Containment

[BoSoxGal]

A documentary from Independent Lens on PBS, focuses on the problem of nuclear energy/weapons waste, and discusses the problem of labeling our waste repositories in a manner that still communicates clearly to humans 28,000 years into the future. Also talks about the ongoing problem called Fukushima.

Not an edge of the seat thing, but an interesting and thoughtful exploration of important issues. A fair bit unnerving at times.

[Jarlaxle]

The fix for waste is the WAMSR: it is a passively-safe reactor, that is FUELED by waste, and consumes it.

[BoSoxGal]

Does nothing whatsoever to address the present nuclear waste problem, which is fairly huge and will stick around the next 300k years.

[Econoline]

Actually, a WAMSR-type reactor would help with current nuclear waste by (1) using it as fuel and thus reducing the quantity of that waste by a couple of orders of magnitude, and (2) by using the fission of this recycled waste to turn the heavier radioactive waste into lighter elements that would remain radioactive for a much shorter timespan—something on the order of 300 years, rather than 300,000 years.


ETA: as for facilities like Fukushima and Chernobyl where there has been a core meltdown and a containment failure...yeah, not much can be done there because there is simply no way of safely handling that sort of spilled radioactive material, which is not sub-critical waste but rather still highly radioactive, dangerous, uncontained fissile material. Another argument for building a different, safer type of reactor.

[BoSoxGal]

I must have totally misunderstood the few articles I just read about how WAMSR reactors work - I do understand that they are a closed system recycling waste, but I don't understand them to be capable of utilizing spent fuel rods from light water reactors, or the waste leftover from weapons production. I'd love to read any resource you can share that would explain it to me.

I'm surprised that the very good documentary I just linked to doesn't offer WAMSR reactors as a solution to our nuclear waste disposal problem. That was a huge oversight.

[Jarlaxle]

It is a new (2-3 years) concept, designed by a group from MIT. The full name is a Waste Annihilating Molten Salt reactor.

[BoSoxGal]

Right, I read several articles. My understanding is that it's a closed system which doesn't produce waste like light water reactors. I didn't read anything, however, which indicated WAMSR can be used to process old waste. We've already got tons and tons of that to deal with, with 300k years until it's degraded to a point it's not harmful to life.

If I've missed something in the analysis, I'd love a source that explains it.

[Econoline]

Here ya go, BSG:

• Nuclear Plant Powered by Spent Fuel
  Reactors could use existing stockpiles of nuclear waste to produce electricity for the world through 2083.
  
  An old nuclear technology is getting another look, and it could mean clean, emission-free electricity, while at the same solving the problem of nuclear waste. It's called a molten salt reactor, and it's an idea that dates to the late 1950s. A start-up called Transatomic Power, based in Cambridge, Mass., is working on a newer version that uses nuclear waste as fuel. Transatomic's founders are Russ Wilcox, formerly the CEO of E-Ink, and Leslie Dewan and Mark Massie, two MIT students.
  
  The reactor still makes waste, but what comes out is radioactive for only 300 years, as opposed to millennia. Transatomic calls it a Waste Annihilating Molten Salt Reactor, or WAMSR.
  
  "It's stuff that is in the middle of the periodic table," said Dewan, Transatomic's chief science officer. "It's a lot easier to isolate."
  
  A big selling point of this design is that it would help deal with the nuclear waste problem. The Nuclear Energy Institute says there are some 67,000 metric tons of uranium from fuel in the United States alone. It can also be built smaller at lower costs out of modular parts.
  
  The WAMSR can do this because unlike current reactors, it doesn't need to use enriched uranium as fuel, and the fuel itself doubles as a coolant. No need to build this near a water source like an ocean or river that can ultimately flood and cause damage.
  
  But first a bit about how nuclear plants work: In commercial nuclear reactors, a core houses fuel rods that contain uranium oxide pellets. The radioactivity from the uranium produces heat. To make electricity, water is piped into the core and turned into steam, which is then used to drive generators. This is called the "light water" design.
  
