Draft Essay: Toward a Thorium Economy
Some related links to subjects brought up here focusing on thorium:
Energy from Thorium Discussion forum This is the everything you wanted to know about Thorium generation but was afraid to ask site.
The Nuclear Green Revolution discussions on thorium and 'alternative energy' debunking.
Description of the Liquid Fluoride Thorium Reactor
Wiki Entry Thorium fuel cycle
Wiki Entry on Dimethyl ether
http://my.barackobama.com/...
This essay (Diary, Blog, etc.) is pro-nuclear energy. It will not deal with the bigger issues of political-economy, sociology, class society, revolution, climate change, etc. It will be a "technological" essay on what it will take, in very small part, to move the planet toward a physical-economy based on the generation of massive amounts of electricity and heat from the element, thorium. I have strong opinions on the above issues. But my method here is one of "material outlook" on the Thorium Economy, how to get there, what it is, why it's necessary.
Thorium is an element about 3 to 4 times more abundant than Uranium. It's chemical symbol is "Th" (and used hereafter for the element). It's atomic weight is 90 (Uranium is 92 by comparison). We really don't know how much there is in usable concentrated forms as there is no prospecting for it anymore.
Th is "fertile". This means it is not "fissionable" like some isotopes of Uranium but it can, when exposed to neutrons, decay into something that is fissionable, and therefore of practical energy use in a reactor: Uranium 233. In this regard, it's similar, in some respects, to Uranium 238 which is also fertile, but not fissionable. The latter decays into plutonium 239, also a very good fuel for reactors, but also used in weapons of mass destruction.
The Thorium Economy is a vision. It is not on the immediate agenda. But it is something I believe will be a reality in this century, but many decades away. We can start now, though, to build toward it. Such a Thorium Economy envisions basically a limitless amount of usable energy, in the form of electricity and process heat (the kind of energy you might find in an oil refinery, chemical plant, aluminum smelter, desalination plant, or district heating: that is heat generated for just the heat energy itself, not electricity). This limitless energy would be powered by thousands of Th fueled nuclear reactors, of many different sizes, designed around their end use.
The use of Th has taken on a new life of late. While a Th reactor was in fact up and running at Oakridge National Laboratory, the powers that be (The old Atomic Energy Commission) saw no interest in Th since uranium was plentiful and one could build WMD with certain types of reactors fuel by uranium. Not so with Th. Plus, the huge industrial infrastructure organized around uranium was omnipotent at that time. The "Uranium-Industrial Complex" killed Thorium as a viable alternative to uranium...until now!
With the rise in research around what are called "Generation IV" nuclear reactors, a new life was breathed into the idea of using Th, again. The Russians, Indians, Canadian and others have various projects employing Th as fuel. The one that will power the Thorium Economy is called the Liquid Fluoride Thorium Reactor of "LFTR" for short.
Not all Generation IV reactors use Th, in fact it's only recently be discussed as part of that development. Some see the use of other types of salts, such as sodium, instead of Fluoride, and some see the use of Fluoride but using uranium fuel instead of Th. The salt is what is used in it's liquid state to suspend and hold the atomic fuel. It also transport the high energy in the form of heat to a heat exhanger where it gives up its energy to a gas that is used to drive a turbine-generator set. This is why the LFTR is a very specific, albeit increasingly more popular, form of the Gen IV reactors.
When I use the term "Thorium Economy" I'm talking about a physical-economy where the overwhelming majority of energy generation...electric power, transportation fuel, mechanical power, process heat is generated by a LFTR. It will drive all economic relations in some way, in the same way the Petroleum/Fossil Ecomomy does today. Why are we going there?
The replacement of fossil fuels as a form of both electrical generation (Coal, natural gas, oil) and transportation fuel (oil derivatives) are causing problems that don't need recitation here.
First, let us talk about the advantages of the LFTR.
- I already mentioned that as a fuel, Th is at least 3 times more abundant than Uranium. The US has enough Th in the state of Idaho, to power 10,000 LFTRs at 1,000 MWs a piece (the size of a large power plant) for 100 years.
