where energy SHOULD be going... 5

[stanford94]

i don't know where engineering is going but i know where energy SHOULD be going.......

http://www.wired.com/magazine/2009/12/ff_new_nukes/

 

[MikeHalloran]

Sounds like a real forehead- slapper.



Mike Halloran
Pembroke Pines, FL, USA

 

[FeX32]

... yea slap the trapper snaps that like to play poker with globe.


Fe

 

[ewh]

No lobbyist money, ain't gonna happen.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[cranky108]

What is this post intended to be about? Engineering or energy?

 

[TheTick]

Good question, considering the wide variety of energy sources that are exploited with no engineering involved.

Honesty may be the best policy, but insanity is a better defense.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help

 

[satchmo]

The article is very much on the non-technical side. You could carry a lump of U238 in your pocket with no harm. New fuel is inspected by hand. It's only dangerous after it has become irradiated. The picture also makes it look as though thorium plants don't need cooling towers. You have to condense the steam from the turbine no matter the heat source.

 

[cranky108]

If I recall the early steam engines did not have turbines, or cooling towers. However, that probally isen't what you had in mind.

 

[stanford94]

cranky....
the post was about a thorium article. read it. it is about the future of energy and given the fact that there are some ENGINEERS in the ENERGY business, i posted it here.

 

[ornerynorsk]

Lack of lobbyist money = lack of weaponability ? I believe that's what the human race is coming down to.

 

[ewh]

Yes... no money because there is insufficient profit motive for those with the $. Uranium is a huge profit center, be it legit or not.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[moltenmetal]

Umm, you don't think there might be a few non-trivial technical problems to solve there? A radioactive working fluid of molten fluoride salt? Who wants to build the first one and test it for forty years?

 

[KENAT]

Read part of an article in National Geographic last night about 'mini nukes' interesting, though not sure how accurate/comprehensive etc.

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[YoungTurk]

Great post (though you should give a hint what the article is about in your post)!

moltenmetal - the first LFTR was built already, though it seems funding and politics prevented long term testing.

In 1965, Weinberg and his team built a working reactor, one that suspended the byproducts of thorium in a molten salt bath, and he spent the rest of his 18-year tenure trying to make thorium the heart of the nation’s atomic power effort. He failed. Uranium reactors had already been established, and Hyman Rickover, de facto head of the US nuclear program, wanted the plutonium from uranium-powered nuclear plants to make bombs.

See also,

http://en.wikipedia.org/wiki/LFTR#The_Molten-Salt_Reactor_Experiment

I don't know enough about nuclear engineering to comment on whether these are valid designs. However, it seems like nuclear hysteria holds the USA back from developing the most obvious source of independent and carbon free energy available. Depending on the long term viability of North American unranium sources, it makes good sense to research nuclear power from other sources.

 

[jenofstructures]

some countries are now trying to use the solar energy big time.Since there's a global warming (and its very hot). I think its better (and i guess safer?) to use these energy that's already around us. Germany had their own version of it.



Poems are made by fools like me, but only God can make a tree. engineers creates wonderful buildings, but only God can creates wonderful minds

 

[moltenmetal]

This thing has a distinct ring of "too good to be true" about it from what I read on the Wiki- the kind of glow that can only be attached to "the one that got away". The re-processing of the molten salt mixture every 10 days to remove fission products in particular sounds like a big deal. It's only when technologies go beyond the pilot to a couple full-scale installations that all the warts are revealed.

Due to uranium supply issues, thorium is definitely where fission technology is ultimately going. It's a question of when, and how- there's enough uranium to make sure this is a long time indeed. Regardless, I don't see the innovation on this technology happening in the 1st world- there's too much liability. Maybe India or China will build one and try it out.

 

[Kcapture]

Ok, one thing at a time.

Molten salt reactors: theoretically they work just as well with any fissile material (U, Pu, Th), and they have the same intrinsic safety features with all 3. Thorium has no special competitive advantage in this configuration.

The main problem with this reactor is associated with materials. All the tests run (mainly in the 60s) show that the damage to the piping and the vessel from this high temperature molten salt is unacceptable. There are also problems associated with the continuous removal of radioactive material from the reacor during operation.

Thorium: unfortunately it is not as "golden" as represented in that article. Th232 (not fissile) needs to be converted in U233 (fissile) to be used in a chain reaction. Using Th in the nuclear industry would add an additional step in the already complicated nuclear value chain where Th is breeded into fuel in other reactors.
Steady state it would work, but it is an additional cost, since the "breeded" fuel would have to be purified from fission products before being fabricated and used.

For this reason Th could not be efficiently used in once-through cycles (US) but would need a reprocessing step (closed cycle), forcing some countries (like teh US) to change regulations.

Finally the current reprocessing technology is geared to U/Pu separation. Nobody has really studied how to efficiently separate Th232/U233/fission products. Another hurdle to overcome before this technology can be adopted.

Footnote 1: there is a lot of Uranium on earth, the cost of recovering it (e.g. from sea water) would progressively go up, but Uranium cost is only about 3% of the full cost of th nuclear kWh. Even doubling it would not be a big deal.
Breeder reactors can convert U238 into fissile Pu multiplying current reserves by a factor 40 (albeit with similar problems to the Th cycle... breeding and reprocessing would become necessary, plus proliferation risk)

Footnote 2: India (that has a lot of Th but very little U) has been studying this technology since the 70s, and pouring a lot (relative to the size of its nuclear industry and economy) into it with very little success.

