Space Discussion Thread

[Benm]

India is literally doing all those things with Thorium as we speak. The processing center in Bombay converts Thorium to U-233

This year they started using that U-233 in existing Reactors.

A dedicated 300mw Reactor is in the final stages at BARC and should be online this year, it will run on U-233 AND use a Thorium blanket to convert Thorium to U-233.

The idea is that facility will produce enough material to fuel several more new U-233 reactors.

I didn't know they were that far along already, i thought most of it was still in the experimental stages, but good on them!

Switching to a mostly thorium cycle would make sense for india since the ore is available domestically and nuclear infrastructure is already in place.

An interesting consequence might be that canada will go for thorium as well, since it also has domestic reserves, and designed the candu (heavy water moderated) reactor which is very suitable to run on U233 breeding more of it from thorium.

 

[AaronT]

I didn't know they were that far along already, i thought most of it was still in the experimental stages, but good on them!

Switching to a mostly thorium cycle would make sense for india since the ore is available domestically and nuclear infrastructure is already in place.

An interesting consequence might be that canada will go for thorium as well, since it also has domestic reserves, and designed the candu (heavy water moderated) reactor which is very suitable to run on U233 breeding more of it from thorium.

A HUGE factor is how easy it is to process Thorium baring ore.

You can chemically separate it.

EXTRACTION AND REFININGtoc
Acidic and alkaline digestion
Although monazite is very stable chemically, it is susceptible to attack by both strong mineral acids (e.g., sulfuric acid, H2SO4) and alkalies (e.g., sodium hydroxide, NaOH). In the acid treatment, finely ground monazite sand is digested at 155 to 230 °C (310 to 445 °F) with highly concentrated (93 percent) H2SO4. This converts both the phosphate and the metal content of the monazite to water-soluble species. The resulting solution is contacted with aqueous ammonia, first precipitating hydrated thorium phosphate as a gelatinous mass and then metathesizing the thorium phosphate to thorium hydroxide. Finally, the crude thorium hydroxide is dissolved in nitric acid to produce a thorium nitrate-containing feed solution suitable for final purification by solvent extraction (see below).


In alkaline digestion, finely ground monazite sand is carefully treated with a concentrated NaOH solution at 138 °C (280 °F) to produce a solid hydroxide product. Any one of several mineral acids is then used to dissolve this solid residue. For example, treatment with hydrochloric acid yields a solution of thorium and rare earth chlorides. Conventionally, thorium is partially separated from the rare earths by addition of NaOH to the acidic chloride solution. The crude thorium hydroxide precipitate is then dissolved in nitric acid for final purification by solvent extraction.

Solvent extraction

For the purification of thorium from residual rare earths and other contaminants present in nitric acid feed solutions, the crude thorium nitrate concentrate is usually contacted with a solution of tributyl phosphate diluted by a suitable hydrocarbon. The resulting organic extract, containing the thorium (and any uranium that may be present), is then contacted countercurrently with a small volume of nitric acid solution in order to remove contaminating rare earths and other metallic impurities to acceptable levels. Finally, the scrubbed tributyl phosphate solution is contacted with a dilute nitric acid solution; this removes, or strips, thorium from the organic solvent into the aqueous solution while retaining uranium (if present) in the organic phase. Thermal concentration of the purified thorium nitrate solution yields a product suitable for the fabrication of gas mantles (see below Chemical compounds). The nitrate can also be calcined to ThO2, which is incorporated into ceramic fuel elements for nuclear reactors or is converted to thorium metal.

Reduction to the metal
Powdered ThO2 can be fluorinated with gaseous hydrogen fluoride (HF), yielding thorium tetrafluoride (ThF4). The metal is obtained by the Spedding process, in which powdered ThF4 is mixed with finely divided calcium (Ca) and a zinc halide (either zinc chloride or zinc fluoride) and placed in a sealed, refractory-lined “bomb.” Upon heating to approximately 650 °C (1,200 °F), an exothermic reaction ensues that reduces the thorium and zinc to metal and produces a slag of calcium chloride or calcium fluoride:



After solidification, the zinc-thorium alloy product is heated above the boiling point of zinc (907 °C, or 1,665 °F) but below the melting temperature of thorium. This evaporates the zinc and leaves a highly purified thorium sponge, which is melted and cast into ingots.



This makes Thorium much cheaper than Uranium/Plutonium that requires centrifugal separation.

Once Thorium is processed you just put it in a bundle and sink it in with the reactor core to transmutate it into U-233 with neutron radiation.

 

[AaronT]

The Thorium fuel cycle also produces Pu-238 vital for medical uses as well as thermal piles used for space probes.

Pu-238 is in extremely short supply.

Pu-238 Supply

 

[paul1598419]

Half way through the reaction to get from thorium 232 to plutonium 238 is the reaction product U235, which is the isotope of uranium that is the most plentiful. Why use a 1000 Kg of Thorium 232 to get to 100 Kg of uranium 235? Is it not possible to use U235 as your starting element?

 

[AaronT]

Half way through the reaction to get from thorium 232 to plutonium 238 is the reaction product U235, which is the isotope of uranium that is the most plentiful. Why use a 1000 Kg of Thorium 232 to get to 100 Kg of uranium 235? Is it not possible to use U235 as your starting element?

Because you still need the highly expensive process of using centrifuges to separate the U-235 from the other isotopes.

Thorium is chemically separable making it MUCH cheaper.

