“Reprocessing LWR waste” is very complex (most people think of PUREX reprocessing), and very controversial, and only reduces the waste a few percent. Geologic storage is very complex, with the concern we can’t store anything for 100,000 years and know it is going to remain safely stored.
When you realize there are many different types of nuclear reactors, not just the Light Water Reactor we’ve been using, you can see other approaches for dealing with LWR waste. There are far simpler methods.
Separating uranium from the nuclear waste is a simple chemical process, fluoride volatility, one already used in enriching light water reactor fuel. After shredding the fuel rods and dissolving them in acid, fluorination makes uranium a gas (molten UF4 becomes gaseous UF6) easily separated from molten waste.
Similarly, we can remove plutonium from LWR waste; melt it, and separate it with known chemical processes. (No, that would not be weapons grade, containing far too many other plutonium isotopes to be used successfully in a weapon. It “would tend to pre-detonate”, killing the terrorists.) Plutonium in any MSR would be fissioned, no need to store it.
Those two steps reduce the waste from Light Water Reactors to almost entirely fission products, a few percent of the original waste.
Virtually all of the fission products have half-lives so short they are safe in under 10 years (83%); 2 require 350 years (17%). We know how to store each of these elements for 350 years. No geological storage (million years) is needed.
(There are some long-term fission products created, but neutron bombardment has them decay to short-term radioactive elements. That happens inside the reactor, where there are always neutrons bombarding the fuel.)
The small remaining amounts of isotopes found in LWR waste with longer half-lives aren’t very radioactive, a function of long half-lives. These can a) be separated and bombarded with neutrons (either in an MSR or a special neutron source) so they are transmuted to elements that have very short half-lives, or b) are fissile, e.g. plutonium, and should be left in an MSR as fuel since they will eventually fission.
Uranium is not highly radioactive. There are small amounts of uranium in most of the earth’s crust and all the oceans. (It is useful in nuclear reactors because it is fissile, not because it is very radioactive.) By itself, it is easy to store safely. For example, this is how we’re storing depleted uranium (lower in U235 than natural uranium): “Depleted uranium can be disposed of as low-level radioactive waste if it is converted to chemically stable uranium oxide compounds, such as triuranium octoxide (U3O8) or uranium dioxide (UO2), which are similar to the chemical form of natural uranium.” and “[these oxides] are generally suitable for near-surface disposal as low-level radioactive waste. Uranium exists in the oxide form in nature, but at significantly diluted concentrations. The specific radioactivity (radioactivity per mass of uranium oxide) of the depleted uranium oxides is less than natural uranium because of the reduction of U234, U235, and the majority of daughter products which are removed during the enrichment process. The majority of these daughter products return to natural levels over the course of several million years.” http://www.nrc.gov/materials/fuel-cycle-fac/ur-deconversion/faq-depleted-ur-decon.html
Instead of storing (geologic time frames), use the uranium in a Molten Salt Reactor (thermal-spectrum MSR can use low-enriched uranium, or fast-spectrum MSR can use un-enriched or depleted uranium) or in some other types of reactor. Eliminate the uranium by fission.
People in the LFTR community are developing the specifications and regulations for storing the fission products (what elements in what amounts would best be stored in which storage method). Some can be stored in glass (vitrification), or something else to keep them in place, and then placed in a metal container. Some will chemically bind with something, to keep them in place in storage. Keeping the fission products each separated, or only with the few fission products that store well, in the same way, makes the storage much simpler. Again, most of the fission products have half-lives under 1 year, so we would need to store them less than 10 years.
Stopping the radiation is a simple “matter”. “Alpha rays could be stopped by thin sheets of paper or aluminium, whereas beta rays could penetrate several millimetres of aluminium.” [http://en.wikipedia.org/wiki/Beta_decay] Gamma rays are very high energy photons (light), stopped by a few meters of packed dirt, or concrete, or more dense materials like lead or depleted uranium.
The big concern about radiation in nuclear waste is that it might move over time, not that we can’t stop the radiation where it is today. But we don’t have to store the isotopes with short half-lives for long time periods, and these are the highly radioactive isotopes, and we don’t have to store them with long half-life isotopes. We clearly can store these safely for much longer than needed.
All the “no solution for the nuclear waste problem” conversation is by people who don’t know there are other types of nuclear reactor than the Light Water Reactor we’ve been using.
Why aren’t we using Molten Salt Reactors or other types of reactors the Atomic Energy Commission and nuclear physicists and nuclear engineers recommended since the early 1960s? The fossil fuel companies convinced US Congress to pick LWR, the one type of nuclear reactor safe enough to use yet expensive enough to never destroy the fossil fuel industry; and Congress likes living in those nice cozy lobbyist pockets.
I am pro-Thorium LFTR and regard it as very important energy technology for the World. However, we need to be realistic about some issues:
(a) waste materials from a Thorium LFTR are radiologically very “hot” when initially removed from the Thorium LFTR reactor, and need to be stored carefully until their radionucleotides have decayed (hard Gamma-ray emitters);
(b) much is said about the Thorium LFTR being unable to generate Plutonium for munitions – this is true – however, a terrorist could theoretically produce a very dangerous dirty bomb by using material imemdiately extracted from a Thorium LFTR in combination with conventional explosives.
Althoug Thorium LFTR’s are potentially a great improvement upon contemporary PWR, they are not without danger which should be taken properly into account.
