In a series of diaries a while back, I discussed the Indian Fast Breeder Reactor program. I indicated at that time that the Indian commercial nuclear program, which is innovative, technically sophisticated and world class, recognizes the importance of the plutonium key to unlocking its huge thorium reserves.
India is building a fast spectrum nuclear reactor - and already operates a fair sized fast spectrum reactor - that are designed to recover 100% of the energy content of its uranium by transmuting into plutonium and fissioning it.
Multiply recycled plutonium is in my view, superior to "once through" plutonium for a variety of reasons, only one of which involves the very high nuclear weapons anti-proliferation value.
The paper from the primary scientific literature I will be discussing today, "Plutonium and the Indian atomic energy programme," comes from the Journal of Nuclear Materials Volume 385, Issue 1, 15 March 2009, Pages 142-147. The author is the Indian nuclear scientist Baldev Raj.
Known exploitable thorium reserves in India are about 360,000 tons - and actual reserves are probably considerably higher - which is enough to fuel every man woman and child on the entire planet for all energy needs including transport - even at the obscene consumption levels now practiced worldwide - for about 60 years. It is enough to fuel India's current energy consumption, about 19 exajoules, for about 1,600 years.
India also has some uranium reserves, but they are less significant. Therefore India intends to recover 100% of the energy value of this uranium; US reactors recover only a few percent before arbitrarily declaring the used fuel to be "waste."
Implicit in recovering 100% of the energy are two things: 1) Multiple fuel recycles of the plutonium into which uranium is transmuted in all nuclear reactors and 2) having reactors that operate on the "fast" spectrum, in which neutrons have speeds much higher than average gas molecules at ordinary temperatures. (In a gas, the average speed (m/s) of a molecule is equal to the square root of the quantity 3kT/m where k is Boltzmann's constant, T is the temperature using the Kelvin scale, and m is the mass of an atom in kg.)
I have described the fast reactors operating and under construction in India already in the diary series linked above. Now at the risk of having to hear from members of the anti-nuke faith - a religious cult that is, in a Pat Robertson kind of way, quite willing to declare itself morally superior to everyone else because (and not "in spite of") of their contempt for scientific knowledge - I will discuss briefly the chemical reprocessing implications of the multiple cycles of plutonium planned in India.
Except for India, no one in the world is planning multiple plutonium recycling schemes, although France, Japan, and Russia already operate plants that carry out single plutonium recycles.
Countries who then burn this singly recycled plutonium include not only the nations that perform the recycling but Belgium, Germany, - although the nuclear infrastructure of Germany is about to be destroyed by the actions of paid off dangerous fossil fuel executives - and Switzerland and a few others, if memory serves me well.
Singly recycled or "once through" plutonium differs from weapons grade plutonium and multiply cycled plutonium - which also differ from each other - in several important ways.
Weapons grade plutonium is generally prepared in reactors that have low burn-ups; they do not get much of the energy value of the plutonium recovered during operations. The reason for this is that for weaponized plutonium, one seeks to have a relatively pure isotopic mixture, typically better than 95% Pu-239, and as little Pu-240 as is possible. In a nuclear reactor, the relative ratio of Pu-240/239 is controlled effectively by the time the fuel spends in the reactor. The less time that the fuel is in the reactor, the lower this ratio will be. (This is one reason why it is expensive and wasteful - besides immoral - to make nuclear weapons.)
On the other hand, for commercial nuclear power purposes, it is desirable to have the fuel in the reactor for as long as possible to increase the "burn-up" of the nuclear fuel. "Burn-up" corresponds to fuel efficiency in the dumb little car CULTure. The higher the burn-up, the lower the fuel costs, and the less down time (for refueling) is required to run the reactor. Plutonium which is obtained from commercial nuclear reactors generally has about 20% Pu-240, because the companies operating them want to have them run flat-out for as long as possible for economic reasons.
Plutonium-240 causes problems with nuclear weapons because it spontaneously emits neutrons. These extra neutrons can cause a nuclear weapon to fizzle, as is widely reported the first North Korean nuclear weapons test did.
Although Plutonium-240 does have some physics implications in commercial reactors (as does Pu-239 because of different properties with delayed neutrons) it is quite readily used these days commercially, giving an extra "kick" for the energy value, requiring therefore, much less mining and lower volume and mass of used fuel components.
For sensible people, as opposed to people participating in naked cult rituals who are heavily involved in soothsaying about nirvana in a distant future, this is a good thing, especially if you believe, as I do, that it is essential to phase out dangerous fossil fuels now, as opposed to some rapturous future.
This type of plutonium "once through" is what is recovered by the French, Russian and Japanese plants.
(The Japanese, as I noted elsewhere, never actually isolate pure plutonium.)
The process that all of these nations use is the Purex process, a solvent extraction process which is, in my view, somewhat primitive, but which still works well enough.
I covered other types of fuel cycles about two and a half years ago. I personally believe the world should move past PUREX, but that's just my opinion.
