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#1 2012-10-27 01:34:48

Rxke
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From: Belgium
Registered: 2003-11-03
Posts: 3,667

Thorium reactors are go! (In India)

http://www.deccanherald.com/content/286 … ities.html

cue heated debate between Louis and... lol

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#2 2012-10-27 08:15:04

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,621
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Re: Thorium reactors are go! (In India)

I'm not entirely sure,  but I think this is based on breeding U-233 from Th-232.  They spent the last decade or so working on this.  You have to start by using the U-238/Pu-239 cycle to breed your U-233 from Th-232,  until you can stockpile enough U-233 to shut the U-Pu cycle down.  The Indians have been working the final reactor design and the U-233 issues in parallel.  Looks like they're just about "there". 

BTW,  nearly everybody has a lot more thorium than uranium.  This is not the first time somebody proposed to do this.  The Canadians proposed this unsuccessfully in the 1950's.  It was no-go because the militaries of the time needed weapons materials,  which this cycle really does not produce very well.  U-233 can make a bomb yes,  but you use a lot more,  and it's bigger and heaver. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#3 2012-10-27 09:07:27

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,768
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Re: Thorium reactors are go! (In India)

Actually U-233 has a "better" neutron absorption cross-section than U-235. I say "better" to avoid arguments about words. What that means is U-233 absorbs neutrons more easily, so you need a smaller critical mass. However, Pu-239 is better yet so it has the smallest critical mass of all. Also U-233 produces more energy per fission, or more energy per mass of fuel, than U-235. Again less than Pu-239, but more than U-235. Call U-233 an "in between" material between U-235 and Pu-239.

Breeding U-233 from Th-232 requires moderated neutrons. You could produce those neutrons with plutonium, but why? U-235 can do the job. A modern Canadian CanDU reactor uses uranium with the same isotope balance as ore dug from the ground. That means ore has to be refined, but not enriched. That was on purpose, so a country could operate nuclear reactors to produce power while not having any enrichment capability what so ever. You need enrichment to concentrate uranium enough for a bomb, so this allows a country to have nuclear reactors without nuclear bombs. Could neutrons from a CanDU reactor breed Th-232 into U-233? A CanDU was not designed as a breeder, but something similar should be possible.

The big catch is you don't need to breed your fuel. A thorium reactor uses Th-232 directly. Inside the reactor itself, it breeds Th-232 into U-233, then consumes the U-233. Since U-233 has a "better" neutron absorption cross-section than Th-232, the reactor splits U-233 as fast as it's made. Don't expect U-233 to build up to anything more than trace quantities, so this reactor cannot be used to make a bomb.

Another feature of a thorium reactor is safety. The reaction requires 2 neutrons for every split: one to breed Th-232 into U-233, the other to split U-233. A uranium reactor only requires 1 neutron. On average each uranium atom split will spit out 3 neutrons, so the a uranium reactor can lose a lot of neutrons while maintaining a reaction. A thorium reactor tends to lose too many neutrons, so the reaction slowly dies down. It requires a small "seed" of highly enriched uranium as a source of neutrons to keep it going. A reflector "stirs" neutrons through the thorium. Notice I said "enriched uranium", not plutonium; meaning a small piece of highly concentrated U-235. It does not require any plutonium at all.

The reason I say "safety" is it cannot melt-down. If an incident occurs, just remove the seed. The thorium reaction will die down, not build up. At Three Mile Island it's coolant leaked, then it overheated to control rods could not be inserted. But a thorium reactor doesn't insert anything, the "seed" sits on top. So it doesn't matter how hot the reactor gets, you can always remove the "seed". Once that's gone, the rest of the reaction slows and stops. That means it will start to cool as soon as the seed is removed. The reaction will stop entirely in less than 3 days; the exact time would require analysis by a nuclear engineer. But that means it just cannot melt down.

I could go on and on, but one of the good features of this reactor is it cannot be used to make a bomb. That's why military doesn't like it, but that exact same reason is why it's good for industry.

Last edited by RobertDyck (2012-10-27 09:30:27)

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#4 2012-11-17 21:27:30

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
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Re: Thorium reactors are go! (In India)

I would like to point out concerns of "Peak Uranium" for U-235.  U-235 constitutes about .7% of natural Uranium, the rest being U-238.  There is only so much Uranium out there, so in the long run breeding cycles are going to be necessary if we would like to continue to use nuclear power.  As far as breeding cycles go, Thorium is a lot more common than Uranium, so it just makes sense.  A mixed cycle might also make sense, I don't know enough about nuclear technology to comment on it.

More generally, I think that nuclear technology would really benefit from research dollars.  Nuclear technology has been pretty stagnant since the 1970s or so, and the incorporation of recent advances in materials and computing technology would really benefit it.  With standardized security for nuclear material and an effective way to dispose of nuclear waste I think that nuclear power has a huge future.

