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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.
Hitachi!
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).
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
>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!
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.
Lets not forget the gov't research labs -- it would be nice if the U.S. gov't didn't shut down such research to appease an ill-informed political interest group.
Otherwise known as "the electorate".
If God forks the Universe every time you roll a die, he'd better have a damned good memory.
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).
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj