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Rocket Doc News Week of May 30,2021

Newsworthy Events in Nuclear Fission

I am stepping back into nuclear physics this week to describe a possible breakthrough in the economics of nuclear fission powerplants, namely traveling-wave reactors (TWRs). Traveling-wave reactors are a specific reactor design that can operate on a mixture of spent fuel rods, thorium, and unenriched uranium. They were first proposed in the 1950s and have been studied intermittently ever since. The concept of a reactor that could breed its own fuel inside the reactor core was initially proposed and studied in 1958 by Savely Moiseevich Feinberg, who called it a "breed-and-burn" reactor.[1] Michael Driscoll published further research on the concept in 1979,[2] as did Lev Feoktistov in 1988,[3] Edward Teller/Lowell Wood in 1995,[4] Hugo van Dam in 2000[5] and Hiroshi Sekimoto in 2001.[6]

The TWR was discussed at the Innovative Nuclear Energy Systems (INES) symposiums in 2004, 2006 and 2010 in Japan where it was called "CANDLE" Reactor, an abbreviation for Constant Axial shape of Neutron flux, nuclides densities and power shape During Life of Energy production.[7] In 2010 Popa-Simil discussed the case of micro-hetero-structures,[8] further detailed in the paper "Plutonium Breeding In Micro-Hetero Structures Enhances the Fuel Cycle", describing a TWR with deep burnout enhanced by plutonium[9] fuel channels and multiple fuel flow. In 2012 it was shown that fission[10] waves are a form of bi-stable reaction diffusion phenomenon.[11]

No TWR has yet been constructed, but in 2006 Intellectual Ventures launched a spin-off named Terrapower to model and commercialize a working design of such a reactor, which later came to be called a "traveling-wave reactor". TerraPower has developed TWR designs for low- to medium- (300 MWe) as well as high-power (~1000 MWe) generation facilities.[12] Bill Gates featured TerraPower in his 2010 TED talk.[13]

In 2010 a group from TerraPower applied for patent EP 2324480 A1 following WO2010019199A1 "Heat pipe nuclear fission deflagration wave reactor cooling". The application was deemed withdrawn in 2014.[14]

In September 2015 TerraPower and the China National Nuclear (CNNC) signed a memorandum of understanding to jointly develop a TWR. TerraPower planned to build a 600 MWe demonstration Plant, the TWR-P, by 2018–2022 followed by larger commercial plants of 1150 MWe in the late 2020s. However, in January 2019 it was announced that the project had been abandoned due to technology transfer limitations placed by the Trump administration. This is a glaring example of the shortsightedness of our Nuclear Energy Commission. They refused to fund the design and test of a breakthrough nuclear fission powerplant, so the Chinese offered and then the Trump administration shut that down.

The news recently got better though. This week TerraPower, PacifiCorp and Wyoming Gov. Mark Gordon announced plans to build a next-generation nuclear power plant on the site of one of the state’s retiring coal plants. The demonstration project will build a fully functioning power plant with the intention of validating TerraPower’s Natrium technology (new name for TWRs). In October 2020, the U.S. Department of Energy (DOE), through its Advanced Reactor Demonstration Program (ARDP), awarded TerraPower $80 million in initial funding to demonstrate the Natrium technology. TerraPower signed the cooperative agreement with DOE in May 2021. To date, Congress has appropriated $160 million for the ARDP and DOE has committed additional funding in the coming years, subject to appropriations.

The Natrium system is a TerraPower and GE Hitachi technology. Along with PacifiCorp and GE Hitachi Nuclear Energy, members of the demonstration project team include engineering and construction partner Bechtel, Energy Northwest, Duke Energy and nearly a dozen additional companies, universities and national laboratory partners. Next steps include further project evaluation, education and outreach, and state and federal regulatory approvals prior to acquisition of a Natrium facility.

The exact location of the nuclear plant will be decided by the end of the year, and the facility should take about seven years to build. It will feature a uranium-fueled, 345-megawatt sodium-cooled fast reactor. The advanced nuclear reactor includes a molten salt-based energy storage system, which can act like a battery and give an energy boost up to 500 megawatts for more than five hours. At that maximum output, the plant will generate enough energy to power 400,000 homes. “It’s the only from-scratch reactor design that’s been done going back to the 1950s, where we can use digital tools to simulate any problem and really optimize all these components,” said Gates in a February interview with GeekWire. “Because nuclear power, despite all the waste and safety and proliferation concerns, the main reason it’s failing right now is that the reactors have gotten so costly to build,” he said. “They’re just not competitive, particularly in a place where natural gas is so incredibly inexpensive.” Figure 1 below shows the Lab where TerraPower is inventing the future of nuclear energy.