On disposal, low level waste can just be held somewhere for a while, "somewhere" potentially meaning a box inside a warehouse where it can't go anywhere.  High level waste can very reasonably just be launched at the Moon.  The Moon won't mind, and because generally reactors don't generate too much high level nuclear waste the transport costs won't be too high (and, of course, they are declining).


-Josh

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#5 2012-11-26 12:44:05

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,621
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Re: Thorium reactors are go! (In India)

Hi JoshNH4H:

The only concern about shooting high-level waste off-earth (other than cost) is flight safety.  What do you do about a launch failure?  There's a way to make the containers survive without leaking,  of course,  but it will be heavy and more expensive.  They did it in the 1950's with that crashworthy reactor vessel that flew in the old NB-36. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#6 2012-12-18 17:38:14

JoshNH4H
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From: Pullman, WA
Registered: 2007-07-15
Posts: 2,526
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Re: Thorium reactors are go! (In India)

That's what I had in mind; Couldn't one simply launch high level waste inside a capsule with re-entry capabilities and integrated rockets to escape a failed launch?  I'm thinking something like the Dragon capsule.  In combination with good design of a containment vessel for the waste it seems pretty safe to me, especially if you don't launch over populated areas.


-Josh

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#7 2017-05-29 19:30:12

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,342

Re: Thorium reactors are go! (In India)

O oh....poke.

We have been talking about nuclear use for mars and due to cost of plutonium we are looking at not getting more than a few units sent to mars. So we are then looking to Thorium which mars seems to have plenty of to build the electrical power systems on mars with.

THORIUM MOLTEN-SALT: The Best Reactor You’ve Never Heard Of

The Forgotten History of Small Nuclear Reactors

Molten Salt Reactors Could Soon Help Power Earth—And One Day Mars

Concept of Small Power Autonomous Molten-Salt Reactor with Micro-Particle Fuel (Reactor MARS)

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#8 2017-05-29 22:05:16

Rxke
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From: Belgium
Registered: 2003-11-03
Posts: 3,667

Re: Thorium reactors are go! (In India)

Thread necrophilia ! smile 

lots of R&D needed before that stuff is launchable....

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#9 2017-05-30 02:54:45

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: Thorium reactors are go! (In India)

Why the poor old moon? We might want to use it.
A large can of high level waste will give out plenty of heat. Sufficient to operate a generator for an electric ion rocket. So a little gas for fuel will enable it to be dropped into the sun or Venus.

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#10 2017-05-30 05:38:29

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Thorium reactors are go! (In India)

There has been much hype around Thorium that I think is unwarranted.

Firstly, Th-232 is a fertile material, not a fissile material.  One cannot use it as fuel in a reactor, one must first breed U-233 through neutron bombardment.  So a thorium reactor must be a breeder reactor.  One advantage that U233 has over U235 is that it produces enough neutrons for self-sustaining fission and breeding at thermal energies, hence the Indian thorium breeder is a moderated heavy water reactor.  There is nothing very exotic about that - the Canadians have been building heavy water reactors for decades.  It is perhaps marginally more economic than a fast reactor, but it lacks the ability to 'fast burn' other heavy actinides, which are not typically fissionable in the thermal spectrum.

I can think of no reason why the use of thorium would eliminate or reduce any safety issues associated with a nuclear reactor.  It generates fission products and decay heat just like any other fission fuel.  Many modern design water based reactors have very low core damage frequency through the use of passive safety features.  But this is a factor of reactor design, it has nothing specifically to do with thorium being used as the source of fuel.  U233 is maybe marginally less toxic than plutonium (it is a beta rather than alpha emitter) but it has similar criticality safety margins, which complicates fuel fabrication just as much with U233 as with Pu239.  Thorium is marginally more abundant than uranium, but neither metal is rare, especially if a breeding cycle is in use.

Last edited by Antius (2017-05-30 05:44:30)

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#11 2017-05-30 13:37:40

louis
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From: UK
Registered: 2008-03-24
Posts: 6,914

Re: Thorium reactors are go! (In India)

Is it then a fair conclusion that no small settlement on Mars, say of under 100 could ever have the necessary labour resources to devote to manufacture a nuclear reactor without potentially compromising the health and safety of the settlement (obviously a much larger settlement, in the hundreds of thousands might be able to) and other priority activities?  I really can't see how a Mars settlement in the early stages could ever have the resources to manufacture nuclear reactors.

Antius wrote:

There has been much hype around Thorium that I think is unwarranted.

Firstly, Th-232 is a fertile material, not a fissile material.  One cannot use it as fuel in a reactor, one must first breed U-233 through neutron bombardment.  So a thorium reactor must be a breeder reactor.  One advantage that U233 has over U235 is that it produces enough neutrons for self-sustaining fission and breeding at thermal energies, hence the Indian thorium breeder is a moderated heavy water reactor.  There is nothing very exotic about that - the Canadians have been building heavy water reactors for decades.  It is perhaps marginally more economic than a fast reactor, but it lacks the ability to 'fast burn' other heavy actinides, which are not typically fissionable in the thermal spectrum.

