Project Pele – Part II. Enabling technologies
Building mobile nuclear power plants will be a challenge, but successfully meeting the challenges could alter the future trajectory of the energy and fuels supply industry.
That is one of the largest and most consequential sectors of our modern, mobile, industrialized economy. There are no guarantees, but compared to many research and development projects, Project Pele has both a reasonable prospect of success and an almost unimaginable potential payoff.
Unsurprisingly, there are skeptics and naysayers who aren’t excited about the prospect of mobile nuclear power plants. The Union of Concerned Scientists’s Dr. Ed Lyman, acting director of UCS’s Nuclear Safety Project , is pessimistic enough about the prospects for success that he has declared that the project “won’t work.” (See Bulletin of Atomic Scientists Feb 22, 2019. “The Pentagon wants to boldly go where no nuclear reactor has gone before. It won’t work.” )
The National Interest chose This Might Be the Military’s Worst Idea Ever as the headline an article by Michael Peck that didn’t match the superlative at all. Instead, it laid out some good reasons why mobile nuclear power plants might be a pretty good idea as long as certain questions can be effectively addressed.
Several other publications produced articles with headlines claiming that “experts” were horrified, critical, or skeptical, but a fair number of those pointed to Ed Lyman as the “expert” and his article in the Bulletin of Atomic Scientists as the place where he documented his concerns.
From my perspective, Dr. Lyman errs by dismissing some of the technical advances that have improved the chances for successful accomplishment of the project’s stated objectives. He has an exaggerated opinion on the risks. He underestimates the potential value of successfully developing the capability to build systems that can meet the stated objectives.
The Army is only a lead customer with the skills and resources required; there are countless potential customers whose interest will be apparent once there is an actual product available for purchase.
A product that comes close to meeting all of the Army’s requirements for Project Dilithium might be especially appealing for settlements in Alaska or The North of Canada. Senator Lisa Murkowski has often expressed the interests her constituents have in small nuclear power systems. They want machines that can operate cleanly for years on small quantities of fuel that eliminate the complex and expensive transportation of diesel fuel.
That problem is essentially the same one that is such a recognized headache for Army planners. Except it’s one that never stops under current available product constraints.
Some proposed options don’t have much of a chance.
I must admit that I think Dr. Lyman is correct in his evaluation of one particular contender in the field. In fact, his opinion of the Los Alamos Special Purpose Reactor (aka Megapower) is a bit less critical than mine. He describes INL’s evaluation of the design as pointing out “several major safety concerns, including vulnerabilities to seismic and flooding events.”
I think he overlooked the part where the evaluators gently told the designers that their beautifully-optimized, computer-designed model cannot be manufactured.
It relies on unobtainable tolerances in drilling ~ 2,000 channels, each 1.5 m long, in a stainless steel monolithic cylinder with 1 mm thick webbing between the channels. Additionally, it envisions the ability to seal about half of those channels at each end to retain fission product gases.
I might be a bit of an outlier, but I believe system designers should make sure their ideas are functionally possible within manufacturing capabilities before they spend too much time determining if they can survive extreme seismic or flooding events.
It turns out that the beautifully optimized but impossible to manufacture design shares one of the perennial problems that have plagued nuclear technology development since the 1940s. It is a substantially scaled up version of a system that has been proven at a smaller scale using highly enriched fissile material. LANL developed Kilopower for a NASA mission to Mars. It worked fine in tests, why not immediately make it 10 times bigger and more powerful?
The prototype power system uses a solid, cast uranium-235 reactor core, about the size of a paper towel roll. Passive sodium heat pipes transfer reactor heat to high-efficiency Stirling engines, which convert the heat to electricity.Demonstration proves nuclear fission system can provide space exploration power
Therefore, this article will continue on the assumption that the only real contenders for near term success in meeting Project Dilithium’s specifications will use a variant of a high temperature gas reactor and a Brayton Cycle heat engine.