  To produce enough heat for the steam, the uranium needs to be highly radioactive. That requires purified or enriched uranium. For a power plant that means that up to about 20 percent of it has to be U-235, an isotope that makes up less than 1 percent of the naturally occurring uranium. (Most of the time the enrichment percentage is lower, on the order of five percent -- the higher levels are used in research reactors and naval vessels).
  
  As the fuel is "burned," the uranium decays into other elements, including plutonium, zirconium, cesium, xenon and iodine. Eventually, enough other elements mix in with the uranium that the nuclear reactions slow down, reducing the efficiency of boiling the water. The fuel is then called "subcritical," or spent, and is put into a waste storage facility.
  
  That's where the WAMSR comes in. Spent fuel from other reactors is dissolved in fluorine to make a molten "salt," a chemical whose elements are bound together by their positive and negative charges. The molten salt is pumped out of the core and into a heat exchanger, where the water is boiled to drive a turbine. Since the heat energy is being transferred to the water, the fuel cools down.
  
  This type of reactor was first proposed as a way of powering a bomber; in the 1960s and 70s there was one operated at the Oak Ridge National Laboratory. But the nuclear industry had settled on the light water reactors, and that became the industry standard.
  
  Because the molten salt behaves like a liquid, it's easier to get it into a shape that allows for self-sustaining reactions, Dewan said. The shape matters because to make sure that neutrons and nuclei hit others (and sustain the fission) it's necessary to reduce the surface area of the fuel as much as possible. A sphere is the perfect shape, but a cylinder works as well. The fission reactions in the molten salt "burn" more of the uranium in it, so eventually much more turns into other elements that don't stay radioactive for so long.
  
  The radioactivity dies down more quickly, too, so it's easier to build containment facilities. Designing a structure to last a few centuries has been done (think of the average cathedral). But to build one that will last ten or a hundred times as long is much harder; let alone figuring out how to warn future people of the danger when it isn't likely anyone will speak English -- or even remember that English existed.
  
  The fuel is also safer. When accidents have happened in power plants, such as at Fukushima in Japan, it was because the cooling systems failed. At Fukushima the generators that powered the water pumps were flooded by a tsunami. The heat built up in the reactor core until there was a meltdown. The result was a release of hydrogen, which exploded.
  
  The WAMSR's core is "plugged" with a chunk of solid material that is actively cooled. If that cooling fails, then the plug melts and the molten salt drains out into a pool Once outside of the reactor vessel it will simply cool off and eventually solidify – and since it isn't in the right shape anymore, the fission reactions won't be self-sustaining. A failure of the cooling system power would stop the reactor, rather than leading to a meltdown.
  
  With all these pluses, outside experts say there are still some problems. Transatomic isn't releasing the details of its design, though Dewan and Massie outlined the basics in a TEDx talk on Nov. 1. She said some of these issues have been addressed.
  
  First is the process of taking the fuel out of the reactor vessel, and replacing it. A number of the fission products in nuclear waste are gases -- notably radioactive iodine, xenon, and cesium. "It's one thing to deal with the solids, it's another to deal with the gaseous fission products," said Jim Malone, chief nuclear fuel development officer at Lightbridge, a company that is working on a thorium reactor design. He said there has to be some method of containment.
  
  Dewan said the fuel would be processed by draining off some of it and removing the "poisons," or elements that slow the nuclear reactions down. But that requires a lot of heavy-duty chemical processing.
  
  As one of the selling points of this kind of reactor is that it would be cheaper to build, having that type of processing plant on-site might alter that calculation, said Tanju Sofu, department manager of the nuclear engineering division at Argonne National Laboratory. "You'd probably need a fuel cycle facility attached to the plant," he said.
  
  Sofu also noted that molten salt needs to be pumped around, and any moving parts have to function for a long time. Many metals when exposed to radiation -- especially the neutrons produced in a reactor -- become brittle over time. Replacing parts inside the core raises the same containment problems that processing the fuel does.
  
