On the Traveling-Wave Reactor

T H E NUCLEAR NEWS INTERVIEW John Gilleland: On the traveling-wave reactor erraPower LLC has been The traveling-wave reactor, in concept, would use launched by the company In- depleted uranium to produce vast amounts of Ttellectual Ventures to design a traveling-wave nuclear reactor that energy without the need for enrichment plants and could run for 100 years without refu- reprocessing facilities, which is why billionaire eling or removing spent fuel. So con- Bill Gates is interested in developing it. vincing is the science behind the con- cept that billionaire Bill Gates has bility into an asset,” he said. gotten involved to help finance the Gilleland, who has a long history in project. applied physics, founded and served for Led by John Gilleland, TerraPow- several years as CEO of Archimedes er’s chief executive officer, a team of Technology Group, which develops so- researchers has run computer simula- lutions to nuclear weapons–waste prob- tions and is doing engineering studies lems. The company created a new tech- that have produced evidence that nology, called the Archimedes filter, to a wave of fission moving slowly separate radioactive materials from through a fuel core could generate a nonradioactive materials. He also did billion watts of electricity continu- advanced energy systems work at ously without refueling. Gilleland not- Bechtel after serving as the U.S. man- ed that these new reactors could re- aging director of ITER (originally the duce the amount of nuclear waste by International Thermonuclear Experi- using existing stockpiles of depleted mental Reactor). uranium as fuel. “By extracting cen- Gilleland, a member of the Ameri- turies’ worth of energy from waste Gilleland: “There is enough depleted and can Nuclear Society, talked about the at enrichment plants, these reactors natural uranium to last for millennia without traveling-wave reactor with NN editors would turn a social and financial lia- any reprocessing.” Rick Michal and E. Michael Blake.

How does the traveling-wave reactor work? a reasonable-sized core. We looked back at some of the work done The basic concept is to use depleted ura- by Edward Teller and Lowell Wood on the nium as a fuel and to need no more than a How did you get involved in the project? breed/ burn concept. It seemed to us that the small amount of enriched uranium to start a Lowell Wood, an internationally recog- concept had promise, but, quite honestly, it reactor. The reactor would be able to operate nized scientist-technologist, played a major looked like something that could not be for decades without refueling and without role in drawing my interest. Other major readily achieved. But we decided that if we chemical separations. In a certain sense, the players in the project are Nathan Myhrvold, ran into certain problems, we could see if way the reactor works is well known. It’s founder of Intellectual Ventures, and Bill there was a way to walk around them. That the typical breeding concept and standard Gates, the chairman and cofounder of Mi- is more or less what the effort has been physics—U-238 going to 239, to neptunium, crosoft. They looked around at the various about since then. Our mission is to try to and finally to plutonium-239—but with a energy systems and came up with this desire bring the concept far enough along by us- twist, which is the traveling wave. In a sense, to improve nuclear and expedite its respon- ing a serious physics and engineering effort the wave can be visualized as two waves—a sible deployment around the world. When I such that a major nuclear player would con- breeding wave moving just ahead of a burn- was called on in December 2006, I thought sider the concept and then embark on de- ing wave that consumes the bred material. I would come in and tell them what was veloping the traveling-wave reactor for Visualize a cylinder a few meters long wrong with their thinking. But, basically, af- commercial deployment. that contains U-238 or depleted uranium. A ter researching the project, I never left. Ter- nugget of uranium enriched to 10 percent is raPower is the first spin-off of Intellectual Why build a better mousetrap? put at one end of the cylinder and a wave 40 Ventures, and Bill Gates is the principal To provide some background, our group centimeters wide is built up that breeds and owner of TerraPower, although there are looked at renewable sources of energy to burns plutonium and produces a gigawatt of others who have a level of ownership. see if they could be counted on to provide electricity as it propagates from one end to for the needs of the United States and the the other. It would take 50 to 60 years for What convinced you that the traveling wave planet. We advocate the pursuit of renew- the wave to go from one end to the other for could work? able sources of energy, but the fact is that

30 NUCLEARNEWS September 2009 they just can’t provide the electric power that the world will need. That is why we will unfortunately end up burning even more coal, which has its well-known envi- ronmental problems, unless we use nuclear. We felt that the full deployment of nuclear could be achieved if we improved some things, namely the risk of proliferation, the economics of new reactors, the fuel supply, and the waste issue. We decided to form a group and start with a blank slate to see if we could address those things.

Have you come up with a design for the re- actor? Preliminarily, yes. We went through the physics reconfirmation of the traveling- wave concept. We looked at what the tech- nology constraints would be and investi- gated the available technologies that could take the required energy densities and sur- vive the material damage problems and so forth. After a lot of work, we came up with something that looks very much like the standard pool-type sodium-cooled reactor. That’s what the engineering firm Burns and Roe is working on for us right now.