Army tested a mobile nuclear power plant in early 1960s. It was a direct Brayton Cycle machine
Here is a quote from an October 2018 study conducted for the Army’s G-4.
ML-1 was a true mobile power plant. Its main advantage was the ability to substitute a single nuclear fuel load to displace and eliminate the need to transport the equivalent of 400,000 gallons of liquid fuel. Unlike the other Army reactors, ML-1 did not use water for coolant, substituting a sealed reactor design with pressurized gas (nitrogen) to drive a closed cycle gas turbine. This design made possible a significant reduction in both size and weight, enabling it to be truck-mobile. The reactor could fit in a standard International Organization for Standardization (ISO) container for ease of shipment by standard military transportation systems.Study on the Use of Mobile Nuclear Power Plants for Ground Operations, Army Deputy Chief of Staff (DCS) G-4 p. 2.2
Though ML-1 worked, it didn’t work well. There were a number of design flaws and unreliable components that led to project schedule delays. By 1966, the Army had lost almost all of its R&D funding as the Johnson Administration attempted to support both an expanding conflict in Vietnam and growing social programs. Programs that weren’t at the top of the performance list were cut.
The Atomic Energy Commission wasn’t interested in pursuing suitable reactor design improvements without a strong demand signal from the military service.
Though it has been almost five decades since the DOD funded a program of for designing and deploying mobile nuclear systems, the supporting technology base has made substantial advances.
Initial concept of using gas to move heat from fission reactors to heat engines
Even if ML-1 had achieved its full design potential without technical issues or delays, it still would have been an inefficient machine. The reactor used in the system was capable of minimally adequate temperatures for a Brayton Cycle; 3 MW of heat would only produce about 300 kW of electrical power.
Brayton Cycle turbo machines were also in their infancy in the early 1960s. The theory was well-established, but functional machines had only been available for a couple of decades. Many of the most common applications for the machines were still in high performance aircraft where the engines were only expected to run for a few hundred hours before being replaced. Brayton Cycle machines had barely begun to penetrate land based power generation, or maritime propulsion.
The fundamental idea of matching a high temperature gas cooled reactor with a simple Brayton Cycle heat engine originated during the final years of the Manhattan Project. Farrington Daniels, Director of the Metalurgical Laboratory in Chicago, had pre-war high temperature industrial experience in developing processes to fix nitrogen from the atmosphere. Once the Met Lab had essentially completed its assignment for the Project, Daniels and his scientific colleagues began meeting informally to discuss ways to put fission energy to productive use.
Daniels suggested a “power pile” composed of uranium spheres mixed with beryllium oxide moderator spheres and cooled by helium gas. The Manhattan District assigned Monsanto to lead the project and provided initial funding in December 1945.
In April, 1946, GE, Westinghouse, Allis-Chamers, the US Navy, the US Army Air Corps and the Clinton Laboratories joined the Manhattan District and Monsanto in the project. They supplied engineers and scientists on an in-kind basis. Everyone on the project knew that it was a pilot system that should be constructed quickly so that it could help develop knowledge of material performance at high temperatures.
The Daniels Pile project was defunded almost as soon as the civilian AEC took over responsibilities from the Manhattan District of the Army Corps of Engineers. Before that happened, Daniels and his team of Project scientists and industrial partners had done enough design work and testing to convince themselves that a gas cooled, beryllium-moderated reactor could operate at high enough temperatures to provide useful information for subsequent design efforts.
Daniels spent at least five more years trying to find funding for his idea, but the AEC monopolized all nuclear work. The appointed commissioners at the top of the organization had determined that America had no need for any new power sources. Instead, the commissioners and their political overseers had determined that the primary mission of the U.S. Atomic Energy Commission was to develop weapons and other military applications.
Aside: The tight linkage in public perception between nuclear energy and nuclear weapons started in the earliest days. It’s quite possible that some of the participants in decisions like naming the AEC wanted to keep scary bombs linked to useful power applications. End Aside.
