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Hitachi Developing Reactor That Burns Nuclear Waste
Zothecula writes The problem with nuclear waste is that it needs to be stored for many thousands of years before it's safe, which is a tricky commitment for even the most stable civilization. To make this situation a bit more manageable, Hitachi, in partnership with MIT, the University of Michigan, and the University of California, Berkeley, is working on new reactor designs that use transuranic nuclear waste for fuel; leaving behind only short-lived radioactive elements.
Can we get more companies doing these please?
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Hitachi!
"as well as higher liklihood of meltdown,"
Nope.
Fukushima's error was that they didn't raise the sea wall like many recommendations had told them too.
They whole design is different, it's not really comparable.
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Mmmmmm, no, you can definitely burn up transuranics and you pretty much HAVE to end up with less at the end of the day, but the question is whether or not you have LESS OF A PROBLEM at the end of the day because there are plenty of "short lived" radionuclides that you really would rather trade for some nice plutonium or americium. On top of that the entire structure, premesis, possibly nearby things, etc will become waste, and even low level waste is costly to deal with. This is the same sort of set of issues that have made it totally uneconomical to reprocess spent fuel. ANY handling is messy, dangerous, and produces a lot of expensive to dispose of waste.
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
If you have a strong enough neutron flux then you can burn the waste (i.e irradiate it until it transmutes to something with a short-enough half-life). Unfortunately, only fast neutron reactors have neutron balance good enough to allow a significant fraction to be diverted for uses other than supporting the chain reaction.
Try here: new reactor design.
Politics; n. : A religion whereby man is god.
What is "neutron saturation transmutation"?
I'm also skeptical of their claims, as it appears to be a thermal-spectrum light water reactor and it's quite difficult to consume TRUs completely in the thermal spectrum, the neutron absorption cross sections are fairly large. Maybe they've got higher enrichment and so shitloads of excess reactivity, so they can afford to lose the neutrons, in which case I seriously hope they have a strong negative temp coefficient. Don't know, would be good to learn the details.
Not sure about the likelihood of meltdown being increased, though. I don't think the decay heat profile of MOX is significantly different from regular enriched Uranium fuel (decay heat melted Fukushima fuel, not fission heat).
By I much prefer inherently safe reactor designs.
I don't think they do so in the breeder cycle - their neutron loss margins are fairly thin, hence why most designs propose extracting at the Pu-238 step (unusable for weapons, but great for space batteries). The burner cycle might be better in this regard. Fast reactors are able to do it, they have plenty of neutrons to spare.
Nuclear waste is only a problem if you have a massive misunderstand as to the scale of the waste. We're not talking about literal mountains of waste, we're talking about under 100,000 tons - for all of it from the USA since forever. You can do one big project and store all of it, nearly indefinitely. The story of Yucca Mountain is what happens when you have to involve people that want a project to fail instead of just getting the damn thing done.
X
Will these new elements have significantly shorter half-lives?
In general the waste from a 4th gen reactor design is cited as being hazardous for a few hundred years. Something manageable, unlike the current situation where we are looking at tens of thousands of years.
They don't, but the ratio of absorption to fission in the thermal spectrum for them is pretty bad, so that can mess up your neutron budget. Depends on the exact composition, though - each reactor produces a slightly different mix and that makes the TRU content in spent fuel fairly heterogeneous, which complicates reactor design and makes fabrication of reliable fuel fairly expensive (hence why MOX fuel only contains the Pu content, not all the other TRUs and even so it's much more expensive than fresh Uranium fuel).
Humm, let's see.
U-238 absorbs a neutron becoming Np-239 then decays to Pu-239
Pu-239 has only a 2/3 probability of fission upon neutron absorption
Water also has the tendency to absorb neutrons
It's no wonder that no TRU burning reactor has been proposed that uses water or helium for cooling, it's always sodium, lead or molten salt as coolant.
Also weird, is Hitachi already has a TRU burning design, the S-PRISM (GE/Hitachi project). Fast sodium reactors are actually known to be workable for that job.
> Fukushima's error was they didn't raise the sea wall
Also, the backup generators to operate pumps were in the basement that flooded. If the generators had been on the roof, it would have been fine.
