recycling nuclear waste

[dragon]

kind of niffty if it works

America alone produces about 2,000 metric tons of nuclear waste annually and our best solution for disposing of it: bury it deep in the Earth. However, a pair of MIT scientists believe they've found not only a better way of eliminating nuclear waste but recycling the deadly detritus into enough clean electricity to power the entire world until 2083. Win, meet win.

The conventional nuclear power method involves inserting radioactive rods into a reactor core where their fissionable material is converted into energy. Problem is, it's not particularly efficient. Over the four years or so that a rod will remain in use, only about three percent of its available nuclear material is expended, leaving 97 percent as "waste." And since nobody seems particularly willing to just fling it into the Sun, this waste must be disposed of in a nuclear repository site like Yucca Mountain, Nevada. Over the past forty years or so, the US has generated 67,500 metric tons of the stuff—enough to cover a football field with spent fuel rods to a depth of seven yards. But what if there were a way to recycle the waste and recapture the remaining energy? There is.

Molten salt reactors are nuclear reactors which use a molten fluoride salt mixture as the primary coolant. These salts have proven to be far superior heat sinks than the helium used in light-water reactors, which greatly reduces the need for supplementary cooling. The nuclear fuel (uranium tetrafluoride) can also be dissolved directly into the coolant as well. When the fluid is inserted into a graphite core, the mix goes critical and drives a turbine to generate electricity. Unlike conventional light-water reactors, an MSR operates at very high temperatures to achieve thermodynamic efficiency but remain at atmospheric pressure to reduce mechanical stress on the system.

The Future of Nuclear Power Runs on the Waste of Our Nuclear PastThe US military has been experimenting with MSRs since the mid '50s, producing both the Aircraft Reactor Experiment in 1954 and the Molten-Salt Reactor Experiment (MSRE) of 1965 conducted at Oak Ridge National Labs. The MSRE produced 7.4 MWth from epithermal thorium molten salts at 650 degrees C—enough to easily power a closed-cycle gas turbine while minimizing the amount of nuclear waste remaining. However, since MSR systems tend to take up more floor space than light-water reactors, the military opted for the latter when installing nuclear power in its subs and ships.

Designed by Transatomic co-founders and former MIT researchers Leslie Dewan and Mark Massie, the Waste Annihilating Molten Salt Reactor (WAMSR) updates the technology utilized in the original Oak Ridge experiment. However, the new system is fuel-agnostic and can run on either the uranium or thorium leftovers from light-water reactors. According to Transatomic's website, their MSR is incredibly efficient—capable of utilizing as much as 98 percent of the remaining fuel's energy (though even a rate of just 50 percent would be a huge improvement)—since fuel suspended in a liquid medium can remain in a reactor for far longer than as a rod, allowing more of the fuel to be used. What's more, reusing this waste as a fuel source would reduce their radioactive lifetimes from hundreds of thousands of years to just hundreds.

The Future of Nuclear Power Runs on the Waste of Our Nuclear PastThe Tansatomic system is also reputedly very user friendly thanks to a pair of idiot-proof safety features. The design of the MSR itself avoids many potential issues by keeping the pressure of the reaction low, this allows the fuel mixture to expand as it heats and self-regulate the fission reaction. If the system gets too hot, the mix will expand far enough to fall below criticality and automatically stop the nuclear reaction. The system also features a freeze-plug, an actively-cooled barrier that leads to a fortified, underground storage vault for the fuel mix. If there's a major power interruption, the active-cooling maintaining the barrier stops, the barrier melts, and the molten salt mix drains into the vault for safe storage until systems can be restored.

