Using the waste heat from a liquid-fluoride thorium reactor to desalinate seawater is something that I’ve been thinking about for a long time. It seems like a perfect opportunity since the reactor needs to reject waste heat in order to produce electricity, and that waste heat will be available in large amounts.
But first of all, why does a reactor produce waste heat? That seems rather…wasteful, doesn’t it? This was one of those principles that took a bit of thinking and studying for me to understand. If thermodynamicists lived on a perfect planet, it would be at absolute zero (about 273 degrees Celsius below zero). It wouldn’t be too fun for the rest of us, but the thermodynamicists would really enjoy it, because all heat could be turned completely to work. Engines could be 100% efficient and there wouldn’t be any waste heat.
But fortunately for the rest of us we don’t live on a planet at absolute zero, so thermodynamicists have to content themselves with engines that are less than 100% efficient and have to reject waste heat. How much waste heat you have to reject depends on how hot you can generate heat in the first place.
Fire can heat water to 100 degrees Celsius (373 Kelvin) before it starts to boil. But if you keep the water under higher pressures it will be hotter when it boils, and you will be able to get work out of the high-pressure steam produced from the hot water. If you let the high-pressure steam expand back to atmospheric pressure, you can get some work out of the steam, like the old steam locomotives of the 1800s. But if you let the steam expand to pressures even below atmospheric pressure you can get even more work out of the steam. The downside of doing this is that you have to condense the steam back to water with outside water at normal pressure. The old locomotives just blew it out the cylinder.
Well, in super-simple terms, that’s what’s going on in nuclear plants and coal plants all over the world. Water is pumped up to high pressure and boiled, and then the steam is expanded to subatmospheric pressures in a big steam turbine and condensed using cooling water, and the process starts all over again. It’s fairly efficient—much more so than the steam locomotive—and let’s you turn about 1/3rd of the heat into electricity. The other 2/3rds of the heat has to be “dumped” into your cooling water.
So maybe all this waste heat can be used for desalination, right? Considering that a 1000 megawatt nuclear power plant has to produce about 3000 megawatts of heat and dump 2000 megawatts of that heat to the cooling water, it would stand to reason that something could be done with all that waste heat, right?
Well, as it turns out, not really. The reason why has to do with the fact that in our pursuit of maximum efficiency, we made the temperature in the steam condenser just about as low as we could get away will. In fact, the pressure in the steam condenser of a typical nuclear power plant is only about 5% of atmospheric pressure. Inside the condenser at 5% atmospheric pressure, steam will condense at a temperature of only 32C (91F). But all of the cooling water flowing over those condensation tubes isn’t going to boil at that temperature. No, it’s going to need something a lot hotter to get it to boil. Hence, no desalination from waste heat.
(to be continued…)
Barack Obama campaigned on a promise to end work on a high-level nuclear waste repository at Yucca Mountain, Nevada. Now, as president, he has followed through on that promise and directed the Department of Energy (DOE) to halt work on Yucca Mountain. This means that all of the spent nuclear fuel generated at each of the 60 different sites around the United States legally must remain onsite indefinitely. Because utilities have paid a tax to the government to take possession of spent nuclear fuel, this also means that the federal government has become legally liable for the costs of storing that spent fuel, either in a pool or in dry casks.
In an article written for Technology Review in December 2004, Matthew Wald argues that sometimes procrastination, especially when it applies to spent nuclear fuel, might be a good thing. The reason procrastination might benefit it has to do with the decay of radioactive isotopes in the spent fuel—the longer we wait, the less radioactivity and heat is emitted by the spent fuel, and the “tighter” you can fit it in an eventual repository. Time also could mean improvements in reactor design and fuel reprocessing. Future reactors might make far less waste, and future reprocessing systems might be more economically attractive than the approaches considered today.
