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Liquid Fluoride Thorium Reactor

by gcarlin
Tags: fluoride, liquid, reactor, thorium
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ShotmanMaslo
#109
Mar13-12, 09:19 AM
P: 17
Quote Quote by Stanley514 View Post
I have some doubts on tens of thousand years.Sounds too good to be true.
Wikipedia gives us info that total extractable world Thorium reserves are estimated at 1 million 600 thousands of tons. http://en.wikipedia.org/wiki/ThoriumIf we divide this number per 7 billions of modern human on Earth inhabitants,we receive weight less than 200 grams per person.
Are they going to tell that if Thorium will be main and primary energy source for humans it will last more than one generation?I have doubts on it...

One more problem: In currently proposed designs of LFTR they suppose to use Liquid FLiBe salt http://en.wikipedia.org/wiki/Liquid_...horium_reactorSo it will require tons of Lithium and Berillium per reactor.Berillium is even much rare than Thorium.And needed for many critical apps.Neither Thorium or Berillium are present in salt water.
There is far more than 1 600 000 tonnes of recoverable Th in the Earths crust. Those numbers refer only to estimated amount in presently known high quality reserves on dry land - easily accessible thorium mineral deposits recoverable at price below X. And considering we have not even seriously looked for thorium, it is probably a gross understatement of real world reserves.

And we can also use far lower quality reserves for LFTR, since thorium fuel price is negligible compared to the value of generated electricity and reactor costs. Even the method advocated by Weinberg - "burning the rocks" - extracting thorium from ordinary soil, has favorable EROEI (energy returned on energy invested), since thorium atom is so energy dense and LFTR uses 99% of the Th fuel, instead of 1% of uranium fuel as ordinary nuclear power plants.

There were threads about this on Energyfromthorium.com forum:
http://www.energyfromthorium.com/for...php?f=2&t=3398
http://www.energyfromthorium.com/for...php?f=2&t=3512
http://energyfromthorium.com/2006/04...e-whole-world/
Stanley514
#110
Mar13-12, 09:38 AM
P: 300
There is a great deal of Th mass in the oceans, not counted in those land based reserve figures. I see a source show 10pg/ml Th in ocean water, or 13.4 million tonnes total.
Concentration of Thorium in seawater is negligibly small,something like
0.0000004 ppm.This is a million times more rare than Uranium.
http://mistupid.com/chemistry/seawatercomp.htm
I guess it would be no practically to retreive it, for sure.

It would be interesting what chemical elements beside Thorium could be used as a fertile
nuclear fuel.Theoretically any element which is havier than Iron could be used to get energy by fission.What about Tungsten?

It would be bigger success if they would manage to get energy from Boron.Such as in fusion reactions.There is 6 trillions of tons of Boron in seawater and it could be retrieved at competitive price already now.
mheslep
#111
Mar13-12, 03:10 PM
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Quote Quote by Stanley514 View Post
Concentration of Thorium in seawater is negligibly small,something like
0.0000004 ppm.This is a million times more rare than Uranium.
http://mistupid.com/chemistry/seawatercomp.htm
I guess it would be no practically to retreive it, for sure.
The Th concentration figure from my reference has a concentration 25X higher than yours in seawater, and Uranium at 4ppb in seawater is 300X higher than Thorium (my reference) in seawater. At that concentration (10pg/ml), 100k cubic meters (100e6 liters) of seawater are required to produce a gram of Th, which as we know produces 1MW-day of heat energy in a reactor. Is that practical? I dunno.




It would be interesting what chemical elements beside Thorium could be used as a fertile
nuclear fuel.Theoretically any element which is havier than Iron could be used to get energy by fission.What about Tungsten?
I don't think net energy is possible with any of the other natural elements besides the the traditional fertile isotopes of thorium and uranium (Th232, U234&238). The problem with using anything else is the process results in a net loss of neutrons. Unless I've missed something*, once all of the U and Th is gone, along with any transuranics made by U and Th, i.e. Pu, then net energy fission is done on this planet.

