It is unclear to some investors whether they can or will stay in the game long enough to collect on these bets. This is where public/private partnerships comes in.

Development of roadmaps by independent developers to achieve commercial success of advanced nuclear reactors are the primary objectives today which are needed to replacing the historical objectives of R&D sandbox milestones pursued by scientists inside government-funded national labs. This is a growing trends as evidenced by the GAIN program, but the funding levels are still way short of what is needed.

Another approach is that start-up models adapted from Silicon Valley are being used to organize the efforts with venture capital funding in the mix.

Lists of Advanced Nuclear Reactor Development Efforts

Gain-logo.pngThe Idaho National Laboratory (INL), Gateway for Accelerated Innovation in Nuclear (GAIN) publishes a directory of developers of advanced nuclear energy technologies, suppliers, and national labs.

It indicates there is strong commercial interest in making Gen IV designs commercial realities and that suppliers are interested in producing the components needed to build them.

This directory, which is updated on a regular basis, was created in partnership between GAIN and the Third Way advanced reactor poliy program, with the help of the United States Nuclear Infrastructure Council (USNIC).  Other listings include;

  • Third Way Update (February 2018),  Interactive Map , and a detailed spreadsheet listing of North American advanced reactor projects with links to their websites.
  • Selected listings in a 65 page directory (PDF file) by Third Way of developers, suppliers, and national laboratories. Pages 1-29 list the developers. (2017)
  • See also a new interactive map (October 2019) of the location of advanced nuclear reactor development efforts in the U.S.
  • Readers may also want to check out the IAEA ARIS Database for a deeper dive into the technologies for each design and work in other countries. This DBMS is incomplete since it relies on developers to update the status of their listings.

Steps Governments Can Take to Speed Up
Development of Advanced Reactors

A 2016 report by the Secretary of Energy Advisory Board concluded that it would take 25 years and $12 billion to commercialize a single advanced reactor concept.  There are lots of reports by think tanks and advocacy groups about how to change government policies that will result in speeding up the development of advanced reactors. There has got to be a better way to get there. Here are a few ideas.

The key steps that governments can take include to speed up commercialization of advanced reactors and to stimulate creation of supply chains include:

  • Fund and support test environments for sodium cooled, high temperature gas cooled, and molten salt designs.
  • Offer cost sharing grants to cover design, testing, and regulatory reviews of advanced designs.
  • Provide for power purchase agreements at federal facilities to make a market for FOAK of these advanced designs.
  • Offer loan guarantees for construction of advanced reactors and tax credits for the first years of production of electricity.
  • Streamline the licensing framework for safety design review and approval of construction.
  • Support R&D for advanced fuels and provide financial incentives to firms to start manufacturing them. Examples include low enriched high assay fuel (LEHAU) and TRIOS (pebble bed) fuel for HTGRs.

For more information, a good place to start is the report by the Breakthrough Institute How to Make Nuclear Innovative.  For the impatient, read the executive summary and watch the brief video on YouTube that covers the report’s key findings.

Progress is Mixed So Far for Advanced Developers

The need for reliable, low-carbon forms of energy has seen interest in Generation IV nuclear technologies increase. In January 2020 Finland’s nuclear regulator Stuk became the latest, following the US and the UK and others, to say it wanted to prepare for the licensing and deployment of new reactor types.

“Globally, significant investments are being made on the development of small modular reactors and the parties showing interest are not just traditional nuclear power companies – many new organizations, such as cities, municipalities and the process industry have also expressed interest in using SMRs for producing heat and power,” Stuk said.

Measuring progress for advanced reactors is somewhat of an apples v. oranges exercise. Progress with one design isn’t directly comparable to another. Here are some highlights of recent hit and misses and the reasons for them. While there are many startups, the examples described here are intended to illustrate various approaches and not to endorse one design or vendor compared to others.


In 2015 TerraPower inked a deal with China National Nuclear Corp. to build the first unit of the 1100 MWe sodium cooled reactor in China and then deploy commercial versions of it to global markets. However, in 2018, an unanticipated turn of the wheel of fortune brought that high-profile effort to a halt. The U.S. government issued a ban on nuclear energy exports to China, which ended the TerraPower effort there.

In 2020 TerraPower and GE-Hitachi Nuclear Energy (GEH) teamed up to respond to an expression of interest from the Department of Energy to work on design of the Versatile Test Reactor (VTR). Both firms have deep expertise in the design of sodium cooled advanced reactors.