But there is the issue of federal liability. Right now, even if it’s in a dry cask, spent fuel legally can’t be moved off of the reactor site. This is where Wald argues for a change in federal policy—essentially a revisiting of the Nuclear Waste Policy Act of 1982, which mandated Yucca Mountain as the only site that could be considered and the only federally-approved approach to spent nuclear fuel management. Wald argues that the federal government must take possession of spent nuclear fuel and should emplace it on a single site. This site would be little more than concrete slab on a secure facility with dry casks free-standing. They would quietly decay and their heat load would go down and down, making future reprocessing of the spent fuel even easier. A single site would be far easier to protect than scores of sites, some of which have now been completely decommissioned except for the spent fuel storage. But to do this would require political initiative and a willing site. The Skull Valley Band of the Goshute Indians in Utah attempted to do such a thing several years ago but was swiftly defeated by the Utah State Legislature. Perhaps another site would be more willing, especially if hosting dry casks of spent nuclear fuel meant economic advantage to the region.
What we’re doing now is not good for utilities or the government.
A lot of the folks that attended the first Thorium Energy Alliance Conference were people that had made their interest in thorium known previously–either through blogs or presentations or so forth. But we did have a few total “newbies” at TEAC1, and one of them was Dr. Mitch Jacoby, senior editor of Chemical and Engineering News. Mitch not only has a Ph.D in physical chemistry but is a reporter, and at TEAC1 he took the big group picture of all of us and started working on a story, which thanks to his diligence and in-depth reporting is available to all of us now:
John Wheeler and I had a chance to talk to Mitch before lunch on the first day of TEAC and Mitch’s enthusiasm was infectious. “How come everyone doesn’t know about this!” he would ask, and John and I would smile and say something like “well, we’re trying to fix that…”
Odds are, Mitch’s article could do more to remedy that problem in a few days than our efforts do in months…
The Department of Energy has an Office of Nuclear Energy (DOE-NE). They have five overall strategic goals:
1. Extend life, improve performance, and sustain health and safety of the current fleet of nuclear power plants
2. Enable new plant builds and improve the affordability of nuclear energy
3. Enable the transition away from fossil fuels in the transportation and industrial sectors
4. Enable sustainable fuel cycles
5. Assure that proliferation risk is not an impediment to nuclear power deployment
The liquid-fluoride thorium reactor, in concert with other molten-salt reactors like the chloride fast reactor, can achieve all of these goals.
The chloride fast reactor can improve the performance and extend the life of existing nuclear power plants (light-water reactors) by providing a sink for their long-lived transuranic waste (plutonium, americium, curium) that would otherwise have to be disposed geologically in a place like Yucca Mountain. Chloride fast reactors can take this “waste” and destroy it through fission, utilizing the neutrons released during fission to produce uranium-233, which in turn will help achieve goals 4 and 5.
For a similar reason, the chloride fast reactor can enable new plant builds by removing the “waste disposal” roadblock from the argument that is so effectively employed by anti-nuclear groups opposed to realization of clean nuclear energy.
The LFTR, and perhaps even the chloride reactor, can achieve goal #3 through the high-temperature nature of their operation. Unlike light-water reactors that have rather low operating temperatures, the fluoride fuel of the LFTR is stable at high temperatures, which enables it to be used to crack hydrogen from water, refine petroleum, crack oil shales or oil sands, and many other high-temperature applications. Previously, if DOE-NE wanted high-temp applications, it had to use gas-cooled reactors which are notoriously bad for reprocessing and closing a fuel cycle, or it could use sodium-cooled fast reactors, which don’t have the high temperatures to achieve these goals. With LFTR you can have both and better: a better fuel cycle, easier to process, easier to close, and the high-temperature applications that we want to achieve. Getting to high-temperatures is the key to using nuclear energy to replace fossil fueled energy in the transportation and industrial sectors.
Goal #4 is a sustainable fuel cycle. By utilizing thorium, a resource three times more abundant than uranium, by being able to fully utilize thorium, and by having a reprocessing system so simple that it is not only co-located with the reactor but likely located inside the primary containment, LFTR can achieve this coal. By using chloride reactors to destroy existing nuclear “waste” we can generate the uranium-233 needed to jump-start this exciting and sustainable future–powered by thorium via the liquid-fluoride thorium reactor.