*I suppose there's always high Z fusion to build it all back up again, but so far that requires a supernova.
mheslep
#112
Mar13-12, 03:37 PM
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Quote Quote by Stanley514 View Post
I have some doubts on tens of thousand years.Sounds too good to be true.
Wikipedia gives us info that total extractable world Thorium reserves are estimated at 1 million 600 thousands of tons. http://en.wikipedia.org/wiki/ThoriumIf we divide this number per 7 billions of modern human on Earth inhabitants,we receive weight less than 200 grams per person.
...
oh, as others have pointed out, that figure refers to reserves, i.e. go to spot X,dig to depth Y, and it is likely that Z tons of Thorium will be found there. As to the total mass of Th on earth, Th is estimated to be 1.5e-5 of the total mass of the earth, ie 15 ppm, or 9 million billion tons.
Stanley514
#113
Mar13-12, 09:46 PM
P: 300
Unless I've missed something*, once all of the U and Th is gone, along with any transuranics made by U and Th, i.e. Pu, then net energy fission is done on this planet.
It is said that one of major constituents of geothermal heat is Potassium-40.
Could we use this element as a fertile fuel somehow?
mheslep
#114
Mar14-12, 09:17 AM
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The heat from P40 is decay heat, not nuclear fission.
etudiant
#115
Mar14-12, 02:03 PM
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A simple search in Bing brings up an excellent summary from the World Nuclear Association here: http://www.eoearth.org/article/Thorium

The punch line in terms of the resource is in the summary of pros and cons:
' The main attractive features are:
• the possibility of utilising a very abundant resource which has hitherto been of so little interest that it has never been quantified properly,
• the production of power with few long-lived transuranic elements in the waste,
• reduced radioactive wastes generally. '

So we don't know how much thorium is to be found because we've never looked.
We do know it is several times more abundant than Uranium and a vastly better burn up fuel.
Surely that is enough to at least work the problem, even if the resource is not a solution for all time.
mheslep
#116
Mar14-12, 03:37 PM
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Quote Quote by etudiant View Post
A simple search in Bing brings up an excellent summary from the World Nuclear Association here: http://www.eoearth.org/article/Thorium

The punch line in terms of the resource is in the summary of pros and cons:
' The main attractive features are:
• the possibility of utilising a very abundant resource which has hitherto been of so little interest that it has never been quantified properly,
• the production of power with few long-lived transuranic elements in the waste,
• reduced radioactive wastes generally. '

So we don't know how much thorium is to be found because we've never looked.
We do know it is several times more abundant than Uranium and a vastly better burn up fuel.
Surely that is enough to at least work the problem, even if the resource is not a solution for all time.
Those are the strong points of the fuel cycle, but I think they are secondary to the reactor fail-safe advantages gain by operating a molten salt reactor, finally providing a path to eliminate 300 atm pressurized water and all that goes with it.
zapperzero
#117
Mar14-12, 05:26 PM
P: 1,042
Quote Quote by mheslep View Post
Those are the strong points of the fuel cycle, but I think they are secondary to the reactor fail-safe advantages gain by operating a molten salt reactor, finally providing a path to eliminate 300 atm pressurized water and all that goes with it.
Correct me if I am wrong, but is there not a secondary cooling loop which uses water, in all MSR designs? How does this constitute "eliminating" it?

I don't think using thorium is a bad idea per se, it's just that I think mixing two un-proven technologies (MSR and HEU-initiated thorium cycle) is not so safe. The Indian approach of modifying the well-known and long-proven CANDU design (for all its flaws) seems to be lower risk. Better the devil we know.
zapperzero
#118
Mar14-12, 05:34 PM
P: 1,042
Quote Quote by mheslep View Post
I don't think net energy is possible with any of the other natural elements besides the the traditional fertile isotopes of thorium and uranium (Th232, U234&238). The problem with using anything else is the process results in a net loss of neutrons. Unless I've missed something*, once all of the U and Th is gone, along with any transuranics made by U and Th, i.e. Pu, then net energy fission is done on this planet.
Why? If you have a reasonable way to produce the required neutrons (such as fusion), you can split atoms all you like, for a net gain in energy. The reaction is not self-sustaining in bulk, is all.
Astronuc
#119
Mar14-12, 07:09 PM
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Quote Quote by zapperzero View Post
Why? If you have a reasonable way to produce the required neutrons (such as fusion), you can split atoms all you like, for a net gain in energy. The reaction is not self-sustaining in bulk, is all.
Not for most nuclei.