Footnote 3: Thorium is not proliferation safe. If you want to use it in nuclear reactors you have to convert it into fissile U233 that can be used in bombs exactly like U235 and Pu239/41.
It would be a more roundabout route, yes... but not much more than Pu, that has been already used for bombs without much of a problem already in 1945 (Nagasaki). I would say that it is proliferation safeR, but it definitively does not eliminate the risk.

Sorry for the lon post. I have been in this industry for too long.

 

[YoungTurk]

Great post Kcapture! I'd love to hear more about reprocessing requirements. Seems like we're not likely to get a Yucca moutain type repository any time soon, so reusing the spent fuel stored at the existing sites is the best idea I've heard.

Can the reprocessed fuel be used in the existing reactor designs? I've read about using "thorium seeded" fuel in exsiting reactor designs which apparently allows a longer and more efficient fuel use, is this correct?

BTW - to jenofstructures, renewable is great, but until we have a proven mass energy storage device there will always be a need for base load generation for when the sun goes down and the wind stops blowing.

 

[Kcapture]

Thank you YoungTurk, I am happy that you found my post helpful.

Reprocessing. A really vast subject.
Nuclear reactors are very inefficient and use a relatively small percentage of the fissile fuel. Moreover U238 captures neutrons, becoming Pu239 (there is a decay chain in between obviously), thus creating new fissile material.

So if you started with Uranium Oxyde enriched at 4% (pretty standard, but note that the enrichment varies by plant and position within the core), that is, 4% U235 and 96% U238 (oxydes), you would end up with something like 1% U235, 1% Pu239 and 240, 3% fission products (the "waste") and the rest still U238.

The bottomline is that we can take the spent fuel, reprocess it to extract the fissile material (U235, Pu239 and 241 mainly), add some more U235 and put it back as fuel in a reactor. This way you get the MOX fuel (Mixed OXyde) to use again in your plants. This is what the Japanese, Russians and French do.

Looking at the numbers above it sounds like a pretty good idea, by reprocessing we avoid wasting fuel. The problem with reprocessing is that you have to deal with a radioactive liquid in your reprocessing plant... very messy and expensive.
Moreover, while enriched Uranium's radioactivity is negligible, MOX fuel is quite radioactive (Am231, a deacay product of Pu241 is the main culprit) so the fuel fabrication needs to be automated in large part, raising the costs.

The bottomline is that, while reprocessing reduced greatly the volume of "waste" (from 100% of the spent fuel to, ideally, 3%), it is really too expensive, as of today.
And I did not even touch the proliferation risk.

This should answer to the first part of your question. To answer the second part, you could "seed" the fuel with Th232 so that, while the U235 gets "consumed" by fission, the Th captures neutrons transforming into U233 and effectively adding fissile material back.

Great, right? It sounds a lot like a free lunch, so there must be a problem somewhere. The problem is that the Th captures neutrons, thus changing the neutronic balance within the reactor. You would have to increase the initial enrichment of your fuel to generate enough neutrons to both sustain the chain reaction and provide neutrons to the Th.
There is also a problem that you can't optimize the reactor both for optimal capture and chain reaction, but that would require a longer discussion.

Having said that, the French and the Russians have experimented with a similar idea in their "fast" reactors. They put a "blanket" of fissionable material around the core(they used U238), that, capturing neutrons would become fissile (Pu, in this case).
This blanket would contribute very little to the energy produced, but would be periodically taken out, reprocessed to extract fissile material that would be fabricated into new fuel and put back in for the next cycle.

SuperPhenix, thanks to this configuration, achieved breeding ratios of 1.2,IIRC, that is, for every atom of fissile material you put in, you would get back 1.2 after reprocessing. This apparently puzzling result is achieved by converting useless U238 into fissile material (U238 is not fissile).

This method described here is what I was talking about when I meantioned in my earlier post that you can effectively multiply (in theory) your fissile Uranium reserves by a factor 40.

The reason why we don't do that? Uranium is (relatively)cheap and fast breeder reactors are even more expensive than the already very expensive thermal (classical) nuclear reactors.
But if we have to, we already have the technology to do all of the above.


NOTE 1: The neutronic behavior of the MOX fuel is different than normal UO2 fuel. Many of the modern thermal reactors can handle both, though.

NOTE 2: "Fast" reactors are reactos that work with a neutron energy spectrum centered on higher energy (Faster neutrons!) that normal "thermal" reactors ("slow" neutrons).
Most of the reactors today are thermal reactors. The Russians are still running their fast breeder reactor (BN-600), while the French have shut down theirs (Phenix and SuperPhoenix) because of the high costs and operational problems.
Look up SuperPhenix, it has been one of the grandest engineering projects in the last century (albeit not very successful)

NOTE 3: take a look at this report we did at MIT a while ago. Among the other things, you will find a discussion on once-through versus closed-cycle.

http://web.mit.edu/nuclearpower/

 

[stanford94]

thank you youngturk, i'm glad you found my post interesting and thought provoking. the amazing thing is that most people have never heard of this fuel.