Goal #5–that of reducing proliferation concerns, can also be achieved through this approach. LFTR can be used to productively consume highly-enriched uranium (HEU), converting it (effectively) to uranium-233 in its blanket. Rather than downblending the HEU and burning it once, LFTR can burn up the HEU and convert it to U-233, which thereafter will fuel the reactor essentially forever through the power of thorium. Chloride reactors can also be used to completely destroy–not merely degrade–both weapons-grade and reactor-grade plutonium. Thorium is worthless in nuclear weapons and no nation or program has ever chosen U-233 as a weapons material because it is inevitably contaminated with the strong gamma emitter U-232, which is impossible to separate. There are thousands of nuclear weapons in the world and none of them use U-233. Furthermore, U-233 in fluid form can be immediately “denatured” by mixing it with abundant U-238 in just a few moments, preventing it from being used even by a suicidal terrorist group. Plutonium can’t be denatured.
In conclusion, by choosing molten-salt reactor technology as the central focus of their nuclear development efforts, the DOE-NE can achieve all of their strategic goals far more quickly and effectively than any other approach. I urge them to turn their attention to this technology and push it forward vigorously.
Yesterday my wife sent me off to the local cotton gin to get some really good rich dirt for her garden beds. Fortunately my neighbor had just the appropriate pickup truck and the right disposition on a Saturday morning for such a job. So we headed off, stopped for gas and some Diet Cokes, and found our way to the cotton gin a few miles from my house.
I had never been to a real cotton gin before, but I had been especially curious for several weeks because we took our daughters to a nearby farm that hosts “agrotourists” each fall and we saw cotton fields as far as the eye could see. I took my daughters up to the edge of the field and explained to them how to pick cotton. If we had lived a century ago, my two oldest daughters (ages 7 and 5) would probably each have already spent one or more years in the backbreaking job of picking cotton by hand. But thanks to modern machinery, such picking is now done by machines with a fraction of the labor.
Cotton is a wonderful substance–it feels like a bit of fluffy white perfection in your hand. But rub it a little and you can feel the cottonseeds in there, and if you attempt to “gin” the cotton by hand you quickly find out just how difficult it is to extract the seeds. Who knows how many man-hours have been spent over the centuries picking out cottonseeds by hand?
So getting to see a real gin in action was a treat. Huge bales of cotton arrive and are fed into the gin on a large, slow-moving conveyor belt. Then the cotton is separated from the seeds and the seeds were literally falling like rain out of this huge machine (about the size of my garage) into a feed system that conveyed them elsewhere. I’m not sure exactly what all they do with the seeds, but eventually the seed hulls ended up in a huge pile in the back of the gin, and that’s what I was there for.
The gin composted the cottonseed hulls, and given enough time they would decompose into a very dark, rich, porous dirt that is like black gold for gardens and flowerbeds. We followed a front-loader behind the gin and while we sat in the air-conditioned truck and in a period of about two minutes, the fellow who drove the front-loader dumped two scoops of cotton dirt into the back of the pickup. I went to the office and paid $10 for these two scoops, and then for the cost of about a gallon of gas, that remarkable machine called a truck did all the work of conveying us and our load of cotton dirt the 5 or 6 miles back to my house while we drank our Diet Cokes.
I love technology. I love that machines can gin cotton and scoop dirt and drive us from here to there. Despite the fact that I had a lot of manual labor ahead of me that day, the vast majority of the work had already been done by the gin, the front-loader, and the truck. Then it was just me and my neighbor and some shovels and my wheelbarrow to finish out the job.
You see, those cotton-seed hulls were “waste” from the ginning process. The gin had more of them than they knew what to do with. Sure, they charged me $10 for the dirt, but they had lots of it and I wouldn’t be surprised if they wouldn’t have given it to me for free. The cotton-seed hulls weren’t very useful when you first had them, but stack them in a big pile and give them some time, and nature can turn them into something quite useful.
In a similar vein, I began thinking of the misnamed mixture we call “nuclear waste”. Does nature “compost” nuclear waste for us?
Anti-nukes love to say “NO!” to that idea. They will tell you that nuclear waste is an evil poison that is nature’s revenge for our wickedness for splitting the atom, and that it is toxic and dangerous forever and nothing will break it down.