Coated particles invented as a way to retain fission products at high temperatures
After several years of unsuccessful efforts to convince various government agencies to pursue atomic power using high temperature gas cooled reactors, Daniels was recruited by the Rockefeller Foundation to create a solar energy research program.
However, his pebble bed reactor concept simmered and was eventually taken up by Rudolf Schulten in Germany. He devised a way to coat actinide fuel particles with fission product-retaining coatings. He also devised a method of assembling thousands of particles along with graphite moderator into 6 cm diameter spheres that could be “piled” into a cylinder to form a critical mass. The spherical shape of the pebbles results in at least 40% of the cylindrical volume being empty and available for a turbulent flow of cooling gas.
The idea of coating actinide fuel sources with refractory style graphite and silicon carbide coatings was nurtured by a minor, but passionate multinational group of technologists for the next 60 years. Another major fuel form, a prismatic graphite block with drilled coolant channels and drilled voids to contain compacts of particle fuel was developed. Several operating reactors including Dragon, Peach Bottom 1, AVR, Ft. St. Vrain, THTR, HTTR, and HTR-10 have provided an increasingly extensive database of fuel and component performance.
A variety of coatings and coating processes have been tested. Fuel kernels of various compositions including actinide (thorium, uranium and plutonium) oxides, carbides and a mixture of the two have been irradiated and examined. A comprehensive summary of the various testing development programs written by P. A. Demkowicz, B. Liu and J. D. Hunn was recently published as Coated particle fuel: Historical perspectives and current progress.
Since 2003, the US Department of Energy has been engaged in a carefully planned series of irradiations and post irradiation examinations for a high potential system that uses a series of four coatings on a kernel of uranium oxy carbide. That program is nearing its completion with final testing aimed at identifying potential issues that might result from exposure of the high temperature fuels to excessive moisture or chemical contaminants.
For certain postulated configurations, including those that can meet the Project Pele requirements, there is no need to wait for the results of those final tests. These systems do not have any pathways that allow water or other contaminants to get into the system. Even the ultimate heat sink is dry atmospheric air.
Contrary to the description Dr. Lyman offered in his dismissive article about the potential for mobile nuclear generators, results from DOE’s Triso fuel development and testing program have been anything but “inconsistent.”
The program has produced consistently impressive data on tens of thousands of irradiated particles. Even with fuel burn ups in the range of 19%, the coatings have provided excellent fission product retention even when heated to 1800 C for extended periods of time.
That temperature offers more than 500 C in margin compared to the highest envisioned fuel operating temperatures and 200 C in margin for the highest possible fuel temperature in the most limiting postulated accident.
None of the operated high temperature reactors using coated particle fuels have used a direct cycle gas turbine. Several aborted design efforts have made enough progress to determine that using helium as a coolant is not too hard, but using it as a working fluid in a Brayton Cycle gas turbine leads to some difficult material and mechanical challenges.
The authors of the G-4 study on the use of mobile nuclear power for ground operations noted the possibility of “carbon dioxide, argon, nitrogen” as options to helium. It also reminded readers that the ML-1, the only direct Brayton Cycle nuclear power system that has been operated in the U.S. used pressurized nitrogen as a working fluid and reactor coolant.
Companies that might be in the running and customers that might be following
There are a handful of relatively new start-up companies that have been focusing their design efforts on very small manufactured reactors that might be suitable for powering remote mines, villages, or forward operating bases.
Holos, Ultra Safe Nuclear, StarCore, and X-Energy all come to mind as companies that are working on designs that might be quickly adapted to meet the requirements specified for Project Dilithium. None of them have been working on designs that are directly applicable because none of them had previously identified an appropriate early adopter customer.
There are other potential customers that are interested in reliable electrical power in places that are not readily reachable by wired transmission systems. They can be in remote areas separated by long distances from the existing grid, on islands separated by expanses of water, on offshore exploration platforms, or on ships whose movements prevent wires from being a possible solution.