Multiply recycled plutonium contains even more plutonium-240, less plutonium-239 - in the high 50 percent range - as well as significant portions of plutonium-241 - a very valuable isotope - and its daughter americium-241 - as well as plutonium-242. Ideally it will also contain - for non-proliferation reasons - significant Pu-238 that can be obtained by incorporating neptunium into the fuel before use. It also contains quantities of the element curium, and - depending on conditions - even some californium. The curium fraction in particular is very radioactive, and generates significant heat.
In turn, this has some implications for reprocessing the fuel, which is why the Indians have looked into modifying the traditional Purex process. The Purex process depends on the use of an extracting agent, tributyl phosphate dissolved in the dangerous fossil fuel product kerosene. (The kerosene can be recycled.)
With this background, I can now discuss the paper cited above, the abstract of which is here.
From the introduction:
Plutonium has a key role to play in the development of atomic
energy in India which is based on a three stage programme tailored
to suit the available resources...
...Pressurised heavy water reactors (PHWR) form the first phase of the program in which 17 reactors have been installed with a capacity of 4120 MWe and this program is already in the commercial phase. Fast breeder reactors (FBR) form the second stage. By enabling the production of 233U, needed for the thorium based reactors of the third stage, FBRs serve as the vital link between the first and the third stages of Indian nuclear energy road map. Use of plutonium-based fuels in FBRs and breeding plutonium using a closed fuel cycle concept are inevitable for India because of the very limited sources of uranium. Fast breeder test reactor (FBTR) at Kalpakkam uses plutonium rich mixed carbide fuels and the 500 MWe prototype fast breeder reactor (PFBR) under construction will use uranium–plutonium mixed oxide fuels...
The fuel efficiency/burn-up for most nuclear power plants in the West is typically - exclusive of CANDU type reactors - around 40 GWd/ton. A "Gwd" is a gigawatt-day, one billion joules per second multiplied by 86,400 seconds, or 86 trillion joules. For their plutonium generating reactors, India has realized a burn-up almost 4 times as high as the typical fuel efficiency of normal commercial nuclear reactors.
Uranium–plutonium mixed carbides containing 70% (Mark-I) and 55% (Mark-II) PuC along with 5–20% mixed sesqui-carbides are being used as the fuels in FBTR. Mark-I fuel pins have reached a burn-up of 155 GWd/t without any failure.
That's impressive. They have some nice photographs of fuel pellets before and after irradiation in the paper.
And now for the part I was talking about:
The carbide fuel pins discharged from FBTR that have been irradiated up to 25, 50 and 100 GWd/t have been successfully reprocessed in the pilot plant CORAL (compact reprocessing facility for advanced fuels in lead cells) for the first time in the world. The flow sheet for carbide fuel reprocessing has been developed based on the ongoing, comprehensive Research and Development programme...
...PUREX process, using tri-n-butyl phosphate (TBP) as the extractant is being used for reprocessing the carbide fuels. TBP has been used successfully as the extractant for the processing of spent thermal reactor fuels worldwide because of its excellent extraction behaviour for U(VI). However, it has limitations for fast reactor fuel reprocessing due to third phase formation in the extraction of tetravalent metal ions [3], aqueous solubility, chemical and radiation degradation, etc. Systematic studies for the development of alternate extractants which do not have the limitations of TBP but at the same time retain its advantages have been carried out...
The Indians have developed several new extractants that seem superior to TBP, as well as a series of new oxidants (which remove electrons from atoms) and reductants (which add electrons) for the process. Separations of uranium and plutonium from fission products is controlled by a series of such oxidations and reductions. Dihexyloctanamide is one extractant that they discovered which seems to be quite promising.
They are already using U-233 obtained from thorium in their test fast breeder reactor:
Compared to mixed oxide fuel, carbide fuel gives higher fuel breeding ratio (BR). For a 500 MWe reactor, a more optimized design than that of PFBR could result in a BR of 1.09 and a simple fuel doubling time of 40 years. With carbide fuel, the BR can be improved to 1.19 and doubling time reduced to 20 years. Quantum increase in BR is achieved with metallic fuels. U–Pu–Zr fuels with varying Zr content have been studied...
U-Pu-Zr fuels were an American invention as part of the foolishly cancelled IFR program, which was canceled more than a decade ago.
India has aggressive nuclear power targets. I figure 4 of the paper, the project - should humanity survive climate change - the program calls for somewhere between 180 and 200 GWe of nuclear power installed in the next 40 years, all of it running on a closed nuclear fuel cycle. For comparison purposes, the current nuclear generating capacity of the United States is about 100 GWe.
Nuclear power plants are the most reliable energy producing machines in the world, typically operating near 90% of capacity utilization. (The only thing which comes close is dangerous coal powered plants, which typically operate at 72% of capacity utilization in the United States.)
If India installs 180 GWe they will be producing about 5 exajoules of pure electricity from nuclear power per year. For comparison purposes, the United States now generates about 15 exajoules of pure electrical energy per year from all sources, including hydroelectric, dangerous coal, dangerous natural gas, dangerous petroleum, nuclear and the weeny solar and wind facilities combined.
US electrical generation, including YTD.
(The units in this table are thousand megawatt-hours and not exajoules; I have converted the units for my text above.)
Current Indian electrical generation from all sources, mostly dangerous coal, is now about 2.4 exajoules.