But the more I research the subject, the more I am coming to another conclusion–nature does “compost” the results of fission, through the very natural process of nuclear decay.
Ever wonder what becomes of uranium after it fissions? I’ve wondered, so I went and found out. Here’s what it turns into, roughly in order of mass:
Xenon, zirconium, neodymium, molybdenum, cerium, cesium, ruthenium, barium, lanthanum, praseodymium, and a dozen or so other elements.
Now here’s what I found to be pretty neat–even though these elements are typically “born” from fission in an unstable and highly-radioactive state, they are decaying quickly towards a stable state, and most of them get there more quickly than you might think.
Take the first one on the list: xenon. There’s a number of radioactive xenon isotopes, including that little booger xenon-135, but the longest-lived among the radioactive isotopes of xenon is xenon-133 with a 5-day half-life. Taking the rule-of-thumb that “ten half-lives and you’re gone” by about 50 days after you pull the fission products out of the reactor, all the xenon would be stable and you could sell it. Is xenon easily to get out? Out of a fluid-fueled reactor like LFTR it’s a piece of cake–it comes right out of solution. Is xenon valuable? Yes! In fact at NASA we say that xenon’s one of the few things that costs about as much to launch into space ($10K/lb) as it is worth. So stable xenon gas could be a valuable byproduct of fission.
What’s next? Neodymium is pretty common from fission (#3 on our list). Neodymium’s longest lived radioactive isotope (147) only has a half-life of 10.9 days, so after 110 days (to be conservative) our neodymium could be extracted and sold. What do we use neodymium for? Hey, do you have any of those little earbud headphones? Ever wonder why they’re so small compared to those clunky headphones we had when we were kids? The answer is small, high-strength neodymium magnets. The wind industry needs lightweight neodymium magnets for their huge generators they put up on those absurdly tall towers. There’s neodymium in my children’s magnet toys. Neodymium is valuable.
Let’s talk about some more–molybdenum, whose longest-lived isotope (99) could be extracted through fluorination to MoF6 and used in medical procedures that would save lives (Tc-99m). Mo-99 has a half-live of 2.8 days, so in a month the molybdenum would have “composted” to readiness.
Barium: Ba-140 is the longest at 12.7 days. Give it 4 months and the barium is “composted”.
Lanthanum: La-140 at 1.7 days. Three weeks to “compost” lanthanum.
Praseodymium: Pr-143 at 13.5 days needs 4 months to “compost”.
Cerium: Ce-144 at 9.5 months takes about 7-8 years to “compost”.
Ruthenium: Ru-106 at 1 yr takes a decade to “compost”.
Then some of the longer-lived stuff is still useful even in its radioactive state. Cesium-137 is quite radioactive and has a half-life of 30 years. But we could use Cs-137 to sterilize medical instruments, destroy pathogens in sewage, or preserve easily-spoiled fruits and vegetables. Cs-137 could be more useful radioactive than stable!
So think about the results of fission like the folks at the gin think about the cottonseed hulls. Give them time and space and after a little while, there will be a lot of things in there that people will really want.
Dr. Barry Brook has read the fine print and followed the references in Jacobson and Delucchi’s upcoming article in Scientific American (you know, that thing that editors are supposed to do?) and found such a stunning lie that our nuclear blogosphere is still reeling that anyone could possibly think that they could get away with telling it:
So what’s “The Ugly”? Well, it’s something utterly egregious and deceptive. In the Sci Amer article, the following objection is raised in order to dismiss the fission of uranium or thorium as clean energy:
Nuclear power results in up to 25 times more carbon emissions than wind energy, when reactor construction and uranium refining and transport are considered.
Hold on. How could this be? I’ve shown here that the “reactor construction” argument is utterly fallacious – wind has a building material footprint over 10 times larger than that of nuclear, on energy parity basis. Further, Peter Lang has shown that wind, once operating, offsets 20 times LESS carbon per unit energy than nuclear power, when a standard natural gas backup for wind is properly considered. I’ve also explained in this post that the emissions stemming from mining, milling, transport and refining of nuclear fuel is vastly overblown, and is of course irrelevant for fast spectrum and molten salt thorium reactors. So…?