- The amount of Th used to generate one GW year (the amount of power about 1 million homes use for one year is 1 ton.) A currently advanced Light Water Reactor under construction in countries today takes about 35 tons of enriched uranium to accomplish this. This amount in Th fuel is approx. 7lbs a day. That is all. To put in more stark terms: 4 people with shovels on ONE day, between 9am and 12 noon, can dig up enough Th to power an entire city for a year. Not to shabby.
- The Th used is 'natural' in that it is only Th dug out of ground and milled to remove rocks and soil. It can then be used directly in the LFTR. Uranium, by contrast, has to be chemically enriched to bring usable levels up to a percentage that will allow a critical reaction. It is an expensive process but necessary to make uranium fuel.
- The amount of Spent Th Fuel (STF) is about equal to the one ton that went into the reactor: an amount that could fit under someone's office desk. In other words, very, very little.
- This Spent Th Fuel is shorter lived than what comes out of a currently running Light Water Reactor. Because the process of the LFTR use the fuel in a liquid, not solid, state, chemical processing of the fuel stream can take place continually, removing the nasty stuff that is considered so dangerous. At the end of a year, this one ton of STF can safely be stored on site. The length of time it takes before it ceases being dangerous is reduced from 10s of thousands of years for the waste of a LWR to only 200 to 300 years. A very manageable period of time. In fact, the amount of dangerous high level waste is about .1% of that of LWR. Not bad.
- The spent nuclear fuel (SNF) from the current fleet of LWRs is not a lot, despite what one might read from the uneducated public media or some environmental organizations. Nevertheless it is an issue. One of the advantages of the LFTR (and some other Gen IV reactors) is that they can literally use the SNF from LWRs and even depleted uranium from the enrichment process as fuel. They can be configured differently than that the LFTR we have a subject here, but they are legitimate sub-sets of the LFTR family. The ENTIRE waste inventory of SNF could be 'eaten' by these specially designed LFTRs.
- The LFTR is smaller than a LWR per MW. The reactor size itself is much smaller. The LFTR runs at atmospheric pressure, meaning everything can be smaller and less robust since we are not talking about high pressure in any part of the reactor itself. Thus the very large over-built containment domes you see surrounding a LWR doesn't need to be built as big. In fact, current discussions involves putting the LFTR underground (or even under water!) to further reduce its above ground profile, provide security and lower engineering costs. Lastly, because the hot molten salt goes through a heat exchanger at high temperatures, current designs envisions using an inert gas, like helium or nitrogen as the heat-transfer fluid, and running it through a high-efficiency closed-cycle "Brayton" cycle gas turbine. These too can be built smaller since they have a much better thermal efficiency that currently used steam turbines.
- Water usage for once through cooling of the turbine can be less because the Brayton cycle gas turbines don't need a large a temperature drop as steam driven "Rankine" cycle turbines.
While it's impossible to really come up with a "price", overall we expect the LFTR to cost half as much or less than a LWR.
To get to the Thorium Economy, it means an expansion of the currently existing nuclear energy infrastructure. The LWR development that is so much in the news these days cannot be put on hold. There will be a large support infrastructure, especially in engineering and operations, overlap between LFTR and LWR. There are other, more pressing reasons why we need to see an expansion of LWR generation in the more immediate setting as well, including and most importantly, the phasing out of coal fired generation over the next 25 years, a majority of which will occur because of the expansion of the existing LWR fleet.
The transition to the Thorium Economy will occur as a phase out over decades of the LWR fleet that is currently being expanded. The shift toward the LFTR can occur commercially probably around 2025. To do this the LFTR scientific community needs a lot of financial support to develop the first prototype(s). It will be an international effort, of course, as there are no real secrets to commercial nuclear technology.
The LFTR configuration will be determined by the needs of the 'customer'. This is includes everyone from large utilities needing dozens of GWs replacement for fossil plants and older LWRs to the Independent System operators needing smaller LFTRs installed at transmission and distribution substations for load balancing and emergencies to oil refineries making synthetic fuels from atmospheric CO2 to desalination plants turning out hundreds of thousands of cubic meters of potable water for cities, industries and irrigation.
