Thorium power has a protactinium problem

https://thebulletin.org/2018/08/thorium-power-has-a-protactinium-problem/

by ArtWomb • 8 years ago

79 24 8 years ago

ohazi2• 8 years ago

I thought the real problem with Thorium is that salt eventually corrodes just about everything, which makes building a reactor that uses molten radioactive salt a bit of a sketchy long-term proposition.

baybal2• 8 years ago

How big it is of a problem? Sodium alloys do the same, if not worse, but industry had metallurgy solutions to deal with it for last 50 years.

ohazi2• 8 years ago

My understanding of the situation is that corrosion is the main issue holding back Thorium reactor design.

Molten sodium is used in the coolant loop of some fast reactors, but it doesn't develop any long-lived radioactive byproducts, so it (and the various parts and fittings that it inevitably corrodes) can be disposed of relatively easily. They don't really have solutions to keep it contained, it eventually eats through everything. You just have to keep it from contacting water and exploding.

nickik5• 8 years ago

The primary problem for a Breeder is actually that it corrodes the graphite. We have the metals that are corrosion resistant for long enough.

The primary problem with the metal is actually just qualifying that it is actually the case. The material they used in the original Molten Salt Experiment was great at resistance but re-qualifying this (or anything) to modern standards is incredibly difficult.

The 'Stable Salt Reactor' for Moltex actually have a solution where they use a slightly different salt that they can put some metal into and the chemistry works out that it will corrode that metal first and the piping is fine.

I however primary believe that for the last 40 years, regulatory approve and path to market were the primary issues. In the molten salt reactor experiment they solved many of these problems in relatively short time with a tiny team of people.

Because of regulations you basically can not develop a test reactor, and all of the nuclear companies basically design directly to production because it would be way to expensive to build a test reactor. Building a tiny research reactor would be an option, but those are limited to sizes that are to small to actually validate your design.

danmaz74• 8 years ago

The material they used in the original Molten Salt Experiment was great at resistance but re-qualifying this (or anything) to modern standards is incredibly difficult.

Care to elaborate? Looks like a very interesting problem.

tim333• 8 years ago

I think the real problem with Thorium from a practical point of view is cost effectiveness. Having to develop a bunch of new technology and reprocess red hot fuel is probably going to work out considerably more expensive just building a conventional reactor which itself is looking like being more expensive than renewables.

andlier• 8 years ago

Protactinium

jwfxpr• 8 years ago

Typo in HN title: it's 'protactinium', not 'proactinium'

sctb• 8 years ago

Updated. Thanks!

ComputerGuru• 8 years ago

Excellent article but in 2018 it really isn’t technical so much as political and economical safeguards that prevent the development and spread of nuclear weapons.

The world does not need an excuse to stop research into nuclear power for another fifty years.

nickik5• 8 years ago

Yes, Thorium is not much better in terms of resistance to proliferation, but I think the reality is that threat of commercial reactors being used for for weapons making is pretty small. That's not how nations made their weapons arsenals.

One point, that is often ignored, about Uranium 232 is that it is super easy to find. Meaning its incredibly easy for the IAEA to say that something containing Uranium 232 was used anywhere or to validate that it did not leave the reactor site.

That said, a lesser known program after the Molten Salt Breeder Experiment at Oak Ridge National Laboratory was the Denatured Molten Salt Reactor, that was specifically designed to be more proliferation resistant (they hope proliferation resistant research would keep their program alive, and it did for a little bit).

This work actually lives on and the company furthers ahead in building a Molten Salt Reactor (Uranium) is the Canada based Terrestrial Energy. They are building the Integrated Molten Salt Reactor.

In both designs you avoid some of these problems you have if you do separation, but rather you just switch to a burner design and burn it all in one big reactor, no piping, no chemical plants and so on.

The problem is once you go to a burner, the primary reason why Thorium is an interesting fuel cycle (>2 neutron fission rate) is lost in a burner. That means the extra work to prove that Thorium is safe is just more work that you have to prove safe to the regulator. Pretty much all Molten Salt companies, even when they have met at a Thorium conference (as Terrestrial Energy did), switch to Uranium because of this issue.

For those interested, here are some of the presentations about the current companies working on Molten Salt Reactors:

- Stable Molten Salt Reactor (https://youtu.be/TvXcoSdXYlk?t=2m40s)

- Integrated Molten Salt Reactor (https://www.youtube.com/watch?v=OgTgV3Kq49U)

- Longer term Liquid fluoride thorium reactor (https://www.youtube.com/watch?v=R3lcIvS7cO0)

acidburnNSA5• 8 years ago

The DMSR was a pivot to avoid the U233 problem but it worked by adding U238 to the mix, which inevitably produces plutonium when irradiated. So it was trying to balance low-quality fissile uranium with low-quantity plutonium. A difficult balance. Still it's too bad the program didn't continue, they were doing great work.

acidburnNSA5• 8 years ago

Quick summary for anyone in a hurry. Thorium-232 fertile material absorbs a neutron in a reactor and quickly transfers through Protactinium-233 to Uranium-233, a fissile fuel. Pa-233 is a strong neutron absorber so reactor designers like to pull it out of the reactor chemically to let it decay to U-233. Problem is, if you pull it out and let it decay and you're a bad guy, you can get fairly pure weapons-grade U-233, which is like U-235 and Plutonium-239.

Countermeasures are to make sure there's some U-238 around to blend it down (but then it makes Plutonium and minor actinides), use faster neutrons (not as affected by the Pa), or install safeguards around the reactor.

I'm a huge proponent of nuclear reactors but I have yet to see a design that is truly proliferation-proof. All reactors require safeguards. It's still well worth getting that low-footprint 24/7 clean energy, which nukes alone can produce.

Thorium is great. It doesn't automatically solve all issues in nuclear. Here are the highlights of modern common Thorium Misconceptions: https://whatisnuclear.com/thorium-myths.html

canhascodez• 8 years ago

I'm a huge proponent of nuclear reactors but I have yet to see a design that is truly proliferation-proof.

I assume this statement is limited to nuclear power generation? You wouldn't extend that to, say, that one Iraqi research reactor?

acidburnNSA5• 8 years ago

Yeah I'm mostly referring to engaging them in their unique ability to make 24/7 clean and low-footprint energy. I don't support using them for making nuclear weapons.

mdorazio• 8 years ago

Thanks for this summary. Personally, I think at some point we're going to have to accept that non-proliferation is kind of a lost cause. We're rapidly approaching a time when anyone with some spare time and internet access can start CRISPRing a new plague or fly a drone spewing sarin above a crowd of people. Going to great lengths to cripple power production to prevent the production of some fissile material is like plugging a leak in your boat when there are multiple torpedoes about to hit. If you can go from some U-233 to a working weapon capable of threatening other nations, there are probably other avenues available to you as well.

acidburnNSA5• 8 years ago

Fully agreed. And it's usually much easier to just get some high-speed centrifuges and enrich uranium and make a very simple gun-type nuclear bomb. This requires no nuclear reactor whatsoever and will not go away if we ban nuclear reactors.

Thorium power has a protactinium problem

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