Well, you have to look to the technical version of the paper to trace the source of the claim. It comes from Jacobson 2009, where he posited that nuclear power means nuclear proliferation, nuclear proliferation leads to nuclear weapons, and this chain of events lead to nuclear war, so they calculate (?!) the carbon footprint of a nuclear war! (integrating a probability of 0 — 1 over a 30 year period). I quote:
4d. Effects of nuclear energy on nuclear war and terrorism damage
Because the production of nuclear weapons material is occurring only in countries that have developed civilian nuclear energy programs, the risk of a limited nuclear exchange between countries or the detonation of a nuclear device by terrorists has increased due to the dissemination of nuclear energy facilities worldwide. As such, it is a valid exercise to estimate the potential number of immediate deaths and carbon emissions due to the burning of buildings and infrastructure associated with the proliferation of nuclear energy facilities and the resulting proliferation of nuclear weapons. The number of deaths and carbon emissions, though, must be multiplied by a probability range of an exchange or explosion occurring to estimate the overall risk of nuclear energy proliferation. Although concern at the time of an explosion will be the deaths and not carbon emissions, policy makers today must weigh all the potential future risks of mortality and carbon emissions when comparing energy sources.
Really, need I say more? Can it really be that such wildly conjectural nonsense is acceptable as a valid scientific argument in the sustainable energy peer-reviewed literature? It seems so, which suggests to me that this academic discipline needs a swift logical kick up its intellectual rear end.
Wow. Jacobson and Delucchi make the absolutely unsupported-by-historial-evidence claim that developing nuclear power leads to nuclear weapons, and that nuclear weapons lead to nuclear way (actually they stop war from happening) and that in a nuclear exchange lots of CO2 will be emitted, so we’ll chalk that up to nuclear power to make it look bad.
Scientific American should recall their publication and expunge this trash from their magazine if they ever hope to be held in high regard again. I know that I just lost any interest in published in their magazine.
A number of months ago my friend Ray Beach at NASA’s Glenn Research Center invited me to come and talk to a meeting of their local INCOSE (International Council on Systems Engineering) group in Cleveland, Ohio. So I got in the car and drove 640 miles last Sunday to be there Monday morning at the Ohio Aerospace Institute where I would give my presentation.
The keynote speaker that day was Dr. Harrison Schmitt. Dr. Schmitt is a member of one of the most elite groups of all humanity: he is one of only twelve men to walk on the surface of the Moon. Dr. Schmitt, back when he was a young man of 37, flew on the Apollo 17 mission to the Taurus-Littrow valley near the Sea of Serenity on the Moon. Dr. Schmitt was the only professionally trained geologist to walk on the Moon, and his mission had a remarkable scientific return because of his presence.
Dr. Schmitt was there talking about how we could go to the Moon and mine it for a rare helium isotope implanted in the lunar surface by the solar wind: helium-3. Helium-3 has some special characteristics in advanced fusion reactors that make it more attractive to some than the standard deuterium-tritium fusion approach pursued. Dr. Schmitt and I had the same goal: clean and abundant energy for humanity.
When it was my turn to speak, I used essentially the same slides I employed in my recent talk at Google, but with some verbal expansion on particular points. Afterward, Dr. Schmitt came up to me in the hallway and asked if I might be interested in giving the presentation at the University of Wisconsin, where he is a professor. I responded enthusiastically in the affirmative.
I do not know whether my arguments for thorium and the liquid-fluoride reactor changed any minds of those present at the meeting, but it was a profound honor to meet a man who has made such an incredible journey. It has never happened in my lifetime and I don’t think it ever will.
On several occasions over the last ten years I’ve had the pleasure of visiting the United Launch Alliance (ULA) rocket construction facility in Decatur, Alabama. This marvelous factory was first built by Boeing exclusively to build the Delta 4 family of rockets, but as time progressed, it later included the construction of Delta 2 rockets and now Atlas 5 rockets as well.