The VTR facility, to be built at a U.S. DOE national lab, is expected to serve as a platform for testing fuels and materials that are needed for a range of advanced nuclear reactors designs. Construction is expected to start by 2022. The VTR will be part of the National Reactor Innovation Center (NRIC) which will be a facility for testing advanced reactor technologies.

nuclear TRLs

TerraPower has a $60M grant from the DOE for its work with Southern, a nuclear utility, and Oak Ridge National Laboratory on its molten chloride salt reactor. Southern and other partners, such as the Electric Power Research Institute, add their resources, including funds and expertise, to the effort.


Conceptual cutaway image of TerraPower molten chloride salt reactor design.  Image: TerraPower

GE-Hitachi Nuclear

Separately, GEH is working on its PRISM reactor, which is a sodium-cooled design based on the Integral Fast Reactor deployed at the Argonne National Laboratory site in Idaho in the 1990s.


Conceptual image of  GEN IV sodium cooled reactor. Image: GEN IV Forum

In October 2018 GE Hitachi Nuclear Energy (GEH) and Southern Nuclear agreed to collaborate in the development and licensing of advanced reactors, including GEH’s sodium-cooled fast reactor design.

In June 2017, four U.S. nuclear energy firms teamed to develop the basis for seeking an NRC design certification under 10CFR50 for the GE-Hitachi (GEH) PRISM advanced nuclear reactor.


X-energy is an American privately held nuclear reactor and fuel design engineering company developing a Generation IV high-temperature gas-cooled nuclear reactor design.

The Xe-100 is a pebble bed high-temperature gas-cooled nuclear reactor design. Each reactor is planned to generate 200 MWt and approximately 75 MWe. The standard Xe-100 “four-pack” plant would generate approximately 300 MWe and will fit on 13 acres.

All of the components for the Xe-100 are planned to be road-transportable, and be installed, rather than constructed, at the project site to streamline construction.

pebblesThe fuel for the Xe-100 is a spherical fuel element, or pebble bed, that utilizes the tristructural-isotropic (TRISO) particle nuclear fuel design with an enrichment of 15.5% U-235.

Global Nuclear Fuel (GNF) and X-energy are collaborating to produce high-assay low-enriched uranium (HALEU) tristructural isotropic (TRISO) particle nuclear fuel, which they expect to be able to produce at lower costs than other potential manufacturers. Their main competition is BWXT which in December 2019 ramped up its TRISO fuel production facility.



Conceptual image of a Pebble Bed reactor using TRISO fuel. Image: World Nuclear Assoc

In January 2016 X-energy was awarded a five-year $53M United States Department of Energy Advanced Reactor Concept Cooperative Agreement award to advance elements of their reactor development.

The staff of the U.S. Nuclear Regulatory Commission (NRC) began pre-application licensing talks with X-Energy in September 2018. A search in the NRC ADAMS DBMS for information on docket number 99902071 shows a list of proprietary presentations to NRC staff.

In November 2019 the firm signed a letter of intent with Jordan for four of the 75 MWe units. The background is that in July 2018 Jordan decided as a matter of policy to replace a prior deal with Rosatom for two 1000 MW VVER commercial nuclear reactors with a plan for small modular reactors including consideration of designs from the U.S. U.K., and South Korea.

Jordan cited the financial burden of funding $10 billion for the two 1,000 MW Rosatom VVERs as he reason for the decision. Rosatom had offered Jordan 50% financing with Jordan having the requirement to raise the other 50% with a combination of government funding and outside investors. The financial plan never came together for Jordan and the plan for two full size 1000 MWe reactors became a non-starter as a result.


In the U.S. Oklo, a developer of a 1.5 MWe micro reactor is furthest along as an advanced design developer in pre-licensing engagement with the NRC.  Work on docket 99902046 began in November 2016. In December 2019, after working under wraps for several years, Oklo unveiled its micro reactor design.

The firm has been in pre-application licensing discussions with the NRC since 2016. In December 2019 the firm disclosed a great deal of technical information about its design in a 177 page presentation that it made public in a meeting with the NRC. The reactor is a sodium cooled design derived in part from the EBR-II which was a 62.5MWth, 19 MW sodium-cooled fast reactor with metallic fuel.

oklo heat pipes

Conceptual diagram by Oklo of how heat pipes would work in its sodium cooled micro reactor

Oklo announced is design is an advanced nuclear reactor that runs on a single fuel load for decades. Calling it the “Aurora Advanced Fission Clean Energy Plant,” the firm says the power plant would be integrated with solar panels to provide communities with 24×7, 365 days/year reliable electrical power.