  Metallurgy and materials science have come a long way since 1959, and Dewan says there is a lot of experience in industry with pumping molten fluoride salts and doing maintenance on complex systems Perhaps the biggest issue will be getting the nuclear fuel itself. Technically, nuclear waste is all property of the Department of Energy, said Mike Mayfield, director of the division of advanced reactors and rulemaking at the Nuclear Regulatory Commission. So there would need to be some discussion of how the fuel is getting processed and working out an agreement to get it.
  
  Even with those obstacles, the WAMSR is still a worthwhile innovation, Sofu said. "In the 1990s the DoE did a study of next generation designs," he said. "The molten salt reactor was one of the four or five most promising concepts. It has a lot of advantages in fuel cycle consideration and resource utilization."
  

[Econoline]

Oh, and here's the TED Talk referred to in the above article:

[BoSoxGal]

So, why aren't we building a bunch of these already?! Seems like they are a wonderful solution to both waste disposal and energy needs problems??

[Lord Jim]

Wow, that's some way cool stuff Econo...

X2

That article doesn't say, but given what's involved, (being able to use nuclear waste as fuel, no additional cooling requirements, etc.) it would seem this process would also be a lot cheaper than existing reactors...

So let's see...

Cheaper, safer, cleaner, and it helps clean up an already existing environmental problem to boot...

No, I'm sorry, this just makes way too much sense to ever happen...

[Econoline]

Well, there are still some engineering and construction problems to be solved before large-scale deployment of these reactors is practical. But these problems are solvable and people are working on solving them. A molten-salt reactor was built and run for 4½ years in the late 1960s at Oak Ridge National Laboratory, so we know that the basic idea works. (And given the current political climate I wouldn't be a bit surprised if China beats the US in the development and deployment of this technology.)

[Bicycle Bill]

So, why aren't we building a bunch of these already?! Seems like they are a wonderful solution to both waste disposal and energy needs problems??

Simple answer: NIMBYs. The same reason we don't have massive wind farms generating electricity without the use of fossil fuels; the same reason we had the recent standoff over the Keystone pipeline across South Dakota; the same reason we have not invested massive resources in other alternate sources of energy such as solar, geo-thermal, or even hydro-electric power (seriously, Las Vegas would not, could not exist as it does today if is wasn't for the electrical power generated by Hoover Dam, or the fresh-water reservoir of Lake Mead behind it).  It's even the reason there are still areas without high-speed internet or dependable cellular phone service.  All because a group of people say, "Sorry, I don't want my view spoiled by wind turbines or solar panels or a cell tower or a power line too close to my house."

Now include the term 'nuclear' around the average person and they immediately envision mushroom clouds, the wastelands that were Hiroshima and Nagasaki, the containment zone around Chernobyl, and the dystopian post-apocalyptic world of "Mad Max" or "The Day After", and once again we're back to the knee-jerk "Not In My Back Yard" response.

-"BB"-

[oldr_n_wsr]

If it has "nuclear" in it's name (or even a hint of it) it is a non-starter.

Much easier to clear cut 300 acres of trees to put in solar panels.
yes, there is that discussion going on for propery near the defunked shoreham nuke plant here on LI

[Econoline]

If it has "nuclear" in it's name (or even a hint of it) it is a non-starter.

Sadly, I think you've hit the nail on the head. (Which is why I mentioned the possibility of China getting there first with this technology. Or maybe somebody will eventually finally succeed at controlled nuclear fusion? Now that would be a real game-changer--one which even the anti-nuke protesters might go along with.)

Much easier to clear cut 300 acres of trees to put in solar panels.
yes, there is that discussion going on for propery near the defunked shoreham nuke plant here on LI

Now that's ridiculous.

[oldr_n_wsr]

Now that's ridiculous.

But true.

Brookhaven lab clear cut some 200 acres (IIRC) for their solar farm.

[Jarlaxle]

Sadly...the NIMBY and BANANA Chicken Littles have stopped nuclear power.