This factory LITERALLY takes in sheets of stock aluminum-6061 at one end of the factory and at the other end a finished Delta 4 rocket emerges. The steps in between were the subject of our tour.
First the sheet aluminum is milled by huge milling machines built by Cincinnati Milacron to create an “isogrid” pattern in the aluminum sheet. This process removes most of the material that was originally present in order to lighten the aluminum sheet while still preserving its strength. For the reason, the Decatur factory produces a vast amount of aluminum to be recycled–in fact, most of the aluminum that enters the facility will end up as aluminum chips.
Then the milled isogrid aluminum panels are bent on a huge machine into an arc 72 degrees in extent. The arced panels are rotated to a vertical position and five of them are positioned in a friction-stir welding machine that “zips” them together through the magic of friction-stir welding into a cylindrical barrel. Each core stage of the Delta 4 rocket has a liquid oxygen tank and a liquid hydrogen tank. The oxygen tank uses one barrel section, the hydrogen tank uses two. A different welding process joins two barrels (for the hydrogen tank) and then adds the single-piece caps to the tanks.
The LOX tank is pressure-tested using water (fairly safe) but the hydrogen tank is pressure-tested using compressed gas (not so safe). This is because water weighs about the same as LOX, but liquid hydrogen weighs so little that there isn’t a fluid that’s a good match, so they simply use gas. Pressure-testing the hydrogen tank is done in a chamber designed to contain the “explosion” if the tank fails. It’s pretty beefy–would make a good tornado shelter.
Then the tanks have spray-on foam applied, cured, and trimmed to create a smooth surface. In the final part of the factory, the LOX tank and hydrogen tank are joined by a composite intertank structure, then another composite thrust structure is added at the aft end of the hydrogen tank and the RS-68 engine is installed. The composite interstage structure is added at the top of the LOX tank if the core is the central or only core in the stack, or if the core is one of the two outerboard cores on the Delta 4 Heavy rocket, a composite “nose cone” structure is added.
The completed core then are sent out of the plant and down the road on a large trailer to the nearby Tennessee River, where they are loaded on a special boat called the Delta Mariner and carried down the river to the Gulf of Mexico. Then they either go around Florida to Cape Canaveral or through the Panama Canal to Vandenberg Air Force Base in California.
From stock aluminum to rocket, all in one building.
Now what does all this have to do with thorium and LFTR? Because I think the production of the Delta 4 rocket in Decatur is analogous to what we will need to do in order to build the hundreds, even thousands of liquid-fluoride reactors needed to power the world safely with thorium. It is not hard for me to envision a future factory where the raw materials for a finished LFTR arrive at one end of the factory: Hastelloy-N, hydrogen fluoride, raw lithium salts, beryllium, purified thorium, graphite prisms, nickel-based piping, heat exchange material, turbine and compressor blades and stator, and electrical generator assemblies.
The Hastelloy would be shaped and bent and welded into the reactor vessel, drain tanks, and another fabrication operation would build the primary containment. Into the primary containment would go the drain tanks first, and then the reactor vessel. Crews would attach and weld the freeze plug system to connect the tanks. The drain tanks would also be piped to external fill and drain systems.
Then the core inlets and outlets would be welded to the reactor vessel, used to connect the reactor to the primary heat exchanger, which would be constructed in another part of the factory. Side piping that would take core and blanket fluids to the integrated reprocessing system would also be added.
In another part of the factory, the gas turbines would be coming together. On a balanced shaft in a large forging would be placed the rotors and stators of the compressor and turbines. The finished casings would have gas inlets and outlets welded to both compressors and turbines.
Finally, the reactor system and the gas turbines would be connected to one another. Gas inlets and outlets would join the reactor system (with the primary heat exchange loop and the gas heaters) to the gas turbines. The entire system would be taken from the factory down to the river or seashore and the completed unit would be lowered into the water, to be towed to the next coal plant to be converted to clean thorium en
With a factory analogous to the Delta 4 plant, I could envision a 400-MWe class LFTR rolling out the door every few weeks. With a production rate of 25 400-MWe cores per year, each factory could be producing 10 gigawatts of clean, baseload energy per year, and that would be a future worth working towards.