I know hindsight is always easy, but it does seem like important stuff in a flood plain should be inspected and thought through once per year by smart people to find glaring problems like this.
>Nuclear waste is only a problem if you have a massive misunderstand as to the scale of the waste.
Incorrect, sir. Nuclear waste is only a problem if you have a massive misunderstanding as to the thing you apply the label of nuclear waste. For it is not nuclear waste, it's unspent nuclear fuel.
It would be foolish to build a massive pointless structure for nothing. Nobody's moving their nuclear "waste." It's not even waste to begin with. It's fuel.
Have you ever heard of a Molten Salt Reactor? The most famous one I know about is the LFTR proposed by Kirk Sorensen. These types of reactors also burn existing nuclear waste, but they do so at atmospheric pressure, and are inherently safe. See: http://www.investing.com/analysis/thorium:-an-alternative-source-of-energy-224358
We could build MSRs on site, so the fuel never has to be transported anywhere. Then we decommission the old dangerous water-based plants and run the safe waste-consuming molten salt reactors.
OCCUPY CARSON CITY presented this idea to the Nevada Committee on High-Level Radioactive Waste 7/2012. https://www.leg.state.nv.us/Interim/76th2011/Committee/StatCom/HLRW/Other/ResponsestotheSOR.pdf
This article confuses me because the Hitachi design is terrible. It uses pressurized water, which introduces all sorts of problems. The Molten Salt design is obviously better. I guess we'll just have to wait until 2020 to see how China does it.
...why didn't science just do this in the damn first place?!
It's never been cost effective. The same way safe coal mining and 100% safe fly ash disposal isn't cost effective. If you need to expend more energy to deal with the waste than you get out of it, it's not worth it.
....but what does the "short-lived radioactive elements" dissolve into? surely not *nothing*? ...how much can we strip away through processes before every part is used? ...how little matter do we need left over before we can eject it from the Earth's atmosphere into the Sun?
If we get it to the point that it's economical to launch in a rocket, then there's so little left that storage shouldn't be a big deal. And if it's safe enough to put on top of a rocket, then it doesn't need to be removed from our biosphere.
Most of the really radioactive waste is extremely dense. So it gets insanely expensive to get it out of earth gravity well. To make matters worse, we have no space launch systems that are reliable enough to use for this type of disposal. It's one thing to have a bunch of highly radioactive material sitting around in a shielded location. It's an entirely bigger problem to have a failed launch blasting toxic crap all over hundreds or thousands of square miles/kilometers.
It's also a waste of of non-renewable material with a high amount of potential energy that we may be able to do something with sometime in the future as our understanding of physics progresses.
Even ignoring the huge amount of energy required to launch something into space, our current launch vehicles are not the most environmentally friendly mode of transportation either.
Fukushima Daiichi's problems began forty years ago when they removed the natural 35 meter bluff that use to be there.
The plant is on a bluff which was originally 35 meters above sea level. During construction, however, TEPCO lowered the height of the bluff by 25 meters. One reason for lowering the bluff was to allow the base of the reactors to be constructed on solid bedrock in order to mitigate the threat posed by earthquakes. Another reason was the lowered height would keep the running costs of the seawater pumps low. TEPCO's analysis of the tsunami risk when planning the site's construction determined that the lower elevation was safe because the sea wall would provide adequate protection for the maximum tsunami assumed by the design basis. However, the lower site elevation did increase the vulnerability for a tsunami larger than anticipated in design.
Not considered in the above would be the simple yet modestly more costly possibility of obviating the need for a sea wall by preserving the bluff and setting the reactors back, using modestly sized canals to cycle the sea water to and fro. That, naturally, wasn't the cheapest conceivable option, so it didn't survive the bean counters. Instead, they removed 25 meters of foothill, a feature that was originally 2.5 times the height of the tsunami before they fucked it up. The whole `bedrock' smokescreen is easily dismissed for the lie that it is; they could have reached bedrock from a setback design with no more difficulty.
This was done for one reason; grading the beach provided cheaper access to the ultimate heat sink, sea water. Less construction cost, less pumping, less maintenance, etc. This isn't lost on the perpetrators either. They know they're at fault and they knew it at the time, whatever lies they tell today notwithstanding.
