Liquid Fluoride Thorium Reactor

mheslep

Thorium decay is proposed as method for commercial power generation? What is the proposed power density? One of the advantages of using molten salts is to move away from pressurized containment in the primary and the consequences of leaving solid fuel uncooled. If the power density is trivial then the problem solves itself without resort to molten fuels.

Stanley514

First of all an effect that they claim to exist still have to be proved.In their patent (?) they claim that many successful experiments been conducted.But in the same time I didn`t read in other sources information that nuclear decay rates could be drastically enhanced with help of common Van-der-Graaf machine.
What is concerning power density I don`t know. For example they make statement like:
Looks like a new way to create a nuclear explosive device...

etudiant

The half life reductions actually achieved in the paper are very small, at the experimental error level really.
So I would be hesitant to accept the kind of huge reductions suggested in the analysis, at least not until some more convincing experimental evidence is forthcoming.
That said, there are active proposals to use thorium fuel bundles in conventional LWRs, based on a lot of solid work done in Russia.
However, these have none of the more speculative elements suggested above, where thorium is burnt down to a few residual short lived actinides. Absent demonstration, it is unwise to rely on such pie in the sky projections.
They remind me altogether too much of the Reagan era NASP, a proposed aerospace plane that would take off and fly to orbital speed. The theory was compelling, the engineering a nightmare. They quit when the design had gone from 50,000 pounds to 1 million pounds, with cost increases to match.

Stanley514

The claimed reductions do not seem to be really small.
If under depletion they mean that few percents of nuclear fuel decayed in few days then it is very significant reduction.For example half-life of Th 230 is 75.000 of years.
Also as I could understand from their claims the higher voltage means better rate reductions.With modern technologies there is no problem to create static electric field up to billions of volts.For exaple tabletop pyroelectric fusion device is claimed to create 25 gigavolts per meter.I think this effect could be easily verified if it exists.

mheslep

Anyone know the scientific basis for asserting that a high E field can change the decay rate of a nucleus? If that was (is?) possible, seems like it throw a large kink in all the historical dating done from isotope ratios, at least in the cosmos where high E fields can occur naturally.

Stanley514

Classical theory suggests that alpha decay and perhaps beta decay obey laws of quantum mechanics and are quantum tunneling effects.Therefore surrounding environment may change decay rates.There is article about another way to trasmutate isotopes with poerful laser radiation.Though it uses lot of energy:
http://www.newscientist.com/article/...ear-waste.html
One more article on beta decay:
https://docs.google.com/viewer?a=v&q...c4vAeByUYtCfcg

mheslep

Well, yes, everything obeys the laws of quantum mechanics.

Therefore?

Thanks for the links. Yes apparently there's some mechanism but it is beyond me.

zapperzero

http://www.freepatentsonline.com/5076971.html

mheslep

Yes the patent link was posted up thread, but it does not help me with the accepted scientific theory behind accelerated decay, especially given this admission in the patent:

Which was also my understanding.

seeyouaunty

There is some observational evidence that radioactive decay rates are not constant like assumed. It has been suggested the sun is somehow influencing the rate of decay.
http://phys.org/news201795438.html

Stanley514

Are you completely sure in it?According to some info some countries refused from U235-Th cycle exacly because very high gamma radioactivity which would require some specific kind of protection that doesn`t exist in any kind of known reactor type.

wizwom

Since 232U is just the alpha decay product of 236Pu, which is found in all spent fuel from Uranium powered reactors, and concentrated in MOX. There is no additional shielding needed.
Google books has Neeb's Radiochemistry of Nuclear Power Plants With Light Water Reactors, and on pg 78-79 he gives activity measurements for spent fuel isotopes from enriched uranium after differeent burnups.

You can compare that yourself to the activity from fission products, which he gives earlier.

The ~2MeV γ is not unusual for reactors, the prompt γ average is 1MeV.

So, really, the 232U "hard gamma" claim is somewhat of a red herring: its a feature of ALL spent fuel - and all Plutonium, all recycled Uranium and all recycled Thorium. Since 228Th has a half life of 1.9 yrs vs. 232U's half life of 68.9 yrs, the concentration of 228Th is determined by 232U, and Thorium recycling shouldn't add any worries.

mesa

So is the general opinion that working on development of LFTR good or bad?
Seems like from what I have read in this thread it is leaning strongly towards good...

wizwom

LFTR has a complex radiological path, and all of it is running at molten fluoride temperatures. Molten fluorides are NOT fun things to work with, they are very active. There are significant engineering hurdles for making a 700 C Material that can handle fluence for a reactor. Since there is no fuel loading - additional reactivity is inserted as needed from 233U-F4 salts in storage as needed, and fission products are removed in a chemical treatment of the main coolanant/fuiel salt, you're going to need materials which can handle 10^15 n/cm^2/s at 700 C for decades, not just a few years.

mesa

I can understand that but some of the Oak Ridge scientists who have worked with this type of reactor seem to think it really wouldn't be that big of a deal to figure out, here is a link:
http://www.youtube.com/watch?v=_yO0Qk-_Gms

Also, don't we have better suited materials today than these guys had 47 years ago?
Are the materials the biggest concern for building this type of reactor?

mesa

I just realized that interview is kind of lengthy, Dick Engel gives his thoughts about these materials at timeframe 23:10 (although I found the interview as a whole really quite insightful).

zapperzero

TL;DL: "we kinda sorta thought we might be able to solve the corrosion problems at some unspecified point in the future because we did a few lab tests"

Yeah. Well.