The Russians have some data on fission of Rn(Z=86)-222, and the cross-section are quite low. One would more likely get an (n, n') or (n,#n) reaction, or some other spallation reaction. They also indicate no fission for Po isotopes, or the cross-sections are so low compared to other spallation reactions that one cannont measure any discernible fission event. Other countries don't have any data regarding fission of isotopes below Ra-223.

http://www.nndc.bnl.gov/sigma/getPlo...&mt=18&nsub=10

See - σ(n,F) - at http://www.nndc.bnl.gov/chart/reCenter.jsp?z=83&n=126 - and select Zoom 5 to see readily fissionable isotopes (that is with thermal neutrons). The lightest is Ra-223 and that has very low cross-section.

For a closer look - http://www.nndc.bnl.gov/chart/reCenter.jsp?z=88&n=135 (Zoom 4) and make sure one picks σ(n,F) at the top bar.
mheslep
#120
Mar14-12, 09:07 PM
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The question was not about the fission likelihood of elements other than U and Pu, but could lesser elements be built up to heavy through repetitive neutron capture and beta decay to arrive at U or Pu the way Thorium can be from a single neutron, i.e. breeding fissionable materials from fertile elements. Clearly this doesn't work in a fission reactor, in which case every neutron captured loses a potential ~200MeV.

I had not considered using the neutrons from a fusion reactor as ZZ suggests, but I see at least two problems with that approach: i) even in neutronic fusion, those neutrons are required to breed tritium in a net energy reactor, i.e. like fission a neutron wasted to build heavy elements wastes a potential 17MeV from making tritium. ii)I have no idea of the cross section and beta decay chain that might be required to breed, say Si into U, or if it is possible without regard to energy. I'd guess somewhere along the way there will no beta decay 'step up' available, only alpha to go down. But without researching the issue, IF the cross section decay chain was advantageous for neutron absorption all the way up to U and Th, I think we would see the production of those elements in stars like ours. We don't, short of heavy element fusion in novae.
mheslep
#121
Mar14-12, 09:46 PM
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Quote Quote by zapperzero View Post
Correct me if I am wrong, but is there not a secondary cooling loop which uses water, in all MSR designs? How does this constitute "eliminating" it?
Could be water or helium gas. Most of the design design discussions focus on gas so they can go Brayton.

In any case the point is not the nature of the cooling loop, but that in an MSR the cooling loop is not needed to prevent catastrophe. The cooling loop could be turned off, lose power, be destroyed by an airplane, and there's no chance of a leak of 300atm water, then flashing to steam, expanding several orders of magnitude trying to escape containment to the outside world. Instead, a frozen plug of salt melts, draining the reactor salt by gravity into a tank where further criticality is impossible and decay heat is not a problem. Furthermore, when the cooling loop power is returned or rebuilt, there's no commercial loss, as the reactor salt is heated and pumped back into the reactor. This event happened several times with the MSR built at Oak Ridge.
zapperzero
#122
Mar15-12, 04:17 AM
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Quote Quote by mheslep View Post
Could be water or helium gas. Most of the design design discussions focus on gas so they can go Brayton.
Gas sounds more reasonable. I didn't know that.
Astronuc
#123
Mar16-12, 10:28 AM
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FYI - Antonio Cammi, Valentino Di Marcello, Lelio Luzzi, Vito Memoli, Marco Enrico Ricotti, A multi-physics modelling approach to the dynamics of Molten Salt Reactors, Annals of Nuclear Energy, Volume 38, Issue 6, June 2011, Pages 1356-1372, ISSN 0306-4549, 10.1016/j.anucene.2011.01.037.
(http://www.sciencedirect.com/science...06454911000582)
Keywords: Molten Salt Reactor; Multi-physics modelling; Thermo-hydrodynamics; Reactor dynamics