I can think of no reason why the use of thorium would eliminate or reduce any safety issues associated with a nuclear reactor.  It generates fission products and decay heat just like any other fission fuel.  Many modern design water based reactors have very low core damage frequency through the use of passive safety features.  But this is a factor of reactor design, it has nothing specifically to do with thorium being used as the source of fuel.  U233 is maybe marginally less toxic than plutonium (it is a beta rather than alpha emitter) but it has similar criticality safety margins, which complicates fuel fabrication just as much with U233 as with Pu239.  Thorium is marginally more abundant than uranium, but neither metal is rare, especially if a breeding cycle is in use.

Last edited by louis (2017-05-30 16:14:45)


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#12 2017-05-30 15:34:01

elderflower
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Registered: 2016-06-19
Posts: 1,262

Re: Thorium reactors are go! (In India)

Well, I have pointed the following out before but, at the risk of being even more boring than usual, here it is again.
The heavy water moderated reactor has one major drawback, and one lesser one, which have prevented, on Earth, their general adoption in power generation. These are, first the huge upfront cost of heavy water which is required in large quantities. The second is that they generate Tritium from that heavy water and this results in widespread opposition because a Tritium supply enables a state to make and maintain Hydrogen weapons.
The first drawback will be much less of a consideration on Mars where heavy water (HDO) is a much higher proportion of the planet's water than is the case on Earth. Production of heavy water is by electrolysis and the Mars settlers will be doing plenty of that, so HDO will be a by-product.

Last edited by elderflower (2017-05-30 15:35:56)

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#13 2017-05-30 16:18:27

louis
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From: UK
Registered: 2008-03-24
Posts: 6,914

Re: Thorium reactors are go! (In India)

elderflower wrote:

Production of heavy water is by electrolysis and the Mars settlers will be doing plenty of that, so HDO will be a by-product.

I can't believe it's that simple!


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#14 2017-05-30 17:32:01

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,342

Re: Thorium reactors are go! (In India)

The main reason thou for not going with the items not of Fission Nuclear Fuels list is due to fear of launching them from earths surface, weapons in orbit ect....

The known fissile materials are:

    Uranium-233
    Uranium-235
    Plutonium-238
    Plutonium-239
    Plutonium-241
    Neptunium-237
    Curium-244

The other was to make use of the insitu source and only ship what we need to get started....

Map of Martian Thorium at Mid-Latitudes

https://en.wikipedia.org/wiki/Mars_ocean_hypothesis

On the Deuterium Abundance on Mars and Some Related Problems

https://www.aip.org/news/2015/deuterium … n-research

Martian Methane Reveals the Red Planet is not a Dead Planet] so there must be free hydrogen somewhere for this to be happening...

We also have He3 as well to make use of once mined from the moon as well to work with.

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#15 2017-05-30 18:03:59

louis
Member
From: UK
Registered: 2008-03-24
Posts: 6,914

Re: Thorium reactors are go! (In India)

Are you seriously saying that building a nuclear reactor on Mars would be as simple as buidling a solar powered turbine? It's not about what's there in terms of the energy resource, it's all about how much labour time and mass/energy input is required to make it a reality.

SpaceNut wrote:

The main reason thou for not going with the items not of Fission Nuclear Fuels list is due to fear of launching them from earths surface, weapons in orbit ect....

The known fissile materials are:

    Uranium-233
    Uranium-235
    Plutonium-238
    Plutonium-239
    Plutonium-241
    Neptunium-237
    Curium-244

The other was to make use of the insitu source and only ship what we need to get started....

Map of Martian Thorium at Mid-Latitudes

https://en.wikipedia.org/wiki/Mars_ocean_hypothesis

On the Deuterium Abundance on Mars and Some Related Problems

https://www.aip.org/news/2015/deuterium … n-research

Martian Methane Reveals the Red Planet is not a Dead Planet] so there must be free hydrogen somewhere for this to be happening...

We also have He3 as well to make use of once mined from the moon as well to work with.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#16 2017-05-30 18:37:49

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,342

Re: Thorium reactors are go! (In India)

That is about what the topic is trying to solve to see at what point will we be able to build what on mars. What scope of equipment, mining processing would it take to get to self sustainablility.

The turbine for the solar is the basically the same turbine used in nuclear systems...just different temperatures to create the power.

The other problem is the output power levels for initial missions are measured in the several 100 Kwatt levels of continous operations. To which the other nuclear reactors are in Mega Watt outputs which is totally overkill.

So we are at the cross roads to identify the correct values for what it takes to mining ice, process it and then to do electrolysis such that we are able to create methane and oxygen in the process.

The same source of power would also run a moxie unit continuously to make oxygen as well to be liquifide for use in the rocket.

Since we can not carry reactors everywhere and the extension cords are only going to be just so long. The batteries are only going to hold a charge for limited periods of time as well we need to come up with solutions.

So we will need magnetic materials to make the motors and turbines as well so are the ores in the remnant field areas such that we can use them to make the magnets needed insitu or are we going to keep sending heavy items on every mission?

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