Figure 1 - A panoramic view of TerraPower’s laboratory shows a full-scale fuel assembly test stand at the center of the frame – with lab facility manager Brian Morris pointing out details toward the left of the frame. The circle that’s painted on the floor indicates how big the nuclear containment vessel would be. (GeekWire Photo / Kevin Lisota)

The cost of building the pilot plant is unclear. Reuters cited an earlier figure of $1 billion, while Gates referred to a “$4 billion demo plant” in the GeekWire interview. In October, TerraPower won $80 million in funding from the U.S. Department of Energy’s Advanced Reactor Demonstration Program to help cover the costs. Gates for many years has been lobbying congress to engage in public-private partnerships to fund innovation in nuclear power. Reuters also noted that Wyoming Sen. John Barrasso co-sponsored legislation that became a law in 2019 that created a path to licensing advanced nuclear reactors. And regarding the “waste and safety and proliferation concerns” — that’s complicated, too. The Union of Concerned Scientists in March issued a report raising challenges to the purported benefits of the TerraPower approach to nuclear energy. I have read the report summary and it basically questions every fact about the TWR that was reached by analysis. If it hasn’t been demonstrated by test it isn’t true. That is why the DOE is funding the Advanced Reactor Demonstration Program.

TWRs use only a small amount (~10%) of enriched uranium-235 or other fissile fuel to "initiate" the nuclear reaction. The remainder of the fuel consists of natural or depleted uranium-238, which can generate power continuously for 40 years or more and remains sealed in the reactor vessel during that time. TWRs require substantially less fuel per kilowatt-hour of electricity than do Light-Water Reactors (LWRs), owing to TWRs' higher fuel burnup, energy density and thermal efficiency. A TWR also accomplishes most of its reprocessing within the reactor core. Spent fuel can be recycled after simple "melt refining", without the chemical separation of plutonium that is required by other kinds of breeder reactors. These features greatly reduce fuel and waste volumes while enhancing proliferation resistance.

Depleted uranium is widely available as a feedstock. Stockpiles in the United States currently contain approximately 700,000 metric tons, which is a byproduct of the existing uranium enrichment process. TerraPower has estimated that the Paducah enrichment facility stockpile alone represents an energy resource equivalent to $100 trillion worth of electricity. TerraPower has also estimated that wide deployment of TWRs could enable projected global stockpiles of depleted uranium to sustain 80% of the world's population at U.S. per capita energy usages for over a millennium!

In principle, TWRs are capable of burning spent fuel from LWRs, which is currently discarded as radioactive waste. Spent LWR fuel is mostly low enriched uranium (LEU) and, in a TWR fast-neutron spectrum, the neutron absorption cross-section of fission products is several orders of magnitude smaller than in a LWR thermal-neutron spectrum. While such an approach could actually bring about an overall reduction in nuclear waste stockpiles, additional technical development is required to realize this capability. TWRs are also capable, in principle, of reusing their own fuel. In any given cycle of operation, only 20–35% of the fuel gets converted to an unusable form; the remaining metal constitutes usable fissile material. Recast and reclad into new driver pellets without chemical separations, this recycled fuel can be used to initiate fission in subsequent cycles of operation, thus displacing the need to enrich uranium altogether.

The TWR concept is not limited to burning uranium with plutonium-239 as the "initiator" in a 238U–239Pu cycle, but may also burn thorium with uranium-233 as the "initiator" in a 232Th–233U cycle. Cost effective, functioning TWRs could literally solve Global Warming by themselves.

A second advanced Fission reactor design is also in the works, In April, Maryland-based X-energy signed an agreement to build an advanced nuclear reactor near Richland, Washington on the Hanford nuclear reservation. The X-energy facility shares its site with Energy Northwest, which runs Washington’s only commercial nuclear plant. X-energy will build an 80-megawatt reactor that could be scaled up to a 320-megawatt “four pack” according to the Tri-City Herald.

X-energy was the other recipient of the DOE’s Advanced Reactor Demonstration Program funding, also winning $80 million in October. X-energy is an American private nuclear reactor and fuel design engineering company. It is developing a Generation IV high-temperature gas-cooled nuclear reactor design. In January 2016 X-energy was awarded a five-year $53MDepartment of Energy (DOE) Advanced Reactor Concept Cooperative Agreement award to advance elements of their reactor development. In 2019, X-energy received funding from the Department of Defense (DoD) to develop small military reactors for use at forward bases.

In October 2020, the company was chosen by the United States Department of Energy as a recipient of a matching grant totaling between $400 million and $4 billion over the next 5 to 7 years for the cost of building a demonstration reactor of their Xe-100, helium cooled pebble-bed reactor (PBR) design. I would view the PBR as a good backup for the TWR design. It will consist of small units that can be built in a factory and trucked out to the operating site, but it doesn’t have the fuel economics of the TWR, and I think we will have trouble converting to nuclear unless it is cost competitive with current fossil fuel powerplants.

President Biden has set a goal of cutting U.S. greenhouse gas emissions by at least half by 2030 compared to 2005 levels. He also continually stresses that cutting greenhouse gases will generate thousands of good-paying union jobs. Building and operating standby nuclear powerplants to back up renewable power sources will generate those jobs, but unfortunately that is not in the Progressives’ playbook. Renewable power usually contributes about 35% of its rated power level over time, so either we build renewables and an energy transmission system far in excess of our real power requirements, or we build a renewable power system to meet our normal power consumption levels and fill in the remaining power consumption requirements with nuclear and hydroelectric standby power. Nuclear power currently provides nearly 20% of U.S. electricity. Renewable power sources including hydroelectric contribute another 20% and fossil fuels make up 60%. Cutting that 60% to 30% while upgrading and expanding our energy generation systems is going to require a major commitment to nuclear power in my opinion and the TWR in particular because it is the only nuclear powerplant that promises to be cost competitive with existing fossil-fuel powerplants.

Tested in the U.S., then sold abroad?

It will cost billions of dollars to build just one next-generation nuclear reactor.– and the financial and regulatory challenges are at least as daunting as the technical challenges. Finding a way to cover the cost has been a bright blip on Bill Gates’ radar screen for the past year.

“Even Bill is not going to fund a multibillion-dollar reactor on his own,” said Marcia Burkey, TerraPower’s senior vice president and chief financial officer. In a series of statements, and in meetings with members of Congress, Gates has talked up the idea of using public-private partnerships to fund advanced nuclear reactor demonstration projects in the United States.

Figure 2 - TerraPower’s fuel assembly test stand is designed to check how fuel rods and other components would stand up to stresses inside a nuclear reactor. (GeekWire Photo / Kevin Lisota)

Until last year, TerraPower was invested in a different sort of public-private partnership … in China. The company and its Chinese partners, led by the state-owned China National Nuclear Corp., were due to break ground on a demonstration reactor that would have gone into operation in the mid-2020s.

The Trump administration’s trade battle with China pushed that plan off the tracks, however. As a result, TerraPower has turned its focus to the Nuclear Energy Leadership Act, or NELA, a congressional measure that would provide federal funding for next-generation nuclear plants.

“In China, we were partnered with CNNC, and they were bringing investment, and they were also supplementing our team with their large engineering workforce,” Levesque said. “So we’re really in the process of recreating that now in the U.S. We’re having some advanced discussions with several partners. I can’t reveal the names of those, but because TerraPower has good technology and we have a great business case, we are putting together several partnerships for our NELA application.”

The bipartisan legislation, which hasn’t yet been approved by either the House or the Senate, calls on the Department of Energy to set up two advanced nuclear power demonstration projects by 2025, and up to five more by 2035. It also lays out a plan for forging federal power purchase agreements. Levesque estimates the total cost of building a demonstration reactor at $3 billion, more or less, depending on the technology used.

TerraPower isn’t the only company likely to seek NELA support: General Atomics, Transatomic Power, Gen4 Energy and Oregon’s own NuScale Power are also on the list of ventures with next-generation nuclear reactor concepts. NuScale is already laying plans for a demonstration reactor at Idaho National Laboratory. That’s a model that TerraPower could follow for its TWR and MCFR concepts.

“We’d like to make them American technologies that we partner with American companies on,” Levesque said. “We’d involve the U.S. national labs in the program. We might even see one of these demos built on a national lab site.” Levesque said the fact that TerraPower’s reactor designs were born in the Pacific Northwest could fuel some “supply chain development in this area.” But will advanced reactor designs fuel a large-scale nuclear renaissance in the U.S.? That’s debatable, largely due to the nation’s current bounty of cheap natural gas.

“The U.S. and Canada are very tough markets,” Levesque acknowledged. “If nuclear isn’t going to be credited at all economically for being carbon-free, then it’s very difficult to compete with today’s natural gas prices. That’s one of the reasons we’re working so hard on advancing MCFR. We think MCFR could have the potential to compete with natural gas.”

