Liquid Fluoride Thorium Reactor

[mheslep]

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]

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]

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/article/pii/S0306454911000582)
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]

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/article/pii/S0306454911000582)
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]

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]

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.

 

[edpell]

Even a MSR reactor core need to be cooled. If the primary cooling loop fails it needs a secondary way to cool. This can be dumping the core into a dump tank that is cool by passive means.

 

[Stanley514]

If people would be able to tap geothermal energy properly
there would be no need in nuclear reactors.There is giant ocean
of magma under our feet.But I think it would require some other
cycle than water cycle.Maybe some electron or thermoelectric cycle?
Earth crust has its own electric charge and should behaive like
thermoelectric?

 

[etudiant]

If people would be able to tap geothermal energy properly
there would be no need in nuclear reactors.There is giant ocean
of magma under our feet.But I think it would require some other
cycle than water cycle.Maybe some electron or thermoelectric cycle?
Earth crust has its own electric charge and should behaive like
thermoelectric?

Based on the geothermal record to date, 'unblemished by success', your reservations about a geothermally powered water cycle may be apprpriate.
However, no other approach is even at the proof of principle level afaik, so the water cycle is pretty much the only game in town for the next decade or so.
Given the scale of the energy needs, it is hard to take untested approaches seriously.

 

[Stanley514]

I do not claim it is seriously but I think insted of water could be used for example Sulfur.It`s boiling point is higher and it possible could give you higher energy density.
Also Earth is known as a good conductor.There is natural thermoelectric currents in Earth which result in magnetic field and Telluric currents which could be registered.I want to know if heat could be transferred through some kind of electric resonance?For example we have hot body which is in electric resonance with cold body.There is some electric resonance beween them.Could it work similar to thermopower?

 

[etudiant]

I do not claim it is seriously but I think insted of water could be used for example Sulfur.It`s boiling point is higher and it possible could give you higher energy density.
Also Earth is known as a good conductor.There is natural thermoelectric currents in Earth which result in magnetic field and Telluric currents which could be registered.I want to know if heat could be transferred through some kind of electric resonance?For example we have hot body which is in electric resonance with cold body.There is some electric resonance beween them.Could it work similar to thermopower?

You're dealing with insights I don't have.
What is a 'telluric current' or an 'electric resonance'?
Presently, I'm unaware of any demonstrated example of power generation from any Earth currents or magnetic fields. I'd be keenly interested if there is any data available.
Sulfur does indeed have a higher boiling point, but also has very little extra heat capacity in the sulfur vapor, so extracting energy from a sulfur turbine is a bear. Sulfur also has all the reactive capacity of hot oxygen, so it is a material that is not to be trifled with.
Warts and all, water is a lot easier to deal with.

 

[Stanley514]

Some inventors patented Alpha decay stimulator with help of
Van Der Graaf generator.http://www.freepatentsonline.com/5076971.html If it comes true
then aneutronic fission reactor would be possible.

 

[mheslep]

Some inventors patented Alpha decay stimulator with help of
Van Der Graaf generator.http://www.freepatentsonline.com/5076971.html If it comes true
then aneutronic fission reactor would be possible.

Alpha decay is unrelated to fission, and in any case has nothing to do with this thread on LFTRs.

 

[Astronuc]

Some inventors patented Alpha decay stimulator with help of
Van Der Graaf generator.http://www.freepatentsonline.com/5076971.html If it comes true
then aneutronic fission reactor would be possible.

As far as I can tell, the patent refers to a more rapid transmutation or decay process, not aneutronic fission. Alpha emission is a decay process; it is not fission. Many radionuclides heavier than lead undergo alpha decay. Far fewer nuclides are fissile.

 

[Stanley514]

Alpha decay is unrelated to fission, and in any case has nothing to do with this thread on LFTRs.

I think that any technology that is designed to be directly competing with LFTR and allows to undestand competitiveness of LFTR has right to be discussed here.I do not care if it is fission or decay,the most important if it is able to produce lot of net energy by decay.

 

[Stanley514]

If the proposed method with Thorium decay stimulation will
succeed and generate net power then it will have following advantages
over LFTR:

1)No neutron radiation is created during all stages of the process.Though some low energy gamma radiation may be result of decay.
2)No Uranium 235 as a kindler is requiered.
3)No long lived isotopes are created.
4)Possibly no any radioactive waste is created as a result of the process.
5)No molten salts are requiered and therefore corrosion is reduced or eliminated.