There is a discussion over at Energy from Thorium about reactor size. The consensus is that even for big generation needs in one location, lots' of little LFTRs can be used instead of one big one. I dissent from this point of view. I see a real mixture, actually.
First, there will be a large 'market' for small, under 100MW reactors. I mentioned the could be sited right in transmission and/or distribution sub-stations (where operators control voltage on the system, among other tasks). The can be used as peaker units since LFTRs can have fast and rapid load changes unlike their bigger LWR cousins. These "Sub-100 LFTRs" also have a huge place in the overall Thorium Economy. 50 MWs of 'heat'...it's often written like this: "75MWt" with the little 't' meaning temperatures can be used to provide valuable process heat to an synthetic fuel refinery making Dimethyl ether. This is a carbon neutral (because you can use CO2 from the air) that is created by combing the carbon in the CO2 and hydrogen. Both compounds can be garnered using energy and heat from a LFTR. Costs are estimated at $2/gallon. Such a "refinery" would run completely on the LFTR energy, providing most of the heat for these processes and some to power the electrical needs of the complex.
These smaller LFTRs, because component size is can be so small can be assembled whole in factories, along the lines of large aircraft manufacturing and automotive assembly, perhaps even in the same factories of the rapidly shrinking aerospace and automobile manufacturing capacity in the United States.
But there will also be needs to vast amounts of centralized electrical generation. LFTRs can power the largest of generators out there: the Alstrom 1800 MW water-cooled generator (60hz). In theory, one can have a LFTR that can produce easily 10GWt for at least 3600MWe. You could put 2 generators on either side of a massive Brayton cycle turbine and run both generators off the one turbine and one reactor. The waste heat, if located on an ocean, can be used in a flash-distillation desalination device to create millions of gallons of water a day. Large clusters of safely built large power LFTRs could use the ocean for cooling and transmit vast amounts of power via HVDC into a "smart-transmission" grid.
Additionally, many of the new technologies currently under development can be applied most easily to a Thorium Economy. Consider Molten Salt Storage. This technology is being developed for the Concentrated Solar Thermal industry where vast tracts of land focus thousands of mirrors on a single spot. This heats up an oil, hot salt or even water to created steam to run a conventional turbine. Some or all of this thermal energy can be diverted to "molten salt storage" and used later after the sun goes down to provide dispatchable MWs into the grid. No one has done this on an industrial scale yet, but if it should come about, the direct thermal heat from a LFTR would be an even more ideal application of this technology. LFTRs cold 'over produce' heat during the day, store the excess in molten salt assemblies, then use it to power the same turbine at night after peak or during peaking times.
The Thorium Economy would see all transportation powered by a combination of electric vehicles for individuals and small company vehicles and dimethyl ether as a diesel substitute for larger transport. Dimethyl ether can be used in airplanes as well since it's essentially jet fuel. Methonanol (as opposed ot the food-consuming ethanol), anther carbon-neutral fuel, can also be synthesized with the process heat of a LFTR.
All of this powered by various forms of LFTRs producing electrical energy, transportation fuel from processed heat.
Ultimately, small LFTRs can be used to power a large condominium complex or office building if tying into to grid is too expensive.
With variable load LFTRs of different sizes; peaking LFTRs that can be turned off and on depending on load, distributed LFTRs of small, <10MWe size, all balancing the area load, the entire worlds economy could be run via Th as a fuel.</p>
Many in the "alternative" energy scene like to use terms like "decentralized" "distributive generation" "diversified". There is nothing particularly valid about any of these terms if they are not valid forms of energy production to begin with. If they don't provide the solutions to humanity's energy needs (such as phasing out coal), they are simply 'feel good' concepts with little practical application. However, the LFTR can provide any combination of generation size and product, especially as regards electrical needs. If the Thorium Economy is indeed the wave of the future; if it is, indeed, a "Thorium Bullet", then we should be turning toward Th as THE energy answer to the worlds energy issues.