This isn't speculation, either. Fukushima Daini did not get submerged, did not melt down and did not contaminate the land and the sea. Why? Primarily because it was built at higher elevation, which is about the only significant difference between these sites.
TEPCO bean counters. End of story.
Maw! Fire up the karma burner!
Fukushima wasn't in a flood plain.
The area is periodically inundated by tsunamis. That would fit most definitions of a "flood". If Fukushima wasn't flooded, then neither was Noah, since that was salt water too.
The problem wasn't glaring except in hindsight.
Nonsense. Plenty of people thought it was a problem before it happened. The area is hit by a big tsunami about every 300 years. There are historical records of the last few, and geological sediment records of many more. The last one was 300 years ago. They were due.
The analyses collectively indicate that the two reactors appear to be able to achieve their design objectives: The RBWR-AC provides an equilibrium-cycle breeding ratio of slightly above 1.0, thus providing for a self-sustaining fuel cycle in which depleted uranium is used for the makeup fuel. The RBWR-TB2 is capable of unlimited continuous recycling of TRU while consuming on the order of 10% of the loaded TRU per recycle (after accounting for the newly generated TRU). Most results confirmed the values estimated by Hitachi. Some differences among the predicted reactivity coefficients need to be evaluated further.
This has the potential to be a game-changer if true, as we could simply use existing reactor designs such as the ABWR (of which there are several operating already) to both burn waste and breed fuel indefinitely from U238 feedstock.
I'm pretty sure the energy required to add a proton to the nucleus of a large atom is prohibitive.
He blatantly made a biblical reference to Noah
The story of Noah did not originate in the Bible. Both the Sumerian Epic of Gilgamesh and the Akkadian Atra-Hasis Epic included the story centuries earlier.
Hitachi means 'sunrise'. :)
Is that this is another solid fuel, boiling water reactor. Which means they have all this Rube-Goldberg-esque over-elaborate over-engineering to control the plant in a shutdown state. And if they miss even one little thing, boom. Steam explosion.
While burning up existing reactor wastes is a Good Thing, there are better, simpler, safer reactor designs for things like that.
Chas - The one, the only.
THANK GOD!!!
It's mostly a United States problem that waste isn't reprocessed. This is now and has been done on an industrial scale in Europe and the U.K. for several decades. For some reason the United States, under the guise of non-proliferation, will not permit reprocessing of spent commercial nuclear reactor fuel.
The story in this article isn't news. Everyone knows how to reprocess spent fuel since before the 1960s. What would be actual "news" is the time at which the United States allows the well-proven, industrial-scale reprocessing to be applied to its own reactors.
Even Canada does it. The United States' nuclear energy policy is laughably stupid. It's a shame, really.
Kriston
What is "neutron saturation transmutation"?
Nuking it until it glows. First you separate your waste into constituent elements (their oxides, whatever) then you irradiate it with neutrons until most of the medium-level waste transmutes into something with a short enough half-life. You can optimize it a bit by playing with neutron energy to maximize the capture by most problematic isotopes. The size of neutron capture cross-section is not an issue, since you don't need those neutrons to support a chain reaction.
The concept is pretty old, but requires a shitload of neutrons (since you typically need to capture multiple neutrons to transmute a single waste atom). The only practical way to get that much is to use a fast neutron reactor. And even then it's marginal. In future, when we get fusion reactors, fusion neutrons could be used much more economically for that.
but it does seem like important stuff in a flood plain
Fukushima wasn't in a flood plain.
Yes it is. Take a look at this US Army topo map (the latitude is (37.427 degrees, its on the coast). It is on an extended flood plain stretching along the coast, created by several rivers (Takase, Maeda, Kuma. Tomioka, etc.) . The whole area is a sea-level marsh consisting of soil deposited by these rivers at flood.
The problem wasn't glaring except in hindsight.
Because, you know, no one had ever seen a tsunami in Japan before. Oh wait, tsunami is a Japanese word. That doesn't seem quite right, does it?
Japan had fifteen of them since 1900, before Tohoku (the slightly dated linked list misses the 2007 Niigata tsunami).
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Depending on radiation exposure, you might be good for 5-7 days....