He said the cost equation looks a lot better outside the United States. “In many other countries, electricity prices are higher,” Levesque said. “Natural gas is more difficult. We think that TWR could be very competitive there, and it’s available today.” We’re being outnumbered by Russia and China by something like 30 or 40 projects to one.

Gates pointed to the issue of global “energy poverty” last week in a posting to his Gates Notes blog. “For the nearly 1 billion people around the world who don’t have access to electricity — or whose access is so unreliable that they can never count on having power — an outage can go on for days or even weeks,” he wrote. “And these outages are more than just an inconvenience. They can be deadly.”

Levesque argues that there’s also a national security angle to nuclear technology.

“We’re being outnumbered by Russia and China by something like 30 or 40 projects to one,” he said. “We’re the country that created civil nuclear technology, but we’re beginning to get shut out of the game. … It’s hugely important for the U.S. to have the technology for carbon avoidance — but it also has serious security implications for the U.S., because if we don’t deploy this next phase of nuclear, we’ll be continuing this trend of losing our edge in nuclear energy.”

That may sound like an abrupt pivot, considering that just a year ago, TerraPower was getting ready to build its first plant in China. But Levesque said TerraPower’s current focus is in tune with the goal of making American nuclear power great again.

“We’re an American company, and we have to follow U.S. export control laws — so when the decision came down, we complied and we ended our work in China,” he said. “We’re not going to the government and saying, ‘You owe us.’ We’re going to the government and saying, ‘We are missing a serious opportunity for America if we don’t demonstrate these technologies.’ ”

Levesque noted that TerraPower has helped train “a new wave of nuclear engineers” over the past decade.

“We have all these young people who are raring to go,” he said. “We have countries like China and Russia copying our old stuff and doing it quite well. …We’re the people with the new stuff, and it’s time to go demonstrate the next technology. That’s our traditional American role. We’ve done it in computing. Now it’s time to do that in nuclear energy.”


1. S. M. Feinberg, "Discussion Comment", Rec. of Proc. Session B-10, ICPUAE, United Nations, Geneva, Switzerland (1958).

2. ^ M. J. Driscoll, B. Atefi, D. D. Lanning, "An Evaluation of the Breed/Burn Fast Reactor Concept", MITNE-229 (Dec. 1979).

3. ^ L. P. Feoktistov, "An analysis of a concept of a physically safe reactor", Preprint IAE-4605/4, in Russian, (1988).

4. ^ E. Teller, M. Ishikawa, and L. Wood, "Completely Automated Nuclear Reactors for Long-Term Operation" (Part I), Proc. of the Frontiers in Physics Symposium, American Physical Society and the American Association of Physics Teachers Texas Meeting, Lubbock, Texas, United States (1995) ; Edward Teller, Muriel Ishikawa, Lowell Wood, Roderick Hyde, John Nuckolls, "Completely Automated Nuclear Reactors for Long-Term Operation II : Toward A Concept-Level Point-Design Of A High-Temperature, Gas-Cooled Central Power Station System (Part II)", Proc. Int. Conf. Emerging Nuclear Energy Systems, ICENES'96, Obninsk, Russia (1996) UCRL-JC-122708-RT2.

5. ^ H. van Dam, "The Self-stabilizing Criticality Wave Reactor", Proc. Of the Tenth International Conference on Emerging Nuclear Energy Systems (ICENES 2000), p. 188, NRG, Petten, Netherlands (2000).

6. ^ H. Sekimoto, K. Ryu, and Y. Yoshimura, "CANDLE: The New Burnup Strategy", Nuclear Science and Engineering, 139, 1–12 (2001).

7. ^ as proposed by Sekimoto in 2001 and 2005 published in Progress in Nuclear Energy

8. ^ "advanced Nuclear Reactor from Fiction to Reality", by Popa-Simil, published in the INES-3 proceeding L. Popa_Simil, Liviu. "Plutonium Futures Plutonium Breeding In Micro-Hetero Structures Enhances the Fuel Cycle". Plutonium Futures 2010.

10. ^ A.G. Osborne, G.D. Recktenwald, M.R. Deinert, "Propagation of a solitary fission wave", Chaos, 22, 0231480 (2012).

11. ^ K. Weaver, C. Ahlfeld, J. Gilleland, C. Whitmer and G. Zimmerman, "Extending the Nuclear Fuel Cycle with Traveling-Wave Reactors", Paper 9294, Proceedings of Global 2009, Paris, France, September 6–11, (2009).

12. ^ Bill Gates. Innovating to zero!. TED. Retrieved 2010-07-13.

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