 

[paul1598419]

I get that the thorium is chemically easier to separate, but you still have some U238 and Pu, which aren't. I was thinking more in terms of a fast breading reactor. It could be set up to use the energy for electricity and the actinides are still there which is what you were looking for anyway.

 

[AaronT]

I get that the thorium is chemically easier to separate, but you still have some U238 and Pu, which aren't. I was thinking more in terms of a fast breading reactor. It could be set up to use the energy for electricity and the actinides are still there which is what you were looking for anyway.

The Thorium fuel cycle is a fast breeder cycle and it yields much more energy than starting with U-238.

 

[paul1598419]

What about U238 and heavy water?

 

[AaronT]

What about U238 and heavy water?

Heavy water reactors are 1940s tech. Even back then the scientists that designed them made it clear that moving to liquidized fuel was the next step.

The future is in Molten Salt Reactors.

Using liquid fuel is more efficient from many standpoints, the simplest to explain is from a mechanical standpoint. It's why we don't use coal to power cars and airplanes.

If you have a couple hours I highly recommend watching this documentary.

THORIUM REMIX 2016 - DOCUMENTARY

 

[Benm]

Natural uranium is problematic indeed, you need a moderator to slow down the neutrons, but not too much, U238 requires relatively high neutron energy to absorb them at a decent rate.

Using a typical system with fuel rods in (heavy) water doesn't really suffice, liquidized bed fuel could.

For thorium it's different though: neutron capture in a 'conventional' heavy water moderated reactor is feasible.

The main reason we don't see more of thorium is actually uranium. As long as supplies are ample there is no real need to switch to thorium.

In some cases, with India being a good example, switching to thorium is preferable because there are vast domestic reserves of thorium but not uranium. This could guarantee energy independence, once the thorium cycle is actually running no extra uranium is needed anymore.

 

[paul1598419]

The main problem with U238 as I see it is the number of actinides left over in the waste. They increase the decay half life of the waste considerably. And with all the old fuel deposits from years of doing this, there are many large amounts of waste that were never stored in any way that would insure they're not leaking out in the future. This is the main reason there aren't any new reactors being made now.

 

[NightExplorer96]

As im sure many of you folks know there are many planned missions to send humans to Mars in the early-mid 2020's which when you think of it is not very far away! How do you think this will plan out?

I personally think trying to colonize space when we have so many problems on Earth already is going to be a huge mistake. If a colony does indeed make it I wouldn't be surprised if many corporations or governments start to spend huge amounts of money toward supporting them and ignoring the rest of the population.

-Alex

 

[AaronT]

As im sure many of you folks know there are many planned missions to send humans to Mars in the early-mid 2020's which when you think of it is not very far away! How do you think this will plan out?

I personally think trying to colonize space when we have so many problems on Earth already is going to be a huge mistake. If a colony does indeed make it I wouldn't be surprised if many corporations or governments start to spend huge amounts of money toward supporting them and ignoring the rest of the population.

-Alex

They are already prepping to test the RS-25 engine that Space X plans to use.

Out at mars solar power barely works for probes. (The largest mars rover maxes out at 130 watts) To supply the power humans and related support systems you will need a small MSR.

MSRs were tested in the 60s. It is just a matter of building one designed to be used in space. Likely to be attached to the ISS for testing and we will see the first nuclear engineer in space.

As to why explore space in light of problems on Earth?

A. Living in space is the ultimate in recycling/resource management. The less you have to bring with you to live the better. Those lessons can be applied directly to reducing the negative impacts of humans on the environment.

B. Where do you think we are going to go when we run out of room here on earth?

C. What better way to protect the Earths environment than by moving some of the population into space to the point less and less people live on Earth.

There was a plan to capture an asteroid and park it around the moon so we could use it for a space station. NASA considers plan to capture an asteroid and turn it into a space station *Link*

However we recently discovered we have 2 moons.

I hope they revive the idea.

IMHO humanity is about to become an interplanetary species.

My minimal criteria for being an interplanetary species would be a self sustaining human life support system in orbit. (A space station that never needs re-supplied).

 

[Benm]

In depends on what the goal of such a space station is. If it is to preserve humanity in case earth is so badly damaged no humans survive, low orbit might not be the safest place to be. A big asteroid impact (say like the one that formed the moon) would obliterate things in an orbit like ISS'.

A colony on mars or perhaps a moon of jupiter would stand far better chances.

One question would be if people actually would want to live in such a place. It would have to be an enclosed space, limited in size to what we can transport. Essentially it would be like a prison, probably including bad food and all. It would also be pretty lawless, it's not likely police will be dispatched to mars if you kill someone to steal someones lunch, and/or make him your luch since meat will be scarse there.

 

[Razako]

Alien Megastructure? 'Tabby's Star' Continues to Baffle Scientists
Alien Megastructure? 'Tabby's Star' Continues to Baffle Scientists

Interesting. Not sure if I believe it's "aliens", but it at least makes me wonder.

 

[Benm]

That's curious indeed, has been in the news for quite some time, and i bet it's some kind of natural phenomenon.

One question is what we'd do if we had the technology. By the time you could build such large structures in space, you'd probably be able to attempt terraforming venus. This would be a huge technical operation we are no where near capable of now, but it could be done at some point.

Mars would be another option, but fundamentally difficult since it's too light to hold an atmosphere. This would mean living under a dome forever.

Venus is perfect in terms of mass if we can remove the current atmosphere. Downside is you get 'days' that last about 4 months effectively on there, but people survive near the poles with polar days and nights that last for months as it is.