A most promising aspect of Thorium LFTR is that it is potentially configurable to burn up, and render harmless in a relatively short timescale, dangerous contemporary nuclear waste for which disposal strategies have not yet really been developed.
I trust above helps to provide a realistic perspective regarding Thorium LFTR.
However, taking all factors into account, it is vital technology that, in the longer term, needs to be developed.
We’d actually not use a thorium-fueled reactor (Th becomes fissile U-233 in the reactor) to use up LWR or weapons fuel. We’d use a fast-spectrum molten salt reactor for U238 (not fissile) and any molten salt reactor for U-235 or Pu-239 (fissile). A LFTR would work, but if you want to feed him LWR waste you wouldn’t double-feed him with Th too.
In view of what is now happening at Fukushima Dai’ichi (namely triple meltdown though containment vessel via lava tubes towards water table, with radioactive waste now leaking into the Pacific Ocean and slowly killing all life there – witness problems now along the California coast, including background radiation 16 times above normal background level), it is unlikely that human beings could manage to operate lots of spatially distributed LFTR’s safely. On studying latest LFTR designs, plus copious literature from CNRS, ORNL, patent documents and similar, Thorium LFTR’s are not the answer. Beware of eloquent LFTR salesmen who try to convince people that LFTR will solve all energy problems; the continuous processing of fuel in a LFTR will generate large quantities of problematic waste, and representsa general safety hazard, as the waste has to be processed when it is radiologically hard. Of course, the eloquent LFTR’s salesmen conveniently forget to mention this.
Fukushima isn’t going to “slowly kill all life there”, not even the immediately surrounding few kilometers of ocean. TEPCO should have diverted ground water around the reactor buildings, during construction. They still can and should. But Fukushima isn’t going to have enough radioactive material carried out to sea for that much damage.
(We are killing much life in the oceans, though. All the world’s chemical pollution is much worse than what nuclear power has done, and would be worse still if we weren’t using nuclear power. CO2 entering the oceans forms carbonic acid, which is currently about 0.1 PH from dissolving plankton and other microscopic shells; there is already enough CO2 in the air to make enough carbonic acid to make most species of plankton extinct. We have only a few decades to fix this, and we can’t generate enough power to fix it except with efficient nuclear power.)
We should monitor all power plants for safe construction (nuclear, coal, oil, natural gas, wind, tidal, solar, etc.) USA has higher standards for operating coal and oil plants than most of the world; even if we include Fukushima as if it were an accident here, nuclear power has caused fewer deaths and less pollution, per gigawatt-year electricity (or comparable energy, since oil is used mainly for transportation) than any other power source we have.
Of course the fission products have to be collected and stored while they are at their peak radioactivity.
We know how to do that. We did that in the 1960s, much of the work of the Molten Salt Reactor Experiment was showing the materials, tools, equipment and procedures worked for removing fission products.
Now, we have vastly improved methods, including robotic capabilities, and monitoring and instrumentation. Of course we can do that today. We handle more complex engineering projects every week.
“generate large quantities of problematic waste, and representsa general safety hazard” — compared to what? The coal industry? 1000kg fuel (becomes 1000kg fission products) for 1 giga-watt-year electricity in MSR. A fraction of one coal train car, per year.
While getting uranium from coal ash piles isn’t practical, there is enough in an average ash pile to produce more energy, in a molten salt reactor, than was made by burning the coal.
The waste from a molten salt reactor, from mining and construction through dismantling, is far lower than any other power we have, including solar (high tech manufacturing) and wind (concrete, metal, rare earth magnets, long distance power lines).
Much of the waste from MSR, after 10 years radioactive decay, is useful for many industries. We know how to separate it, store it, verify it is stored properly, and ship each chemical when it is safe for another industry to use.
Maybe we should use the coal ash ponds for storing containers of fission products, since the coal could block alpha, beta and gamma radiation? It’s already a toxic chemical site…
hello George, nice article, even 5 years later, I’m no scientist just a fan of the tech. My interest in the tech is to reuse all of the spent fuel rods from LWRs in a total cost of generating power at less than 9cent / Kwh. This cost would include EVERYTHING, cost of the plant, storage of waste, manpower (jobs are good), EVERYTHING. Everybody is hopping on the solar band wagon but what is the total cost INCLUDING production and storage of battery waste as well as solar panel waste / Kwh. Do you know of any simple charts that compare the TOTAL cost of wind/solar/nuclear(reuse of spent rods only)/coal/natural gas — this chart includes the ENVIRONMENTAL impact of the tech and the COST of this impact. I’ve talked with PA state representatives but I need to keep it fairly simple for them and for me.
[George’s reply — Some MSR designs can use spent fuel from LWR, see especially Fast Spectrum Molten Salt Reactor Options (fast spectrum MSR can fission U238 directly, with the inherent safety of all Molten Salt Reactors; thermal spectrum MSR can convert U238 to Pu239 inside the reactor, and fission that). Hargraves in “Thorium: Energy Cheaper Than Coal” (2012) covers how to calculate the total cost of energy systems; of course you would have to put in the new costs of solar photovoltaic equipment. The main thing to remember to include in total cost of a solar system is the financial and environmental costs of energy storage for the longest time of bad weather in that location; that time would be several weeks even for “sunny Phoenix” or months for places with a long overcast winter. Alternatively, you have to include the financial and environmental costs of a natural gas plant to provide backup for the solar plant. Molten Salt Reactors should generate the amount of power needed to meet demand, a higher percentage of the time than even coal plants do.]
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