3 ms·

Wait wait wait, you're going to have to provide a citation for this claim that corrosion is not a problem. I was told by faculty with joint appointments in mat

Wait wait wait, you're going to have to provide a citation for this claim that corrosion is not a problem. I was told by faculty with joint appointments in matsci and nuclear engineering that it is a major issue and that while they've developed some alloys that look reasonable in the recent past it's still academic research unproven in scale up. Holding molten salts is really hard... they corrode the heck out of even high end commodity stainless steels (this I know from professional work). Protective coatings help for sure, but they crack over time, especially with any thermal cycling. Inconel and similar alloys maybe, but it's really not straightforward to block grain boundary corrosion! Add to that neutron embrittlement... I've not kept super up to date, but it's hard to imagine that these alloys went from academically unproven to industrially certified in the last seven years.

InclinedPlane 11y ago
Hastelloy-N, it's expensive stuff but it works. Corrosion is one of the difficulties of molten salt reactor designs, but it's manageable with the right materials. And the tradeoff is that you don't need an enormous high-strength containment vessel (because everything radiological is at 1 atm), you don't need to pump water into the thing constantly to avoid "really bad things" happening (Fukushima), etc, etc.
- jpgvm 11y ago
  Exactly this. Specifically you should read the findings of the MSRE (Molten Salt Reactor Experiment) at ORNL. Wikipedia has a relatively laymans explanation of the state of the Hastelloy-N when the experiment concluded.[1] It's worth mentioning Hastelloy-N isn't that expensive all things considered. It would probably come out to a small percentage of the reactors total cost factoring in R&D expenditure etc. [1] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment#Results https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment...
  - InclinedPlane 11y ago
    Additionally, while using a lot of Hastelloy-N would be expensive, in the context of a full reactor it's a modest expense. Especially when you compare it against the extremely enormous forgings and gigantic reinforced concrete structures that traditional lightwater reactors use. Overall you end up with a much smaller and much safer reactor. And one that can burn existing high-level transuranic waste as well. It's such a huge win it's criminal we're not spending billions in R&D right now.
    - neltnerb 11y ago
      Well, thanks for the citation. I'm now much more confused about why this is what I was told in class by an expert in the field. Maybe he meant specifically the difficulty of finding a steel up to the challenge, it was a decade ago so some fidelity may have been lost!
Gibbon1 11y ago
I know not much about material science, except for some very painful experiences in an industrial setting+. But I have a feeling people tend to think fluoride salts are going to be as docile when molten and exposed to a high radiation flux as they are as room temperature solids. + Ethylene-oxide gas + moisture + heat -> plying rough trade on supposedly compatible materials. Not my problem but a customer I worked with had a gamma ray sterilization unit. There were some limit switches which they needed to replace after ten years. Replacements, same part number, manufacture swore up and down they were identical, would crack after three to six months.
DennisP 11y ago
Oak Ridge ran an MSR for four years without difficulty. One solution is to just do that, rather than trying to make a reactor last 60 years. At least two startups are going that route. ThorCon's design is a plant with reactor cores as replaceable "cans," each lasting four years in production plus four years of cool-down before shipping to a reprocessing facility. Terrestrial Energy has sealed 7-year units.

InclinedPlane 11y ago

Hastelloy-N, it's expensive stuff but it works. Corrosion is one of the difficulties of molten salt reactor designs, but it's manageable with the right materials. And the tradeoff is that you don't need an enormous high-strength containment vessel (because everything radiological is at 1 atm), you don't need to pump water into the thing constantly to avoid "really bad things" happening (Fukushima), etc, etc.

jpgvm 11y ago
Exactly this. Specifically you should read the findings of the MSRE (Molten Salt Reactor Experiment) at ORNL. Wikipedia has a relatively laymans explanation of the state of the Hastelloy-N when the experiment concluded.[1] It's worth mentioning Hastelloy-N isn't that expensive all things considered. It would probably come out to a small percentage of the reactors total cost factoring in R&D expenditure etc. [1] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment#Results https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment...
- InclinedPlane 11y ago
  Additionally, while using a lot of Hastelloy-N would be expensive, in the context of a full reactor it's a modest expense. Especially when you compare it against the extremely enormous forgings and gigantic reinforced concrete structures that traditional lightwater reactors use. Overall you end up with a much smaller and much safer reactor. And one that can burn existing high-level transuranic waste as well. It's such a huge win it's criminal we're not spending billions in R&D right now.
  - neltnerb 11y ago
    Well, thanks for the citation. I'm now much more confused about why this is what I was told in class by an expert in the field. Maybe he meant specifically the difficulty of finding a steel up to the challenge, it was a decade ago so some fidelity may have been lost!

Gibbon1 11y ago

I know not much about material science, except for some very painful experiences in an industrial setting+. But I have a feeling people tend to think fluoride salts are going to be as docile when molten and exposed to a high radiation flux as they are as room temperature solids. + Ethylene-oxide gas + moisture + heat -> plying rough trade on supposedly compatible materials. Not my problem but a customer I worked with had a gamma ray sterilization unit. There were some limit switches which they needed to replace after ten years. Replacements, same part number, manufacture swore up and down they were identical, would crack after three to six months.

DennisP 11y ago

Oak Ridge ran an MSR for four years without difficulty. One solution is to just do that, rather than trying to make a reactor last 60 years. At least two startups are going that route. ThorCon's design is a plant with reactor cores as replaceable "cans," each lasting four years in production plus four years of cool-down before shipping to a reprocessing facility. Terrestrial Energy has sealed 7-year units.