 

[mheslep]

If the proposed method with Thorium decay stimulation will
succeed and generate net power then it will have following advantages
over LFTR:

...
5)No molten salts are requiered and therefore corrosion is reduced or eliminated.

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]

Thorium decay is proposed as method for commercial power generation? What is the proposed power density?

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:

The Van de Graaff voltage φ ignites radioactive waste. If the burn is going too slowly, re-ignite with an eφΔt less than the initial value. High voltages may be hazardous. For example. φ=2 MV predicted to convert the half-life of U238 to one second. Before initiating a decontamination procedure, the composition of the fuel should be determined.

Looks like a new way to create a nuclear explosive device...

 

[etudiant]

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...

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 half life reductions actually achieved in the paper are very small

The claimed reductions do not seem to be really small.

Tests were conducted to show that a positive or negative voltage on a Van de Graaff generator accelerates beta and alpha decay. One beta and two alpha emitters were placed inside the generator sphere, charged to a voltage of 350+75 kv, for a period of twelve hours. When the voltage was switched off, the measured activity oscillated through substantial variations. After three days the measured depletion was about 1% for Tl 204, about 7% for Po 210 and about 2.6% for Th 230. After seven days, the depletion had increased to about 5.3%, about 55.3% and about 81.8%, respectively. It is expected that the depletion will continue to background for all three sources within about 60 days.

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]

Anyone know the scientific basis for asserting that a high E field can change the decay rate of a nucleus?

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/dn4056-giant-laser-transmutes-nuclear-waste.html
One more article on beta decay:
https://docs.google.com/viewer?a=v&q=cache:LHqNU5fpQsQJ:www.wmsym.org/archives/1984/V1/89.pdf+enhancing+beta+decay&hl=en&gl=ca&pid=bl&srcid=ADGEEShSMs5WWU6kBB-AcKWsOaOfWQnHCN16-M3kqxFvhCasep3QAxtzaxeveGXqQe2zfwHIp0NLLZvTqMP2PpAI6BqAI66nL6YaZD5OJIdfJzjWwjL77xH6lA28soR0hH6K1vSaMCOS&sig=AHIEtbQ1qwIfKk2LCN4Nc4vAeByUYtCfcg

 

[mheslep]

Classical theory suggests that alpha decay and perhaps beta decay obey laws of quantum mechanics and are quantum tunneling effects.

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

Therefore surrounding environment may change decay rates.

Therefore?

There is article about another way to trasmutate isotopes with poerful laser radiation.Though it uses lot of energy:
http://www.newscientist.com/article/dn4056-giant-laser-transmutes-nuclear-waste.html
One more article on beta decay:
https://docs.google.com/viewer?a=v&q=cache:LHqNU5fpQsQJ:www.wmsym.org/archives/1984/V1/89.pdf+enhancing+beta+decay&hl=en&gl=ca&pid=bl&srcid=ADGEEShSMs5WWU6kBB-AcKWsOaOfWQnHCN16-M3kqxFvhCasep3QAxtzaxeveGXqQe2zfwHIp0NLLZvTqMP2PpAI6BqAI66nL6YaZD5OJIdfJzjWwjL77xH6lA28soR0hH6K1vSaMCOS&sig=AHIEtbQ1qwIfKk2LCN4Nc4vAeByUYtCfcg

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

 

[zapperzero]

Therefore?

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

 

[mheslep]

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

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:

Generally speaking, the scientific community believes that the decay rate of a radioactive nucleus is immutable. However, it is possible to ...

Which was also my understanding.

 

[seeyouaunty]

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.

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.

long-term observation of the decay rate of silicon-32 and radium-226 seemed to show a small seasonal variation. The decay rate was ever so slightly faster in winter than in summer

http://phys.org/news201795438.html

 

[Stanley514]

Stanley, the gamma radioactivity from U232 decay chain is only an issue if someone wants to isolate the uranium bred in the reactor and run away with it - then there is additional protection in the Th/U cycle which is not necessarily present in U235 or U238/Pu239 based fuels.

As long as the uranium stays in the reactor (as it should), this activity is insignificant compared to all the "regular" gammas associated with the fission process and FP decays. Therefore there are no additional measures or costs due to U232 activity.

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.