Abstract
This paper presents a multi-physics modelling (MPM) approach developed for the study of the dynamics of the Molten Salt Reactor (MSR), which has been reconsidered as one of the future nuclear power plants in the framework of the Generation IV International Forum for its several potentialities. The proposed multi-physics modelling is aimed at the description of the coupling between heat transfer, fluid dynamics and neutronics characteristics in a typical MSR core channel, taking into account the spatial effects of the most relevant physical quantities. In particular, as far as molten salt thermo-hydrodynamics is concerned, Navier–Stokes equations are used with the turbulence treatment according to the RANS (Reynolds Averaged Navier–Stokes) scheme, while the heat transfer is taken into account through the energy balance equations for the fuel salt and the graphite. As far as neutronics is concerned, the two-group diffusion theory is adopted, where the group constants (computed by means of the neutron transport code NEWT of SCALE 5.1) are included into the model in order to describe the neutron flux and the delayed neutron precursor distributions, the system time constants, and the temperature feedback effects of both graphite and fuel salt. The developed MPM approach is implemented in the unified simulation environment offered by COMSOL Multiphysics®, and is applied to study the behaviour of the system in steady-state conditions and under several transients (i.e., reactivity insertion due to control rod movements, fuel mass flow rate variations due to the change of the pump working conditions, presence of periodic perturbations), pointing out some advantages offered with respect to the conventional approaches employed in literature for the MSRs.
mheslep
#124
Mar16-12, 10:36 AM
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Quote Quote by Astronuc View Post
FYI - Antonio Cammi, Valentino Di Marcello, Lelio Luzzi, Vito Memoli, Marco Enrico Ricotti, A multi-physics modelling approach to the dynamics of Molten Salt Reactors, Annals of Nuclear Energy, Volume 38, Issue 6, June 2011, Pages 1356-1372, ISSN 0306-4549, 10.1016/j.anucene.2011.01.037.
(http://www.sciencedirect.com/science...06454911000582)
Keywords: Molten Salt Reactor; Multi-physics modelling; Thermo-hydrodynamics; Reactor dynamics
Thanks! A modern model in the literature, vice on a pop web site, is overdue.
wizwom
#125
Mar19-12, 07:57 PM
P: 71
Quote Quote by zapperzero View Post
Correct me if I am wrong, but is there not a secondary cooling loop which uses water, in all MSR designs? How does this constitute "eliminating" it?

I don't think using thorium is a bad idea per se, it's just that I think mixing two un-proven technologies (MSR and HEU-initiated thorium cycle) is not so safe. The Indian approach of modifying the well-known and long-proven CANDU design (for all its flaws) seems to be lower risk. Better the devil we know.
Because you are using the reaction mass itself as your primary cooling loop, and it is liquid salts, you have very low pressure, basically just the pressure required for moving the fluid.

The heat exchangers, even if they run dry on the secondary side, they will still be safe, and thus can use the much more efficient single pass heat exchangers, which were banned from PWR use after TMI. In TMi the loss of heat take-off caused the core to melt, but in a MSR, the core is already and intentionally melted.

And no, the technology is proven, just not developed. ORNL's LFTR program proved that the system was able to make thermal power, which is all you need from a NSSS.

A layman should read http://home.earthlink.net/~bhoglund/mSR_Adventure.html to get an idea of what was done, and why it stopped.
mheslep
#126
Mar20-12, 12:00 AM
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That ORNL reactor simulated the idea starting with U233; it never used Thorium, so the Protactinium did not have to be chemically removed while it decayed to U233. There's still a bit of proving to do yet.


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