Because they cannot be reached by wires, they must either rely on diesel or gas turbine generators or they must do without power. In virtually all cases, the unconnected customers survive with a combination of very expensive power from burning refined petroleum in relatively small machines and doing without many of the electrically powered support systems that many of us take for granted.
Those with the fewest resources lean more heavily on doing without power. That often makes their lives a struggle without hope of improvement through industry, education or increased productivity.
Many of these potential customers could benefit from the availability of power from machines with the same characteristics that a military forward operating base needs, so potential suppliers have always identified the military as a potential customer.
Because the DOD’s need to reduce logistics vulnerabilities can be more directly measured in lives lost and dollars spent, it could be an early adopter that provides an accelerating market pull.
Small, manufactured nuclear systems are going to be available fairly soon even without the DOD, but its more pressing needs might provide more resources that enable design completions and manufacturing cost reductions. These will help customers with fewer current resources to afford the power systems that they could already put to good use if they were on the shelf now.
My primary concern about Project Pele is tied to the US military’s notorious belief that the technologies it uses are somehow so unique that they must be surrounded by a dense thicket of secrecy, even if they are merely ruggedized versions of power generators or ship propulsion engines that could be used in a wide variety of applications.
Those secrecy rules not only bind up initial development, but they cause enormous cost increases by requiring unique support systems provided by contractors that fiercely protect their special relationships with military leaders, congressional appropriators, and even presidential candidates/office holders.
What about vulnerabilities that Lyman described?
In his BAS article on mobile nuclear plants, Dr. Lyman expressed concerns about the vulnerability of mobile nuclear plants in a hostile environment. One feature of nuclear power systems that many critics forget is the fact that they require robust shielding systems.
The same layers of dense metals and hydrogen containing materials like concrete, plastic and water that protect people from radiation would do a very good job of protecting reactors from penetrating projectiles.
Compared to the diesel and kerosene storage containers needed for current power generators, mobile nuclear should require fewer protective resources.
Even in the unlikely situation that an explosive can be delivered into a properly shielded reactor core, it’s probable that most radioactive material will be effectively retained. Coated particles might be dispersed a short distance, but they seem too dense to be carried very far. It’s probably worthwhile to perform testing to verify this theory.
One of the specific statements made by Dr. Lyman is a myth that continues to be propagated in even the most informed and supportive circles of people with nuclear expertise. He called graphite “the combustible material that brought the world an 11-day radioactive fire after the April 1986 Chernobyl explosion”.
Nuclear grade graphite might be pure carbon, but it isn’t combustible. It’s structure is far too ordered to offer any available sites for the kind of rapid oxidation required for combustion. At Chernobyl, graphite heated to temperatures high enough to produce a red glow was dispersed and landed on combustible materials in the building structure. Those are the materials that actually burned. (Source: Prerelease of a forthcoming IAEA publication on graphite in nuclear reactors.)
Bottom line is that Project Pele is a fascinating reach forward that is worth watching. I encourage all decision makers involved to be as transparent as possible, while paying attention to the need to protect certain kinds of details.
I suspect this is far less of an issue than you believe it to be. You’re assuming that you’d start with one huge solid billet and machine out the channels. It would be far easier to start with 2000 cylindrical tubes and make strips to fill the gaps between them by rolling out some bar stock to pad out the tubes into hexagons. You lay the whole mess up piece by piece, put it in a vacuum chamber and heat it up to diffusion-bond it all together. When you take it out, THEN you have one piece (Holy solid billet, Batman!).
Perhaps you can start by filling, sealing and leak-testing the tubes before the diffusion bonding step. If keeping everything subcritical is a major issue, build and fuse the reactor core in two halves to prevent even the possibility of a criticality accident.
The world would be a much better place if Ed Lyman, Harvey Wasserman and all of the people paying them to lie to the public simply dropped dead.
Would one of the newish 3D printing/sintering processes be applicable?
I seriously doubt it. They have major issues with porosity, which is what you’d expect from a form built up from millions of droplets instead of being cast, forged or rolled to fully consolidate it.