The Aurora plant is designed produce about 1.5 MWe of electric power, while also having the ability to produce usable process heat for residential or commercial applications. The plant uses metal uranium fuel. Heat pipes carry the heat to a heat exchanger, and a power conversion cycle converts the heat into electricity.

The Idaho National Laboratory (INL) is working with the company on fuel development and qualification. OKLO is a partner with the INL on a DOE ARPA-E $1.8 million award of federal funding. INL and its partners are proposing a next generation metal fuel in support of a megawatt-scale compact fast reactor – being developed by Oklo Inc – that is  sized for off-grid applications.

Also, in December 2019 Oklo received a site permit to build one of its micro reactors, once it is licensed by the NRC, at the Idaho National Laboratory. The site license is the first in the U.S. for an advanced reactor and it is the second site license granted by the Department of Energy for a new commercial reactor to be built at the Idaho site.

In 2015 UAMPS, a Utah-based consortium of rocky mountain region electric utilities, also received a site license from the Department of Energy for a nuclear power station to be built at the Idaho National Laboratory by NuScale using the firm’s 60 MW LWR type SMR. NuScale says it will break ground by 2022 and be operational by 2026. The firm says it is on schedule to complete its safety design review with the NRC this year.


Canada is becoming key center of work on small modular reactors. With a population one-tenth the size of the U.S., it sees the future of decarbonization in a range of less costly SMR designs including PWRs, molten salt, and high temperature gas reactors.

The Canadian Nuclear Laboratory (CNL) has been the primary driver of support for innovation. The Laboratory is spearheading multiple efforts to promote advanced designs through cost sharing and technical support of various developers.

Several Canadian SMR developers have made significant progress through a multi-phase qualification process to be selected to get further support from CNL. Terrestrial Energy is one of them and is at the head of the pack for pre-licensing vendor design reviews with CNSC.

ARC Nuclear and New Brunswick Power have agreed to work together to develop, licence and build an advanced SMR based on ARC Nuclear’s ARC-100 Generation IV sodium-cooled fast reactor technology. In this design the basic elements of the Integral Fast Reactor will live again.

ARC-100-Reactor (1)

Conceptual diagram of cut away of ARC-100. Image: ARC-100

New Brunswick Energy Solutions also announced the participation of Moltex Energy in a research cluster that will work on R&D on SMR technology based on molten salt technology.

Among the Hits, These Projects Struck Out


transatomicThe demise of Transatomic, a U.S.-based startup, in September 2018 created by two MIT PhD graduates, is an unintended object lesson that media attention does not guarantee technical success.

To its credit, the firm’s two key developers acknowledged that their calculations for the reactor’s expected performance did not pan out. The firm has archived its work as open source so that other developers of advanced designs can learn from their experience.

Transatomic had raised more than $4 million from Founders Fund, Acadia Woods Partners, and others. Venture Capitalist Peter Thiel was an early investor and touted his funding commitments to nuclear  energy in an OP ED in the New York Times.

The firm was already on its second wind having earlier determined that its technology could not generate electricity 75 times more efficiently than conventional light-water reactors using the energy potential in spent nuclear fuel.

The forced restart, which is not an uncommon event among advanced technology firms, put them behind rivals like TerraPower and Terrestrial Energy. Both of these firms have committed to plans to eventually build and test demonstration reactors with their designs.

Leslie Dewan, one of Transatomic’s two founders, told the MIT Technology Review the longer timeline and reduced performance advantage made it harder to raise the necessary additional funding, which was around $15 million.

“We weren’t able to scale up the company rapidly enough to build a reactor in a reasonable time frame,” Dewan said.


At one time Japan had a vision of a “plutonium fueled” economy using the metal extracted from spent fuel generated by light water reactors to make mixed oxide fuel (MOX) and other specialty fuels for advanced reactors. The failure of the plan left Japan with a large inventory of plutonium and not much to show for the effort.

A total of 47 tonnes of plutonium have accumulated by Japan so far raising fears among other southeast Asia nations about what Japan might do with it. Most of it is embedded in spent nuclear fuel from light water reactors which makes it very expensive and dangerous to reprocess to extract the PU-239 for use in nuclear weapons. Only 10 tonnes are actually in Japan. The rest is held in France and the U.K.

