It's going to be at least another two decades before any commercial models are built, but researchers are at work designing the Generation IV nuclear reactors. Unlike the generation II and III models now in use that use water to cool and control the fission (preventing runaway reactions, subsequent meltdowns and the environmental apocalypse that would result), the leading contender for cooling material for the Gen IV reactors is molten sodium. Not sodium chloride (plain, unreactive table salt), but sodium metal. The same sodium metal that burns uncontrollably when it comes into contact with water. This is what will surround the reactor of the future. I'm sure there's good reasons for all this, but really, can this possibly be on the whole a good idea?
Well this is the second article here that is..... meaningless/uninformative.
Why so ???
I agree with <a href="http://www.popsci.com/users/vorazechul">vorazechul</a>. I'm also guessing <a href="http://www.popsci.com/environment/article/2008-02/climate-change%E2%80%94don%E2%80%99t-blame-it-sun">"Climate Change—Don’t Blame It on the Sun"</a> would have to be the other article.
I am posing this question to the editor: Are you going to give us the rest of the story or are you going to leave us with this small, almost meaningless story?
I understand that this isn't Scientific American and trying to go to the depths that they go to might erode your customer/reader base, but putting a story this small is equivalent to "here's a taste... you can't have anymore...EVER!"
this would be a great idea (the sodium does not degrade the material as water does), however, there have been problems with it. In the hills around my home town, simi valley, they were experimenting on a reactor like this, and had a radiation leak. This is because the molten sodium needs pumps, which need lubricants to keep working. Some of the lubricant leaked into the sodium, and made it very thick, which gummed up the works.
"I'm sure there's good reasons for all this, but really, can this possibly be on the whole a good idea?"
Classical example of lazy journalism.
More science less popular please.
In response to your comment about the lubricants leaking into the sodium coolant: Do you think that it would be possible to use a magnet driven pump? One that uses magnets to suspend and turn the impeller, thus reducing the need for lubricants and, the possibilty of coolant/lubricant interaction. This type of pump would have nearly no friction between moving parts. Or do you think this type of pump would not be reliable enough to use in such a critical component? A pump such as this would require multiple redundant power sources. If you lost power and the pumps stoped functioning it would be Chernobyl all over again. The power would have to come from an outside source. When the reactor is offline and not making power, the pumps would still have to run durring shut down and start up procedures. I ask this to markbart7, as he seems to be the only one that didn't knock the article and had something to add.
For the others, I, too, am disapointed by the lack of information in the "article" but, it may be that this is a lead in to another, more in depth, piece in an upcoming issue. It's also possible that there was not much more information to include right now, and Michael Moyer was simply looking for opinions or ideas on the subject.
But molten sodium would already be pretty hot, right?
It would make sense to use something else that is cooler.
What tempurature does sodium melt at anyways?
sodium melts at 370.87 K (97.72 °C, 207.9 °F) obviously just less than the boiling point of water . . .
how easy is pure sodium to find? I mean . . . water is pretty prolific, hence not a very expensive coolant . . .
I grew up near Sizewell Powerstation in Suffolk, England . . . the reactors used sea water as a coolant . . . it was pumped in and pumped back out again . . . it was the warmest stretch of the North Sea for miles around . . . great for swimming :D Heysham 2 in Lancashire, England used the same principle.
The point is . . . are they making the product prohibitively expensive to stop its expansion????
Just a thought . . .
There are a variety of "sodium" reactors. SFR, MSR, MSCR, MSFR. The biggest accident risk is a primary coolant leak. This article only mentions one of 6 potential GENIV reactors currently being researched by the Generation IV International Forum (GIF). Three are thermal neutron reactors and three are fast neutron reactors. Two of the six are salt type; Molten Salt Fueled Reactor (MSFR) and Molten Salt Cooled Reactor (MSCR), and they are quite different. MSFR’s and MSCR’s can be either thermal or fast reactors depending on the design. An MSR is thermal while an SFR is fast. Reactor manufacturers want to push the MSCR design because it guarantees them profit due to the need for fabricated fuel. MSFR's don’t need enriched fuel or fabrication, which makes them cheaper, but draws opposition from reactor manufacturers who loose out on profits.
An MSCR is a thermal reactor and uses molten fluoride salt with the nuclear fuel dissolved into it (uranium tetrafluoride UF4) as the fuel. There is "fuel salt" and "coolant salt." Fuel salt doesn't burn in water or air. Coolant salt is located in the two heat exchangers. The fuel salt gets pumped to heat exchanger #1 and transfers heat to the coolant salt. Coolant salt is pumped to heat exchanger #2 which heats water into steam and runs the turbine. Molten salt can be used in batteries as an electrolyte or as the heat transfer fluid in a solar power plant.
Molten salt type reactors were first researched in the mid 50's and there have been a couple of experimental plants built and run for quite some time from temperatures starting at 650C up to 950C. One benefit is that the core is under low pressure, so the chance of an explosion due to over pressurization is lessened. It also removes the need for a high pressure containment vessel for the core, a very expensive item. These reactors are more efficient than light water reactors. They can be made large or small depending on the need.
As with all reactors there are concerns - the salt is water soluble and toxic and when cooled produces poisonous fluorine gas. Molten salt is also highly corrosive, more so at high temperatures combined with neutron embrittlement. This could eventually lead to a leak, even with the use of exotic alloys. Alloys must be found that can withstand the corrosive properties of the molten salt and the intense radiation. Just remember, reactors are built by the lowest bidder.
A very poor article. Until NIMBY is no longer the standard, we can't deal with nuclear waste.
Sodium has some real uses, but since we already have about 10,000 kilos of military plutonium in stock world wide, we probably don't need the technology.
See the links if you want to learn something about sodium.
good info without an axe to grind.
The only problem I pose with magnetic pumps is the fluid force of molten sodium is so high that it would take an extremely large generator to power the magnetics. Also molten sodium is magnetic, so the propellers would have to be grounded from the internals of the pump, so to decrease chances of "gumming up" the inlet/outlet stocks.
Sorry everyone, I should have included more info with the post, but sent it off as I was dashing to another talk. Here is the Generation IV International Forum home page:
And specifically, more information about the sodium-cooled system:
Come on guys, no need to be so harsh. Yeah, so this post is not a 1000-word masterpiece, but so what? The posts you're complaining about, as I judge from the tags, came from the AAAS (American Association for the Advancement of Science) conference last week in Boston. They were obviously meant to briefly highlight some of the more interesting talks, not give in-depth analyses. I agree that well-reported posts are great, but are the occasional short-post overviews really worthy of angry complaints?
(And no, I don't work for PopSci.)
For a magnetic pump, you could use something along the lines of a coil-gun concept. Run the molten sodium through a locomotive magnetic coil.
My biggest problem with this reactor type though, is if it does go the way of Chernobyl, it is going to be far worse. Any kind of coolant leak would spill the liquid sodium onto the ground, which would react with any water violently. The coolant would also be radioactive, adding more problems. Then there is the fact that there will be water in the reactor, unless they have devised some other way of generating electricity that we don't know about. If there was an event in which both the reactor coolant and the water coolant lines were ruptured at the same time, it would make Chernobyl look like a firecracker in comparison.
I am of the party that they should be going towards the helium cooled pebble bed reactors, instead as something as dangerous as sodium.