Sintering is one of the ways that cheap bearings are made; they have enough porosity to impregnate them with grease. This is not the sort of material you use for confining fission gases.
Thank you. I did not know that stuff.
You might find this interesting:
Question: could you make such a thing using a casting process, by first creating solid cylinders of a material with a higher melting point than your metal (maybe a ceramic?), and an outer cylinder to contain the whole thing, then physically securing the ceramic cylinders at their ends, then pouring molten metal into the empty space around the small cylinders, and inside the big cylinder. Then, once the metal cools, pull the ceramic cylinders out, leaving channels?
Ed Lyman pessimistic about something nuclear?? You don’t say, Rod!!
I really don’t understand why this guy gets so much attention. Shouting very loud for very long and being negative about everything nuclear doesn’t make you an expert. It makes you anti-nuclear and not to be trusted as expert. Even a cursory investigation into this guy’s history will quickly reveal him to just be anti-nuclear. The N-word triggers a negative default writing mode in this guy.
Waste problem? Well let’s have a 100,000 year triple redundant repository in the middle of nowhere. “no that will never work”.
Safety problem? Ok let’s have reactors with passive backup cooling so they will work without power. “no that will never work”. Gravity after all is quite unreliable, and it’s not like hot water kettles ever work.
Fuel meltdown problem? Well why don’t we have molten salt reactors or high melting TRISO fuel to avoid that. You guessed it, “no that will never work” and for “reasons X Y Z that we’ve just made up”.
New simpler nuclear reactors that are safer and cheaper to build? “no that’s just cutting corners by the evil evil nuclear industry!!!”. And “it won’t work either”.
The Union of Concerned Scientists should be concerned about their bias overwhelming rationale. If you don’t want people working on solutions then perhaps you have to wonder if you worry so much about supposed “problems”, Ed.
Nuclear Safety Project? Well I’m glad that’s there. After all, nuclear power is the safest power source we have, safer than coal, oil, gas, and even wind and solar. And just last year alone, a grand total of zero people died from commercial nuclear power operations in North-America! Outrageous. I’m very glad that money and effort are being spent on a Nuclear Safety Project.
A Bed Pillows Safety Project would save a lot more lives. Lots of people die from suffucating in pillows. It’s an outrage that we don’t go out in the street with big signs calling for the death of the evil pillow industry. It’d make sleeping uncomfortable, but at least it will save lives. But people like Lyman aren’t interested in saving lives, or even safety in general… they just want to self-confirm and self-perpetrate their ideologies. They’ve decided that nuclear power is evil, and any and all effort, half-truth, and even straigth down lies are justified to stop it’s advance anywhere at any time.
It’s not possible to reason with these people.
What diameter are the holes? Pretty high aspect ratios are possible with good accuracy using EDM laser drilling.
I suspect there might be issues with voids in a billet so large, and one leak would risk the whole piece. This is why I think building up from tubes and filler pieces would be the way to go; you could examine and test every channel beforehand.
You’re missing the point about how materials behave under accumulated damage from Neutron fluence
How far away are combat outposts from forward operating bases on average?
With horizontal drilling borrowed from the fracking shale gas industry, could you drill and underground sabotage proof power line from the nuclear powered FOB to the combat outpost?
“I think he overlooked the part where the evaluators gently told the designers that their beautifully-optimized, computer-designed model cannot be manufactured.”
I love it! I’ve been destroying evinci on any site that discusses it and allows comments.
Such an obviously bad design. Oh the state of our experts at LANL. These products are simply a MCNP training program for the new crop of post-docs at LANL.