Do you foresee government involvement in your project? Yes, but not initially. Eventually, we might pursue an industrial partnership to develop the reactor core and the infrastruc- ture needed to convert spent fuel from a light-water reactor to metal fuel for the trav- eling-wave reactor, for example. But we think that by sticking to a private initiative at this time, we can move along rapidly and be somewhat more immune to the ups and downs of government funding. TerraPower has been developing conceptual designs for small as well as large-capacity traveling-wave reactors. The company said that a combination of advances available in Could you talk about some of the research existing component technologies, such as compact intermediate heat exchangers (the light that has been done? tan vertical rectangle and the brown vertical rectangle) and electromagnetic pumps (not We took the existing Monte Carlo–based shown), has enabled it to focus its principal innovations on the design of a core (red) that neutronics modeling tools and rebuilt them. can sustain a traveling wave of fission in multiple kinds of fuel. (Graphic: W. Wayt Gibbs, That project was led by Charles Whitmer, Intellectual Ventures, and Ash Odedra, TerraPower, LLC) an astrophysicist who is also a computer genius. We now have our own tools that are neutrons to the great extent that it is sup- ally converted to plutonium? able to perform three-dimensional analy- posed to? Initially, we are trying to hold the burnup ses. We’ve checked our codes against Re- This is a fast-neutron system, and so it’s down to 20 percent, but with development bus and other codes. Lawrence Berkeley the standard reaction, and the plutonium is we may get to 30 percent and eventually to National Laboratory ran tests to compare putting out the spectrum. At the very high the order of 50 percent with improved ma- results with us, and Argonne National Lab- end, the neutrons are quite fast, and the re- terials or recladding. oratory also provided us with calibrations action is quite insensitive to the presence to check that we’re on the right track. This of the fission products. We cannot do it This leaves you with a lot of U-238. Is the all involved a couple of years of very in- with a thermal system because that would idea that eventually further input of en- tense development. be much too sensitive to the fission prod- riched uranium would convert back to plu- ucts. The multiplication that we get in the tonium? How have you used the code? fast-neutron system is high enough to al- Even if we leave 50 percent of the U-238 It allows us to watch the wave establish it- low both the breeding and burning of plu- as waste, we will have made a huge amount self in 3-D and breed and burn. We have tonium. We have to be able to sustain this more energy than is possible with an LWR tracked about 2500 daughter products. The breeding long enough to convert from a using a once-through fuel cycle. There is code is developed to the point that we can breeding phase to a burning phase. That in- enough depleted and natural uranium to last track very carefully what happens when we volves a very severe environment for the for millennia without any reprocessing. The move fuel rods around and see what would materials. It’s the reason that this idea reactor would have, at one end, a sort of ig- go on for many decades in the reactor. hasn’t been done before. niter of enriched U-235 that would start the wave. After that, the breeding and burning How does the reactor actually produce fast How much of the depleted uranium is actu- would sustain itself theoretically forever. If

September 2009 NUCLEARNEWS 31 INTERVIEW : JOHNGILLELAND we have a long enough cylinder of depleted Why are you using liquid sodium as the heat Greenspan, who is a renowned nuclear en- uranium or natural uranium, the wave will transfer medium? gineering professor at the University of breed and burn for an infinite length of time. We think liquid sodium is the best for this California at Berkeley; Pavel Hejzlar, our In other words, we don’t need to load any case, but we are looking without prejudice lead reactor designer, who ran a number of enriched uranium ever again to keep this at others. We took our engineering test de- nuclear-related projects at the Massachu- thing going. In the real world, we would sign to great depths with the sodium because setts Institute of Technology; Jacopo Buon- have the wave propagate through the core the machines have operated already with en- giorno, of MIT, who is working with Pavel for as long as we wanted—five years, 20 ergy densities in the range of 200–300 on fuel performance modeling; John Nuck- years, or 50 years or longer. Then we would megawatts per cubic meter. It turns out that olls, who was the director at Lawrence stop it and add more depleted uranium rods we need that sort of high-energy density in Livermore National Laboratory; Charles and then just start it again. We can start and order to have the right conditions for the Ahlfeld, an accomplished nuclear engineer stop this wave with control rods just as we wave propagation. We looked at bismuth who has led much of our engineering ef- would a regular reactor. For each traveling- and bismuth lead for heat transfer. For those, fort; and Kevan Weaver, from Idaho Na- wave reactor, we need this igniter only once we thought we would hold back for a while tional Laboratory, who is now directing our in the life of the reactor. After that, the en- because there are well-known corrosion technology research and development ef- riched material is never needed again. problems associated with them. We con- fort. There are others, too, who are promi- ducted an exercise to find a path that would nent and well respected in the nuclear field. If no enriched material is needed, there is involve the minimum technology develop- We have about a dozen people who have no need for enrichment facilities, is there? ment and to develop only those things that been involved in fast-reactor design, con- That’s correct. Once we have this type of are essential to the achievement of this wave struction, and operation. reactor going, we don’t need enrichment propagation and the benefits that accrue plants. All we need to get one reactor going from it. As we looked around, we found that What about organizational cooperation? is some enriched uranium, because after that the sodium-cooled system pretty much fit. Argonne is using its extensive experi- we could borrow a few rods from it to start Looking at the Phénix fast spectrum test re- ence to benchmark our efforts and conduct up and form the wave in the next reactor, and actor in France or Monju in Japan as exam- safety analyses. Ken Czerwinski is leading so on. Further, there is enough natural ura- ples, we decided that slightly larger versions an effort at the University of Nevada at Las nium and depleted uranium available that of them could accommodate one of the trav- Vegas to test irradiated materials for us. we can supply the world for thousands of eling-wave cores. The only development we We’re also talking with Idaho National years with energy without the need for re- would need, at least to start on this path to Laboratory and other institutions about processing as it’s known today. The base fission, would be the work on the core itself. supporting UNLV to do further testing of case for us is to take natural or depleted ura- those materials. Finally, Columbia Basin nium, make metal fuel out of it, and use it as What is the timeline for your project? Consulting Group is coordinating a virtual a basic fuel for the operation of this plant for If things go well, we could have our first “who’s who” of engineers who were in- some decades. You can choose your lifetime power-producing system in the 2020 time volved in the design, construction, and op- for the plant and the refueling schedule, but frame, but that is making a lot of assump- eration of the Fast Flux Test Facility and it’s your choice whether you run the plant tions. We are starting out with a different other fast reactors. for some tens of years without refueling or core configuration, but everything else— a slightly shorter or longer time. During that fuel rods, materials, and so forth—is the When all is said and done with the reactor’s whole period of time, the fuel is in the reac- same as something that has been tested be- fuel cycle, are all the minor actinides tor vessel. You fuel it, and perhaps 50 years fore in reactors, so we think the time frame burned up? later you decide to take the fuel out. But is achievable. We’re also trying, as much as No. We are looking at that issue, both you’re not continually taking fuel out and possible, to stick to the normal practices with and without recladding the fuel. It ap- putting it in wet or dry storage, so the reac- that one uses in making nuclear fuel. pears that the reactor will leave behind less tor can be deployed widely without having plutonium than would an LWR per unit of to build new enrichment facilities—a big Who are the other players in Terra Power? energy produced. boost for nonproliferation. I have mentioned Bill Gates, the financial founder and owner of TerraPower, and So, there are still fission products at the Is there a moderator approach that helps Nathan Myhrvold, the founder and CEO of end? ensure that you get the fast-neutron pro- Intellectual Ventures and the former chief Yes, the products are still in the reactor. portion that you want? technical officer of Microsoft. Bill and They are not out where people can get to We’re always fighting to keep it as hard Nathan are both highly involved in the proj- them. But by using this once-through sys- a spectrum as possible and the losses as low ect in a technical way and not just in fund- tem, we are achieving effectively about 100 as possible. But, in fact, the art form here is ing it, and so we have had some rather times more energy production from a giv- to minimize the amount of what I’ll call the interesting marathon sessions with both en mass of uranium than we can using an moderating and loss materials. of them. Other team members are David LWR. That’s the motivation. Higher burnup, McAlees, a nuclear expert who has exten- burning what right now is waste—namely Has anyone ever tried to create this wave sive experience as an executive in the nu- depleted uranium—yields this incredible in the real world? clear business world and who was cochair production. We figured out that we could No. People have, of course, done breed- of Siemens’ Nuclear Division, and one of supply every person on earth with the U.S. ing of plutonium from U-238 and studied it his former colleagues, Roger Reynolds, level of per capita energy consumption for in the real world. That is sort of our physics who was the chief technical officer of Are- 1000 years if we can make the traveling- calibration. But we take the same physics va in the United States. wave reactor go. It’s not just our opinion. and say, “OK, if we could find a way to al- On the physics side, we have a number It’s the reason lots of people from many low the cladding and the structure to take a of people who are known in the field: places are involved. I like what Charles much bigger beating from those high-ener- Charles Whitmer, who is working with Forsberg of MIT said: If this works, we will gy neutrons, or learn to live with them, what Tom Weaver and George Zimmerman, both need only “one enrichment plant per plan- could we do?” One thing we could do is Lawrence Prize winners from Lawrence et.” I would add, “Only for a while.” It’s a sustain this breeding and burning wave. Livermore National Laboratory; Ehud stunning thing to think about.

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