The company claims that each reactor will be capable of generating 500 megawatts of power at a price of $1.5 billion apiece. That may sound like a lot but realize Westinghouse's new AP1000 light-water reactor only produces double that output and costs a cool $7 billion. What's more, these reactors are expected to be small enough to be constructed at a factory and shipped whole to the installation site where they can start chewing through the $7.1 trillion worth of untapped electricity sitting in our nuclear stockpiles.

link

[Borgholio]

I remember reading in Popular Science awhile back about using fast-neutron reactors (liquid metal cooled) to burn nearly all of the material that is generally wasted by traditional water-cooled reactors. Using that method, we could use our own nuclear waste as fuel and not have to mine any fresh uranium for 300 years or so. Only downside is that liquid metal reactors make people nervous due to the fact that if the coolant comes into contact with water, it explodes quite easily.

[Guardsman Bass]

There was a TED presentation where they talked about it, here. Skip the first 6-7 minutes, since it's the person introducing them talks forever.

[Irbis]

Don't worry, we will pick better choice* than this radioactive crap. Humanity as a species proved long ago it's far above things like common sense.

* including but not limited to toxic solar panels, river-killing hydroenergy, bird-killing and space-taking wind plants, greenhouse gases producing oil and coal burners. Think of Chernobyl! And tsunamis!

[Sky Captain]

Environmentalists really should support development of this type of reactor. They usually oppose nuclear energy because of long lived waste it create. Even if every reactor in the world is shut down right now the already produced spent fuel would remain and would have to be dealt with one way or other. Using it up as future reactor fuel and in the process destroying the hazardous long lived isotopes really sounds the best possible option. The spent fuel is already there sitting at reactor sites. There is no need to destroy the ladscape to mine it like we happily do when mining coal. Reactors running on spent fuel from previous generation nuclear plants would really well go together with whole Reduce Reuse Recycle thing environmentalists like to talk so much.

[PeZook]

I remember reading in Popular Science awhile back about using fast-neutron reactors (liquid metal cooled) to burn nearly all of the material that is generally wasted by traditional water-cooled reactors. Using that method, we could use our own nuclear waste as fuel and not have to mine any fresh uranium for 300 years or so. Only downside is that liquid metal reactors make people nervous due to the fact that if the coolant comes into contact with water, it explodes quite easily.

Well, for what it's worth, Russians used liquid lead cooled reactors on SUBMARINES (the Alfas) for thirty years without a single accident. Well, IIRC once a pierside steam generator has failed, resulting in the coolant solidifying in the pipes - the reactor has to be replaced, but that was that.

[Sea Skimmer]

The Alfa class had constant coolant leaks and were impossible to refuel. None lasted over 12 years in service, except a single boat that had the reactor replaced with a pressurized water type. Liquid metal coolant is a terrible idea. We don't need it either, a fast neutron breeder reactor that uses water is possible, its just nobody has gotten very far designing one. Nor is anyone very fond of designing a reactor, because it will only work with at least part of the fuel being highly enriched uranium, and it would produce huge amounts of plutonium. In effect its only acceptable for a nuclear weapon state, and even then its not exactly desirable.

[His Divine Shadow]

Is that really that much of a danger to be realistic? To begin with only the western world is likely to use such designs and the plutonium will be used as fuel instead of for weapons and it'd be safely guarded. Even if some 2nd rate terrorist nation tried, isn't it likely to be very difficult for them to get hold of plutonium or even build the reactors to make their own. And aren't plutonium based bombs very difficult to build, beyond the technological reach of most of the people we would prefer not to have them.

[Irbis]

We don't need it either, a fast neutron breeder reactor that uses water is possible, its just nobody has gotten very far designing one. Nor is anyone very fond of designing a reactor, because it will only work with at least part of the fuel being highly enriched uranium, and it would produce huge amounts of plutonium. In effect its only acceptable for a nuclear weapon state, and even then its not exactly desirable.

Nuclear weapon state? Let's see, which states have safe access to such materials already - Canada, Japan, USA, China, Russia, UK, France, Germany, India, Italy, Israel.

Isn't the 11 above states wast majority of population and/or industry on Earth and solving energy problems just in these would basically solve it for planet as a whole?