I’ve always questioned the choice here with MegaPower/eVinci of the proposed gun-drilled monolith core structure because a fasces of clad fuel/moderator rods and heat pipes, banded together with compression rings or sleeve with interstitial bonding (NaK) is an intuitively more robust design for accommodating anisotropic expansion from peaking, and swelling, deformation, cracking from burnup. Plus, you could disassemble it if it was as I say. I’d like to say LANL knows what they are doing, but does anybody actually know what they are doing in this age where prototypes are rarely built? Megapower/evinci is a MCNP and thermodynamic training course for a new crop of LANL postdocs. It’s the national lab equivalent of OJT.
I found it sort of amusing that you did a better job being the critic than the critics. I guess spending years reading this stuff has given you a keen insight in what they are going to say or write before they even do it.
Here is an aside comment. You noted the old problem of a design looking good on paper but may not be buildable. This seems to be somewhat common problem. Should it be a prerequisite for design firms to have design personnel spend time in the “field?” Unfortunately, I guess the “field” may not fully exist for some of these products.
” Should it be a prerequisite for design firms to have design personnel spend time in the “field?” ”
Not only a prerequisite it should be a requirement and part of the bid proposal. As a NPP startup manager my group started reviewing all designs before the concrete was poured. Amazing some of the problems that a trivial walk through would uncover/find. For example control system cabinets so close to the wall or other obstructions that the doors would not fully open preventing removal of some of the larger components and in some cases so close that even with the doors removed it was still physically impossible. No overhead pad-eyes to lift equipment during required maintenance.
Problem I still have with the next generation is that every few years from the start of commercial Nuclear Power till I retired another type of corrosion was discovered requiring changes in plant water chemistry and/or sealing/welding methods. Chemicals and products were discovered that had to be banned from the plant. Many changes needed to prevent stress induced cracking/corrosion. Heat-up/cool-down methods had to be adjusted to limit stress, and methods changed on the sealing of tubes in tube sheets. And thinking of the problems of sealing tubes in tube sheets, how are some of the methods above for making very small “tubes” going to work? Some of the methods we experimented with 40 years ago seem very similar and did not work. What kind of stress induced cracking/corrosion is a salt coolant going to cause? Are they looking at this?
Thanks for this thorough rebuttal of Mr Lyman.
Well researched and accurate.
Hi Rod, I’m interested if you have or will watch HBO’s “Chernobyl” and provide commentary? Thank you
Tom Hewitt — There is a new book by Plokhy just now reviewed in the Moscow Times. In my opinion the book is likely to be more accurate than the HBO documentary.
Thank you David. I will check it out.
@Tom Hewett: Here are links to Michael Shellenberger’s reviews:
The reason they fictionalize nuclear disasters like Chernobyl is because they kill so few people.
Top UCLA doctor denounces depiction of radiation in HBO’s Chernobyl as wrong and dangerous.
…but good intentions and factual analysis aside, correcting this disaster is going to be a bit of an uphill slog. I wish Rod and his colleagues the very best with it.
Those two articles were exactly what I needed to read. Thank you Ed.
(posting here because I have no idea what e-mail to use these days.)
Rod, this is the study I’d heard of but not seen until just days ago:
It has supposedly been “corrected” by this later study:
I note that the “correction” is (a) congruent with the LNT hypothesis (more or less) and (b) that it is behind a paywall, so nobody unwilling to pay for access can dig into the details. This, IMO, makes it immediately suspicious. Who paid for this follow-up study? Could this be ANOTHER smoking gun?
Engineer-Poet, I followed your second link and was able to read the entire paper. I have no institutional access privileges.
The paper is mildly supportive of radiation hormesis.
You’re talking about the overview paper. It’s this paper which supposedly corrects the first Taiwan study:
It’s behind a $30 paywall.
The BNC Discussion Forum
is now available for registering.
The sections are Energy and also Climate Change. The organization is topical while moderation is post facto.
Commenters here on Atomic Insights are particularly encouraged to also join the discussion on the BNC Discussion Forum.
You can get
“Estimates of Relative Risks for Cancers in a Population after Prolonged Low-Dose-Rate Radiation Exposure: A Follow-up Assessment from 1983 to 2005”
And yes, LNT is pretty dubious to put that mildly.
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