The Rokkasho plant is designed to extract 8 tonnes of plutonium a year from spent nuclear fuel and reprocess it into MOX fuel. A back of the envelope calculation indicates that amount could produce about 400 PWR type MOX fuel assemblies a year. Given the rate at which Japan’s restart of its reactor fleet is taking place, from a stocks and flows perspective, it may make a dent in the inventory, but it won’t catch up.

The problem, and it is the white elephant in the room, is that the plant has been under construction for over two decades. Its initial cost estimate of about $7 billion has ballooned to $27 billion and the completion date is still two-to-three years in the future.

Unlike Russia’s work with its “BN” series of fast reactors, Japan has not committed to a robust R&D program to design and build fast reactors that could burn MOX fuel. In November 2017 after years of technical difficulties, Japan’s government shut down the Monju fast reactor.

Its design was innovative which may have been part of the problem. According to the World Nuclear Association, it has three coolant loops, used 198 MOX fuel assemblies surrounded by 172 blanket assemblies, and operated at 714 MWt, 280 MWe gross and 246 MW electrical.

Japan has said previously that the path forward for disposition of the surplus plutonium is to convert it in MOX, but given the slow pace of restarts of its commercial light water reactors that can burn OX up to 30% of their cores, that seems like a distant prospect for now.  For now Japan continues to contract with Framatome to produce MOX fuel assemblies for use in its PWRs.


In September 2019 France ended its plans to build a prototype Generation IV sodium-cooled fast breeder nuclear reactor known as Astrid. The Atomic and Alternative Energies Commission (CEA) said it would suspend the 600-MW Astrid FBR project, which was planned for CEA’s Marcoule nuclear site in southern France.

“In the current energy market situation, the industrial development of fourth-generation reactors is not planned before the second half of this century,” the CEA said.

The agency told the French news media, “the project is dead and the agency is spending no more time or money on it.”

Defining Value for Advanced Reactors

The two biggest challenges remain getting through the licensing process and convincing a nuclear utility, based on experiences with prototypes, that an advanced design can be built on time, within budget, and operated at a profit.

Until these milestones are met, some advanced reactors operating solely for electricity generation may remain somewhere in the middle of the technology ‘S’ curve until a first of a kind success crosses the finish line.

Others, with the right levels of support, may get to build a first-of-a-kind unit, but the main product won’t be just electricity. It will be heat for multiple uses and customers.

Revising the product definition (heat) and revenue objectives (multiple uses of high heat) may be one of the biggest contributions to success for advanced reactors.

At the end of the day all vendors, large and small, still have to do the same thing, and that is convince a customer they can build their design on time and within budget.

Sama Bilbao y León, head of the division of nuclear technology development and economics at the OECD Nuclear Energy Agency, put it this way in a January 2020 interview,

“My contention is that economics is the biggest problem nuclear energy faces right now. We, the nuclear community, really need to get our act together. The ball is in our court as far as I am concerned. There are opportunities for policymakers, market designers, financiers and others to support the nuclear sector, but first of all the ball is in our court: we need to show that we can build nuclear power plants on time and on budget.”

And once the unit is built, the utility must also be convinced that the new design can be operated safely, reliably, and, most important, can do it as a profit by making heat for all the applications that will use it.

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2 Responses to A Forecast for the Future of GEN IV Reactors ~ A 50/50 Chance of Success for Three Types

  1. Pingback: A Forecast for the Future of GEN IV Reactors ~ A 50/50 Chance of Success for Three Types - Neutron Bytes - Pro-Nuclear Power Blogs - Nuclear Street - Nuclear Power Plant News, Jobs, and Careers

  2. Maury Markowitz says:

    “is to offer heat as the primary output of their plants”

    There is really no economic basis for this statement. Any given amount of heat has much less economic worth than the amount of electricity needed to produce it, which is precisely why nuclear plants turn their heat into electricity.

    Proponents have been talking about using NPP for process heat since the 1950s, and to date, there are exactly zero examples of a successful system. And that’s not for lack of trying; the UK’s designs were constantly sold as process heat providers, and their later AGR’s were suited for it due to their higher than normal outlet temperatures. Zero use. At least two of the German designs were likewise pitched for process heat use, and they too went nowhere. The US and USSR also had such designs, or at least trial balloons for them, and also saw no use.

    I simply see no credible scenario where NPPs can provide economically competitive process heat. Coal is cheap, and even it’s not able to compete on the electricity side of things any more, so the demand curve is going to plummet, making the NPP argument that much more difficult.


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